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Exploring ideas for static configuration

Browse Source 
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
This commit is contained in:
Christopher Haster
2020-11-23 00:53:07 -06:00
parent ef9ba2d912
commit c44427f9ec
18 changed files with 873 additions and 627 deletions
Download Patch File Download Diff File Expand all files Collapse all files

82
tests/test_alloc.toml
View File

@@ -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");
@@ -358,7 +358,7 @@ 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
@@ -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",