Exploring inlined mutable configuration

Currently littlefs uses a separate mutable state struct and immutable config struct. This lets users place the config struct in ROM where possible. However the recent addition of LFS_STATICCFG raises the question of if this split is still valuable. If the config is copied into the mutable struct at runtime, this allows a couple things: 1. Easier user interface, config can be stack allocated, no need to store the config struct for the lifetime of littlefs in OSs. 2. Avoids duplication when littlefs would need to change config based on observed superblocks, such as LFS_NAME_MAX limits 3. In theory, access to a single struct is faster/smaller as it avoids an additional load instruction. Unfortunately, inlining the dynamic config runs into several issues: 1. The code size actually increases with this change! From digging into this it's for a couple reasons: - Copying the config over takes code. - C has notorious problems with pointer aliasing, accessing constants from a const struct actually allows C to assume the values aren't going to change in more situations. This suggests it may be possible to reduce the code size more by loading the config pointer into a variable, but I haven't explored this probably not-worth-it optimization. - Even assuming deduplication of superblock-dependent configuration, the config struct is significantly larger than the mutable struct, and it turns out combining these two exceeds the limits of immediate-relative-loads, discarding the possible code size improvement from avoiding a second dereference. 2. The implementation of dynamic configuration differs significantly from the static configuration. This adds mess into the compile-time #ifdefs needed to support both options.
Changed callbacks to take user-provided context directly
2025-10-31 16:14:16 +01:00 · 2020-11-28 20:13:32 -06:00 · 2020-11-28 20:02:18 -06:00 · 2020-11-28 19:52:21 -06:00 · 2020-11-28 19:51:08 -06:00 · 2020-11-28 19:15:24 -06:00
29 changed files with 1375 additions and 1099 deletions
--- a/.travis.yml
+++ b/.travis.yml
@@ -208,6 +208,31 @@ jobs:
    script:
      - make test TFLAGS+="-k --valgrind"

+  # test minimal compilation using static configs
+  - stage: test
+    env:
+      - NAME=littlefs-minimal
+      - CC="arm-linux-gnueabi-gcc --static -mthumb"
+      - CFLAGS="-Werror
+            -DLFS_STATICCFG -DLFS_FILE_STATICCFG
+            -DLFS_READ_SIZE=16
+            -DLFS_PROG_SIZE=16
+            -DLFS_BLOCK_SIZE=512
+            -DLFS_BLOCK_COUNT=1024
+            -DLFS_BLOCK_CYCLES=-1
+            -DLFS_CACHE_SIZE=64
+            -DLFS_LOOKAHEAD_SIZE=16
+            -DLFS_NO_ASSERT -DLFS_NO_DEBUG -DLFS_NO_WARN -DLFS_NO_ERROR"
+    if: branch !~ -prefix$
+    install:
+      - *install-common
+      - sudo apt-get install
+            gcc-arm-linux-gnueabi
+            libc6-dev-armel-cross
+      - arm-linux-gnueabi-gcc --version
+    # report-size will compile littlefs and report the size
+    script: [*report-size]
+
  # self-host with littlefs-fuse for fuzz test
  - stage: test
    env:
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@ lfs_t lfs;
 lfs_file_t file;

 // configuration of the filesystem is provided by this struct
-const struct lfs_config cfg = {
+const struct lfs_cfg cfg = {
    // block device operations
    .read  = user_provided_block_device_read,
    .prog  = user_provided_block_device_prog,
--- a/bd/lfs_filebd.c
+++ b/bd/lfs_filebd.c
@@ -10,21 +10,18 @@
 #include <unistd.h>
 #include <errno.h>

-int lfs_filebd_createcfg(const struct lfs_config *cfg, const char *path,
-        const struct lfs_filebd_config *bdcfg) {
-    LFS_FILEBD_TRACE("lfs_filebd_createcfg(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
+int lfs_filebd_createcfg(lfs_filebd_t *bd, const char *path,
+        const struct lfs_filebd_cfg *cfg) {
+    LFS_FILEBD_TRACE("lfs_filebd_createcfg(%p, \"%s\", %p {"
                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
-                "\"%s\", "
-                "%p {.erase_value=%"PRId32"})",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
-            path, (void*)bdcfg, bdcfg->erase_value);
-    lfs_filebd_t *bd = cfg->context;
-    bd->cfg = bdcfg;
+                ".erase_size=%"PRIu32", .erase_count=%"PRIu32", "
+                ".erase_value=%"PRId32"})",
+            (void*)bd, path, (void*)cfg,
+            cfg->read_size, cfg->prog_size, cfg->erase_size, cfg->erase_count,
+            cfg->erase_value);
+
+    // copy over config
+    bd->cfg = *cfg;

    // open file
    bd->fd = open(path, O_RDWR | O_CREAT, 0666);
@@ -38,26 +35,8 @@ int lfs_filebd_createcfg(const struct lfs_config *cfg, const char *path,
    return 0;
 }

-int lfs_filebd_create(const struct lfs_config *cfg, const char *path) {
-    LFS_FILEBD_TRACE("lfs_filebd_create(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
-                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
-                "\"%s\")",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
-            path);
-    static const struct lfs_filebd_config defaults = {.erase_value=-1};
-    int err = lfs_filebd_createcfg(cfg, path, &defaults);
-    LFS_FILEBD_TRACE("lfs_filebd_create -> %d", err);
-    return err;
-}
-
-int lfs_filebd_destroy(const struct lfs_config *cfg) {
-    LFS_FILEBD_TRACE("lfs_filebd_destroy(%p)", (void*)cfg);
-    lfs_filebd_t *bd = cfg->context;
+int lfs_filebd_destroy(lfs_filebd_t *bd) {
+    LFS_FILEBD_TRACE("lfs_filebd_destroy(%p)", (void*)bd);
    int err = close(bd->fd);
    if (err < 0) {
        err = -errno;
@@ -68,26 +47,25 @@ int lfs_filebd_destroy(const struct lfs_config *cfg) {
    return 0;
 }

-int lfs_filebd_read(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_filebd_read(lfs_filebd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size) {
    LFS_FILEBD_TRACE("lfs_filebd_read(%p, "
                "0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
-            (void*)cfg, block, off, buffer, size);
-    lfs_filebd_t *bd = cfg->context;
+            (void*)bd, block, off, buffer, size);

    // check if read is valid
-    LFS_ASSERT(off  % cfg->read_size == 0);
-    LFS_ASSERT(size % cfg->read_size == 0);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(off  % bd->cfg.read_size == 0);
+    LFS_ASSERT(size % bd->cfg.read_size == 0);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // zero for reproducability (in case file is truncated)
-    if (bd->cfg->erase_value != -1) {
-        memset(buffer, bd->cfg->erase_value, size);
+    if (bd->cfg.erase_value != -1) {
+        memset(buffer, bd->cfg.erase_value, size);
    }

    // read
    off_t res1 = lseek(bd->fd,
-            (off_t)block*cfg->block_size + (off_t)off, SEEK_SET);
+            (off_t)block*bd->cfg.erase_size + (off_t)off, SEEK_SET);
    if (res1 < 0) {
        int err = -errno;
        LFS_FILEBD_TRACE("lfs_filebd_read -> %d", err);
@@ -105,21 +83,21 @@ int lfs_filebd_read(const struct lfs_config *cfg, lfs_block_t block,
    return 0;
 }

-int lfs_filebd_prog(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_filebd_prog(lfs_filebd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size) {
-    LFS_FILEBD_TRACE("lfs_filebd_prog(%p, 0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
-            (void*)cfg, block, off, buffer, size);
-    lfs_filebd_t *bd = cfg->context;
+    LFS_FILEBD_TRACE("lfs_filebd_prog(%p, "
+                "0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
+            (void*)bd, block, off, buffer, size);

    // check if write is valid
-    LFS_ASSERT(off  % cfg->prog_size == 0);
-    LFS_ASSERT(size % cfg->prog_size == 0);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(off  % bd->cfg.prog_size == 0);
+    LFS_ASSERT(size % bd->cfg.prog_size == 0);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // check that data was erased? only needed for testing
-    if (bd->cfg->erase_value != -1) {
+    if (bd->cfg.erase_value != -1) {
        off_t res1 = lseek(bd->fd,
-                (off_t)block*cfg->block_size + (off_t)off, SEEK_SET);
+                (off_t)block*bd->cfg.erase_size + (off_t)off, SEEK_SET);
        if (res1 < 0) {
            int err = -errno;
            LFS_FILEBD_TRACE("lfs_filebd_prog -> %d", err);
@@ -135,13 +113,13 @@ int lfs_filebd_prog(const struct lfs_config *cfg, lfs_block_t block,
                return err;
            }

-            LFS_ASSERT(c == bd->cfg->erase_value);
+            LFS_ASSERT(c == bd->cfg.erase_value);
        }
    }

    // program data
    off_t res1 = lseek(bd->fd,
-            (off_t)block*cfg->block_size + (off_t)off, SEEK_SET);
+            (off_t)block*bd->cfg.erase_size + (off_t)off, SEEK_SET);
    if (res1 < 0) {
        int err = -errno;
        LFS_FILEBD_TRACE("lfs_filebd_prog -> %d", err);
@@ -159,24 +137,23 @@ int lfs_filebd_prog(const struct lfs_config *cfg, lfs_block_t block,
    return 0;
 }

-int lfs_filebd_erase(const struct lfs_config *cfg, lfs_block_t block) {
-    LFS_FILEBD_TRACE("lfs_filebd_erase(%p, 0x%"PRIx32")", (void*)cfg, block);
-    lfs_filebd_t *bd = cfg->context;
+int lfs_filebd_erase(lfs_filebd_t *bd, lfs_block_t block) {
+    LFS_FILEBD_TRACE("lfs_filebd_erase(%p, 0x%"PRIx32")", (void*)bd, block);

    // check if erase is valid
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // erase, only needed for testing
-    if (bd->cfg->erase_value != -1) {
-        off_t res1 = lseek(bd->fd, (off_t)block*cfg->block_size, SEEK_SET);
+    if (bd->cfg.erase_value != -1) {
+        off_t res1 = lseek(bd->fd, (off_t)block*bd->cfg.erase_size, SEEK_SET);
        if (res1 < 0) {
            int err = -errno;
            LFS_FILEBD_TRACE("lfs_filebd_erase -> %d", err);
            return err;
        }

-        for (lfs_off_t i = 0; i < cfg->block_size; i++) {
-            ssize_t res2 = write(bd->fd, &(uint8_t){bd->cfg->erase_value}, 1);
+        for (lfs_off_t i = 0; i < bd->cfg.erase_size; i++) {
+            ssize_t res2 = write(bd->fd, &(uint8_t){bd->cfg.erase_value}, 1);
            if (res2 < 0) {
                int err = -errno;
                LFS_FILEBD_TRACE("lfs_filebd_erase -> %d", err);
@@ -189,10 +166,10 @@ int lfs_filebd_erase(const struct lfs_config *cfg, lfs_block_t block) {
    return 0;
 }

-int lfs_filebd_sync(const struct lfs_config *cfg) {
-    LFS_FILEBD_TRACE("lfs_filebd_sync(%p)", (void*)cfg);
+int lfs_filebd_sync(lfs_filebd_t *bd) {
+    LFS_FILEBD_TRACE("lfs_filebd_sync(%p)", (void*)bd);
+
    // file sync
-    lfs_filebd_t *bd = cfg->context;
    int err = fsync(bd->fd);
    if (err) {
        err = -errno;
--- a/bd/lfs_filebd.h
+++ b/bd/lfs_filebd.h
@@ -8,11 +8,9 @@
 #define LFS_FILEBD_H

 #include "lfs.h"
-#include "lfs_util.h"

 #ifdef __cplusplus
-extern "C"
-{
+extern "C" {
 #endif


@@ -24,7 +22,21 @@ extern "C"
 #endif

 // filebd config (optional)
-struct lfs_filebd_config {
+struct lfs_filebd_cfg {
+    // Minimum size of block read. All read operations must be a
+    // multiple of this value.
+    lfs_size_t read_size;
+
+    // Minimum size of block program. All program operations must be a
+    // multiple of this value.
+    lfs_size_t prog_size;
+
+    // Size of an erasable block.
+    lfs_size_t erase_size;
+
+    // Number of erasable blocks on the device.
+    lfs_size_t erase_count;
+
    // 8-bit erase value to use for simulating erases. -1 does not simulate
    // erases, which can speed up testing by avoiding all the extra block-device
    // operations to store the erase value.
@@ -34,40 +46,39 @@ struct lfs_filebd_config {
 // filebd state
 typedef struct lfs_filebd {
    int fd;
-    const struct lfs_filebd_config *cfg;
+    struct lfs_filebd_cfg cfg;
 } lfs_filebd_t;


-// Create a file block device using the geometry in lfs_config
-int lfs_filebd_create(const struct lfs_config *cfg, const char *path);
-int lfs_filebd_createcfg(const struct lfs_config *cfg, const char *path,
-        const struct lfs_filebd_config *bdcfg);
+// Create a file block device using the geometry in lfs_filebd_cfg
+int lfs_filebd_createcfg(lfs_filebd_t *bd, const char *path,
+        const struct lfs_filebd_cfg *cfg);

 // Clean up memory associated with block device
-int lfs_filebd_destroy(const struct lfs_config *cfg);
+int lfs_filebd_destroy(lfs_filebd_t *bd);

 // Read a block
-int lfs_filebd_read(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_filebd_read(lfs_filebd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size);

 // Program a block
 //
 // The block must have previously been erased.
-int lfs_filebd_prog(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_filebd_prog(lfs_filebd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size);

 // Erase a block
 //
 // A block must be erased before being programmed. The
 // state of an erased block is undefined.
-int lfs_filebd_erase(const struct lfs_config *cfg, lfs_block_t block);
+int lfs_filebd_erase(lfs_filebd_t *bd, lfs_block_t block);

 // Sync the block device
-int lfs_filebd_sync(const struct lfs_config *cfg);
+int lfs_filebd_sync(lfs_filebd_t *bd);


 #ifdef __cplusplus
-} /* extern "C" */
+}
 #endif

 #endif
--- a/bd/lfs_rambd.c
+++ b/bd/lfs_rambd.c
@@ -6,26 +6,24 @@
 */
 #include "bd/lfs_rambd.h"

-int lfs_rambd_createcfg(const struct lfs_config *cfg,
-        const struct lfs_rambd_config *bdcfg) {
-    LFS_RAMBD_TRACE("lfs_rambd_createcfg(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
+int lfs_rambd_createcfg(lfs_rambd_t *bd,
+        const struct lfs_rambd_cfg *cfg) {
+    LFS_RAMBD_TRACE("lfs_filebd_createcfg(%p, %p {"
                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
-                "%p {.erase_value=%"PRId32", .buffer=%p})",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
-            (void*)bdcfg, bdcfg->erase_value, bdcfg->buffer);
-    lfs_rambd_t *bd = cfg->context;
-    bd->cfg = bdcfg;
+                ".erase_size=%"PRIu32", .erase_count=%"PRIu32", "
+                ".erase_value=%"PRId32", .buffer=%p})",
+            (void*)bd, (void*)cfg,
+            cfg->read_size, cfg->prog_size, cfg->erase_size, cfg->erase_count,
+            cfg->erase_value, cfg->buffer);
+
+    // copy over config
+    bd->cfg = *cfg;

    // allocate buffer?
-    if (bd->cfg->buffer) {
-        bd->buffer = bd->cfg->buffer;
+    if (bd->cfg.buffer) {
+        bd->buffer = bd->cfg.buffer;
    } else {
-        bd->buffer = lfs_malloc(cfg->block_size * cfg->block_count);
+        bd->buffer = lfs_malloc(bd->cfg.erase_size * bd->cfg.erase_count);
        if (!bd->buffer) {
            LFS_RAMBD_TRACE("lfs_rambd_createcfg -> %d", LFS_ERR_NOMEM);
            return LFS_ERR_NOMEM;
@@ -33,108 +31,89 @@ int lfs_rambd_createcfg(const struct lfs_config *cfg,
    }

    // zero for reproducability?
-    if (bd->cfg->erase_value != -1) {
-        memset(bd->buffer, bd->cfg->erase_value,
-                cfg->block_size * cfg->block_count);
+    if (bd->cfg.erase_value != -1) {
+        memset(bd->buffer, bd->cfg.erase_value,
+                bd->cfg.erase_size * bd->cfg.erase_count);
    }

