mirror of
https://github.com/eledio-devices/thirdparty-littlefs.git
synced 2025-10-31 00:32:38 +01:00
Updated DESIGN.md to reflect v2 changes
Now with graphs! Images are stored on the branch gh-images in an effort to avoid binary bloat in the git history. Also spruced up SPEC.md and README.md and ran a spellechecker over the documentation. Favorite typo so far was dependendent, which is, in fact, not a word.
This commit is contained in:
Christopher Haster
271
SPEC.md
271
SPEC.md
@@ -1,9 +1,9 @@
|
||||
## The little filesystem technical specification
|
||||
## littlefs technical specification
|
||||
|
||||
This is the technical specification of the little filesystem. This document
|
||||
covers the technical details of how the littlefs is stored on disk for
|
||||
introspection and tool development. This document assumes you are familiar
|
||||
with the design of the littlefs, for more info on how littlefs works check
|
||||
introspection and tooling. This document assumes you are familiar with the
|
||||
design of the littlefs, for more info on how littlefs works check
|
||||
out [DESIGN.md](DESIGN.md).
|
||||
|
||||
```
|
||||
@@ -18,22 +18,21 @@ out [DESIGN.md](DESIGN.md).
|
||||
## Some quick notes
|
||||
|
||||
- littlefs is a block-based filesystem. The disk is divided into an array of
|
||||
evenly sized blocks that are used as the logical unit of storage. Block
|
||||
pointers are stored in 32 bits.
|
||||
evenly sized blocks that are used as the logical unit of storage.
|
||||
|
||||
- Block pointers are stored in 32 bits, with the special value `0xffffffff`
|
||||
representing a null block address.
|
||||
|
||||
- In addition to the logical block size (which usually matches the erase
|
||||
block size), littlefs also uses a program block size and read block size.
|
||||
These determine the alignment of block device operations, but aren't needed
|
||||
for portability.
|
||||
These determine the alignment of block device operations, but don't need
|
||||
to be consistent for portability.
|
||||
|
||||
- By default, any values in littlefs are stored in little-endian byte order.
|
||||
|
||||
- The littlefs uses the value of `0xffffffff` to represent a null
|
||||
block address.
|
||||
- By default, all values in littlefs are stored in little-endian byte order.
|
||||
|
||||
## Directories / Metadata pairs
|
||||
|
||||
Metadata pairs form the backbone of the littlefs and provide a system for
|
||||
Metadata pairs form the backbone of littlefs and provide a system for
|
||||
distributed atomic updates. Even the superblock is stored in a metadata pair.
|
||||
|
||||
As their name suggests, a metadata pair is stored in two blocks, with one block
|
||||
@@ -91,14 +90,14 @@ alignment.
|
||||
|
||||
Metadata block fields:
|
||||
|
||||
- **Revision count (32-bits)** - Incremented every erase cycle. If both blocks
|
||||
contain valid commits, only the block with the most recent revision count
|
||||
should be used. Sequence comparison must be used to avoid issues with
|
||||
integer overflow.
|
||||
1. **Revision count (32-bits)** - Incremented every erase cycle. If both blocks
|
||||
contain valid commits, only the block with the most recent revision count
|
||||
should be used. Sequence comparison must be used to avoid issues with
|
||||
integer overflow.
|
||||
|
||||
- **CRC (32-bits)** - Detects corruption from power-loss or other write
|
||||
issues. Uses a CRC-32 with a polynomial of `0x04c11db7` initialized
|
||||
with `0xffffffff`.
|
||||
2. **CRC (32-bits)** - Detects corruption from power-loss or other write
|
||||
issues. Uses a CRC-32 with a polynomial of `0x04c11db7` initialized
|
||||
with `0xffffffff`.
|
||||
|
||||
Entries themselves are stored as a 32-bit tag followed by a variable length
|
||||
blob of data. But exactly how these tags are stored is a little bit tricky.
