mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 02:39:48 +00:00
![Niklas Söderlund](/assets/img/avatar_default.png)
Add a warning for fixes tags that does not follow community conventions. Link: https://lkml.kernel.org/r/20220914100255.1048460-1-niklas.soderlund@corigine.com Signed-off-by: Niklas Söderlund <niklas.soderlund@corigine.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Reviewed-by: Louis Peens <louis.peens@corigine.com> Reviewed-by: Philippe Schenker <philippe.schenker@toradex.com> Acked-by: Dwaipayan Ray <dwaipayanray1@gmail.com> Reviewed-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Acked-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Acked-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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ReStructuredText
1256 lines
40 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0-only
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==========
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Checkpatch
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==========
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Checkpatch (scripts/checkpatch.pl) is a perl script which checks for trivial
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style violations in patches and optionally corrects them. Checkpatch can
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also be run on file contexts and without the kernel tree.
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Checkpatch is not always right. Your judgement takes precedence over checkpatch
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messages. If your code looks better with the violations, then its probably
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best left alone.
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Options
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=======
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This section will describe the options checkpatch can be run with.
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Usage::
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./scripts/checkpatch.pl [OPTION]... [FILE]...
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Available options:
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- -q, --quiet
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Enable quiet mode.
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- -v, --verbose
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Enable verbose mode. Additional verbose test descriptions are output
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so as to provide information on why that particular message is shown.
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- --no-tree
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Run checkpatch without the kernel tree.
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- --no-signoff
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Disable the 'Signed-off-by' line check. The sign-off is a simple line at
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the end of the explanation for the patch, which certifies that you wrote it
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or otherwise have the right to pass it on as an open-source patch.
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Example::
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Signed-off-by: Random J Developer <random@developer.example.org>
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Setting this flag effectively stops a message for a missing signed-off-by
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line in a patch context.
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- --patch
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Treat FILE as a patch. This is the default option and need not be
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explicitly specified.
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- --emacs
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Set output to emacs compile window format. This allows emacs users to jump
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from the error in the compile window directly to the offending line in the
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patch.
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- --terse
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Output only one line per report.
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- --showfile
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Show the diffed file position instead of the input file position.
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- -g, --git
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Treat FILE as a single commit or a git revision range.
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Single commit with:
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- <rev>
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- <rev>^
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- <rev>~n
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Multiple commits with:
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- <rev1>..<rev2>
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- <rev1>...<rev2>
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- <rev>-<count>
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- -f, --file
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Treat FILE as a regular source file. This option must be used when running
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checkpatch on source files in the kernel.
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- --subjective, --strict
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Enable stricter tests in checkpatch. By default the tests emitted as CHECK
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do not activate by default. Use this flag to activate the CHECK tests.
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- --list-types
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Every message emitted by checkpatch has an associated TYPE. Add this flag
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to display all the types in checkpatch.
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Note that when this flag is active, checkpatch does not read the input FILE,
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and no message is emitted. Only a list of types in checkpatch is output.
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- --types TYPE(,TYPE2...)
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Only display messages with the given types.
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Example::
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./scripts/checkpatch.pl mypatch.patch --types EMAIL_SUBJECT,BRACES
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- --ignore TYPE(,TYPE2...)
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Checkpatch will not emit messages for the specified types.
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Example::
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./scripts/checkpatch.pl mypatch.patch --ignore EMAIL_SUBJECT,BRACES
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- --show-types
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By default checkpatch doesn't display the type associated with the messages.
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Set this flag to show the message type in the output.
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- --max-line-length=n
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Set the max line length (default 100). If a line exceeds the specified
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length, a LONG_LINE message is emitted.
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The message level is different for patch and file contexts. For patches,
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a WARNING is emitted. While a milder CHECK is emitted for files. So for
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file contexts, the --strict flag must also be enabled.
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- --min-conf-desc-length=n
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Set the Kconfig entry minimum description length, if shorter, warn.
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- --tab-size=n
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Set the number of spaces for tab (default 8).
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- --root=PATH
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PATH to the kernel tree root.
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This option must be specified when invoking checkpatch from outside
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the kernel root.
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- --no-summary
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Suppress the per file summary.
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- --mailback
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Only produce a report in case of Warnings or Errors. Milder Checks are
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excluded from this.
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- --summary-file
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Include the filename in summary.
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- --debug KEY=[0|1]
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Turn on/off debugging of KEY, where KEY is one of 'values', 'possible',
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'type', and 'attr' (default is all off).
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- --fix
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This is an EXPERIMENTAL feature. If correctable errors exists, a file
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<inputfile>.EXPERIMENTAL-checkpatch-fixes is created which has the
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automatically fixable errors corrected.
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- --fix-inplace
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EXPERIMENTAL - Similar to --fix but input file is overwritten with fixes.
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DO NOT USE this flag unless you are absolutely sure and you have a backup
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in place.
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- --ignore-perl-version
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Override checking of perl version. Runtime errors maybe encountered after
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enabling this flag if the perl version does not meet the minimum specified.
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- --codespell
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Use the codespell dictionary for checking spelling errors.
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- --codespellfile
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Use the specified codespell file.