    LFS_RAMBD_TRACE("lfs_rambd_createcfg -> %d", 0);
    return 0;
 }

-int lfs_rambd_create(const struct lfs_config *cfg) {
-    LFS_RAMBD_TRACE("lfs_rambd_create(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
-                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"})",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count);
-    static const struct lfs_rambd_config defaults = {.erase_value=-1};
-    int err = lfs_rambd_createcfg(cfg, &defaults);
-    LFS_RAMBD_TRACE("lfs_rambd_create -> %d", err);
-    return err;
-}
-
-int lfs_rambd_destroy(const struct lfs_config *cfg) {
-    LFS_RAMBD_TRACE("lfs_rambd_destroy(%p)", (void*)cfg);
+int lfs_rambd_destroy(lfs_rambd_t *bd) {
+    LFS_RAMBD_TRACE("lfs_rambd_destroy(%p)", (void*)bd);
    // clean up memory
-    lfs_rambd_t *bd = cfg->context;
-    if (!bd->cfg->buffer) {
+    if (!bd->cfg.buffer) {
        lfs_free(bd->buffer);
    }
    LFS_RAMBD_TRACE("lfs_rambd_destroy -> %d", 0);
    return 0;
 }

-int lfs_rambd_read(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_rambd_read(lfs_rambd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size) {
    LFS_RAMBD_TRACE("lfs_rambd_read(%p, "
                "0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
-            (void*)cfg, block, off, buffer, size);
-    lfs_rambd_t *bd = cfg->context;
+            (void*)bd, block, off, buffer, size);

    // check if read is valid
-    LFS_ASSERT(off  % cfg->read_size == 0);
-    LFS_ASSERT(size % cfg->read_size == 0);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(off  % bd->cfg.read_size == 0);
+    LFS_ASSERT(size % bd->cfg.read_size == 0);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // read data
-    memcpy(buffer, &bd->buffer[block*cfg->block_size + off], size);
+    memcpy(buffer, &bd->buffer[block*bd->cfg.erase_size + off], size);

    LFS_RAMBD_TRACE("lfs_rambd_read -> %d", 0);
    return 0;
 }

-int lfs_rambd_prog(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_rambd_prog(lfs_rambd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size) {
    LFS_RAMBD_TRACE("lfs_rambd_prog(%p, "
                "0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
-            (void*)cfg, block, off, buffer, size);
-    lfs_rambd_t *bd = cfg->context;
+            (void*)bd, block, off, buffer, size);

    // check if write is valid
-    LFS_ASSERT(off  % cfg->prog_size == 0);
-    LFS_ASSERT(size % cfg->prog_size == 0);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(off  % bd->cfg.prog_size == 0);
+    LFS_ASSERT(size % bd->cfg.prog_size == 0);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // check that data was erased? only needed for testing
-    if (bd->cfg->erase_value != -1) {
+    if (bd->cfg.erase_value != -1) {
        for (lfs_off_t i = 0; i < size; i++) {
-            LFS_ASSERT(bd->buffer[block*cfg->block_size + off + i] ==
-                    bd->cfg->erase_value);
+            LFS_ASSERT(bd->buffer[block*bd->cfg.erase_size + off + i] ==
+                    bd->cfg.erase_value);
        }
    }

    // program data
-    memcpy(&bd->buffer[block*cfg->block_size + off], buffer, size);
+    memcpy(&bd->buffer[block*bd->cfg.erase_size + off], buffer, size);

    LFS_RAMBD_TRACE("lfs_rambd_prog -> %d", 0);
    return 0;
 }

-int lfs_rambd_erase(const struct lfs_config *cfg, lfs_block_t block) {
-    LFS_RAMBD_TRACE("lfs_rambd_erase(%p, 0x%"PRIx32")", (void*)cfg, block);
-    lfs_rambd_t *bd = cfg->context;
+int lfs_rambd_erase(lfs_rambd_t *bd, lfs_block_t block) {
+    LFS_RAMBD_TRACE("lfs_rambd_erase(%p, 0x%"PRIx32")", (void*)bd, block);

    // check if erase is valid
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // erase, only needed for testing
-    if (bd->cfg->erase_value != -1) {
-        memset(&bd->buffer[block*cfg->block_size],
-                bd->cfg->erase_value, cfg->block_size);
+    if (bd->cfg.erase_value != -1) {
+        memset(&bd->buffer[block*bd->cfg.erase_size],
+                bd->cfg.erase_value, bd->cfg.erase_size);
    }

    LFS_RAMBD_TRACE("lfs_rambd_erase -> %d", 0);
    return 0;
 }

-int lfs_rambd_sync(const struct lfs_config *cfg) {
-    LFS_RAMBD_TRACE("lfs_rambd_sync(%p)", (void*)cfg);
+int lfs_rambd_sync(lfs_rambd_t *bd) {
+    LFS_RAMBD_TRACE("lfs_rambd_sync(%p)", (void*)bd);
    // sync does nothing because we aren't backed by anything real
-    (void)cfg;
+    (void)bd;
    LFS_RAMBD_TRACE("lfs_rambd_sync -> %d", 0);
    return 0;
 }
--- a/bd/lfs_rambd.h
+++ b/bd/lfs_rambd.h
@@ -8,11 +8,9 @@
 #define LFS_RAMBD_H

 #include "lfs.h"
-#include "lfs_util.h"

 #ifdef __cplusplus
-extern "C"
-{
+extern "C" {
 #endif


@@ -24,7 +22,21 @@ extern "C"
 #endif

 // rambd config (optional)
-struct lfs_rambd_config {
+struct lfs_rambd_cfg {
+    // Minimum size of block read. All read operations must be a
+    // multiple of this value.
+    lfs_size_t read_size;
+
+    // Minimum size of block program. All program operations must be a
+    // multiple of this value.
+    lfs_size_t prog_size;
+
+    // Size of an erasable block.
+    lfs_size_t erase_size;
+
+    // Number of erasable blocks on the device.
+    lfs_size_t erase_count;
+
    // 8-bit erase value to simulate erasing with. -1 indicates no erase
    // occurs, which is still a valid block device
    int32_t erase_value;
@@ -36,40 +48,39 @@ struct lfs_rambd_config {
 // rambd state
 typedef struct lfs_rambd {
    uint8_t *buffer;
-    const struct lfs_rambd_config *cfg;
+    struct lfs_rambd_cfg cfg;
 } lfs_rambd_t;


-// Create a RAM block device using the geometry in lfs_config
-int lfs_rambd_create(const struct lfs_config *cfg);
-int lfs_rambd_createcfg(const struct lfs_config *cfg,
-        const struct lfs_rambd_config *bdcfg);
+// Create a RAM block device using the geometry in lfs_cfg
+int lfs_rambd_createcfg(lfs_rambd_t *bd,
+        const struct lfs_rambd_cfg *cfg);

 // Clean up memory associated with block device
-int lfs_rambd_destroy(const struct lfs_config *cfg);
+int lfs_rambd_destroy(lfs_rambd_t *bd);

 // Read a block
-int lfs_rambd_read(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_rambd_read(lfs_rambd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size);

 // Program a block
 //
 // The block must have previously been erased.
-int lfs_rambd_prog(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_rambd_prog(lfs_rambd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size);

 // Erase a block
 //
 // A block must be erased before being programmed. The
 // state of an erased block is undefined.
-int lfs_rambd_erase(const struct lfs_config *cfg, lfs_block_t block);
+int lfs_rambd_erase(lfs_rambd_t *bd, lfs_block_t block);

 // Sync the block device
-int lfs_rambd_sync(const struct lfs_config *cfg);
+int lfs_rambd_sync(lfs_rambd_t *bd);


 #ifdef __cplusplus
-} /* extern "C" */
+}
 #endif

 #endif
--- a/bd/lfs_testbd.c
+++ b/bd/lfs_testbd.c
@@ -10,185 +10,164 @@
 #include <stdlib.h>


-int lfs_testbd_createcfg(const struct lfs_config *cfg, const char *path,
-        const struct lfs_testbd_config *bdcfg) {
-    LFS_TESTBD_TRACE("lfs_testbd_createcfg(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
+int lfs_testbd_createcfg(lfs_testbd_t *bd, const char *path,
+        const struct lfs_testbd_cfg *cfg) {
+    LFS_TESTBD_TRACE("lfs_testbd_createcfg(%p, \"%s\", %p {"
                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
-                "\"%s\", "
-                "%p {.erase_value=%"PRId32", .erase_cycles=%"PRIu32", "
+                ".erase_size=%"PRIu32", .erase_count=%"PRIu32", "
+                ".erase_value=%"PRId32", .erase_cycles=%"PRIu32", "
                ".badblock_behavior=%"PRIu8", .power_cycles=%"PRIu32", "
                ".buffer=%p, .wear_buffer=%p})",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
-            path, (void*)bdcfg, bdcfg->erase_value, bdcfg->erase_cycles,
-            bdcfg->badblock_behavior, bdcfg->power_cycles,
-            bdcfg->buffer, bdcfg->wear_buffer);
-    lfs_testbd_t *bd = cfg->context;
-    bd->cfg = bdcfg;
+            (void*)bd, path, (void*)cfg,
+            cfg->read_size, cfg->prog_size, cfg->erase_size, cfg->erase_count,
+            cfg->erase_value, cfg->erase_cycles,
+            cfg->badblock_behavior, cfg->power_cycles,
+            cfg->buffer, cfg->wear_buffer);
+
+    // copy over config
+    bd->cfg = *cfg;

    // setup testing things
    bd->persist = path;
-    bd->power_cycles = bd->cfg->power_cycles;
+    bd->power_cycles = bd->cfg.power_cycles;

-    if (bd->cfg->erase_cycles) {
-        if (bd->cfg->wear_buffer) {
-            bd->wear = bd->cfg->wear_buffer;
+    if (bd->cfg.erase_cycles) {
+        if (bd->cfg.wear_buffer) {
+            bd->wear = bd->cfg.wear_buffer;
        } else {
-            bd->wear = lfs_malloc(sizeof(lfs_testbd_wear_t)*cfg->block_count);
+            bd->wear = lfs_malloc(sizeof(lfs_testbd_wear_t)*cfg->erase_count);
            if (!bd->wear) {
                LFS_TESTBD_TRACE("lfs_testbd_createcfg -> %d", LFS_ERR_NOMEM);
                return LFS_ERR_NOMEM;
            }
        }

-        memset(bd->wear, 0, sizeof(lfs_testbd_wear_t) * cfg->block_count);
+        memset(bd->wear, 0, sizeof(lfs_testbd_wear_t) * bd->cfg.erase_count);
    }

    // create underlying block device
    if (bd->persist) {
-        bd->u.file.cfg = (struct lfs_filebd_config){
-            .erase_value = bd->cfg->erase_value,
-        };
-        int err = lfs_filebd_createcfg(cfg, path, &bd->u.file.cfg);
+        int err = lfs_filebd_createcfg(&bd->impl.filebd, path,
+                &(struct lfs_filebd_cfg){
+                    .read_size=bd->cfg.read_size,
+                    .prog_size=bd->cfg.prog_size,
+                    .erase_size=bd->cfg.erase_size,
+                    .erase_count=bd->cfg.erase_count,
+                    .erase_value=bd->cfg.erase_value});
        LFS_TESTBD_TRACE("lfs_testbd_createcfg -> %d", err);
        return err;
    } else {
-        bd->u.ram.cfg = (struct lfs_rambd_config){
-            .erase_value = bd->cfg->erase_value,
-            .buffer = bd->cfg->buffer,
-        };
-        int err = lfs_rambd_createcfg(cfg, &bd->u.ram.cfg);
+        int err = lfs_rambd_createcfg(&bd->impl.rambd,
+                &(struct lfs_rambd_cfg){
+                    .read_size=bd->cfg.read_size,
+                    .prog_size=bd->cfg.prog_size,
+                    .erase_size=bd->cfg.erase_size,
+                    .erase_count=bd->cfg.erase_count,
+                    .erase_value=bd->cfg.erase_value,
+                    .buffer=bd->cfg.buffer});
        LFS_TESTBD_TRACE("lfs_testbd_createcfg -> %d", err);
        return err;
    }
 }

-int lfs_testbd_create(const struct lfs_config *cfg, const char *path) {
-    LFS_TESTBD_TRACE("lfs_testbd_create(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
-                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
-                "\"%s\")",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
-            path);
-    static const struct lfs_testbd_config defaults = {.erase_value=-1};
-    int err = lfs_testbd_createcfg(cfg, path, &defaults);
-    LFS_TESTBD_TRACE("lfs_testbd_create -> %d", err);
-    return err;
-}
-
-int lfs_testbd_destroy(const struct lfs_config *cfg) {
-    LFS_TESTBD_TRACE("lfs_testbd_destroy(%p)", (void*)cfg);
-    lfs_testbd_t *bd = cfg->context;
-    if (bd->cfg->erase_cycles && !bd->cfg->wear_buffer) {
+int lfs_testbd_destroy(lfs_testbd_t *bd) {
+    LFS_TESTBD_TRACE("lfs_testbd_destroy(%p)", (void*)bd);
+    if (bd->cfg.erase_cycles && !bd->cfg.wear_buffer) {
        lfs_free(bd->wear);
    }

    if (bd->persist) {
-        int err = lfs_filebd_destroy(cfg);
+        int err = lfs_filebd_destroy(&bd->impl.filebd);
        LFS_TESTBD_TRACE("lfs_testbd_destroy -> %d", err);
        return err;
    } else {
-        int err = lfs_rambd_destroy(cfg);
+        int err = lfs_rambd_destroy(&bd->impl.rambd);
        LFS_TESTBD_TRACE("lfs_testbd_destroy -> %d", err);
        return err;
    }
 }

 /// Internal mapping to block devices ///
-static int lfs_testbd_rawread(const struct lfs_config *cfg, lfs_block_t block,
+static int lfs_testbd_rawread(lfs_testbd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size) {
-    lfs_testbd_t *bd = cfg->context;
    if (bd->persist) {
-        return lfs_filebd_read(cfg, block, off, buffer, size);
+        return lfs_filebd_read(&bd->impl.filebd, block, off, buffer, size);
    } else {
-        return lfs_rambd_read(cfg, block, off, buffer, size);
+        return lfs_rambd_read(&bd->impl.rambd, block, off, buffer, size);
    }
 }

-static int lfs_testbd_rawprog(const struct lfs_config *cfg, lfs_block_t block,
+static int lfs_testbd_rawprog(lfs_testbd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size) {
-    lfs_testbd_t *bd = cfg->context;
    if (bd->persist) {
-        return lfs_filebd_prog(cfg, block, off, buffer, size);
+        return lfs_filebd_prog(&bd->impl.filebd, block, off, buffer, size);
    } else {
-        return lfs_rambd_prog(cfg, block, off, buffer, size);
+        return lfs_rambd_prog(&bd->impl.rambd, block, off, buffer, size);
    }
 }

-static int lfs_testbd_rawerase(const struct lfs_config *cfg,
+static int lfs_testbd_rawerase(lfs_testbd_t *bd,
        lfs_block_t block) {
-    lfs_testbd_t *bd = cfg->context;
    if (bd->persist) {
-        return lfs_filebd_erase(cfg, block);
+        return lfs_filebd_erase(&bd->impl.filebd, block);
    } else {
-        return lfs_rambd_erase(cfg, block);
+        return lfs_rambd_erase(&bd->impl.rambd, block);
    }
 }

-static int lfs_testbd_rawsync(const struct lfs_config *cfg) {
-    lfs_testbd_t *bd = cfg->context;
+static int lfs_testbd_rawsync(lfs_testbd_t *bd) {
    if (bd->persist) {
-        return lfs_filebd_sync(cfg);
+        return lfs_filebd_sync(&bd->impl.filebd);
    } else {
-        return lfs_rambd_sync(cfg);
+        return lfs_rambd_sync(&bd->impl.rambd);
    }
 }

 /// block device API ///
-int lfs_testbd_read(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_testbd_read(lfs_testbd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size) {
    LFS_TESTBD_TRACE("lfs_testbd_read(%p, "
                "0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
-            (void*)cfg, block, off, buffer, size);
-    lfs_testbd_t *bd = cfg->context;
+            (void*)bd, block, off, buffer, size);

    // check if read is valid
-    LFS_ASSERT(off  % cfg->read_size == 0);
-    LFS_ASSERT(size % cfg->read_size == 0);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(off  % bd->cfg.read_size == 0);
+    LFS_ASSERT(size % bd->cfg.read_size == 0);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // block bad?
-    if (bd->cfg->erase_cycles && bd->wear[block] >= bd->cfg->erase_cycles &&
-            bd->cfg->badblock_behavior == LFS_TESTBD_BADBLOCK_READERROR) {
+    if (bd->cfg.erase_cycles && bd->wear[block] >= bd->cfg.erase_cycles &&
+            bd->cfg.badblock_behavior == LFS_TESTBD_BADBLOCK_READERROR) {
        LFS_TESTBD_TRACE("lfs_testbd_read -> %d", LFS_ERR_CORRUPT);
        return LFS_ERR_CORRUPT;
    }