|
||||
@@ -159,7 +158,7 @@ Here's a more complete example of metadata block containing 4 entries:
|
||||
| | | || |
|
||||
| |-------------------+-------------------| || |
|
||||
| | tag CxCRC | CRC | || /
|
||||
| |-------------------+-------------------| ||
|
||||
| |-------------------+-------------------| ||
|
||||
| | tag CRCxA' | data A' | || \
|
||||
| |-------------------+ | || |
|
||||
| | | || |
|
||||
@@ -167,7 +166,7 @@ Here's a more complete example of metadata block containing 4 entries:
|
||||
| | | tag CRCxA' | | || |
|
||||
| |--------------+-------------------+----| || |
|
||||
| | CRC | padding | || /
|
||||
| |--------------+----+-------------------| ||
|
||||
| |--------------+----+-------------------| ||
|
||||
| | tag CRCxA'' | data A'' | <---. \
|
||||
| |-------------------+ | ||| |
|
||||
| | | ||| |
|
||||
@@ -179,12 +178,12 @@ Here's a more complete example of metadata block containing 4 entries:
|
||||
| | | tag Dx| |||| |
|
||||
| |---------+-------------------+---------| |||| |
|
||||
| |CRC | CRC | | |||| /
|
||||
| |---------+-------------------+ | ||||
|
||||
| |---------+-------------------+ | ||||
|
||||
| | unwritten storage | |||| more commits
|
||||
| | | |||| |
|
||||
| | | |||| v
|
||||
| | | ||||
|
||||
| | | ||||
|
||||
| | | |||| v
|
||||
| | | ||||
|
||||
| | | ||||
|
||||
| '---------------------------------------' ||||
|
||||
'---------------------------------------' |||'- most recent A
|
||||
||'-- most recent B
|
||||
@@ -198,7 +197,7 @@ So in littlefs, 32-bit tags describe every type of metadata. And this means
|
||||
_every_ type of metadata, including file entries, directory fields, and
|
||||
global state. Even the CRCs used to mark the end of commits get their own tag.
|
||||
|
||||
Because of this, the tag format contains some densely packed informtaion. Note
|
||||
Because of this, the tag format contains some densely packed information. Note
|
||||
that there are multiple levels of types which break down into more info:
|
||||
|
||||
```
|
||||
@@ -214,9 +213,9 @@ that there are multiple levels of types which break down into more info:
|
||||
```
|
||||
|
||||
|
||||
Before we go further, there's one VERY important thing to note. These tags are
|
||||
NOT stored in little-endian. Tags stored in commits are actually stored in
|
||||
big-endian (and is the only thing in littlefs stored in big-endian). This
|
||||
Before we go further, there's one important thing to note. These tags are
|
||||
**not** stored in little-endian. Tags stored in commits are actually stored
|
||||
in big-endian (and is the only thing in littlefs stored in big-endian). This
|
||||
little bit of craziness comes from the fact that the valid bit must be the
|
||||
first bit in a commit, and when converted to little-endian, the valid bit finds
|
||||
itself in byte 4. We could restructure the tag to store the valid bit lower,
|
||||
@@ -228,26 +227,26 @@ invalid and can be used for null values.
|
||||
|
||||
Metadata tag fields:
|
||||
|
||||
- **Valid bit (1-bit)** - Indicates if the tag is valid.
|
||||
1. **Valid bit (1-bit)** - Indicates if the tag is valid.
|
||||
|
||||
- **Type3 (11-bits)** - Type of the tag. This field is broken down further
|
||||
into a 3-bit abstract type and an 8-bit chunk field. Note that the value
|
||||
`0x000` is invalid and not assigned a type.
|
||||
2. **Type3 (11-bits)** - Type of the tag. This field is broken down further
|
||||
into a 3-bit abstract type and an 8-bit chunk field. Note that the value
|
||||
`0x000` is invalid and not assigned a type.
|
||||
|
||||
- **Type1 (3-bits)** - Abstract type of the tag. Groups the tags into
|
||||
8 categories that facilitate bitmasked lookups.
|
||||
3. **Type1 (3-bits)** - Abstract type of the tag. Groups the tags into
|
||||
8 categories that facilitate bitmasked lookups.
|
||||
|
||||
- **Chunk (8-bits)** - Chunk field used for various purposes by the different
|
||||
abstract types. type1+chunk+id form a unique identifier for each tag in the
|
||||
metadata block.
|
||||
4. **Chunk (8-bits)** - Chunk field used for various purposes by the different
|
||||
abstract types. type1+chunk+id form a unique identifier for each tag in the
|
||||
metadata block.
|
||||
|
||||
- **Id (10-bits)** - File id associated with the tag. Each file in a metadata
|
||||
block gets a unique id which is used to associate tags with that file. The
|
||||
special value `0x3ff` is used for any tags that are not associated with a
|
||||
file, such as directory and global metadata.
|
||||
5. **Id (10-bits)** - File id associated with the tag. Each file in a metadata
|
||||
block gets a unique id which is used to associate tags with that file. The
|
||||
special value `0x3ff` is used for any tags that are not associated with a
|
||||
file, such as directory and global metadata.