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Default is '/usr/share/codespell/dictionary.txt'.
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- --typedefsfile
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Read additional types from this file.
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- --color[=WHEN]
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Use colors 'always', 'never', or only when output is a terminal ('auto').
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Default is 'auto'.
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- --kconfig-prefix=WORD
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Use WORD as a prefix for Kconfig symbols (default is `CONFIG_`).
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- -h, --help, --version
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Display the help text.
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Message Levels
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==============
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Messages in checkpatch are divided into three levels. The levels of messages
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in checkpatch denote the severity of the error. They are:
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- ERROR
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This is the most strict level. Messages of type ERROR must be taken
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seriously as they denote things that are very likely to be wrong.
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- WARNING
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This is the next stricter level. Messages of type WARNING requires a
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more careful review. But it is milder than an ERROR.
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- CHECK
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This is the mildest level. These are things which may require some thought.
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Type Descriptions
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=================
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This section contains a description of all the message types in checkpatch.
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.. Types in this section are also parsed by checkpatch.
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.. The types are grouped into subsections based on use.
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Allocation style
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----------------
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**ALLOC_ARRAY_ARGS**
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The first argument for kcalloc or kmalloc_array should be the
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number of elements. sizeof() as the first argument is generally
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wrong.
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See: https://www.kernel.org/doc/html/latest/core-api/memory-allocation.html
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**ALLOC_SIZEOF_STRUCT**
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The allocation style is bad. In general for family of
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allocation functions using sizeof() to get memory size,
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constructs like::
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p = alloc(sizeof(struct foo), ...)
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should be::
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p = alloc(sizeof(*p), ...)
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#allocating-memory
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**ALLOC_WITH_MULTIPLY**
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Prefer kmalloc_array/kcalloc over kmalloc/kzalloc with a
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sizeof multiply.
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See: https://www.kernel.org/doc/html/latest/core-api/memory-allocation.html
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API usage
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---------
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**ARCH_DEFINES**
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Architecture specific defines should be avoided wherever
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possible.
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**ARCH_INCLUDE_LINUX**
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Whenever asm/file.h is included and linux/file.h exists, a
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conversion can be made when linux/file.h includes asm/file.h.
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However this is not always the case (See signal.h).
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This message type is emitted only for includes from arch/.
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**AVOID_BUG**
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BUG() or BUG_ON() should be avoided totally.
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Use WARN() and WARN_ON() instead, and handle the "impossible"
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error condition as gracefully as possible.
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See: https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on
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**CONSIDER_KSTRTO**
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The simple_strtol(), simple_strtoll(), simple_strtoul(), and
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simple_strtoull() functions explicitly ignore overflows, which
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may lead to unexpected results in callers. The respective kstrtol(),
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kstrtoll(), kstrtoul(), and kstrtoull() functions tend to be the
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correct replacements.
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See: https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
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**CONSTANT_CONVERSION**
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Use of __constant_<foo> form is discouraged for the following functions::
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__constant_cpu_to_be[x]
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__constant_cpu_to_le[x]
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__constant_be[x]_to_cpu
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__constant_le[x]_to_cpu
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__constant_htons
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__constant_ntohs
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Using any of these outside of include/uapi/ is not preferred as using the
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function without __constant_ is identical when the argument is a
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constant.
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In big endian systems, the macros like __constant_cpu_to_be32(x) and
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cpu_to_be32(x) expand to the same expression::
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#define __constant_cpu_to_be32(x) ((__force __be32)(__u32)(x))
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#define __cpu_to_be32(x) ((__force __be32)(__u32)(x))
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In little endian systems, the macros __constant_cpu_to_be32(x) and
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cpu_to_be32(x) expand to __constant_swab32 and __swab32. __swab32
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has a __builtin_constant_p check::
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#define __swab32(x) \
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(__builtin_constant_p((__u32)(x)) ? \
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___constant_swab32(x) : \
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__fswab32(x))
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So ultimately they have a special case for constants.
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Similar is the case with all of the macros in the list. Thus
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using the __constant_... forms are unnecessarily verbose and
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not preferred outside of include/uapi.
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See: https://lore.kernel.org/lkml/1400106425.12666.6.camel@joe-AO725/
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**DEPRECATED_API**
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Usage of a deprecated RCU API is detected. It is recommended to replace
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old flavourful RCU APIs by their new vanilla-RCU counterparts.
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The full list of available RCU APIs can be viewed from the kernel docs.
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See: https://www.kernel.org/doc/html/latest/RCU/whatisRCU.html#full-list-of-rcu-apis
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**DEPRECATED_VARIABLE**
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EXTRA_{A,C,CPP,LD}FLAGS are deprecated and should be replaced by the new
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flags added via commit f77bf01425b1 ("kbuild: introduce ccflags-y,
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asflags-y and ldflags-y").