    // read
-    int err = lfs_testbd_rawread(cfg, block, off, buffer, size);
+    int err = lfs_testbd_rawread(bd, block, off, buffer, size);
    LFS_TESTBD_TRACE("lfs_testbd_read -> %d", err);
    return err;
 }

-int lfs_testbd_prog(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_testbd_prog(lfs_testbd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size) {
    LFS_TESTBD_TRACE("lfs_testbd_prog(%p, "
                "0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
-            (void*)cfg, block, off, buffer, size);
-    lfs_testbd_t *bd = cfg->context;
+            (void*)bd, block, off, buffer, size);

    // check if write is valid
-    LFS_ASSERT(off  % cfg->prog_size == 0);
-    LFS_ASSERT(size % cfg->prog_size == 0);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(off  % bd->cfg.prog_size == 0);
+    LFS_ASSERT(size % bd->cfg.prog_size == 0);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // block bad?
-    if (bd->cfg->erase_cycles && bd->wear[block] >= bd->cfg->erase_cycles) {
-        if (bd->cfg->badblock_behavior ==
+    if (bd->cfg.erase_cycles && bd->wear[block] >= bd->cfg.erase_cycles) {
+        if (bd->cfg.badblock_behavior ==
                LFS_TESTBD_BADBLOCK_PROGERROR) {
            LFS_TESTBD_TRACE("lfs_testbd_prog -> %d", LFS_ERR_CORRUPT);
            return LFS_ERR_CORRUPT;
-        } else if (bd->cfg->badblock_behavior ==
+        } else if (bd->cfg.badblock_behavior ==
                LFS_TESTBD_BADBLOCK_PROGNOOP ||
-                bd->cfg->badblock_behavior ==
+                bd->cfg.badblock_behavior ==
                LFS_TESTBD_BADBLOCK_ERASENOOP) {
            LFS_TESTBD_TRACE("lfs_testbd_prog -> %d", 0);
            return 0;
@@ -196,7 +175,7 @@ int lfs_testbd_prog(const struct lfs_config *cfg, lfs_block_t block,
    }

    // prog
-    int err = lfs_testbd_rawprog(cfg, block, off, buffer, size);
+    int err = lfs_testbd_rawprog(bd, block, off, buffer, size);
    if (err) {
        LFS_TESTBD_TRACE("lfs_testbd_prog -> %d", err);
        return err;
@@ -207,7 +186,7 @@ int lfs_testbd_prog(const struct lfs_config *cfg, lfs_block_t block,
        bd->power_cycles -= 1;
        if (bd->power_cycles == 0) {
            // sync to make sure we persist the last changes
-            assert(lfs_testbd_rawsync(cfg) == 0);
+            assert(lfs_testbd_rawsync(bd) == 0);
            // simulate power loss
            exit(33);
        }
@@ -217,21 +196,20 @@ int lfs_testbd_prog(const struct lfs_config *cfg, lfs_block_t block,
    return 0;
 }

-int lfs_testbd_erase(const struct lfs_config *cfg, lfs_block_t block) {
-    LFS_TESTBD_TRACE("lfs_testbd_erase(%p, 0x%"PRIx32")", (void*)cfg, block);
-    lfs_testbd_t *bd = cfg->context;
+int lfs_testbd_erase(lfs_testbd_t *bd, lfs_block_t block) {
+    LFS_TESTBD_TRACE("lfs_testbd_erase(%p, 0x%"PRIx32")", (void*)bd, block);

    // check if erase is valid
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    // block bad?
-    if (bd->cfg->erase_cycles) {
-        if (bd->wear[block] >= bd->cfg->erase_cycles) {
-            if (bd->cfg->badblock_behavior ==
+    if (bd->cfg.erase_cycles) {
+        if (bd->wear[block] >= bd->cfg.erase_cycles) {
+            if (bd->cfg.badblock_behavior ==
                    LFS_TESTBD_BADBLOCK_ERASEERROR) {
                LFS_TESTBD_TRACE("lfs_testbd_erase -> %d", LFS_ERR_CORRUPT);
                return LFS_ERR_CORRUPT;
-            } else if (bd->cfg->badblock_behavior ==
+            } else if (bd->cfg.badblock_behavior ==
                    LFS_TESTBD_BADBLOCK_ERASENOOP) {
                LFS_TESTBD_TRACE("lfs_testbd_erase -> %d", 0);
                return 0;
@@ -243,7 +221,7 @@ int lfs_testbd_erase(const struct lfs_config *cfg, lfs_block_t block) {
    }

    // erase
-    int err = lfs_testbd_rawerase(cfg, block);
+    int err = lfs_testbd_rawerase(bd, block);
    if (err) {
        LFS_TESTBD_TRACE("lfs_testbd_erase -> %d", err);
        return err;
@@ -254,7 +232,7 @@ int lfs_testbd_erase(const struct lfs_config *cfg, lfs_block_t block) {
        bd->power_cycles -= 1;
        if (bd->power_cycles == 0) {
            // sync to make sure we persist the last changes
-            assert(lfs_testbd_rawsync(cfg) == 0);
+            assert(lfs_testbd_rawsync(bd) == 0);
            // simulate power loss
            exit(33);
        }
@@ -264,36 +242,34 @@ int lfs_testbd_erase(const struct lfs_config *cfg, lfs_block_t block) {
    return 0;
 }

-int lfs_testbd_sync(const struct lfs_config *cfg) {
-    LFS_TESTBD_TRACE("lfs_testbd_sync(%p)", (void*)cfg);
-    int err = lfs_testbd_rawsync(cfg);
+int lfs_testbd_sync(lfs_testbd_t *bd) {
+    LFS_TESTBD_TRACE("lfs_testbd_sync(%p)", (void*)bd);
+    int err = lfs_testbd_rawsync(bd);
    LFS_TESTBD_TRACE("lfs_testbd_sync -> %d", err);
    return err;
 }


 /// simulated wear operations ///
-lfs_testbd_swear_t lfs_testbd_getwear(const struct lfs_config *cfg,
+lfs_testbd_swear_t lfs_testbd_getwear(lfs_testbd_t *bd,
        lfs_block_t block) {
-    LFS_TESTBD_TRACE("lfs_testbd_getwear(%p, %"PRIu32")", (void*)cfg, block);
-    lfs_testbd_t *bd = cfg->context;
+    LFS_TESTBD_TRACE("lfs_testbd_getwear(%p, %"PRIu32")", (void*)bd, block);

    // check if block is valid
-    LFS_ASSERT(bd->cfg->erase_cycles);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(bd->cfg.erase_cycles);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    LFS_TESTBD_TRACE("lfs_testbd_getwear -> %"PRIu32, bd->wear[block]);
    return bd->wear[block];
 }

-int lfs_testbd_setwear(const struct lfs_config *cfg,
+int lfs_testbd_setwear(lfs_testbd_t *bd,
        lfs_block_t block, lfs_testbd_wear_t wear) {
-    LFS_TESTBD_TRACE("lfs_testbd_setwear(%p, %"PRIu32")", (void*)cfg, block);
-    lfs_testbd_t *bd = cfg->context;
+    LFS_TESTBD_TRACE("lfs_testbd_setwear(%p, %"PRIu32")", (void*)bd, block);

    // check if block is valid
-    LFS_ASSERT(bd->cfg->erase_cycles);
-    LFS_ASSERT(block < cfg->block_count);
+    LFS_ASSERT(bd->cfg.erase_cycles);
+    LFS_ASSERT(block < bd->cfg.erase_count);

    bd->wear[block] = wear;

--- a/bd/lfs_testbd.h
+++ b/bd/lfs_testbd.h
@@ -9,13 +9,11 @@
 #define LFS_TESTBD_H

 #include "lfs.h"
-#include "lfs_util.h"
 #include "bd/lfs_rambd.h"
 #include "bd/lfs_filebd.h"

 #ifdef __cplusplus
-extern "C"
-{
+extern "C" {
 #endif


@@ -45,7 +43,21 @@ typedef uint32_t lfs_testbd_wear_t;
 typedef int32_t  lfs_testbd_swear_t;

 // testbd config, this is required for testing
-struct lfs_testbd_config {
+struct lfs_testbd_cfg {
+    // Minimum size of block read. All read operations must be a
+    // multiple of this value.
+    lfs_size_t read_size;
+
+    // Minimum size of block program. All program operations must be a
+    // multiple of this value.
+    lfs_size_t prog_size;
+
+    // Size of an erasable block.
+    lfs_size_t erase_size;
+
+    // Number of erasable blocks on the device.
+    lfs_size_t erase_count;
+
    // 8-bit erase value to use for simulating erases. -1 does not simulate
    // erases, which can speed up testing by avoiding all the extra block-device
    // operations to store the erase value.
@@ -72,70 +84,63 @@ struct lfs_testbd_config {
 // testbd state
 typedef struct lfs_testbd {
    union {
-        struct {
-            lfs_filebd_t bd;
-            struct lfs_filebd_config cfg;
-        } file;
-        struct {
-            lfs_rambd_t bd;
-            struct lfs_rambd_config cfg;
-        } ram;
-    } u;
+        lfs_filebd_t filebd;
+        lfs_rambd_t rambd;
+    } impl;

    bool persist;
    uint32_t power_cycles;
    lfs_testbd_wear_t *wear;

-    const struct lfs_testbd_config *cfg;
+    struct lfs_testbd_cfg cfg;
 } lfs_testbd_t;


 /// Block device API ///

-// Create a test block device using the geometry in lfs_config
+// Create a test block device using the geometry in lfs_cfg
 //
 // Note that filebd is used if a path is provided, if path is NULL
 // testbd will use rambd which can be much faster.
-int lfs_testbd_create(const struct lfs_config *cfg, const char *path);
-int lfs_testbd_createcfg(const struct lfs_config *cfg, const char *path,
-        const struct lfs_testbd_config *bdcfg);
+int lfs_testbd_createcfg(lfs_testbd_t *bd, const char *path,
+        const struct lfs_testbd_cfg *cfg);

 // Clean up memory associated with block device
-int lfs_testbd_destroy(const struct lfs_config *cfg);
+int lfs_testbd_destroy(lfs_testbd_t *bd);

 // Read a block
-int lfs_testbd_read(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_testbd_read(lfs_testbd_t *bd, lfs_block_t block,
        lfs_off_t off, void *buffer, lfs_size_t size);

 // Program a block
 //
 // The block must have previously been erased.
-int lfs_testbd_prog(const struct lfs_config *cfg, lfs_block_t block,
+int lfs_testbd_prog(lfs_testbd_t *bd, lfs_block_t block,
        lfs_off_t off, const void *buffer, lfs_size_t size);

 // Erase a block
 //
 // A block must be erased before being programmed. The
 // state of an erased block is undefined.
-int lfs_testbd_erase(const struct lfs_config *cfg, lfs_block_t block);
+int lfs_testbd_erase(lfs_testbd_t *bd, lfs_block_t block);

 // Sync the block device
-int lfs_testbd_sync(const struct lfs_config *cfg);
+int lfs_testbd_sync(lfs_testbd_t *bd);


 /// Additional extended API for driving test features ///

 // Get simulated wear on a given block
-lfs_testbd_swear_t lfs_testbd_getwear(const struct lfs_config *cfg,
+lfs_testbd_swear_t lfs_testbd_getwear(lfs_testbd_t *bd,
        lfs_block_t block);

 // Manually set simulated wear on a given block
-int lfs_testbd_setwear(const struct lfs_config *cfg,
+int lfs_testbd_setwear(lfs_testbd_t *bd,
        lfs_block_t block, lfs_testbd_wear_t wear);


 #ifdef __cplusplus
-} /* extern "C" */
+}
 #endif

 #endif
--- a/lfs.c
+++ b/lfs.c
--- a/lfs.h
+++ b/lfs.h
@@ -7,12 +7,10 @@
 #ifndef LFS_H
 #define LFS_H

-#include <stdint.h>
-#include <stdbool.h>
+#include "lfs_util.h"

 #ifdef __cplusplus
-extern "C"
-{
+extern "C" {
 #endif


@@ -66,26 +64,6 @@ typedef uint32_t lfs_block_t;
 #define LFS_ATTR_MAX 1022
 #endif

-// Possible error codes, these are negative to allow
-// valid positive return values
-enum lfs_error {
-    LFS_ERR_OK          = 0,    // No error
-    LFS_ERR_IO          = -5,   // Error during device operation
-    LFS_ERR_CORRUPT     = -84,  // Corrupted
-    LFS_ERR_NOENT       = -2,   // No directory entry
-    LFS_ERR_EXIST       = -17,  // Entry already exists
-    LFS_ERR_NOTDIR      = -20,  // Entry is not a dir
-    LFS_ERR_ISDIR       = -21,  // Entry is a dir
-    LFS_ERR_NOTEMPTY    = -39,  // Dir is not empty
-    LFS_ERR_BADF        = -9,   // Bad file number
-    LFS_ERR_FBIG        = -27,  // File too large
-    LFS_ERR_INVAL       = -22,  // Invalid parameter
-    LFS_ERR_NOSPC       = -28,  // No space left on device
-    LFS_ERR_NOMEM       = -12,  // No more memory available
-    LFS_ERR_NOATTR      = -61,  // No data/attr available
-    LFS_ERR_NAMETOOLONG = -36,  // File name too long
-};
-
 // File types
 enum lfs_type {
    // file types
@@ -147,32 +125,33 @@ enum lfs_whence_flags {
 };


+#if !defined(LFS_STATICCFG)
 // Configuration provided during initialization of the littlefs
-struct lfs_config {
+struct lfs_cfg {
    // Opaque user provided context that can be used to pass
    // information to the block device operations
-    void *context;
+    void *ctx;

    // Read a region in a block. Negative error codes are propogated
    // to the user.
-    int (*read)(const struct lfs_config *c, lfs_block_t block,
+    int (*read)(void *ctx, lfs_block_t block,
            lfs_off_t off, void *buffer, lfs_size_t size);

    // Program a region in a block. The block must have previously
    // been erased. Negative error codes are propogated to the user.
    // May return LFS_ERR_CORRUPT if the block should be considered bad.
-    int (*prog)(const struct lfs_config *c, lfs_block_t block,
+    int (*prog)(void *ctx, lfs_block_t block,
            lfs_off_t off, const void *buffer, lfs_size_t size);

    // Erase a block. A block must be erased before being programmed.
    // The state of an erased block is undefined. Negative error codes
    // are propogated to the user.
    // May return LFS_ERR_CORRUPT if the block should be considered bad.
-    int (*erase)(const struct lfs_config *c, lfs_block_t block);
+    int (*erase)(void *ctx, lfs_block_t block);

    // Sync the state of the underlying block device. Negative error codes
    // are propogated to the user.
-    int (*sync)(const struct lfs_config *c);
+    int (*sync)(void *ctx);