|
||||
|
||||
- **Length (10-bits)** - Length of the data in bytes. The special value
|
||||
`0x3ff` indicates that this tag has been deleted.
|
||||
6. **Length (10-bits)** - Length of the data in bytes. The special value
|
||||
`0x3ff` indicates that this tag has been deleted.
|
||||
|
||||
## Metadata types
|
||||
|
||||
@@ -274,7 +273,7 @@ array of files.
|
||||
---
|
||||
#### `0x0xx` LFS_TYPE_NAME
|
||||
|
||||
Associates the id with a file name and file type.
|
||||
Associates the id with a file name and file type.
|
||||
|
||||
The data contains the file name stored as an ASCII string (may be expanded to
|
||||
UTF8 in the future).
|
||||
@@ -300,9 +299,9 @@ Layout of the name tag:
|
||||
|
||||
Name fields:
|
||||
|
||||
- **file type (8-bits)** - Type of the file.
|
||||
1. **file type (8-bits)** - Type of the file.
|
||||
|
||||
- **file name** - File name stored as an ASCII string.
|
||||
2. **file name** - File name stored as an ASCII string.
|
||||
|
||||
---
|
||||
#### `0x001` LFS_TYPE_REG
|
||||
@@ -335,14 +334,15 @@ across a linked-list of metadata pairs rooted on the blocks 0 and 1. The last
|
||||
metadata pair doubles as the root directory of the filesystem.
|
||||
|
||||
```
|
||||
.--------. .--------. .--------. .--------. .--------.
|
||||
| super |->| super |->| super |->| super |->| file B |
|
||||
| block | | block | | block | | block | | file C |
|
||||
| | | | | | | file A | | file D |
|
||||
.--------. .--------. .--------. .--------. .--------.
|
||||
.| super |->| super |->| super |->| super |->| file B |
|
||||
|| block | || block | || block | || block | || file C |
|
||||
|| | || | || | || file A | || file D |
|
||||
|'--------' |'--------' |'--------' |'--------' |'--------'
|
||||
'--------' '--------' '--------' '--------' '--------'
|
||||
|
||||
\---------------+----------------/ \---------+---------/
|
||||
superblock pairs root directory
|
||||
\----------------+----------------/ \----------+----------/
|
||||
superblock pairs root directory
|
||||
```
|
||||
|
||||
The filesystem starts with only the root directory. The superblock metadata
|
||||
@@ -366,48 +366,41 @@ Layout of the superblock name tag and inline-struct tag:
|
||||
'----------------- valid bit
|
||||
|
||||
tag data
|
||||
[-- 32 --][-- 32 --|-- 32 --|
|
||||
[1|- 11 -| 10 | 10 ][-- 32 --|-- 32 --|
|
||||
^ ^ ^ ^ ^- version ^- block size
|
||||
[-- 32 --][-- 32 --|-- 32 --|-- 32 --]
|
||||
[1|- 11 -| 10 | 10 ][-- 32 --|-- 32 --|-- 32 --]
|
||||
^ ^ ^ ^ ^- version ^- block size ^- block count
|
||||
| | | | [-- 32 --|-- 32 --|-- 32 --]
|
||||
| | | | [-- 32 --|-- 32 --|-- 32 --]
|
||||
| | | | ^- name max ^- file max ^- attr max
|
||||
| | | '- size (24)
|
||||
| | '------ id (0)
|
||||
| '------------ type (0x201)
|
||||
'----------------- valid bit
|
||||
|
||||
data (cont)
|
||||
|-- 32 --|-- 32 --|-- 32 --|
|
||||
|-- 32 --|-- 32 --|-- 32 --|
|
||||
^- block count ^- name max ^- file max
|
||||
|
||||
data (cont)
|
||||
|-- 32 --]
|
||||
|-- 32 --]
|
||||
^- attr max
|
||||
```
|
||||
|
||||
Superblock fields:
|
||||
|
||||
- **Magic string (8-bytes)** - Magic string indicating the presence of littlefs
|
||||
on the device. Must be the string "littlefs".
|
||||
1. **Magic string (8-bytes)** - Magic string indicating the presence of
|
||||
littlefs on the device. Must be the string "littlefs".
|
||||
|
||||
- **Version (32-bits)** - The version of littlefs at format time. The version
|
||||
is encoded in a 32-bit value with the upper 16-bits containing the major
|
||||
version, and the lower 16-bits containing the minor version.