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The following conversion scheme maybe used::
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EXTRA_AFLAGS -> asflags-y
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EXTRA_CFLAGS -> ccflags-y
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EXTRA_CPPFLAGS -> cppflags-y
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EXTRA_LDFLAGS -> ldflags-y
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See:
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1. https://lore.kernel.org/lkml/20070930191054.GA15876@uranus.ravnborg.org/
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2. https://lore.kernel.org/lkml/1313384834-24433-12-git-send-email-lacombar@gmail.com/
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3. https://www.kernel.org/doc/html/latest/kbuild/makefiles.html#compilation-flags
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**DEVICE_ATTR_FUNCTIONS**
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The function names used in DEVICE_ATTR is unusual.
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Typically, the store and show functions are used with <attr>_store and
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<attr>_show, where <attr> is a named attribute variable of the device.
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Consider the following examples::
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static DEVICE_ATTR(type, 0444, type_show, NULL);
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static DEVICE_ATTR(power, 0644, power_show, power_store);
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The function names should preferably follow the above pattern.
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See: https://www.kernel.org/doc/html/latest/driver-api/driver-model/device.html#attributes
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**DEVICE_ATTR_RO**
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The DEVICE_ATTR_RO(name) helper macro can be used instead of
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DEVICE_ATTR(name, 0444, name_show, NULL);
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Note that the macro automatically appends _show to the named
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attribute variable of the device for the show method.
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See: https://www.kernel.org/doc/html/latest/driver-api/driver-model/device.html#attributes
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**DEVICE_ATTR_RW**
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The DEVICE_ATTR_RW(name) helper macro can be used instead of
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DEVICE_ATTR(name, 0644, name_show, name_store);
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Note that the macro automatically appends _show and _store to the
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named attribute variable of the device for the show and store methods.
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See: https://www.kernel.org/doc/html/latest/driver-api/driver-model/device.html#attributes
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**DEVICE_ATTR_WO**
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The DEVICE_AATR_WO(name) helper macro can be used instead of
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DEVICE_ATTR(name, 0200, NULL, name_store);
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Note that the macro automatically appends _store to the
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named attribute variable of the device for the store method.
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See: https://www.kernel.org/doc/html/latest/driver-api/driver-model/device.html#attributes
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**DUPLICATED_SYSCTL_CONST**
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Commit d91bff3011cf ("proc/sysctl: add shared variables for range
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check") added some shared const variables to be used instead of a local
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copy in each source file.
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Consider replacing the sysctl range checking value with the shared
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one in include/linux/sysctl.h. The following conversion scheme may
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be used::
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&zero -> SYSCTL_ZERO
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&one -> SYSCTL_ONE
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&int_max -> SYSCTL_INT_MAX
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See:
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1. https://lore.kernel.org/lkml/20190430180111.10688-1-mcroce@redhat.com/
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2. https://lore.kernel.org/lkml/20190531131422.14970-1-mcroce@redhat.com/
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**ENOSYS**
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ENOSYS means that a nonexistent system call was called.
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Earlier, it was wrongly used for things like invalid operations on
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otherwise valid syscalls. This should be avoided in new code.
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See: https://lore.kernel.org/lkml/5eb299021dec23c1a48fa7d9f2c8b794e967766d.1408730669.git.luto@amacapital.net/
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**ENOTSUPP**
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ENOTSUPP is not a standard error code and should be avoided in new patches.
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EOPNOTSUPP should be used instead.
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See: https://lore.kernel.org/netdev/20200510182252.GA411829@lunn.ch/
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**EXPORT_SYMBOL**
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EXPORT_SYMBOL should immediately follow the symbol to be exported.
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**IN_ATOMIC**
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in_atomic() is not for driver use so any such use is reported as an ERROR.
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Also in_atomic() is often used to determine if sleeping is permitted,
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but it is not reliable in this use model. Therefore its use is
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strongly discouraged.
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However, in_atomic() is ok for core kernel use.
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See: https://lore.kernel.org/lkml/20080320201723.b87b3732.akpm@linux-foundation.org/
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**LOCKDEP**
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The lockdep_no_validate class was added as a temporary measure to
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prevent warnings on conversion of device->sem to device->mutex.
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It should not be used for any other purpose.
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See: https://lore.kernel.org/lkml/1268959062.9440.467.camel@laptop/
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**MALFORMED_INCLUDE**
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The #include statement has a malformed path. This has happened
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because the author has included a double slash "//" in the pathname
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accidentally.
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**USE_LOCKDEP**
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lockdep_assert_held() annotations should be preferred over
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assertions based on spin_is_locked()
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See: https://www.kernel.org/doc/html/latest/locking/lockdep-design.html#annotations
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**UAPI_INCLUDE**
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No #include statements in include/uapi should use a uapi/ path.
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**USLEEP_RANGE**
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usleep_range() should be preferred over udelay(). The proper way of
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using usleep_range() is mentioned in the kernel docs.
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See: https://www.kernel.org/doc/html/latest/timers/timers-howto.html#delays-information-on-the-various-kernel-delay-sleep-mechanisms
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Comments
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--------
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**BLOCK_COMMENT_STYLE**
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The comment style is incorrect. The preferred style for multi-
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line comments is::
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/*
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* This is the preferred style
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* for multi line comments.
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*/
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The networking comment style is a bit different, with the first line
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not empty like the former::
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/* This is the preferred comment style
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* for files in net/ and drivers/net/
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*/
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting
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**C99_COMMENTS**
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C99 style single line comments (//) should not be used.