    // Minimum size of a block read. All read operations will be a
    // multiple of this value.
@@ -241,6 +220,90 @@ struct lfs_config {
    // LFS_ATTR_MAX when zero.
    lfs_size_t attr_max;
 };
+#else
+// Static configuration if LFS_STATICCFG is defined, there are defaults
+// for some of these, but some are required. For full documentation, see
+// the lfs_cfg struct above.
+
+// Block device operations
+int lfs_read(lfs_block_t block,
+        lfs_off_t off, void *buffer, lfs_size_t size);
+int lfs_prog(lfs_block_t block,
+        lfs_off_t off, const void *buffer, lfs_size_t size);
+int lfs_erase(lfs_block_t block);
+int lfs_sync(void);
+
+// Required configuration
+#ifndef LFS_READ_SIZE
+#error "LFS_STATICCFG requires LFS_READ_SIZE"
+#endif
+#ifndef LFS_PROG_SIZE
+#error "LFS_STATICCFG requires LFS_PROG_SIZE"
+#endif
+#ifndef LFS_BLOCK_SIZE
+#error "LFS_STATICCFG requires LFS_BLOCK_SIZE"
+#endif
+#ifndef LFS_BLOCK_COUNT
+#error "LFS_STATICCFG requires LFS_BLOCK_COUNT"
+#endif
+#ifndef LFS_BLOCK_CYCLES
+#error "LFS_STATICCFG requires LFS_BLOCK_CYCLES"
+#endif
+#ifndef LFS_CACHE_SIZE
+#error "LFS_STATICCFG requires LFS_CACHE_SIZE"
+#endif
+#ifndef LFS_LOOKAHEAD_SIZE
+#error "LFS_STATICCFG requires LFS_LOOKAHEAD_SIZE"
+#endif
+
+// Optional configuration
+#ifndef LFS_READ_BUFFER
+#define LFS_READ_BUFFER NULL
+#endif
+#ifndef LFS_PROG_BUFFER
+#define LFS_PROG_BUFFER NULL
+#endif
+#ifndef LFS_LOOKAHEAD_BUFFER
+#define LFS_LOOKAHEAD_BUFFER NULL
+#endif
+#endif
+
+#if !defined(LFS_FILE_STATICCFG)
+// Optional configuration provided during lfs_file_opencfg
+struct lfs_file_cfg {
+    // Optional statically allocated file buffer. Must be cache_size.
+    // By default lfs_malloc is used to allocate this buffer.
+    void *buffer;
+
+    // Optional list of custom attributes related to the file. If the file
+    // is opened with read access, these attributes will be read from disk
+    // during the open call. If the file is opened with write access, the
+    // attributes will be written to disk every file sync or close. This
+    // write occurs atomically with update to the file's contents.
+    //
+    // Custom attributes are uniquely identified by an 8-bit type and limited
+    // to LFS_ATTR_MAX bytes. When read, if the stored attribute is smaller
+    // than the buffer, it will be padded with zeros. If the stored attribute
+    // is larger, then it will be silently truncated. If the attribute is not
+    // found, it will be created implicitly.
+    struct lfs_attr *attrs;
+
+    // Number of custom attributes in the list
+    lfs_size_t attr_count;
+};
+#else
+// Static configuration if LFS_FILE_STATICCFG is defined. For full
+// documentation, see the lfs_file_cfg struct above.
+#ifndef LFS_FILE_BUFFER
+#define LFS_FILE_BUFFER NULL
+#endif
+#ifndef LFS_FILE_ATTRS
+#define LFS_FILE_ATTRS ((struct lfs_attr*)NULL)
+#endif
+#ifndef LFS_FILE_ATTR_COUNT
+#define LFS_FILE_ATTR_COUNT 0
+#endif
+#endif

 // File info structure
 struct lfs_info {
@@ -271,29 +334,6 @@ struct lfs_attr {
    lfs_size_t size;
 };

-// Optional configuration provided during lfs_file_opencfg
-struct lfs_file_config {
-    // Optional statically allocated file buffer. Must be cache_size.
-    // By default lfs_malloc is used to allocate this buffer.
-    void *buffer;
-
-    // Optional list of custom attributes related to the file. If the file
-    // is opened with read access, these attributes will be read from disk
-    // during the open call. If the file is opened with write access, the
-    // attributes will be written to disk every file sync or close. This
-    // write occurs atomically with update to the file's contents.
-    //
-    // Custom attributes are uniquely identified by an 8-bit type and limited
-    // to LFS_ATTR_MAX bytes. When read, if the stored attribute is smaller
-    // than the buffer, it will be padded with zeros. If the stored attribute
-    // is larger, then it will be silently truncated. If the attribute is not
-    // found, it will be created implicitly.
-    struct lfs_attr *attrs;
-
-    // Number of custom attributes in the list
-    lfs_size_t attr_count;
-};
-

 /// internal littlefs data structures ///
 typedef struct lfs_cache {
@@ -343,7 +383,9 @@ typedef struct lfs_file {
    lfs_off_t off;
    lfs_cache_t cache;

-    const struct lfs_file_config *cfg;
+#ifndef LFS_FILE_STATICCFG
+    struct lfs_file_cfg cfg;
+#endif
 } lfs_file_t;

 typedef struct lfs_superblock {
@@ -386,10 +428,9 @@ typedef struct lfs {
        uint32_t *buffer;
    } free;

-    const struct lfs_config *cfg;
-    lfs_size_t name_max;
-    lfs_size_t file_max;
-    lfs_size_t attr_max;
+#ifndef LFS_STATICCFG
+    struct lfs_cfg cfg;
+#endif

 #ifdef LFS_MIGRATE
    struct lfs1 *lfs1;
@@ -399,16 +440,38 @@ typedef struct lfs {

 /// Filesystem functions ///

-// Format a block device with the littlefs
+#if defined(LFS_STATICCFG)
+// Format a block device with littlefs
+//
+// Requires a littlefs object. This clobbers the littlefs object, and does
+// not leave the filesystem mounted.
+//
+// Returns a negative error code on failure.
+int lfs_format(lfs_t *lfs);
+#endif
+
+#if !defined(LFS_STATICCFG)
+// Format a block device with littlefs with per-filesystem configuration
 //
 // Requires a littlefs object and config struct. This clobbers the littlefs
 // object, and does not leave the filesystem mounted. The config struct must
 // be zeroed for defaults and backwards compatibility.
 //
 // Returns a negative error code on failure.
-int lfs_format(lfs_t *lfs, const struct lfs_config *config);
+int lfs_formatcfg(lfs_t *lfs, const struct lfs_cfg *config);
+#endif

-// Mounts a littlefs
+#if defined(LFS_STATICCFG)
+// Mounts littlefs
+//
+// Requires a littlefs object and static configuration.
+//
+// Returns a negative error code on failure.
+int lfs_mount(lfs_t *lfs);
+#endif
+
+#if !defined(LFS_STATICCFG)
+// Mounts a littlefs with per-filesystem configuration
 //
 // Requires a littlefs object and config struct. Multiple filesystems
 // may be mounted simultaneously with multiple littlefs objects. Both
@@ -416,7 +479,8 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *config);
 // be zeroed for defaults and backwards compatibility.
 //
 // Returns a negative error code on failure.
-int lfs_mount(lfs_t *lfs, const struct lfs_config *config);
+int lfs_mountcfg(lfs_t *lfs, const struct lfs_cfg *config);
+#endif

 // Unmounts a littlefs
 //
@@ -490,7 +554,8 @@ int lfs_removeattr(lfs_t *lfs, const char *path, uint8_t type);
 int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
        const char *path, int flags);

-// Open a file with extra configuration
+#if !defined(LFS_FILE_STATICCFG)
+// Open a file with per-file configuration
 //
 // The mode that the file is opened in is determined by the flags, which
 // are values from the enum lfs_open_flags that are bitwise-ored together.
@@ -502,7 +567,8 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
 // Returns a negative error code on failure.
 int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
        const char *path, int flags,
-        const struct lfs_file_config *config);
+        const struct lfs_file_cfg *config);
+#endif

 // Close a file
 //
@@ -632,24 +698,39 @@ lfs_ssize_t lfs_fs_size(lfs_t *lfs);
 // Returns a negative error code on failure.
 int lfs_fs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data);

-#ifdef LFS_MIGRATE
+#if defined(LFS_MIGRATE) && defined(LFS_STATICCFG)
 // Attempts to migrate a previous version of littlefs
 //
 // Behaves similarly to the lfs_format function. Attempts to mount
 // the previous version of littlefs and update the filesystem so it can be
 // mounted with the current version of littlefs.
 //
+// Requires a littlefs object. This clobbers the littlefs object, and does
+// not leave the filesystem mounted.
+//
+// Returns a negative error code on failure.
+int lfs_migrate(lfs_t *lfs, const struct lfs_cfg *cfg);
+#endif
+
+#if defined(LFS_MIGRATE) && !defined(LFS_STATICCFG)
+// Attempts to migrate a previous version of littlefs with per-filesystem
+// configuration
+//
+// Behaves similarly to the lfs_format function. Attempts to mount
+// the previous version of littlefs and update the filesystem so it can be
+// mounted with the current version of littlefs.
+//
 // Requires a littlefs object and config struct. This clobbers the littlefs
 // object, and does not leave the filesystem mounted. The config struct must
 // be zeroed for defaults and backwards compatibility.
 //
 // Returns a negative error code on failure.
-int lfs_migrate(lfs_t *lfs, const struct lfs_config *cfg);
+int lfs_migratecfg(lfs_t *lfs, const struct lfs_cfg *cfg);
 #endif


 #ifdef __cplusplus
-} /* extern "C" */
+}
 #endif

 #endif
--- a/lfs_util.c
+++ b/lfs_util.c
@@ -7,7 +7,7 @@
 #include "lfs_util.h"

 // Only compile if user does not provide custom config
-#ifndef LFS_CONFIG
+#ifndef LFS_UTIL


 // Software CRC implementation with small lookup table
--- a/lfs_util.h
+++ b/lfs_util.h
@@ -3,20 +3,21 @@
 *
 * Copyright (c) 2017, Arm Limited. All rights reserved.
 * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Can be overridden by users with their own configuration by defining
+ * LFS_UTIL as a header file (-DLFS_UTIL=my_lfs_util.h)
+ *
+ * If LFS_UTIL is defined, none of the default definitions will be
+ * emitted and must be provided by the user's header file. To start, I would
+ * suggest copying lfs_util.h and modifying as needed.
 */
 #ifndef LFS_UTIL_H
 #define LFS_UTIL_H

-// Users can override lfs_util.h with their own configuration by defining
-// LFS_CONFIG as a header file to include (-DLFS_CONFIG=lfs_config.h).
-//
-// If LFS_CONFIG is used, none of the default utils will be emitted and must be
-// provided by the config file. To start, I would suggest copying lfs_util.h
-// and modifying as needed.
-#ifdef LFS_CONFIG
+#ifdef LFS_UTIL
 #define LFS_STRINGIZE(x) LFS_STRINGIZE2(x)
 #define LFS_STRINGIZE2(x) #x
-#include LFS_STRINGIZE(LFS_CONFIG)
+#include LFS_STRINGIZE(LFS_UTIL)
 #else

 // System includes
@@ -39,11 +40,32 @@
 #endif

 #ifdef __cplusplus
-extern "C"
-{
+extern "C" {
 #endif


+// Possible error codes, these are negative to allow valid positive
+// return values. May be redefined to system-specific error codes as long
+// as they fit in a negative integer.
+enum lfs_error {
+    LFS_ERR_OK          = 0,    // No error
+    LFS_ERR_IO          = -5,   // Error during device operation
+    LFS_ERR_CORRUPT     = -84,  // Corrupted
+    LFS_ERR_NOENT       = -2,   // No directory entry
+    LFS_ERR_EXIST       = -17,  // Entry already exists
+    LFS_ERR_NOTDIR      = -20,  // Entry is not a dir
+    LFS_ERR_ISDIR       = -21,  // Entry is a dir
+    LFS_ERR_NOTEMPTY    = -39,  // Dir is not empty
+    LFS_ERR_BADF        = -9,   // Bad file number
+    LFS_ERR_FBIG        = -27,  // File too large
+    LFS_ERR_INVAL       = -22,  // Invalid parameter
+    LFS_ERR_NOSPC       = -28,  // No space left on device
+    LFS_ERR_NOMEM       = -12,  // No more memory available
+    LFS_ERR_NOATTR      = -61,  // No data/attr available
+    LFS_ERR_NAMETOOLONG = -36,  // File name too long
+};
+
+
 // Macros, may be replaced by system specific wrappers. Arguments to these
 // macros must not have side-effects as the macros can be removed for a smaller
 // code footprint
@@ -150,8 +172,8 @@ static inline uint32_t lfs_popc(uint32_t a) {

 // Find the sequence comparison of a and b, this is the distance
 // between a and b ignoring overflow
-static inline int lfs_scmp(uint32_t a, uint32_t b) {
-    return (int)(unsigned)(a - b);
+static inline int32_t lfs_scmp(uint32_t a, uint32_t b) {
+    return (int32_t)(uint32_t)(a - b);
 }

 // Convert between 32-bit little-endian and native order
@@ -227,7 +249,7 @@ static inline void lfs_free(void *p) {


 #ifdef __cplusplus
-} /* extern "C" */
+}
 #endif

 #endif
--- a/scripts/test.py
+++ b/scripts/test.py
@@ -34,13 +34,43 @@ $(foreach target,$(SRC),$(eval $(FLATTEN)))
 %.test: %.test.o $(foreach f,$(subst /,.,$(SRC:.c=.o)),%.$f)
    $(CC) $(CFLAGS) $^ $(LFLAGS) -o $@
 """
-GLOBALS = """
+BEFORE_MAIN = """
+const char *lfs_testbd_path;
+uint32_t lfs_testbd_cycles;
+
+int lfs_testbd_readctx(void *ctx, lfs_block_t block,
+        lfs_off_t off, void *buffer, lfs_size_t size) {
+    return lfs_testbd_read((lfs_testbd_t*)ctx, block, off, buffer, size);
+}
+
+int lfs_testbd_progctx(void *ctx, lfs_block_t block,
+        lfs_off_t off, const void *buffer, lfs_size_t size) {
+    return lfs_testbd_prog((lfs_testbd_t*)ctx, block, off, buffer, size);
+}
+
+int lfs_testbd_erasectx(void *ctx, lfs_block_t block) {
+    return lfs_testbd_erase((lfs_testbd_t*)ctx, block);
+}
+
+int lfs_testbd_syncctx(void *ctx) {
+    return lfs_testbd_sync((lfs_testbd_t*)ctx);
+}
+"""
+BEFORE_TESTS = """
 //////////////// AUTOGENERATED TEST ////////////////
 #include "lfs.h"
 #include "bd/lfs_testbd.h"
 #include <stdio.h>
+
 extern const char *lfs_testbd_path;
 extern uint32_t lfs_testbd_cycles;
+
+extern int lfs_testbd_readctx(void *ctx, lfs_block_t block,
+        lfs_off_t off, void *buffer, lfs_size_t size);
+extern int lfs_testbd_progctx(void *ctx, lfs_block_t block,
+        lfs_off_t off, const void *buffer, lfs_size_t size);
+extern int lfs_testbd_erasectx(void *ctx, lfs_block_t block);
+extern int lfs_testbd_syncctx(void *ctx);
 """
 DEFINES = {
    'LFS_READ_SIZE': 16,
@@ -66,12 +96,12 @@ PROLOGUE = """
    __attribute__((unused)) lfs_size_t size;
    __attribute__((unused)) int err;
    
-    __attribute__((unused)) const struct lfs_config cfg = {
-        .context        = &bd,
-        .read           = lfs_testbd_read,
-        .prog           = lfs_testbd_prog,
-        .erase          = lfs_testbd_erase,
-        .sync           = lfs_testbd_sync,
+    __attribute__((unused)) const struct lfs_cfg cfg = {
+        .ctx            = &bd,
+        .read           = lfs_testbd_readctx,
+        .prog           = lfs_testbd_progctx,
+        .erase          = lfs_testbd_erasectx,
+        .sync           = lfs_testbd_syncctx,
        .read_size      = LFS_READ_SIZE,
        .prog_size      = LFS_PROG_SIZE,
        .block_size     = LFS_BLOCK_SIZE,
@@ -81,18 +111,22 @@ PROLOGUE = """
        .lookahead_size = LFS_LOOKAHEAD_SIZE,
    };

-    __attribute__((unused)) const struct lfs_testbd_config bdcfg = {
+    __attribute__((unused)) const struct lfs_testbd_cfg bdcfg = {
+        .read_size          = LFS_READ_SIZE,
+        .prog_size          = LFS_PROG_SIZE,
+        .erase_size         = LFS_BLOCK_SIZE,
+        .erase_count        = LFS_BLOCK_COUNT,
        .erase_value        = LFS_ERASE_VALUE,
        .erase_cycles       = LFS_ERASE_CYCLES,
        .badblock_behavior  = LFS_BADBLOCK_BEHAVIOR,
        .power_cycles       = lfs_testbd_cycles,
    };

-    lfs_testbd_createcfg(&cfg, lfs_testbd_path, &bdcfg) => 0;
+    lfs_testbd_createcfg(&bd, lfs_testbd_path, &bdcfg) => 0;
 """
 EPILOGUE = """
    // epilogue
-    lfs_testbd_destroy(&cfg) => 0;
+    lfs_testbd_destroy(&bd) => 0;
 """
 PASS = '\033[32m✓\033[0m'
 FAIL = '\033[31m✗\033[0m'
@@ -468,7 +502,7 @@ class TestSuite:
    def build(self, **args):
        # build test files
        tf = open(self.path + '.test.c.t', 'w')
-        tf.write(GLOBALS)
+        tf.write(BEFORE_TESTS)
        if self.code is not None:
            tf.write('#line %d "%s"\n' % (self.code_lineno, self.path))
            tf.write(self.code)
@@ -483,14 +517,13 @@ class TestSuite:
                    for line in f:
                        tfs[case.in_].write(line)
                tfs[case.in_].write('\n')
-                tfs[case.in_].write(GLOBALS)
+                tfs[case.in_].write(BEFORE_TESTS)

            tfs[case.in_].write('\n')
            case.build(tfs[case.in_], **args)