|
||||
2. **Version (32-bits)** - The version of littlefs at format time. The version
|
||||
is encoded in a 32-bit value with the upper 16-bits containing the major
|
||||
version, and the lower 16-bits containing the minor version.
|
||||
|
||||
This specification describes version 2.0 (`0x00020000`).
|
||||
This specification describes version 2.0 (`0x00020000`).
|
||||
|
||||
- **Block size (32-bits)** - Size of the logical block size used by the
|
||||
filesystem in bytes.
|
||||
3. **Block size (32-bits)** - Size of the logical block size used by the
|
||||
filesystem in bytes.
|
||||
|
||||
- **Block count (32-bits)** - Number of blocks in the filesystem.
|
||||
4. **Block count (32-bits)** - Number of blocks in the filesystem.
|
||||
|
||||
- **Name max (32-bits)** - Maximum size of file names in bytes.
|
||||
5. **Name max (32-bits)** - Maximum size of file names in bytes.
|
||||
|
||||
- **File max (32-bits)** - Maximum size of files in bytes.
|
||||
6. **File max (32-bits)** - Maximum size of files in bytes.
|
||||
|
||||
- **Attr max (32-bits)** - Maximum size of file attributes in bytes.
|
||||
7. **Attr max (32-bits)** - Maximum size of file attributes in bytes.
|
||||
|
||||
The superblock must always be the first entry (id 0) in a metdata pair as well
|
||||
The superblock must always be the first entry (id 0) in a metadata pair as well
|
||||
as be the first entry written to the block. This means that the superblock
|
||||
entry can be read from a device using offsets alone.
|
||||
|
||||
@@ -419,7 +412,7 @@ Associates the id with an on-disk data structure.
|
||||
The exact layout of the data depends on the data structure type stored in the
|
||||
chunk field and can be one of the following.
|
||||
|
||||
Any type of struct supercedes all other structs associated with the id. For
|
||||
Any type of struct supersedes all other structs associated with the id. For
|
||||
example, appending a ctz-struct replaces an inline-struct on the same file.
|
||||
|
||||
---
|
||||
@@ -431,12 +424,13 @@ Directories in littlefs are stored on disk as a linked-list of metadata pairs,
|
||||
each pair containing any number of files in alphabetical order.
|
||||
|
||||
```
|
||||
|
|
||||
v
|
||||
.--------. .--------. .--------. .--------. .--------. .--------.
|
||||
| file A |->| file D |->| file G |->| file I |->| file J |->| file M |
|
||||
| file B | | file E | | file H | | | | file K | | file N |
|
||||
| file C | | file F | | | | | | file L | | |
|
||||
|
|
||||
v
|
||||
.--------. .--------. .--------. .--------. .--------. .--------.
|
||||
.| file A |->| file D |->| file G |->| file I |->| file J |->| file M |
|
||||
|| file B | || file E | || file H | || | || file K | || file N |
|
||||
|| file C | || file F | || | || | || file L | || |
|
||||
|'--------' |'--------' |'--------' |'--------' |'--------' |'--------'
|
||||
'--------' '--------' '--------' '--------' '--------' '--------'
|
||||
```
|
||||
|
||||
@@ -460,15 +454,15 @@ Layout of the dir-struct tag:
|
||||
|
||||
Dir-struct fields:
|
||||
|
||||
- **Metadata pair (8-bytes)** - Pointer to the first metadata-pair
|
||||
in the directory.
|
||||
1. **Metadata pair (8-bytes)** - Pointer to the first metadata-pair
|
||||
in the directory.
|
||||
|
||||
---
|
||||
#### `0x201` LFS_TYPE_INLINESTRUCT
|
||||
|
||||
Gives the id an inline data structure.
|
||||
|
||||
Inline structs store small files that can fit in the metdata pair. In this
|
||||
Inline structs store small files that can fit in the metadata pair. In this
|
||||
case, the file data is stored directly in the tag's data area.
|
||||
|
||||
Layout of the inline-struct tag:
|
||||
@@ -485,7 +479,7 @@ Layout of the inline-struct tag:
|
||||
|
||||
Inline-struct fields:
|
||||
|
||||
- **Inline data** - File data stored directly in the metadata-pair.
|
||||
1. **Inline data** - File data stored directly in the metadata-pair.
|
||||
|
||||
---
|
||||
#### `0x202` LFS_TYPE_CTZSTRUCT
|
||||
@@ -497,12 +491,13 @@ are stored in a skip-list in reverse, with a pointer to the head of the
|
||||
skip-list. Note that the head of the skip-list and the file size is enough
|
||||
information to read the file.