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Prefer the block comment style instead.
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting
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**DATA_RACE**
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Applications of data_race() should have a comment so as to document the
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reasoning behind why it was deemed safe.
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See: https://lore.kernel.org/lkml/20200401101714.44781-1-elver@google.com/
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**FSF_MAILING_ADDRESS**
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Kernel maintainers reject new instances of the GPL boilerplate paragraph
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directing people to write to the FSF for a copy of the GPL, since the
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FSF has moved in the past and may do so again.
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So do not write paragraphs about writing to the Free Software Foundation's
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mailing address.
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See: https://lore.kernel.org/lkml/20131006222342.GT19510@leaf/
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Commit message
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--------------
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**BAD_SIGN_OFF**
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The signed-off-by line does not fall in line with the standards
|
|
specified by the community.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#developer-s-certificate-of-origin-1-1
|
|
|
|
**BAD_STABLE_ADDRESS_STYLE**
|
|
The email format for stable is incorrect.
|
|
Some valid options for stable address are::
|
|
|
|
1. stable@vger.kernel.org
|
|
2. stable@kernel.org
|
|
|
|
For adding version info, the following comment style should be used::
|
|
|
|
stable@vger.kernel.org # version info
|
|
|
|
**COMMIT_COMMENT_SYMBOL**
|
|
Commit log lines starting with a '#' are ignored by git as
|
|
comments. To solve this problem addition of a single space
|
|
infront of the log line is enough.
|
|
|
|
**COMMIT_MESSAGE**
|
|
The patch is missing a commit description. A brief
|
|
description of the changes made by the patch should be added.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
|
|
|
|
**EMAIL_SUBJECT**
|
|
Naming the tool that found the issue is not very useful in the
|
|
subject line. A good subject line summarizes the change that
|
|
the patch brings.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
|
|
|
|
**FROM_SIGN_OFF_MISMATCH**
|
|
The author's email does not match with that in the Signed-off-by:
|
|
line(s). This can be sometimes caused due to an improperly configured
|
|
email client.
|
|
|
|
This message is emitted due to any of the following reasons::
|
|
|
|
- The email names do not match.
|
|
- The email addresses do not match.
|
|
- The email subaddresses do not match.
|
|
- The email comments do not match.
|
|
|
|
**MISSING_SIGN_OFF**
|
|
The patch is missing a Signed-off-by line. A signed-off-by
|
|
line should be added according to Developer's certificate of
|
|
Origin.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin
|
|
|
|
**NO_AUTHOR_SIGN_OFF**
|
|
The author of the patch has not signed off the patch. It is
|
|
required that a simple sign off line should be present at the
|
|
end of explanation of the patch to denote that the author has
|
|
written it or otherwise has the rights to pass it on as an open
|
|
source patch.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin
|
|
|
|
**DIFF_IN_COMMIT_MSG**
|
|
Avoid having diff content in commit message.
|
|
This causes problems when one tries to apply a file containing both
|
|
the changelog and the diff because patch(1) tries to apply the diff
|
|
which it found in the changelog.
|
|
|
|
See: https://lore.kernel.org/lkml/20150611134006.9df79a893e3636019ad2759e@linux-foundation.org/
|
|
|
|
**GERRIT_CHANGE_ID**
|
|
To be picked up by gerrit, the footer of the commit message might
|
|
have a Change-Id like::
|
|
|
|
Change-Id: Ic8aaa0728a43936cd4c6e1ed590e01ba8f0fbf5b
|
|
Signed-off-by: A. U. Thor <author@example.com>
|
|
|
|
The Change-Id line must be removed before submitting.
|
|
|
|
**GIT_COMMIT_ID**
|
|
The proper way to reference a commit id is:
|
|
commit <12+ chars of sha1> ("<title line>")
|
|
|
|
An example may be::
|
|
|
|
Commit e21d2170f36602ae2708 ("video: remove unnecessary
|
|
platform_set_drvdata()") removed the unnecessary
|
|
platform_set_drvdata(), but left the variable "dev" unused,
|
|
delete it.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
|
|
|
|
**BAD_FIXES_TAG**
|
|
The Fixes: tag is malformed or does not follow the community conventions.
|
|
This can occur if the tag have been split into multiple lines (e.g., when
|
|
pasted in an email program with word wrapping enabled).