+        tf.write(BEFORE_MAIN)
        tf.write('\n')
-        tf.write('const char *lfs_testbd_path;\n')
-        tf.write('uint32_t lfs_testbd_cycles;\n')
        tf.write('int main(int argc, char **argv) {\n')
        tf.write(4*' '+'int case_         = (argc > 1) ? atoi(argv[1]) : 0;\n')
        tf.write(4*' '+'int perm          = (argc > 2) ? atoi(argv[2]) : 0;\n')
--- a/tests/test_alloc.toml
+++ b/tests/test_alloc.toml
@@ -9,12 +9,12 @@ code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};
    lfs_file_t files[FILES];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "breakfast") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int n = 0; n < FILES; n++) {
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &files[n], path,
@@ -31,7 +31,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int n = 0; n < FILES; n++) {
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
@@ -51,13 +51,13 @@ define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-6)) / FILES)'
 code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "breakfast") => 0;
    lfs_unmount(&lfs) => 0;

    for (int n = 0; n < FILES; n++) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &file, path,
                LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
@@ -70,7 +70,7 @@ code = '''
        lfs_unmount(&lfs) => 0;
    }

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int n = 0; n < FILES; n++) {
        sprintf(path, "breakfast/%s", names[n]);
        lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
@@ -92,14 +92,14 @@ code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};
    lfs_file_t files[FILES];

-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    for (int c = 0; c < CYCLES; c++) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        lfs_mkdir(&lfs, "breakfast") => 0;
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &files[n], path,
@@ -116,7 +116,7 @@ code = '''
        }
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
@@ -129,7 +129,7 @@ code = '''
        }
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_remove(&lfs, path) => 0;
@@ -146,15 +146,15 @@ define.CYCLES = [1, 10]
 code = '''
    const char *names[FILES] = {"bacon", "eggs", "pancakes"};

-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    for (int c = 0; c < CYCLES; c++) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        lfs_mkdir(&lfs, "breakfast") => 0;
        lfs_unmount(&lfs) => 0;

        for (int n = 0; n < FILES; n++) {
-            lfs_mount(&lfs, &cfg) => 0;
+            lfs_mountcfg(&lfs, &cfg) => 0;
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &file, path,
                    LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
@@ -167,7 +167,7 @@ code = '''
            lfs_unmount(&lfs) => 0;
        }

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
@@ -180,7 +180,7 @@ code = '''
        }
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int n = 0; n < FILES; n++) {
            sprintf(path, "breakfast/%s", names[n]);
            lfs_remove(&lfs, path) => 0;
@@ -192,8 +192,8 @@ code = '''

 [[case]] # exhaustion test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
    size = strlen("exhaustion");
    memcpy(buffer, "exhaustion", size);
@@ -216,7 +216,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_RDONLY);
    size = strlen("exhaustion");
    lfs_file_size(&lfs, &file) => size;
@@ -229,8 +229,8 @@ code = '''
 [[case]] # exhaustion wraparound test
 define.SIZE = '(((LFS_BLOCK_SIZE-8)*(LFS_BLOCK_COUNT-4)) / 3)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    lfs_file_open(&lfs, &file, "padding", LFS_O_WRONLY | LFS_O_CREAT);
    size = strlen("buffering");
@@ -263,7 +263,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "exhaustion", LFS_O_RDONLY);
    size = strlen("exhaustion");
    lfs_file_size(&lfs, &file) => size;
@@ -276,8 +276,8 @@ code = '''

 [[case]] # dir exhaustion test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // find out max file size
    lfs_mkdir(&lfs, "exhaustiondir") => 0;
@@ -328,8 +328,8 @@ in = "lfs.c"
 define.LFS_ERASE_CYCLES = 0xffffffff
 define.LFS_BADBLOCK_BEHAVIOR = 'LFS_TESTBD_BADBLOCK_READERROR'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    // first fill to exhaustion to find available space
    lfs_file_open(&lfs, &file, "pacman", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "waka");
@@ -358,11 +358,11 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // remount to force an alloc scan
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // but mark the head of our file as a "bad block", this is force our
    // scan to bail early
-    lfs_testbd_setwear(&cfg, fileblock, 0xffffffff) => 0;
+    lfs_testbd_setwear(&bd, fileblock, 0xffffffff) => 0;
    lfs_file_open(&lfs, &file, "ghost", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "chomp");
    size = strlen("chomp");
@@ -377,7 +377,7 @@ code = '''

    // now reverse the "bad block" and try to write the file again until we
    // run out of space
-    lfs_testbd_setwear(&cfg, fileblock, 0) => 0;
+    lfs_testbd_setwear(&bd, fileblock, 0) => 0;
    lfs_file_open(&lfs, &file, "ghost", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    strcpy((char*)buffer, "chomp");
    size = strlen("chomp");
@@ -393,7 +393,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // check that the disk isn't hurt
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "pacman", LFS_O_RDONLY) => 0;
    strcpy((char*)buffer, "waka");
    size = strlen("waka");
@@ -416,8 +416,8 @@ define.LFS_BLOCK_SIZE = 512
 define.LFS_BLOCK_COUNT = 1024
 if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // find out max file size
    lfs_mkdir(&lfs, "exhaustiondir") => 0;
@@ -487,8 +487,8 @@ define.LFS_BLOCK_SIZE = 512
 define.LFS_BLOCK_COUNT = 1024
 if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // create one block hole for half a directory
    lfs_file_open(&lfs, &file, "bump", LFS_O_WRONLY | LFS_O_CREAT) => 0;
@@ -510,7 +510,7 @@ code = '''

    // remount to force reset of lookahead
    lfs_unmount(&lfs) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // open hole
    lfs_remove(&lfs, "bump") => 0;
@@ -532,8 +532,8 @@ define.LFS_BLOCK_SIZE = 512
 define.LFS_BLOCK_COUNT = 1024
 if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // fill completely with two files
    lfs_file_open(&lfs, &file, "exhaustion1",
@@ -560,7 +560,7 @@ code = '''

    // remount to force reset of lookahead
    lfs_unmount(&lfs) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // rewrite one file
    lfs_file_open(&lfs, &file, "exhaustion1",
@@ -597,8 +597,8 @@ define.LFS_BLOCK_SIZE = 512
 define.LFS_BLOCK_COUNT = 1024
 if = 'LFS_BLOCK_SIZE == 512 && LFS_BLOCK_COUNT == 1024'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // fill completely with two files
    lfs_file_open(&lfs, &file, "exhaustion1",
@@ -625,7 +625,7 @@ code = '''

    // remount to force reset of lookahead
    lfs_unmount(&lfs) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // rewrite one file with a hole of one block
    lfs_file_open(&lfs, &file, "exhaustion1",
--- a/tests/test_attrs.toml
+++ b/tests/test_attrs.toml
@@ -1,14 +1,14 @@
 [[case]] # set/get attribute
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "hello") => 0;
    lfs_file_open(&lfs, &file, "hello/hello", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_write(&lfs, &file, "hello", strlen("hello")) => strlen("hello");
    lfs_file_close(&lfs, &file);
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(buffer, 0, sizeof(buffer));
    lfs_setattr(&lfs, "hello", 'A', "aaaa",   4) => 0;
    lfs_setattr(&lfs, "hello", 'B', "bbbbbb", 6) => 0;
@@ -60,7 +60,7 @@ code = '''

    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(buffer, 0, sizeof(buffer));
    lfs_getattr(&lfs, "hello", 'A', buffer,    4) => 4;
    lfs_getattr(&lfs, "hello", 'B', buffer+4,  9) => 9;
@@ -78,15 +78,15 @@ code = '''

 [[case]] # set/get root attribute
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "hello") => 0;
    lfs_file_open(&lfs, &file, "hello/hello", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_write(&lfs, &file, "hello", strlen("hello")) => strlen("hello");
    lfs_file_close(&lfs, &file);
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(buffer, 0, sizeof(buffer));
    lfs_setattr(&lfs, "/", 'A', "aaaa",   4) => 0;
    lfs_setattr(&lfs, "/", 'B', "bbbbbb", 6) => 0;
@@ -137,7 +137,7 @@ code = '''
    lfs_getattr(&lfs, "/", 'C', buffer+10, 5) => 5;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(buffer, 0, sizeof(buffer));
    lfs_getattr(&lfs, "/", 'A', buffer,    4) => 4;
    lfs_getattr(&lfs, "/", 'B', buffer+4,  9) => 9;
@@ -155,22 +155,22 @@ code = '''

 [[case]] # set/get file attribute
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "hello") => 0;
    lfs_file_open(&lfs, &file, "hello/hello", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_write(&lfs, &file, "hello", strlen("hello")) => strlen("hello");
    lfs_file_close(&lfs, &file);
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(buffer, 0, sizeof(buffer));
    struct lfs_attr attrs1[] = {
        {'A', buffer,    4},
        {'B', buffer+4,  6},
        {'C', buffer+10, 5},
    };
-    struct lfs_file_config cfg1 = {.attrs=attrs1, .attr_count=3};
+    struct lfs_file_cfg cfg1 = {.attrs=attrs1, .attr_count=3};

    lfs_file_opencfg(&lfs, &file, "hello/hello", LFS_O_WRONLY, &cfg1) => 0;
    memcpy(buffer,    "aaaa",   4);
@@ -228,7 +228,7 @@ code = '''
        {'B', buffer+4,  9},
        {'C', buffer+13, 5},
    };
-    struct lfs_file_config cfg2 = {.attrs=attrs2, .attr_count=3};
+    struct lfs_file_cfg cfg2 = {.attrs=attrs2, .attr_count=3};
    lfs_file_opencfg(&lfs, &file, "hello/hello", LFS_O_RDWR, &cfg2) => 0;
    memcpy(buffer+4,  "fffffffff", 9);
    lfs_file_close(&lfs, &file) => 0;
@@ -238,14 +238,14 @@ code = '''

    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(buffer, 0, sizeof(buffer));
    struct lfs_attr attrs3[] = {
        {'A', buffer,    4},
        {'B', buffer+4,  9},
        {'C', buffer+13, 5},
    };
-    struct lfs_file_config cfg3 = {.attrs=attrs3, .attr_count=3};
+    struct lfs_file_cfg cfg3 = {.attrs=attrs3, .attr_count=3};

    lfs_file_opencfg(&lfs, &file, "hello/hello", LFS_O_RDONLY, &cfg3) => 0;
    lfs_file_close(&lfs, &file) => 0;
@@ -262,15 +262,15 @@ code = '''

 [[case]] # deferred file attributes
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "hello") => 0;
    lfs_file_open(&lfs, &file, "hello/hello", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_write(&lfs, &file, "hello", strlen("hello")) => strlen("hello");
    lfs_file_close(&lfs, &file);
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_setattr(&lfs, "hello/hello", 'B', "fffffffff",  9) => 0;
    lfs_setattr(&lfs, "hello/hello", 'C', "ccccc",      5) => 0;

@@ -280,7 +280,7 @@ code = '''
        {'C', "",     0},
        {'D', "hhhh", 4},
    };
-    struct lfs_file_config cfg1 = {.attrs=attrs1, .attr_count=3};
+    struct lfs_file_cfg cfg1 = {.attrs=attrs1, .attr_count=3};

    lfs_file_opencfg(&lfs, &file, "hello/hello", LFS_O_WRONLY, &cfg1) => 0;

--- a/tests/test_badblocks.toml
+++ b/tests/test_badblocks.toml
@@ -16,12 +16,12 @@ define.NAMEMULT = 64
 define.FILEMULT = 1
 code = '''
    for (lfs_block_t badblock = 2; badblock < LFS_BLOCK_COUNT; badblock++) {
-        lfs_testbd_setwear(&cfg, badblock-1, 0) => 0;
-        lfs_testbd_setwear(&cfg, badblock, 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, badblock-1, 0) => 0;
+        lfs_testbd_setwear(&bd, badblock, 0xffffffff) => 0;
        
-        lfs_format(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int i = 1; i < 10; i++) {
            for (int j = 0; j < NAMEMULT; j++) {
                buffer[j] = '0'+i;
@@ -46,7 +46,7 @@ code = '''
        }
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (int i = 1; i < 10; i++) {
            for (int j = 0; j < NAMEMULT; j++) {
                buffer[j] = '0'+i;
@@ -90,12 +90,12 @@ define.NAMEMULT = 64
 define.FILEMULT = 1
 code = '''
    for (lfs_block_t i = 0; i < (LFS_BLOCK_COUNT-2)/2; i++) {
-        lfs_testbd_setwear(&cfg, i+2, 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, i+2, 0xffffffff) => 0;
    }
    
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 1; i < 10; i++) {
        for (int j = 0; j < NAMEMULT; j++) {
            buffer[j] = '0'+i;
@@ -120,7 +120,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 1; i < 10; i++) {
        for (int j = 0; j < NAMEMULT; j++) {
            buffer[j] = '0'+i;
@@ -163,12 +163,12 @@ define.NAMEMULT = 64
 define.FILEMULT = 1
 code = '''
    for (lfs_block_t i = 0; i < (LFS_BLOCK_COUNT-2)/2; i++) {
-        lfs_testbd_setwear(&cfg, (2*i) + 2, 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, (2*i) + 2, 0xffffffff) => 0;
    }
    
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 1; i < 10; i++) {
        for (int j = 0; j < NAMEMULT; j++) {
            buffer[j] = '0'+i;
@@ -193,7 +193,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 1; i < 10; i++) {
        for (int j = 0; j < NAMEMULT; j++) {
            buffer[j] = '0'+i;
@@ -233,9 +233,9 @@ define.LFS_BADBLOCK_BEHAVIOR = [
    'LFS_TESTBD_BADBLOCK_ERASENOOP',
 ]
 code = '''
-    lfs_testbd_setwear(&cfg, 0, 0xffffffff) => 0;
-    lfs_testbd_setwear(&cfg, 1, 0xffffffff) => 0;
+    lfs_testbd_setwear(&bd, 0, 0xffffffff) => 0;
+    lfs_testbd_setwear(&bd, 1, 0xffffffff) => 0;

-    lfs_format(&lfs, &cfg) => LFS_ERR_NOSPC;
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_formatcfg(&lfs, &cfg) => LFS_ERR_NOSPC;
+    lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
 '''
--- a/tests/test_dirs.toml
+++ b/tests/test_dirs.toml
@@ -1,7 +1,7 @@
 [[case]] # root
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -17,16 +17,16 @@ code = '''
 [[case]] # many directory creation
 define.N = 'range(0, 100, 3)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "dir%03d", i);
        lfs_mkdir(&lfs, path) => 0;
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -48,16 +48,16 @@ code = '''
 [[case]] # many directory removal
 define.N = 'range(3, 100, 11)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "removeme%03d", i);
        lfs_mkdir(&lfs, path) => 0;
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -75,14 +75,14 @@ code = '''
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "removeme%03d", i);
        lfs_remove(&lfs, path) => 0;
    }
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -98,16 +98,16 @@ code = '''
 [[case]] # many directory rename
 define.N = 'range(3, 100, 11)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "test%03d", i);
        lfs_mkdir(&lfs, path) => 0;
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -125,7 +125,7 @@ code = '''
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        char oldpath[128];
        char newpath[128];
@@ -135,7 +135,7 @@ code = '''
    }
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -158,10 +158,10 @@ code = '''
 define.N = [5, 11]
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    for (int i = 0; i < N; i++) {
@@ -237,9 +237,9 @@ code = '''
 [[case]] # file creation
 define.N = 'range(3, 100, 11)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "file%03d", i);
        lfs_file_open(&lfs, &file, path,
@@ -248,7 +248,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -270,9 +270,9 @@ code = '''
 [[case]] # file removal
 define.N = 'range(0, 100, 3)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "removeme%03d", i);
        lfs_file_open(&lfs, &file, path,
@@ -281,7 +281,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -299,14 +299,14 @@ code = '''
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "removeme%03d", i);
        lfs_remove(&lfs, path) => 0;
    }
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -322,9 +322,9 @@ code = '''
 [[case]] # file rename
 define.N = 'range(0, 100, 3)'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "test%03d", i);
        lfs_file_open(&lfs, &file, path,
@@ -333,7 +333,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -351,7 +351,7 @@ code = '''
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        char oldpath[128];
        char newpath[128];
@@ -361,7 +361,7 @@ code = '''
    }
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -384,10 +384,10 @@ code = '''
 define.N = [5, 25]
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    for (int i = 0; i < N; i++) {
@@ -462,21 +462,21 @@ code = '''

 [[case]] # nested directories
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "potato") => 0;
    lfs_file_open(&lfs, &file, "burito",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "potato/baked") => 0;
    lfs_mkdir(&lfs, "potato/sweet") => 0;
    lfs_mkdir(&lfs, "potato/fried") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "potato") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -498,21 +498,21 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // try removing?
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_remove(&lfs, "potato") => LFS_ERR_NOTEMPTY;
    lfs_unmount(&lfs) => 0;