|
||||
|
||||
How exactly CTZ skip-lists work is a bit complicted. A full explanation can be
|
||||
How exactly CTZ skip-lists work is a bit complicated. A full explanation can be
|
||||
found in the [DESIGN.md](DESIGN.md#ctz-skip-lists).
|
||||
|
||||
A quick summary: For every nth block where n is divisible by 2^x, the block
|
||||
contains a pointer to block n-2^x. These pointers are stored in increasing
|
||||
order of x in each block of the file before the actual data.
|
||||
A quick summary: For every _n_‍th block where _n_ is divisible by
|
||||
2‍_ˣ_, that block contains a pointer to block _n_-2‍_ˣ_.
|
||||
These pointers are stored in increasing order of _x_ in each block of the file
|
||||
before the actual data.
|
||||
|
||||
```
|
||||
|
|
||||
@@ -536,15 +531,15 @@ Layout of the CTZ-struct tag:
|
||||
|
||||
CTZ-struct fields:
|
||||
|
||||
- **File head (32-bits)** - Pointer to the block that is the head of the
|
||||
file's CTZ skip-list.
|
||||
1. **File head (32-bits)** - Pointer to the block that is the head of the
|
||||
file's CTZ skip-list.
|
||||
|
||||
- **File size (32-bits)** - Size of the file in bytes.
|
||||
2. **File size (32-bits)** - Size of the file in bytes.
|
||||
|
||||
---
|
||||
#### `0x3xx` LFS_TYPE_USERATTR
|
||||
|
||||
Attaches a user attribute to an id.
|
||||
Attaches a user attribute to an id.
|
||||
|
||||
littlefs has a concept of "user attributes". These are small user-provided
|
||||
attributes that can be used to store things like timestamps, hashes,
|
||||
@@ -571,9 +566,9 @@ Layout of the user-attr tag:
|
||||
|
||||
User-attr fields:
|
||||
|
||||
- **Attr type (8-bits)** - Type of the user attributes.
|
||||
1. **Attr type (8-bits)** - Type of the user attributes.
|
||||
|
||||
- **Attr data** - The data associated with the user attribute.
|
||||
2. **Attr data** - The data associated with the user attribute.
|
||||
|
||||
---
|
||||
#### `0x6xx` LFS_TYPE_TAIL
|
||||
@@ -586,21 +581,23 @@ which indicates if the following metadata pair is a part of the directory
|
||||
(hard-tail) or only used to traverse the filesystem (soft-tail).
|
||||
|
||||
```
|
||||
.--------.
|
||||
| dir A |-.
|
||||
|softtail| |
|
||||
.--------.
|
||||
.| dir A |-.
|
||||
||softtail| |
|
||||
.--------| |-'
|
||||
| '--------'
|
||||
| |'--------'
|
||||
| '---|--|-'
|
||||
| .-' '-------------.
|
||||
| v v
|
||||
| .--------. .--------. .--------.
|
||||
'->| dir B |->| dir B |->| dir C |
|
||||
|hardtail| |softtail| | |
|
||||
| | | | | |
|
||||
'--------' '--------' '--------'
|
||||
||hardtail| ||softtail| || |
|
||||
|| | || | || |
|
||||
|'--------' |'--------' |'--------'
|
||||
'--------' '--------' '--------'
|
||||
```
|
||||
|
||||
Currently any type supercedes any other preceding tails in the metadata pair,
|
||||
Currently any type supersedes any other preceding tails in the metadata pair,
|
||||
but this may change if additional metadata pair state is added.
|
||||
|
||||
A note about the metadata pair linked-list: Normally, this linked-list contains
|
||||
@@ -611,10 +608,10 @@ exactly this flag is stored is described below.
|
||||
|
||||
When the sync flag is set:
|
||||
|
||||
- The linked-list may contain an orphaned directory that has been removed in
|
||||
the filesystem.
|
||||
- The linked-list may contain a metadata pair with a bad block that has been
|
||||
replaced in the filesystem.
|
||||
1. The linked-list may contain an orphaned directory that has been removed in
|
||||
the filesystem.
|
||||
2. The linked-list may contain a metadata pair with a bad block that has been
|
||||
replaced in the filesystem.
|
||||
|
||||
If the sync flag is set, the threaded linked-list must be checked for these
|
||||
errors before it can be used reliably. Note that the threaded linked-list can
|
||||
@@ -635,9 +632,9 @@ Layout of the tail tag:
|
||||
|
||||
Tail fields:
|
||||
|
||||
- **Tail type (8-bits)** - Type of the tail pointer.