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
|
|
|
|
|
|
Comparison style
|
|
----------------
|
|
|
|
**ASSIGN_IN_IF**
|
|
Do not use assignments in if condition.
|
|
Example::
|
|
|
|
if ((foo = bar(...)) < BAZ) {
|
|
|
|
should be written as::
|
|
|
|
foo = bar(...);
|
|
if (foo < BAZ) {
|
|
|
|
**BOOL_COMPARISON**
|
|
Comparisons of A to true and false are better written
|
|
as A and !A.
|
|
|
|
See: https://lore.kernel.org/lkml/1365563834.27174.12.camel@joe-AO722/
|
|
|
|
**COMPARISON_TO_NULL**
|
|
Comparisons to NULL in the form (foo == NULL) or (foo != NULL)
|
|
are better written as (!foo) and (foo).
|
|
|
|
**CONSTANT_COMPARISON**
|
|
Comparisons with a constant or upper case identifier on the left
|
|
side of the test should be avoided.
|
|
|
|
|
|
Indentation and Line Breaks
|
|
---------------------------
|
|
|
|
**CODE_INDENT**
|
|
Code indent should use tabs instead of spaces.
|
|
Outside of comments, documentation and Kconfig,
|
|
spaces are never used for indentation.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#indentation
|
|
|
|
**DEEP_INDENTATION**
|
|
Indentation with 6 or more tabs usually indicate overly indented
|
|
code.
|
|
|
|
It is suggested to refactor excessive indentation of
|
|
if/else/for/do/while/switch statements.
|
|
|
|
See: https://lore.kernel.org/lkml/1328311239.21255.24.camel@joe2Laptop/
|
|
|
|
**SWITCH_CASE_INDENT_LEVEL**
|
|
switch should be at the same indent as case.
|
|
Example::
|
|
|
|
switch (suffix) {
|
|
case 'G':
|
|
case 'g':
|
|
mem <<= 30;
|
|
break;
|
|
case 'M':
|
|
case 'm':
|
|
mem <<= 20;
|
|
break;
|
|
case 'K':
|
|
case 'k':
|
|
mem <<= 10;
|
|
fallthrough;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#indentation
|
|
|
|
**LONG_LINE**
|
|
The line has exceeded the specified maximum length.
|
|
To use a different maximum line length, the --max-line-length=n option
|
|
may be added while invoking checkpatch.
|
|
|
|
Earlier, the default line length was 80 columns. Commit bdc48fa11e46
|
|
("checkpatch/coding-style: deprecate 80-column warning") increased the
|
|
limit to 100 columns. This is not a hard limit either and it's
|
|
preferable to stay within 80 columns whenever possible.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#breaking-long-lines-and-strings
|
|
|
|
**LONG_LINE_STRING**
|
|
A string starts before but extends beyond the maximum line length.
|
|
To use a different maximum line length, the --max-line-length=n option
|
|
may be added while invoking checkpatch.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#breaking-long-lines-and-strings
|
|
|
|
**LONG_LINE_COMMENT**
|
|
A comment starts before but extends beyond the maximum line length.
|
|
To use a different maximum line length, the --max-line-length=n option
|
|
may be added while invoking checkpatch.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#breaking-long-lines-and-strings
|
|
|
|
**SPLIT_STRING**
|
|
Quoted strings that appear as messages in userspace and can be
|
|
grepped, should not be split across multiple lines.
|
|
|
|
See: https://lore.kernel.org/lkml/20120203052727.GA15035@leaf/
|
|
|
|
**MULTILINE_DEREFERENCE**
|
|
A single dereferencing identifier spanned on multiple lines like::
|
|
|
|
struct_identifier->member[index].
|
|
member = <foo>;
|
|
|
|
is generally hard to follow. It can easily lead to typos and so makes
|
|
the code vulnerable to bugs.
|
|
|
|
If fixing the multiple line dereferencing leads to an 80 column
|
|
violation, then either rewrite the code in a more simple way or if the
|
|
starting part of the dereferencing identifier is the same and used at
|
|
multiple places then store it in a temporary variable, and use that
|
|
temporary variable only at all the places. For example, if there are
|
|
two dereferencing identifiers::
|
|
|
|
member1->member2->member3.foo1;
|
|
member1->member2->member3.foo2;
|
|
|
|
then store the member1->member2->member3 part in a temporary variable.
|
|
It not only helps to avoid the 80 column violation but also reduces
|
|
the program size by removing the unnecessary dereferences.
|
|
|
|
But if none of the above methods work then ignore the 80 column
|
|
violation because it is much easier to read a dereferencing identifier
|
|
on a single line.
|
|
|
|
**TRAILING_STATEMENTS**
|
|
Trailing statements (for example after any conditional) should be
|
|
on the next line.
|
|
Statements, such as::
|
|
|
|
if (x == y) break;
|
|
|
|
should be::
|
|
|
|
if (x == y)
|
|
break;
|
|
|
|
|
|
Macros, Attributes and Symbols
|
|
------------------------------
|
|
|
|
**ARRAY_SIZE**
|
|
The ARRAY_SIZE(foo) macro should be preferred over
|
|
sizeof(foo)/sizeof(foo[0]) for finding number of elements in an
|
|
array.
|
|
|
|
The macro is defined in include/linux/kernel.h::
|
|
|
|
#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
|
|
|
|
**AVOID_EXTERNS**
|
|
Function prototypes don't need to be declared extern in .h
|
|
files. It's assumed by the compiler and is unnecessary.
|
|
|
|
**AVOID_L_PREFIX**
|
|
Local symbol names that are prefixed with `.L` should be avoided,
|
|
as this has special meaning for the assembler; a symbol entry will
|
|
not be emitted into the symbol table. This can prevent `objtool`
|
|
from generating correct unwind info.