    // try renaming?
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "potato", "coldpotato") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "coldpotato", "warmpotato") => 0;
    lfs_rename(&lfs, "warmpotato", "hotpotato") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_remove(&lfs, "potato") => LFS_ERR_NOENT;
    lfs_remove(&lfs, "coldpotato") => LFS_ERR_NOENT;
    lfs_remove(&lfs, "warmpotato") => LFS_ERR_NOENT;
@@ -520,7 +520,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // try cross-directory renaming
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "coldpotato") => 0;
    lfs_rename(&lfs, "hotpotato/baked", "coldpotato/baked") => 0;
    lfs_rename(&lfs, "coldpotato", "hotpotato") => LFS_ERR_NOTEMPTY;
@@ -536,7 +536,7 @@ code = '''
    lfs_remove(&lfs, "hotpotato") => LFS_ERR_NOTEMPTY;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "hotpotato") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -558,7 +558,7 @@ code = '''
    lfs_unmount(&lfs) => 0;
    
    // final remove
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_remove(&lfs, "hotpotato") => LFS_ERR_NOTEMPTY;
    lfs_remove(&lfs, "hotpotato/baked") => 0;
    lfs_remove(&lfs, "hotpotato") => LFS_ERR_NOTEMPTY;
@@ -568,7 +568,7 @@ code = '''
    lfs_remove(&lfs, "hotpotato") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -587,8 +587,8 @@ code = '''
 [[case]] # recursive remove
 define.N = [10, 100]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "prickly-pear") => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "prickly-pear/cactus%03d", i);
@@ -611,7 +611,7 @@ code = '''
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs);

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_remove(&lfs, "prickly-pear") => LFS_ERR_NOTEMPTY;

    lfs_dir_open(&lfs, &dir, "prickly-pear") => 0;
@@ -636,22 +636,22 @@ code = '''
    lfs_remove(&lfs, "prickly-pear") => LFS_ERR_NOENT;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_remove(&lfs, "prickly-pear") => LFS_ERR_NOENT;
    lfs_unmount(&lfs) => 0;
 '''

 [[case]] # other error cases
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "potato") => 0;
    lfs_file_open(&lfs, &file, "burito",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    lfs_mkdir(&lfs, "potato") => LFS_ERR_EXIST;
    lfs_mkdir(&lfs, "burito") => LFS_ERR_EXIST;
@@ -696,7 +696,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // or on disk
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "/") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(info.type == LFS_TYPE_DIR);
@@ -718,8 +718,8 @@ code = '''
 [[case]] # directory seek
 define.COUNT = [4, 128, 132]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "hello") => 0;
    for (int i = 0; i < COUNT; i++) {
        sprintf(path, "hello/kitty%03d", i);
@@ -728,7 +728,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    for (int j = 2; j < COUNT; j++) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        lfs_dir_open(&lfs, &dir, "hello") => 0;
        lfs_dir_read(&lfs, &dir, &info) => 1;
        assert(strcmp(info.name, ".") == 0);
@@ -779,8 +779,8 @@ code = '''
 [[case]] # root seek
 define.COUNT = [4, 128, 132]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < COUNT; i++) {
        sprintf(path, "hi%03d", i);
        lfs_mkdir(&lfs, path) => 0;
@@ -788,7 +788,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    for (int j = 2; j < COUNT; j++) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        lfs_dir_open(&lfs, &dir, "/") => 0;
        lfs_dir_read(&lfs, &dir, &info) => 1;
        assert(strcmp(info.name, ".") == 0);
--- a/tests/test_entries.toml
+++ b/tests/test_entries.toml
@@ -10,8 +10,8 @@ code = '''
    uint8_t wbuffer[1024];
    uint8_t rbuffer[1024];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // write hi0 20
    sprintf(path, "hi0"); size = 20;
@@ -99,8 +99,8 @@ code = '''
    uint8_t wbuffer[1024];
    uint8_t rbuffer[1024];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // write hi0 20
    sprintf(path, "hi0"); size = 20;
@@ -188,8 +188,8 @@ code = '''
    uint8_t wbuffer[1024];
    uint8_t rbuffer[1024];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // write hi0 200
    sprintf(path, "hi0"); size = 200;
@@ -261,8 +261,8 @@ code = '''
    uint8_t wbuffer[1024];
    uint8_t rbuffer[1024];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // write hi0 200
    sprintf(path, "hi0"); size = 200;
@@ -350,8 +350,8 @@ code = '''
    uint8_t wbuffer[1024];
    uint8_t rbuffer[1024];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // write hi0 200
    sprintf(path, "hi0"); size = 200;
@@ -454,8 +454,8 @@ code = '''
    uint8_t wbuffer[1024];
    uint8_t rbuffer[1024];

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // write hi0 200
    sprintf(path, "hi0"); size = 200;
@@ -549,9 +549,9 @@ code = '''

 [[case]] # create too big
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(path, 'm', 200);
    path[200] = '\0';

@@ -574,9 +574,9 @@ code = '''

 [[case]] # resize too big
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    memset(path, 'm', 200);
    path[200] = '\0';

--- a/tests/test_evil.toml
+++ b/tests/test_evil.toml
@@ -9,10 +9,10 @@ define.INVALSET = [0x3, 0x1, 0x2]
 in = "lfs.c"
 code = '''
    // create littlefs
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // change tail-pointer to invalid pointers
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
    lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
@@ -23,7 +23,7 @@ code = '''
    lfs_deinit(&lfs) => 0;

    // test that mount fails gracefully
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
 '''

 [[case]] # invalid dir pointer test
@@ -31,14 +31,14 @@ define.INVALSET = [0x3, 0x1, 0x2]
 in = "lfs.c"
 code = '''
    // create littlefs
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // make a dir
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "dir_here") => 0;
    lfs_unmount(&lfs) => 0;

    // change the dir pointer to be invalid
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
    // make sure id 1 == our directory
@@ -57,7 +57,7 @@ code = '''

    // test that accessing our bad dir fails, note there's a number
    // of ways to access the dir, some can fail, but some don't
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "dir_here", &info) => 0;
    assert(strcmp(info.name, "dir_here") == 0);
    assert(info.type == LFS_TYPE_DIR);
@@ -77,16 +77,16 @@ in = "lfs.c"
 define.SIZE = [10, 1000, 100000] # faked file size
 code = '''
    // create littlefs
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // make a file
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "file_here",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

    // change the file pointer to be invalid
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
    // make sure id 1 == our file
@@ -103,7 +103,7 @@ code = '''

    // test that accessing our bad file fails, note there's a number
    // of ways to access the dir, some can fail, but some don't
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "file_here", &info) => 0;
    assert(strcmp(info.name, "file_here") == 0);
    assert(info.type == LFS_TYPE_REG);
@@ -125,9 +125,9 @@ define.SIZE = ['2*LFS_BLOCK_SIZE', '3*LFS_BLOCK_SIZE', '4*LFS_BLOCK_SIZE']
 in = "lfs.c"
 code = '''
    // create littlefs
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // make a file
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "file_here",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;
    for (int i = 0; i < SIZE; i++) {
@@ -137,7 +137,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;
    // change pointer in CTZ skip-list to be invalid
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
    // make sure id 1 == our file and get our CTZ structure
@@ -154,17 +154,17 @@ code = '''
    lfs_ctz_fromle32(&ctz);
    // rewrite block to contain bad pointer
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, ctz.head, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, ctz.head, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    uint32_t bad = lfs_tole32(0xcccccccc);
    memcpy(&bbuffer[0], &bad, sizeof(bad));
    memcpy(&bbuffer[4], &bad, sizeof(bad));
-    cfg.erase(&cfg, ctz.head) => 0;
-    cfg.prog(&cfg, ctz.head, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_erase(&bd, ctz.head) => 0;
+    lfs_testbd_prog(&bd, ctz.head, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    lfs_deinit(&lfs) => 0;

    // test that accessing our bad file fails, note there's a number
    // of ways to access the dir, some can fail, but some don't
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "file_here", &info) => 0;
    assert(strcmp(info.name, "file_here") == 0);
    assert(info.type == LFS_TYPE_REG);
@@ -187,10 +187,10 @@ define.INVALSET = [0x3, 0x1, 0x2]
 in = "lfs.c"
 code = '''
    // create littlefs
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // create an invalid gstate
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
    lfs_fs_prepmove(&lfs, 1, (lfs_block_t [2]){
@@ -202,7 +202,7 @@ code = '''
    // test that mount fails gracefully
    // mount may not fail, but our first alloc should fail when
    // we try to fix the gstate
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "should_fail") => LFS_ERR_CORRUPT;
    lfs_unmount(&lfs) => 0;
 '''
@@ -213,10 +213,10 @@ code = '''
 in = "lfs.c"
 code = '''
    // create littlefs
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // change tail-pointer to point to ourself
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
    lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
@@ -225,20 +225,20 @@ code = '''
    lfs_deinit(&lfs) => 0;

    // test that mount fails gracefully
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
 '''

 [[case]] # metadata-pair threaded-list 2-length loop test
 in = "lfs.c"
 code = '''
    // create littlefs with child dir
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "child") => 0;
    lfs_unmount(&lfs) => 0;

    // find child
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_block_t pair[2];
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
@@ -255,20 +255,20 @@ code = '''
    lfs_deinit(&lfs) => 0;

    // test that mount fails gracefully
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
 '''

 [[case]] # metadata-pair threaded-list 1-length child loop test
 in = "lfs.c"
 code = '''
    // create littlefs with child dir
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "child") => 0;
    lfs_unmount(&lfs) => 0;

    // find child
-    lfs_init(&lfs, &cfg) => 0;
+    lfs_initcommon(&lfs, &cfg) => 0;
    lfs_mdir_t mdir;
    lfs_block_t pair[2];
    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
@@ -284,5 +284,5 @@ code = '''
    lfs_deinit(&lfs) => 0;

    // test that mount fails gracefully
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
 '''
--- a/tests/test_exhaustion.toml
+++ b/tests/test_exhaustion.toml
@@ -11,14 +11,14 @@ define.LFS_BADBLOCK_BEHAVIOR = [
 ]
 define.FILES = 10
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "roadrunner") => 0;
    lfs_unmount(&lfs) => 0;

    uint32_t cycle = 0;
    while (true) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (uint32_t i = 0; i < FILES; i++) {
            // chose name, roughly random seed, and random 2^n size
            sprintf(path, "roadrunner/test%d", i);
@@ -71,7 +71,7 @@ code = '''

 exhausted:
    // should still be readable
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (uint32_t i = 0; i < FILES; i++) {
        // check for errors
        sprintf(path, "roadrunner/test%d", i);
@@ -96,11 +96,11 @@ define.LFS_BADBLOCK_BEHAVIOR = [
 ]
 define.FILES = 10
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    uint32_t cycle = 0;
    while (true) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (uint32_t i = 0; i < FILES; i++) {
            // chose name, roughly random seed, and random 2^n size
            sprintf(path, "test%d", i);
@@ -153,7 +153,7 @@ code = '''

 exhausted:
    // should still be readable
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (uint32_t i = 0; i < FILES; i++) {
        // check for errors
        sprintf(path, "test%d", i);
@@ -180,18 +180,18 @@ code = '''

    for (int run = 0; run < 2; run++) {
        for (lfs_block_t b = 0; b < LFS_BLOCK_COUNT; b++) {
-            lfs_testbd_setwear(&cfg, b,
+            lfs_testbd_setwear(&bd, b,
                    (b < run_block_count[run]) ? 0 : LFS_ERASE_CYCLES) => 0;
        }

-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        lfs_mkdir(&lfs, "roadrunner") => 0;
        lfs_unmount(&lfs) => 0;

        uint32_t cycle = 0;
        while (true) {
-            lfs_mount(&lfs, &cfg) => 0;
+            lfs_mountcfg(&lfs, &cfg) => 0;
            for (uint32_t i = 0; i < FILES; i++) {
                // chose name, roughly random seed, and random 2^n size
                sprintf(path, "roadrunner/test%d", i);
@@ -244,7 +244,7 @@ code = '''

 exhausted:
        // should still be readable
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (uint32_t i = 0; i < FILES; i++) {
            // check for errors
            sprintf(path, "roadrunner/test%d", i);
@@ -272,15 +272,15 @@ code = '''

    for (int run = 0; run < 2; run++) {
        for (lfs_block_t b = 0; b < LFS_BLOCK_COUNT; b++) {
-            lfs_testbd_setwear(&cfg, b,
+            lfs_testbd_setwear(&bd, b,
                    (b < run_block_count[run]) ? 0 : LFS_ERASE_CYCLES) => 0;
        }

-        lfs_format(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;

        uint32_t cycle = 0;
        while (true) {
-            lfs_mount(&lfs, &cfg) => 0;
+            lfs_mountcfg(&lfs, &cfg) => 0;
            for (uint32_t i = 0; i < FILES; i++) {
                // chose name, roughly random seed, and random 2^n size
                sprintf(path, "test%d", i);
@@ -333,7 +333,7 @@ code = '''

 exhausted:
        // should still be readable
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (uint32_t i = 0; i < FILES; i++) {
            // check for errors
            sprintf(path, "test%d", i);
@@ -358,14 +358,14 @@ define.CYCLES = 100
 define.FILES = 10
 if = 'LFS_BLOCK_CYCLES < CYCLES/10'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "roadrunner") => 0;
    lfs_unmount(&lfs) => 0;

    uint32_t cycle = 0;
    while (cycle < CYCLES) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        for (uint32_t i = 0; i < FILES; i++) {
            // chose name, roughly random seed, and random 2^n size
            sprintf(path, "roadrunner/test%d", i);
@@ -418,7 +418,7 @@ code = '''

 exhausted:
    // should still be readable
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (uint32_t i = 0; i < FILES; i++) {
        // check for errors
        sprintf(path, "roadrunner/test%d", i);
@@ -434,7 +434,7 @@ exhausted:
    lfs_testbd_wear_t maxwear = 0;
    // skip 0 and 1 as superblock movement is intentionally avoided
    for (lfs_block_t b = 2; b < LFS_BLOCK_COUNT; b++) {
-        lfs_testbd_wear_t wear = lfs_testbd_getwear(&cfg, b);
+        lfs_testbd_wear_t wear = lfs_testbd_getwear(&bd, b);
        printf("%08x: wear %d\n", b, wear);
        assert(wear >= 0);
        if (wear < minwear) {
@@ -453,7 +453,7 @@ exhausted:
    // find standard deviation^2
    lfs_testbd_wear_t dev2 = 0;
    for (lfs_block_t b = 2; b < LFS_BLOCK_COUNT; b++) {
-        lfs_testbd_wear_t wear = lfs_testbd_getwear(&cfg, b);
+        lfs_testbd_wear_t wear = lfs_testbd_getwear(&bd, b);
        assert(wear >= 0);
        lfs_testbd_swear_t diff = wear - avgwear;
        dev2 += diff*diff;
--- a/tests/test_files.toml
+++ b/tests/test_files.toml
@@ -1,8 +1,8 @@

 [[case]] # simple file test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "hello",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    size = strlen("Hello World!")+1;
@@ -11,7 +11,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "hello", LFS_O_RDONLY) => 0;
    lfs_file_read(&lfs, &file, buffer, size) => size;
    assert(strcmp((char*)buffer, "Hello World!") == 0);
@@ -23,10 +23,10 @@ code = '''
 define.SIZE = [32, 8192, 262144, 0, 7, 8193]
 define.CHUNKSIZE = [31, 16, 33, 1, 1023]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // write
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    srand(1);
@@ -41,7 +41,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => SIZE;
    srand(1);
@@ -62,10 +62,10 @@ define.SIZE1 = [32, 8192, 131072, 0, 7, 8193]
 define.SIZE2 = [32, 8192, 131072, 0, 7, 8193]
 define.CHUNKSIZE = [31, 16, 1]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // write
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    srand(1);
@@ -80,7 +80,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => SIZE1;
    srand(1);
@@ -96,7 +96,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // rewrite
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_WRONLY) => 0;
    srand(2);
    for (lfs_size_t i = 0; i < SIZE2; i += CHUNKSIZE) {
@@ -110,7 +110,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => lfs_max(SIZE1, SIZE2);
    srand(2);
@@ -144,10 +144,10 @@ define.SIZE1 = [32, 8192, 131072, 0, 7, 8193]
 define.SIZE2 = [32, 8192, 131072, 0, 7, 8193]
 define.CHUNKSIZE = [31, 16, 1]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // write
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    srand(1);
@@ -162,7 +162,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => SIZE1;
    srand(1);
@@ -178,7 +178,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // append
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_WRONLY | LFS_O_APPEND) => 0;
    srand(2);
    for (lfs_size_t i = 0; i < SIZE2; i += CHUNKSIZE) {
@@ -192,7 +192,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => SIZE1 + SIZE2;
    srand(1);
@@ -221,10 +221,10 @@ define.SIZE1 = [32, 8192, 131072, 0, 7, 8193]
 define.SIZE2 = [32, 8192, 131072, 0, 7, 8193]
 define.CHUNKSIZE = [31, 16, 1]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;