|
||||
1. **Tail type (8-bits)** - Type of the tail pointer.
|
||||
|
||||
- **Metadata pair (8-bytes)** - Pointer to the next metadata-pair.
|
||||
2. **Metadata pair (8-bytes)** - Pointer to the next metadata-pair.
|
||||
|
||||
---
|
||||
#### `0x600` LFS_TYPE_SOFTTAIL
|
||||
@@ -668,18 +665,18 @@ littlefs has a concept of "global state". This is a small set of state that
|
||||
can be updated by a commit to _any_ metadata pair in the filesystem.
|
||||
|
||||
The way this works is that the global state is stored as a set of deltas
|
||||
distributed across the filesystem such that the global state can by found by
|
||||
distributed across the filesystem such that the global state can be found by
|
||||
the xor-sum of these deltas.
|
||||
|
||||
```
|
||||
.--------. .--------. .--------. .--------. .--------.
|
||||
| |->| gstate |->| |->| gstate |->| gstate |
|
||||
| | | 0x23 | | | | 0xff | | 0xce |
|
||||
| | | | | | | | | |
|
||||
'--------' '--------' '--------' '--------' '--------'
|
||||
| | |
|
||||
v v v
|
||||
0x00 --> xor ------------------> xor ------> xor --> gstate 0x12
|
||||
.--------. .--------. .--------. .--------. .--------.
|
||||
.| |->| gdelta |->| |->| gdelta |->| gdelta |
|
||||
|| | || 0x23 | || | || 0xff | || 0xce |
|
||||
|| | || | || | || | || |
|
||||
|'--------' |'--------' |'--------' |'--------' |'--------'
|
||||
'--------' '----|---' '--------' '----|---' '----|---'
|
||||
v v v
|
||||
0x00 --> xor ------------------> xor ------> xor --> gstate = 0x12
|
||||
```
|
||||
|
||||
Note that storing globals this way is very expensive in terms of storage usage,
|
||||
@@ -730,17 +727,17 @@ Layout of the move state:
|
||||
|
||||
Move state fields:
|
||||
|
||||
- **Sync bit (1-bit)** - Indicates if the metadata pair threaded linked-list is
|
||||
in-sync. If set, the threaded linked-list should be checked for errors.
|
||||
1. **Sync bit (1-bit)** - Indicates if the metadata pair threaded linked-list
|
||||
is in-sync. If set, the threaded linked-list should be checked for errors.
|
||||
|
||||
- **Move type (11-bits)** - Type of move being performed. Must be either
|
||||
`0x000`, indicating no move, or `0x4ff` indicating the source file should
|
||||
be deleted.
|
||||
2. **Move type (11-bits)** - Type of move being performed. Must be either
|
||||
`0x000`, indicating no move, or `0x4ff` indicating the source file should
|
||||
be deleted.
|
||||
|
||||
- **Move id (10-bits)** - The file id being moved.
|
||||
3. **Move id (10-bits)** - The file id being moved.
|
||||
|
||||
- **Metadata pair (8-bytes)** - Pointer to the metadata-pair containing
|
||||
the move.
|
||||
4. **Metadata pair (8-bytes)** - Pointer to the metadata-pair containing
|
||||
the move.
|
||||
|
||||
---
|
||||
#### `0x5xx` LFS_TYPE_CRC
|
||||
@@ -778,13 +775,13 @@ Layout of the CRC tag:
|
||||
|
||||
CRC fields:
|
||||
|
||||
- **Valid state (1-bit)** - Indicates the expected value of the valid bit for
|
||||
any tags in the next commit.
|
||||
1. **Valid state (1-bit)** - Indicates the expected value of the valid bit for
|
||||
any tags in the next commit.
|
||||
|
||||
- **CRC (32-bits)** - CRC-32 with a polynomial of `0x04c11db7` initialized with
|
||||
`0xffffffff`.
|
||||
2. **CRC (32-bits)** - CRC-32 with a polynomial of `0x04c11db7` initialized
|
||||
with `0xffffffff`.
|
||||
|
||||
- **Padding** - Padding to the next program-aligned boundary. No guarantees are
|
||||
made about the contents.
|
||||
3. **Padding** - Padding to the next program-aligned boundary. No guarantees
|
||||
are made about the contents.
|
||||
|
||||
---
|
||||
|
||||
Reference in New Issue
Block a user