|
|
|
|
Symbols with STB_LOCAL binding may still be used, and `.L` prefixed
|
|
local symbol names are still generally usable within a function,
|
|
but `.L` prefixed local symbol names should not be used to denote
|
|
the beginning or end of code regions via
|
|
`SYM_CODE_START_LOCAL`/`SYM_CODE_END`
|
|
|
|
**BIT_MACRO**
|
|
Defines like: 1 << <digit> could be BIT(digit).
|
|
The BIT() macro is defined via include/linux/bits.h::
|
|
|
|
#define BIT(nr) (1UL << (nr))
|
|
|
|
**CONST_READ_MOSTLY**
|
|
When a variable is tagged with the __read_mostly annotation, it is a
|
|
signal to the compiler that accesses to the variable will be mostly
|
|
reads and rarely(but NOT never) a write.
|
|
|
|
const __read_mostly does not make any sense as const data is already
|
|
read-only. The __read_mostly annotation thus should be removed.
|
|
|
|
**DATE_TIME**
|
|
It is generally desirable that building the same source code with
|
|
the same set of tools is reproducible, i.e. the output is always
|
|
exactly the same.
|
|
|
|
The kernel does *not* use the ``__DATE__`` and ``__TIME__`` macros,
|
|
and enables warnings if they are used as they can lead to
|
|
non-deterministic builds.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/kbuild/reproducible-builds.html#timestamps
|
|
|
|
**DEFINE_ARCH_HAS**
|
|
The ARCH_HAS_xyz and ARCH_HAVE_xyz patterns are wrong.
|
|
|
|
For big conceptual features use Kconfig symbols instead. And for
|
|
smaller things where we have compatibility fallback functions but
|
|
want architectures able to override them with optimized ones, we
|
|
should either use weak functions (appropriate for some cases), or
|
|
the symbol that protects them should be the same symbol we use.
|
|
|
|
See: https://lore.kernel.org/lkml/CA+55aFycQ9XJvEOsiM3txHL5bjUc8CeKWJNR_H+MiicaddB42Q@mail.gmail.com/
|
|
|
|
**DO_WHILE_MACRO_WITH_TRAILING_SEMICOLON**
|
|
do {} while(0) macros should not have a trailing semicolon.
|
|
|
|
**INIT_ATTRIBUTE**
|
|
Const init definitions should use __initconst instead of
|
|
__initdata.
|
|
|
|
Similarly init definitions without const require a separate
|
|
use of const.
|
|
|
|
**INLINE_LOCATION**
|
|
The inline keyword should sit between storage class and type.
|
|
|
|
For example, the following segment::
|
|
|
|
inline static int example_function(void)
|
|
{
|
|
...
|
|
}
|
|
|
|
should be::
|
|
|
|
static inline int example_function(void)
|
|
{
|
|
...
|
|
}
|
|
|
|
**MISPLACED_INIT**
|
|
It is possible to use section markers on variables in a way
|
|
which gcc doesn't understand (or at least not the way the
|
|
developer intended)::
|
|
|
|
static struct __initdata samsung_pll_clock exynos4_plls[nr_plls] = {
|
|
|
|
does not put exynos4_plls in the .initdata section. The __initdata
|
|
marker can be virtually anywhere on the line, except right after
|
|
"struct". The preferred location is before the "=" sign if there is
|
|
one, or before the trailing ";" otherwise.
|
|
|
|
See: https://lore.kernel.org/lkml/1377655732.3619.19.camel@joe-AO722/
|
|
|
|
**MULTISTATEMENT_MACRO_USE_DO_WHILE**
|
|
Macros with multiple statements should be enclosed in a
|
|
do - while block. Same should also be the case for macros
|
|
starting with `if` to avoid logic defects::
|
|
|
|
#define macrofun(a, b, c) \
|
|
do { \
|
|
if (a == 5) \
|
|
do_this(b, c); \
|
|
} while (0)
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl
|
|
|
|
**PREFER_FALLTHROUGH**
|
|
Use the `fallthrough;` pseudo keyword instead of
|
|
`/* fallthrough */` like comments.
|
|
|
|
**TRAILING_SEMICOLON**
|
|
Macro definition should not end with a semicolon. The macro
|
|
invocation style should be consistent with function calls.
|
|
This can prevent any unexpected code paths::
|
|
|
|
#define MAC do_something;
|
|
|
|
If this macro is used within a if else statement, like::
|
|
|
|
if (some_condition)
|
|
MAC;
|
|
|
|
else
|
|
do_something;
|
|
|
|
Then there would be a compilation error, because when the macro is
|
|
expanded there are two trailing semicolons, so the else branch gets
|
|
orphaned.
|
|
|
|
See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/
|
|
|
|
**SINGLE_STATEMENT_DO_WHILE_MACRO**
|
|
For the multi-statement macros, it is necessary to use the do-while
|
|
loop to avoid unpredictable code paths. The do-while loop helps to
|
|
group the multiple statements into a single one so that a
|
|
function-like macro can be used as a function only.
|
|
|
|
But for the single statement macros, it is unnecessary to use the
|
|
do-while loop. Although the code is syntactically correct but using
|
|
the do-while loop is redundant. So remove the do-while loop for single
|
|
statement macros.