    // write
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    srand(1);
@@ -239,7 +239,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => SIZE1;
    srand(1);
@@ -255,7 +255,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // truncate
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_WRONLY | LFS_O_TRUNC) => 0;
    srand(2);
    for (lfs_size_t i = 0; i < SIZE2; i += CHUNKSIZE) {
@@ -269,7 +269,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // read
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => SIZE2;
    srand(2);
@@ -290,10 +290,10 @@ define.SIZE = [32, 0, 7, 2049]
 define.CHUNKSIZE = [31, 16, 65]
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    err = lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY);
@@ -344,10 +344,10 @@ define = [
 ]
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    err = lfs_file_open(&lfs, &file, "avacado", LFS_O_RDONLY);
@@ -406,9 +406,9 @@ code = '''
 [[case]] # many files
 define.N = 300
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // create N files of 7 bytes
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "file_%03d", i);
        lfs_file_open(&lfs, &file, path,
@@ -431,9 +431,9 @@ code = '''
 [[case]] # many files with power cycle
 define.N = 300
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // create N files of 7 bytes
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        sprintf(path, "file_%03d", i);
        lfs_file_open(&lfs, &file, path,
@@ -446,7 +446,7 @@ code = '''
        lfs_unmount(&lfs) => 0;

        char rbuffer[1024];
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        lfs_file_open(&lfs, &file, path, LFS_O_RDONLY) => 0;
        lfs_file_read(&lfs, &file, rbuffer, size) => size;
        assert(strcmp(rbuffer, wbuffer) == 0);
@@ -459,10 +459,10 @@ code = '''
 define.N = 300
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }
    // create N files of 7 bytes
    for (int i = 0; i < N; i++) {
--- a/tests/test_interspersed.toml
+++ b/tests/test_interspersed.toml
@@ -5,8 +5,8 @@ define.FILES = [4, 10, 26]
 code = '''
    lfs_file_t files[FILES];
    const char alphas[] = "abcdefghijklmnopqrstuvwxyz";
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int j = 0; j < FILES; j++) {
        sprintf(path, "%c", alphas[j]);
        lfs_file_open(&lfs, &files[j], path,
@@ -64,8 +64,8 @@ define.SIZE = [10, 100]
 define.FILES = [4, 10, 26]
 code = '''
    const char alphas[] = "abcdefghijklmnopqrstuvwxyz";
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int j = 0; j < FILES; j++) {
        sprintf(path, "%c", alphas[j]);
        lfs_file_open(&lfs, &file, path,
@@ -77,7 +77,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "zzz", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    for (int j = 0; j < FILES; j++) {
        lfs_file_write(&lfs, &file, (const void*)"~", 1) => 1;
@@ -115,8 +115,8 @@ code = '''
 [[case]] # remove inconveniently test
 define.SIZE = [10, 100]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_t files[3];
    lfs_file_open(&lfs, &files[0], "e", LFS_O_WRONLY | LFS_O_CREAT) => 0;
    lfs_file_open(&lfs, &files[1], "f", LFS_O_WRONLY | LFS_O_CREAT) => 0;
@@ -180,10 +180,10 @@ code = '''
    lfs_file_t files[FILES];
    const char alphas[] = "abcdefghijklmnopqrstuvwxyz";

-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    for (int j = 0; j < FILES; j++) {
--- a/tests/test_move.toml
+++ b/tests/test_move.toml
@@ -1,7 +1,7 @@
 [[case]] # move file
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -13,11 +13,11 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hello", "c/hello") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -57,8 +57,8 @@ code = '''

 [[case]] # noop move, yes this is legal
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "hi") => 0;
    lfs_rename(&lfs, "hi", "hi") => 0;
    lfs_mkdir(&lfs, "hi/hi") => 0;
@@ -74,8 +74,8 @@ code = '''
 [[case]] # move file corrupt source
 in = "lfs.c"
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -87,28 +87,28 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hello", "c/hello") => 0;
    lfs_unmount(&lfs) => 0;

    // corrupt the source
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -150,8 +150,8 @@ code = '''
 in = "lfs.c"
 if = 'LFS_PROG_SIZE <= 0x3fe' # only works with one crc per commit
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -163,44 +163,44 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hello", "c/hello") => 0;
    lfs_unmount(&lfs) => 0;

    // corrupt the source
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

    // corrupt the destination
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "c") => 0;
    block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -242,8 +242,8 @@ code = '''
 in = "lfs.c"
 if = 'LFS_PROG_SIZE <= 0x3fe' # only works with one crc per commit
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -255,49 +255,49 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hello", "c/hello") => 0;
    lfs_unmount(&lfs) => 0;

    // corrupt the source
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

    // corrupt the destination
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "c") => 0;
    block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

    // continue move
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hello", "c/hello") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -338,10 +338,10 @@ code = '''
 [[case]] # simple reentrant move file
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }
    err = lfs_mkdir(&lfs, "a");
    assert(!err || err == LFS_ERR_EXIST);
@@ -354,7 +354,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    while (true) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        // there should never exist _2_ hello files
        int count = 0;
        if (lfs_stat(&lfs, "a/hello", &info) == 0) {
@@ -384,7 +384,7 @@ code = '''
        assert(count <= 1);
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        if (lfs_stat(&lfs, "a/hello", &info) == 0 && info.size > 0) {
            lfs_rename(&lfs, "a/hello", "b/hello") => 0;
        } else if (lfs_stat(&lfs, "b/hello", &info) == 0) {
@@ -407,7 +407,7 @@ code = '''
        lfs_unmount(&lfs) => 0;
    }

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -447,8 +447,8 @@ code = '''

 [[case]] # move dir
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -459,11 +459,11 @@ code = '''
    lfs_mkdir(&lfs, "a/hi/ohayo") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hi", "c/hi") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -513,8 +513,8 @@ code = '''
 [[case]] # move dir corrupt source
 in = "lfs.c"
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -525,28 +525,28 @@ code = '''
    lfs_mkdir(&lfs, "a/hi/ohayo") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hi", "c/hi") => 0;
    lfs_unmount(&lfs) => 0;

    // corrupt the source
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -597,8 +597,8 @@ code = '''
 in = "lfs.c"
 if = 'LFS_PROG_SIZE <= 0x3fe' # only works with one crc per commit
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -609,44 +609,44 @@ code = '''
    lfs_mkdir(&lfs, "a/hi/ohayo") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hi", "c/hi") => 0;
    lfs_unmount(&lfs) => 0;

    // corrupt the source
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

    // corrupt the destination
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "c") => 0;
    block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -697,8 +697,8 @@ code = '''
 in = "lfs.c"
 if = 'LFS_PROG_SIZE <= 0x3fe' # only works with one crc per commit
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -709,49 +709,49 @@ code = '''
    lfs_mkdir(&lfs, "a/hi/ohayo") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hi", "c/hi") => 0;
    lfs_unmount(&lfs) => 0;

    // corrupt the source
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

    // corrupt the destination
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "c") => 0;
    block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

    // continue move
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hi", "c/hi") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -801,10 +801,10 @@ code = '''
 [[case]] # simple reentrant move dir
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }
    err = lfs_mkdir(&lfs, "a");
    assert(!err || err == LFS_ERR_EXIST);
@@ -817,7 +817,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    while (true) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        // there should never exist _2_ hi directories
        int count = 0;
        if (lfs_stat(&lfs, "a/hi", &info) == 0) {
@@ -843,7 +843,7 @@ code = '''
        assert(count <= 1);
        lfs_unmount(&lfs) => 0;

-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        if (lfs_stat(&lfs, "a/hi", &info) == 0) {
            lfs_rename(&lfs, "a/hi", "b/hi") => 0;
        } else if (lfs_stat(&lfs, "b/hi", &info) == 0) {
@@ -868,7 +868,7 @@ code = '''
        lfs_unmount(&lfs) => 0;
    }

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "a") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    assert(strcmp(info.name, ".") == 0);
@@ -917,8 +917,8 @@ code = '''

 [[case]] # move state stealing
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "a") => 0;
    lfs_mkdir(&lfs, "b") => 0;
    lfs_mkdir(&lfs, "c") => 0;
@@ -930,17 +930,17 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "a/hello", "b/hello") => 0;
    lfs_unmount(&lfs) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "b/hello", "c/hello") => 0;
    lfs_unmount(&lfs) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_rename(&lfs, "c/hello", "d/hello") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "a/hello", LFS_O_RDONLY) => LFS_ERR_NOENT;
    lfs_file_open(&lfs, &file, "b/hello", LFS_O_RDONLY) => LFS_ERR_NOENT;
    lfs_file_open(&lfs, &file, "c/hello", LFS_O_RDONLY) => LFS_ERR_NOENT;
@@ -954,12 +954,12 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_remove(&lfs, "b") => 0;
    lfs_remove(&lfs, "c") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "a", &info) => 0;
    lfs_stat(&lfs, "b", &info) => LFS_ERR_NOENT;
    lfs_stat(&lfs, "c", &info) => LFS_ERR_NOENT;
@@ -981,8 +981,8 @@ code = '''
 # Other specific corner cases
 [[case]] # create + delete in same commit with neighbors
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // littlefs keeps files sorted, so we know the order these will be in
    lfs_file_open(&lfs, &file, "/1.move_me",
@@ -1127,8 +1127,8 @@ code = '''
 # Other specific corner cases
 [[case]] # create + delete + delete in same commit with neighbors
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // littlefs keeps files sorted, so we know the order these will be in
    lfs_file_open(&lfs, &file, "/1.move_me",
@@ -1283,8 +1283,8 @@ code = '''

 [[case]] # create + delete in different dirs with neighbors
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    // littlefs keeps files sorted, so we know the order these will be in
    lfs_mkdir(&lfs, "/dir.1") => 0;
@@ -1523,8 +1523,8 @@ in = "lfs.c"
 define.RELOCATIONS = 'range(0x3+1)'
 define.LFS_ERASE_CYCLES = 0xffffffff
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    lfs_mkdir(&lfs, "/parent") => 0;
    lfs_mkdir(&lfs, "/parent/child") => 0;
@@ -1569,14 +1569,14 @@ code = '''
    // force specific directories to relocate
    if (RELOCATIONS & 0x1) {
        lfs_dir_open(&lfs, &dir, "/parent");
-        lfs_testbd_setwear(&cfg, dir.m.pair[0], 0xffffffff) => 0;
-        lfs_testbd_setwear(&cfg, dir.m.pair[1], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[0], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[1], 0xffffffff) => 0;
        lfs_dir_close(&lfs, &dir) => 0;
    }
    if (RELOCATIONS & 0x2) {
        lfs_dir_open(&lfs, &dir, "/parent/child");
-        lfs_testbd_setwear(&cfg, dir.m.pair[0], 0xffffffff) => 0;
-        lfs_testbd_setwear(&cfg, dir.m.pair[1], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[0], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[1], 0xffffffff) => 0;
        lfs_dir_close(&lfs, &dir) => 0;
    }

@@ -1660,8 +1660,8 @@ in = "lfs.c"
 define.RELOCATIONS = 'range(0x7+1)'
 define.LFS_ERASE_CYCLES = 0xffffffff
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    lfs_mkdir(&lfs, "/parent") => 0;
    lfs_mkdir(&lfs, "/parent/child") => 0;
@@ -1707,20 +1707,20 @@ code = '''
    // force specific directories to relocate
    if (RELOCATIONS & 0x1) {
        lfs_dir_open(&lfs, &dir, "/parent");
-        lfs_testbd_setwear(&cfg, dir.m.pair[0], 0xffffffff) => 0;
-        lfs_testbd_setwear(&cfg, dir.m.pair[1], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[0], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[1], 0xffffffff) => 0;
        lfs_dir_close(&lfs, &dir) => 0;
    }
    if (RELOCATIONS & 0x2) {
        lfs_dir_open(&lfs, &dir, "/parent/sibling");
-        lfs_testbd_setwear(&cfg, dir.m.pair[0], 0xffffffff) => 0;
-        lfs_testbd_setwear(&cfg, dir.m.pair[1], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[0], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[1], 0xffffffff) => 0;
        lfs_dir_close(&lfs, &dir) => 0;
    }
    if (RELOCATIONS & 0x4) {
        lfs_dir_open(&lfs, &dir, "/parent/child");
-        lfs_testbd_setwear(&cfg, dir.m.pair[0], 0xffffffff) => 0;
-        lfs_testbd_setwear(&cfg, dir.m.pair[1], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[0], 0xffffffff) => 0;
+        lfs_testbd_setwear(&bd, dir.m.pair[1], 0xffffffff) => 0;
        lfs_dir_close(&lfs, &dir) => 0;
    }

--- a/tests/test_orphans.toml
+++ b/tests/test_orphans.toml
@@ -2,8 +2,8 @@
 in = "lfs.c"
 if = 'LFS_PROG_SIZE <= 0x3fe' # only works with one crc per commit
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "parent") => 0;
    lfs_mkdir(&lfs, "parent/orphan") => 0;
    lfs_mkdir(&lfs, "parent/child") => 0;
@@ -13,29 +13,29 @@ code = '''
    // corrupt the child's most recent commit, this should be the update
    // to the linked-list entry, which should orphan the orphan. Note this
    // makes a lot of assumptions about the remove operation.
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "parent/child") => 0;
    lfs_block_t block = dir.m.pair[0];
    lfs_dir_close(&lfs, &dir) => 0;
    lfs_unmount(&lfs) => 0;
    uint8_t bbuffer[LFS_BLOCK_SIZE];
-    cfg.read(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_read(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
    int off = LFS_BLOCK_SIZE-1;
    while (off >= 0 && bbuffer[off] == LFS_ERASE_VALUE) {
        off -= 1;
    }
    memset(&bbuffer[off-3], LFS_BLOCK_SIZE, 3);
-    cfg.erase(&cfg, block) => 0;
-    cfg.prog(&cfg, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
-    cfg.sync(&cfg) => 0;
+    lfs_testbd_erase(&bd, block) => 0;
+    lfs_testbd_prog(&bd, block, 0, bbuffer, LFS_BLOCK_SIZE) => 0;
+    lfs_testbd_sync(&bd) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "parent/orphan", &info) => LFS_ERR_NOENT;
    lfs_stat(&lfs, "parent/child", &info) => 0;
    lfs_fs_size(&lfs) => 8;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "parent/orphan", &info) => LFS_ERR_NOENT;
    lfs_stat(&lfs, "parent/child", &info) => 0;
    lfs_fs_size(&lfs) => 8;
@@ -48,7 +48,7 @@ code = '''
    lfs_fs_size(&lfs) => 8;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "parent/orphan", &info) => LFS_ERR_NOENT;
    lfs_stat(&lfs, "parent/child", &info) => 0;
    lfs_stat(&lfs, "parent/otherchild", &info) => 0;
@@ -66,10 +66,10 @@ define = [
    {FILES=3,  DEPTH=3, CYCLES=20},
 ]
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    srand(1);
--- a/tests/test_paths.toml
+++ b/tests/test_paths.toml
@@ -1,8 +1,8 @@

 [[case]] # simple path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "tea") => 0;
    lfs_mkdir(&lfs, "tea/hottea") => 0;
    lfs_mkdir(&lfs, "tea/warmtea") => 0;
@@ -23,8 +23,8 @@ code = '''

 [[case]] # redundant slashes
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "tea") => 0;
    lfs_mkdir(&lfs, "tea/hottea") => 0;
    lfs_mkdir(&lfs, "tea/warmtea") => 0;
@@ -47,8 +47,8 @@ code = '''

 [[case]] # dot path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "tea") => 0;
    lfs_mkdir(&lfs, "tea/hottea") => 0;
    lfs_mkdir(&lfs, "tea/warmtea") => 0;
@@ -73,8 +73,8 @@ code = '''

 [[case]] # dot dot path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "tea") => 0;
    lfs_mkdir(&lfs, "tea/hottea") => 0;
    lfs_mkdir(&lfs, "tea/warmtea") => 0;
@@ -103,8 +103,8 @@ code = '''

 [[case]] # trailing dot path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "tea") => 0;
    lfs_mkdir(&lfs, "tea/hottea") => 0;
    lfs_mkdir(&lfs, "tea/warmtea") => 0;
@@ -125,8 +125,8 @@ code = '''

 [[case]] # leading dot path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, ".milk") => 0;
    lfs_stat(&lfs, ".milk", &info) => 0;
    strcmp(info.name, ".milk") => 0;
@@ -137,8 +137,8 @@ code = '''

 [[case]] # root dot dot path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "tea") => 0;
    lfs_mkdir(&lfs, "tea/hottea") => 0;
    lfs_mkdir(&lfs, "tea/warmtea") => 0;
@@ -161,8 +161,8 @@ code = '''

 [[case]] # invalid path tests
 code = '''
-    lfs_format(&lfs, &cfg);
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg);
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "dirt", &info) => LFS_ERR_NOENT;
    lfs_stat(&lfs, "dirt/ground", &info) => LFS_ERR_NOENT;
    lfs_stat(&lfs, "dirt/ground/earth", &info) => LFS_ERR_NOENT;
@@ -182,8 +182,8 @@ code = '''

 [[case]] # root operations
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "/", &info) => 0;
    assert(strcmp(info.name, "/") == 0);
    assert(info.type == LFS_TYPE_DIR);
@@ -198,8 +198,8 @@ code = '''

 [[case]] # root representations
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "/", &info) => 0;
    assert(strcmp(info.name, "/") == 0);
    assert(info.type == LFS_TYPE_DIR);
@@ -223,8 +223,8 @@ code = '''

 [[case]] # superblock conflict test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "littlefs", &info) => LFS_ERR_NOENT;
    lfs_remove(&lfs, "littlefs") => LFS_ERR_NOENT;

@@ -239,8 +239,8 @@ code = '''

 [[case]] # max path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "coffee") => 0;
    lfs_mkdir(&lfs, "coffee/hotcoffee") => 0;
    lfs_mkdir(&lfs, "coffee/warmcoffee") => 0;
@@ -263,8 +263,8 @@ code = '''

 [[case]] # really big path test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_mkdir(&lfs, "coffee") => 0;
    lfs_mkdir(&lfs, "coffee/hotcoffee") => 0;
    lfs_mkdir(&lfs, "coffee/warmcoffee") => 0;
--- a/tests/test_relocations.toml
+++ b/tests/test_relocations.toml
@@ -4,9 +4,9 @@ define.ITERATIONS = 20
 define.COUNT = 10
 define.LFS_BLOCK_CYCLES = [8, 1]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // fill up filesystem so only ~16 blocks are left
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "padding", LFS_O_CREAT | LFS_O_WRONLY) => 0;
    memset(buffer, 0, 512);
    while (LFS_BLOCK_COUNT - lfs_fs_size(&lfs) > 16) {
@@ -17,7 +17,7 @@ code = '''
    lfs_mkdir(&lfs, "child") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int j = 0; j < ITERATIONS; j++) {
        for (int i = 0; i < COUNT; i++) {
            sprintf(path, "child/test%03d_loooooooooooooooooong_name", i);
@@ -47,7 +47,7 @@ code = '''
    }
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_dir_open(&lfs, &dir, "child") => 0;
    lfs_dir_read(&lfs, &dir, &info) => 1;
    lfs_dir_read(&lfs, &dir, &info) => 1;
@@ -70,9 +70,9 @@ define.ITERATIONS = 20
 define.COUNT = 10
 define.LFS_BLOCK_CYCLES = [8, 1]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    // fill up filesystem so only ~16 blocks are left
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "padding", LFS_O_CREAT | LFS_O_WRONLY) => 0;
    memset(buffer, 0, 512);
    while (LFS_BLOCK_COUNT - lfs_fs_size(&lfs) > 16) {
@@ -83,7 +83,7 @@ code = '''
    lfs_mkdir(&lfs, "child") => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int j = 0; j < ITERATIONS; j++) {
        for (int i = 0; i < COUNT; i++) {
            sprintf(path, "child/test%03d_loooooooooooooooooong_name", i);
@@ -155,10 +155,10 @@ define = [
    {FILES=3,  DEPTH=3, CYCLES=20, LFS_BLOCK_CYCLES=1},
 ]
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    srand(1);
@@ -217,10 +217,10 @@ define = [
    {FILES=3,  DEPTH=3, CYCLES=20, LFS_BLOCK_CYCLES=1},
 ]
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    srand(1);
--- a/tests/test_seek.toml
+++ b/tests/test_seek.toml
@@ -9,8 +9,8 @@ define = [
    {COUNT=4,   SKIP=2},
 ]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
    size = strlen("kittycatcat");
@@ -21,7 +21,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty", LFS_O_RDONLY) => 0;

    lfs_soff_t pos = -1;
@@ -78,8 +78,8 @@ define = [
    {COUNT=4,   SKIP=2},
 ]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
    size = strlen("kittycatcat");
@@ -90,7 +90,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty", LFS_O_RDWR) => 0;

    lfs_soff_t pos = -1;
@@ -133,8 +133,8 @@ code = '''
 define.COUNT = 132
 define.OFFSETS = '"{512, 1020, 513, 1021, 511, 1019, 1441}"'
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
    size = strlen("kittycatcat");
@@ -145,7 +145,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty", LFS_O_RDWR) => 0;

    size = strlen("hedgehoghog");
@@ -193,8 +193,8 @@ define = [
    {COUNT=4,   SKIP=3},
 ]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
    size = strlen("kittycatcat");
@@ -204,7 +204,7 @@ code = '''
    }
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "kitty", LFS_O_RDWR) => 0;

    size = strlen("kittycatcat");
@@ -241,8 +241,8 @@ code = '''
 [[case]] # inline write and seek
 define.SIZE = [2, 4, 128, 132]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "tinykitty",
            LFS_O_RDWR | LFS_O_CREAT) => 0;
    int j = 0;
@@ -310,10 +310,10 @@ code = '''
 define.COUNT = [4, 64, 128]
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }
    err = lfs_file_open(&lfs, &file, "kitty", LFS_O_RDONLY);
    assert(!err || err == LFS_ERR_NOENT);
--- a/tests/test_superblocks.toml
+++ b/tests/test_superblocks.toml
@@ -1,37 +1,37 @@
 [[case]] # simple formatting test
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
 '''

 [[case]] # mount/unmount
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_unmount(&lfs) => 0;
 '''

 [[case]] # reentrant format
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }
    lfs_unmount(&lfs) => 0;
 '''

 [[case]] # invalid mount
 code = '''
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
 '''

 [[case]] # expanding superblock
 define.LFS_BLOCK_CYCLES = [32, 33, 1]
 define.N = [10, 100, 1000]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
        lfs_file_open(&lfs, &file, "dummy",
                LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
@@ -44,7 +44,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // one last check after power-cycle
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "dummy",
            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
    lfs_file_close(&lfs, &file) => 0;
@@ -58,9 +58,9 @@ code = '''
 define.LFS_BLOCK_CYCLES = [32, 33, 1]
 define.N = [10, 100, 1000]
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
    for (int i = 0; i < N; i++) {
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
        // remove lingering dummy?
        err = lfs_stat(&lfs, "dummy", &info);
        assert(err == 0 || (err == LFS_ERR_NOENT && i == 0));
@@ -80,7 +80,7 @@ code = '''
    }

    // one last check after power-cycle
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "dummy", &info) => 0;
    assert(strcmp(info.name, "dummy") == 0);
    assert(info.type == LFS_TYPE_REG);
@@ -92,10 +92,10 @@ define.LFS_BLOCK_CYCLES = [2, 1]
 define.N = 24
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }

    for (int i = 0; i < N; i++) {
@@ -119,7 +119,7 @@ code = '''
    lfs_unmount(&lfs) => 0;

    // one last check after power-cycle
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_stat(&lfs, "dummy", &info) => 0;
    assert(strcmp(info.name, "dummy") == 0);
    assert(info.type == LFS_TYPE_REG);
--- a/tests/test_truncate.toml
+++ b/tests/test_truncate.toml
@@ -2,8 +2,8 @@
 define.MEDIUMSIZE = [32, 2048]
 define.LARGESIZE = 8192
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldynoop",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;

@@ -17,7 +17,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;
    
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldynoop", LFS_O_RDWR) => 0;
    lfs_file_size(&lfs, &file) => LARGESIZE;

@@ -27,7 +27,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldynoop", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => MEDIUMSIZE;

@@ -46,8 +46,8 @@ code = '''
 define.MEDIUMSIZE = [32, 2048]
 define.LARGESIZE = 8192
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldyread",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;

@@ -61,7 +61,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldyread", LFS_O_RDWR) => 0;
    lfs_file_size(&lfs, &file) => LARGESIZE;

@@ -78,7 +78,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldyread", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => MEDIUMSIZE;

@@ -95,12 +95,12 @@ code = '''

 [[case]] # write, truncate, and read
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "sequence",
            LFS_O_RDWR | LFS_O_CREAT | LFS_O_TRUNC) => 0;

-    size = lfs_min(lfs.cfg->cache_size, sizeof(buffer)/2);
+    size = lfs_min(lfs.cfg.cache_size, sizeof(buffer)/2);
    lfs_size_t qsize = size / 4;
    uint8_t *wb = buffer;
    uint8_t *rb = buffer + size;
@@ -149,8 +149,8 @@ code = '''
 define.MEDIUMSIZE = [32, 2048]
 define.LARGESIZE = 8192
 code = '''
-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldywrite",
            LFS_O_WRONLY | LFS_O_CREAT) => 0;

@@ -164,7 +164,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldywrite", LFS_O_RDWR) => 0;
    lfs_file_size(&lfs, &file) => LARGESIZE;

@@ -181,7 +181,7 @@ code = '''
    lfs_file_close(&lfs, &file) => 0;
    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;
    lfs_file_open(&lfs, &file, "baldywrite", LFS_O_RDONLY) => 0;
    lfs_file_size(&lfs, &file) => MEDIUMSIZE;

@@ -202,10 +202,10 @@ define.MEDIUMSIZE = [32, 1024]
 define.LARGESIZE = 2048
 reentrant = true
 code = '''
-    err = lfs_mount(&lfs, &cfg);
+    err = lfs_mountcfg(&lfs, &cfg);
    if (err) {
-        lfs_format(&lfs, &cfg) => 0;
-        lfs_mount(&lfs, &cfg) => 0;
+        lfs_formatcfg(&lfs, &cfg) => 0;
+        lfs_mountcfg(&lfs, &cfg) => 0;
    }
    err = lfs_file_open(&lfs, &file, "baldy", LFS_O_RDONLY);
    assert(!err || err == LFS_ERR_NOENT);
@@ -312,8 +312,8 @@ code = '''
    const lfs_off_t *hotsizes   = configs[CONFIG].hotsizes;
    const lfs_off_t *coldsizes  = configs[CONFIG].coldsizes;

-    lfs_format(&lfs, &cfg) => 0;
-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_formatcfg(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    for (unsigned i = 0; i < COUNT; i++) {
        sprintf(path, "hairyhead%d", i);
@@ -340,7 +340,7 @@ code = '''

    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    for (unsigned i = 0; i < COUNT; i++) {
        sprintf(path, "hairyhead%d", i);
@@ -367,7 +367,7 @@ code = '''

    lfs_unmount(&lfs) => 0;

-    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mountcfg(&lfs, &cfg) => 0;

    for (unsigned i = 0; i < COUNT; i++) {
        sprintf(path, "hairyhead%d", i);
Author	SHA1	Message	Date
Christopher Haster	f9324d1443	Exploring inlined mutable configuration Currently littlefs uses a separate mutable state struct and immutable config struct. This lets users place the config struct in ROM where possible. However the recent addition of LFS_STATICCFG raises the question of if this split is still valuable. If the config is copied into the mutable struct at runtime, this allows a couple things: 1. Easier user interface, config can be stack allocated, no need to store the config struct for the lifetime of littlefs in OSs. 2. Avoids duplication when littlefs would need to change config based on observed superblocks, such as LFS_NAME_MAX limits 3. In theory, access to a single struct is faster/smaller as it avoids an additional load instruction. Unfortunately, inlining the dynamic config runs into several issues: 1. The code size actually increases with this change! From digging into this it's for a couple reasons: - Copying the config over takes code. - C has notorious problems with pointer aliasing, accessing constants from a const struct actually allows C to assume the values aren't going to change in more situations. This suggests it may be possible to reduce the code size more by loading the config pointer into a variable, but I haven't explored this probably not-worth-it optimization. - Even assuming deduplication of superblock-dependent configuration, the config struct is significantly larger than the mutable struct, and it turns out combining these two exceeds the limits of immediate-relative-loads, discarding the possible code size improvement from avoiding a second dereference. 2. The implementation of dynamic configuration differs significantly from the static configuration. This adds mess into the compile-time #ifdefs needed to support both options.	2020-11-28 20:13:32 -06:00
Christopher Haster	a7cdd563f6	Changed callbacks to take user-provided context directly This is a style change to make littlefs's callbacks consistent with most callback declarations found in C. That is, taking in a user-provided `void`. Previously, these callbacks took a pointer to the config struct itself, which indirectly contained a user provided context, and this gets the job done, but taking in a callback with a `void` is arguably more expected, has a better chance of integrating with C++/OS-specific code, and is more likely to be optimized out by a clever compiler. --- As a part of these changes, the geometry for the test bds needed to be moved into bd specific configuration objects. This is a good change as it also allows for testing situations where littlefs's geometry does not match the underlying bd.	2020-11-28 20:02:18 -06:00
Christopher Haster	a549413077	Rename config structs to cfg structs Since this is already going to be a breaking API change, this renames structs/variables named _config -> _cfg. This is in order to be consistent with functions such as lfs_file_opencfg.	2020-11-28 19:52:21 -06:00
Christopher Haster	3f6f88778a	Added minimal build+size reporting to CI based on static config	2020-11-28 19:51:08 -06:00
Christopher Haster	c44427f9ec	Exploring ideas for static configuration As an embedded library, littlefs's configuration straddles two worlds. In most cases the configuration is usually constant at build time, but when integrated into OSs, the configuration needs to be dynamically configurable. To help with this, littlefs has a separate lfs_config struct that can be placed into ROM when possible. But you know what's better than ROM configuration? Truely inlinable static configuration known at compile-time. In addition to avoiding the RAM cost, compile-time configuration allows for additional compiler optimizations, such as constexpr-elimination and removal of unused code-paths. So how to enable static configuration? 1. define LFS_STATICCFG 2. implement callbacks as global functions: - lfs_read - lfs_prog - lfs_erase - lfs_sync 2. define the now-required constants that configure littlefs: - LFS_READ_SIZE - LFS_PROG_SIZE - LFS_BLOCK_SIZE - LFS_BLOCK_COUNT - LFS_BLOCK_CYCLES - LFS_CACHE_SIZE - LFS_LOOKAHEAD_SIZE - LFS_READ_BUFFER (optional) - LFS_PROG_BUFFER (optional) - LFS_LOOKAHEAD_BUFFER (optional) - LFS_NAME_MAX (optional) - LFS_FILE_MAX (optional) - LFS_ATTR_MAX (optional) Note, there is a separate configuration for the file configuration, this can be enabled/disabled independently of LFS_STATICCFG. You will likely want to define this as well if you are looking for the smallest code size. In order to avoid a mess of #ifdefs, the internals of littlefs use a simple macro that redirects to either the dynamic or static config at compile time: #ifdef LFS_STATICCFG #define LFS_CFG_READ_SIZE(lfs) ((void)lfs, LFS_READ_SIZE) #else #define LFS_CFG_READ_SIZE(lfs) lfs->cfg->read_size #endif Unfortunately it does look like there still may be a lot of issues related to warnings of comparisons against constants... If only C had a way to ignore warnings on individual statements... Original idea by apmorton	2020-11-28 19:15:24 -06:00
Christopher Haster	ef9ba2d912	A number of small lfs_util.h QOL changes - Changed the name of the LFS_CONFIG macro to LFS_UTIL to avoid confusion with the lfs_config struct. This also hints that LFS_UTIL is related to lfs_util.h. LFS_UTIL allows the user to override lfs_util.h so they can provide their own system-level dependencies such as malloc, tracing, builtins, stdint definitions, string.h, and others. - Removed stdlib includes from lfs.h, these should all go through lfs_util.h to let users override these definitions if stdlib is unavailable on their system. - Moved error code definitions to lfs_util.h. This lets users override the error codes to replace them with their own error codes and avoid a translation layer in some situations. Note the error codes must still be in the range of a negative int. - Used proper stdint definitions in lfs_scmp.	2020-11-28 18:58:10 -06:00