|
|
|
|
**WEAK_DECLARATION**
|
|
Using weak declarations like __attribute__((weak)) or __weak
|
|
can have unintended link defects. Avoid using them.
|
|
|
|
|
|
Functions and Variables
|
|
-----------------------
|
|
|
|
**CAMELCASE**
|
|
Avoid CamelCase Identifiers.
|
|
|
|
See: https://www.kernel.org/doc/html/latest/process/coding-style.html#naming
|
|
|
|
**CONST_CONST**
|
|
Using `const <type> const *` is generally meant to be
|
|
written `const <type> * const`.
|
|
|
|
**CONST_STRUCT**
|
|
Using const is generally a good idea. Checkpatch reads
|
|
a list of frequently used structs that are always or
|
|
almost always constant.
|
|
|
|
The existing structs list can be viewed from
|
|
`scripts/const_structs.checkpatch`.
|
|
|
|
See: https://lore.kernel.org/lkml/alpine.DEB.2.10.1608281509480.3321@hadrien/
|
|
|
|
**EMBEDDED_FUNCTION_NAME**
|
|
Embedded function names are less appropriate to use as
|
|
refactoring can cause function renaming. Prefer the use of
|
|
"%s", __func__ to embedded function names.
|
|
|
|
Note that this does not work with -f (--file) checkpatch option
|
|
as it depends on patch context providing the function name.
|
|
|
|
**FUNCTION_ARGUMENTS**
|
|
This warning is emitted due to any of the following reasons:
|
|
|
|
1. Arguments for the function declaration do not follow
|
|
the identifier name. Example::
|
|
|
|
void foo
|
|
(int bar, int baz)
|
|
|
|
This should be corrected to::
|
|
|
|
void foo(int bar, int baz)
|
|
|
|
2. Some arguments for the function definition do not
|
|
have an identifier name. Example::
|
|
|
|
void foo(int)
|
|
|
|
All arguments should have identifier names.
|
|
|
|
**FUNCTION_WITHOUT_ARGS**
|
|
Function declarations without arguments like::
|
|
|
|
int foo()
|
|
|
|
should be::
|
|
|
|
int foo(void)
|
|
|
|
**GLOBAL_INITIALISERS**
|
|
Global variables should not be initialized explicitly to
|
|
0 (or NULL, false, etc.). Your compiler (or rather your
|
|
loader, which is responsible for zeroing out the relevant
|
|
sections) automatically does it for you.
|
|
|
|
**INITIALISED_STATIC**
|
|
Static variables should not be initialized explicitly to zero.
|
|
Your compiler (or rather your loader) automatically does
|
|
it for you.
|
|
|
|
**MULTIPLE_ASSIGNMENTS**
|
|
Multiple assignments on a single line makes the code unnecessarily
|
|
complicated. So on a single line assign value to a single variable
|
|
only, this makes the code more readable and helps avoid typos.
|
|
|
|
**RETURN_PARENTHESES**
|
|
return is not a function and as such doesn't need parentheses::
|
|
|
|
return (bar);
|
|
|
|
can simply be::
|
|
|
|
return bar;
|
|
|
|
|
|
Permissions
|
|
-----------
|
|
|
|
**DEVICE_ATTR_PERMS**
|
|
The permissions used in DEVICE_ATTR are unusual.
|
|
Typically only three permissions are used - 0644 (RW), 0444 (RO)
|
|
and 0200 (WO).
|
|
|
|
See: https://www.kernel.org/doc/html/latest/filesystems/sysfs.html#attributes
|
|
|
|
**EXECUTE_PERMISSIONS**
|
|
There is no reason for source files to be executable. The executable
|
|
bit can be removed safely.
|
|
|
|
**EXPORTED_WORLD_WRITABLE**
|
|
Exporting world writable sysfs/debugfs files is usually a bad thing.
|
|
When done arbitrarily they can introduce serious security bugs.
|
|
In the past, some of the debugfs vulnerabilities would seemingly allow
|
|
any local user to write arbitrary values into device registers - a
|
|
situation from which little good can be expected to emerge.
|
|
|
|
See: https://lore.kernel.org/linux-arm-kernel/cover.1296818921.git.segoon@openwall.com/
|
|
|
|
**NON_OCTAL_PERMISSIONS**
|
|
Permission bits should use 4 digit octal permissions (like 0700 or 0444).
|
|
Avoid using any other base like decimal.
|
|
|
|
**SYMBOLIC_PERMS**
|
|
Permission bits in the octal form are more readable and easier to
|
|
understand than their symbolic counterparts because many command-line
|
|
tools use this notation. Experienced kernel developers have been using
|
|
these traditional Unix permission bits for decades and so they find it
|
|
easier to understand the octal notation than the symbolic macros.
|
|
For example, it is harder to read S_IWUSR|S_IRUGO than 0644, which
|
|
obscures the developer's intent rather than clarifying it.
|
|
|
|
See: https://lore.kernel.org/lkml/CA+55aFw5v23T-zvDZp-MmD_EYxF8WbafwwB59934FV7g21uMGQ@mail.gmail.com/
|
|
|
|
|
|
Spacing and Brackets
|
|
--------------------
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**ASSIGNMENT_CONTINUATIONS**
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Assignment operators should not be written at the start of a
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line but should follow the operand at the previous line.
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**BRACES**
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The placement of braces is stylistically incorrect.
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The preferred way is to put the opening brace last on the line,
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and put the closing brace first::
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if (x is true) {
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we do y
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}
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This applies for all non-functional blocks.
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However, there is one special case, namely functions: they have the
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opening brace at the beginning of the next line, thus::
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int function(int x)
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{
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body of function
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}
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
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**BRACKET_SPACE**
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Whitespace before opening bracket '[' is prohibited.
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There are some exceptions:
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1. With a type on the left::
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int [] a;
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2. At the beginning of a line for slice initialisers::
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[0...10] = 5,
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3. Inside a curly brace::
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= { [0...10] = 5 }
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**CONCATENATED_STRING**
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Concatenated elements should have a space in between.
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Example::
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printk(KERN_INFO"bar");
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should be::
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printk(KERN_INFO "bar");
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**ELSE_AFTER_BRACE**
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`else {` should follow the closing block `}` on the same line.
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
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**LINE_SPACING**
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Vertical space is wasted given the limited number of lines an
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editor window can display when multiple blank lines are used.
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
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**OPEN_BRACE**
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The opening brace should be following the function definitions on the
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next line. For any non-functional block it should be on the same line
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as the last construct.
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
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**POINTER_LOCATION**
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When using pointer data or a function that returns a pointer type,
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the preferred use of * is adjacent to the data name or function name
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and not adjacent to the type name.
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Examples::
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char *linux_banner;
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unsigned long long memparse(char *ptr, char **retptr);
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char *match_strdup(substring_t *s);
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
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**SPACING**
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Whitespace style used in the kernel sources is described in kernel docs.
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
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**TRAILING_WHITESPACE**
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Trailing whitespace should always be removed.
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Some editors highlight the trailing whitespace and cause visual
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distractions when editing files.
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
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**UNNECESSARY_PARENTHESES**
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Parentheses are not required in the following cases:
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1. Function pointer uses::
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(foo->bar)();
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could be::
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foo->bar();
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2. Comparisons in if::
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if ((foo->bar) && (foo->baz))
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if ((foo == bar))
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could be::
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if (foo->bar && foo->baz)
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if (foo == bar)
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3. addressof/dereference single Lvalues::
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&(foo->bar)
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*(foo->bar)
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could be::
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&foo->bar
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*foo->bar
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**WHILE_AFTER_BRACE**
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while should follow the closing bracket on the same line::
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do {
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...
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} while(something);
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See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
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Others
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------
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**CONFIG_DESCRIPTION**
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Kconfig symbols should have a help text which fully describes
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it.
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**CORRUPTED_PATCH**
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The patch seems to be corrupted or lines are wrapped.
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Please regenerate the patch file before sending it to the maintainer.
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**CVS_KEYWORD**
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Since linux moved to git, the CVS markers are no longer used.
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So, CVS style keywords ($Id$, $Revision$, $Log$) should not be
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added.
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**DEFAULT_NO_BREAK**
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switch default case is sometimes written as "default:;". This can
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cause new cases added below default to be defective.
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A "break;" should be added after empty default statement to avoid
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unwanted fallthrough.
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**DOS_LINE_ENDINGS**
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For DOS-formatted patches, there are extra ^M symbols at the end of
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the line. These should be removed.
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**DT_SCHEMA_BINDING_PATCH**
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DT bindings moved to a json-schema based format instead of
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freeform text.
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See: https://www.kernel.org/doc/html/latest/devicetree/bindings/writing-schema.html
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**DT_SPLIT_BINDING_PATCH**
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Devicetree bindings should be their own patch. This is because
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bindings are logically independent from a driver implementation,
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they have a different maintainer (even though they often
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are applied via the same tree), and it makes for a cleaner history in the
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DT only tree created with git-filter-branch.
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See: https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters
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**EMBEDDED_FILENAME**
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Embedding the complete filename path inside the file isn't particularly
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useful as often the path is moved around and becomes incorrect.
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**FILE_PATH_CHANGES**
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Whenever files are added, moved, or deleted, the MAINTAINERS file
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patterns can be out of sync or outdated.
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So MAINTAINERS might need updating in these cases.
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**MEMSET**
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The memset use appears to be incorrect. This may be caused due to
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badly ordered parameters. Please recheck the usage.
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**NOT_UNIFIED_DIFF**
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The patch file does not appear to be in unified-diff format. Please
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regenerate the patch file before sending it to the maintainer.
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**PRINTF_0XDECIMAL**
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Prefixing 0x with decimal output is defective and should be corrected.
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**SPDX_LICENSE_TAG**
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The source file is missing or has an improper SPDX identifier tag.
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The Linux kernel requires the precise SPDX identifier in all source files,
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and it is thoroughly documented in the kernel docs.
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See: https://www.kernel.org/doc/html/latest/process/license-rules.html
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**TYPO_SPELLING**
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Some words may have been misspelled. Consider reviewing them.
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