.. SPDX-License-Identifier: GPL-2.0-only ==========Checkpatch========== Checkpatch (scripts/checkpatch.pl) is a perl script which checks for trivialstyle violations in patches and optionally corrects them.  Checkpatch canalso be run on file contexts and without the kernel tree. Checkpatch is not always right. Your judgement takes precedence over checkpatchmessages.  If your code looks better with the violations, then its probablybest left alone.  Options======= This section will describe the options checkpatch can be run with. Usage::   ./scripts/checkpatch.pl [OPTION]... [FILE]... Available options:  - -q,  --quiet    Enable quiet mode.  - -v,  --verbose   Enable verbose mode.  Additional verbose test descriptions are output   so as to provide information on why that particular message is shown.  - --no-tree    Run checkpatch without the kernel tree.  - --no-signoff    Disable the 'Signed-off-by' line check.  The sign-off is a simple line at   the end of the explanation for the patch, which certifies that you wrote it   or otherwise have the right to pass it on as an open-source patch.    Example:: 	 Signed-off-by: Random J Developer <random@developer.example.org>    Setting this flag effectively stops a message for a missing signed-off-by   line in a patch context.  - --patch    Treat FILE as a patch.  This is the default option and need not be   explicitly specified.  - --emacs    Set output to emacs compile window format.  This allows emacs users to jump   from the error in the compile window directly to the offending line in the   patch.  - --terse    Output only one line per report.  - --showfile    Show the diffed file position instead of the input file position.  - -g,  --git    Treat FILE as a single commit or a git revision range.    Single commit with:    - <rev>   - <rev>^   - <rev>~n    Multiple commits with:    - <rev1>..<rev2>   - <rev1>...<rev2>   - <rev>-<count>  - -f,  --file    Treat FILE as a regular source file.  This option must be used when running   checkpatch on source files in the kernel.  - --subjective,  --strict    Enable stricter tests in checkpatch.  By default the tests emitted as CHECK   do not activate by default.  Use this flag to activate the CHECK tests.  - --list-types    Every message emitted by checkpatch has an associated TYPE.  Add this flag   to display all the types in checkpatch.    Note that when this flag is active, checkpatch does not read the input FILE,   and no message is emitted.  Only a list of types in checkpatch is output.  - --types TYPE(,TYPE2...)    Only display messages with the given types.    Example::      ./scripts/checkpatch.pl mypatch.patch --types EMAIL_SUBJECT,BRACES  - --ignore TYPE(,TYPE2...)    Checkpatch will not emit messages for the specified types.    Example::      ./scripts/checkpatch.pl mypatch.patch --ignore EMAIL_SUBJECT,BRACES  - --show-types    By default checkpatch doesn't display the type associated with the messages.   Set this flag to show the message type in the output.  - --max-line-length=n    Set the max line length (default 100).  If a line exceeds the specified   length, a LONG_LINE message is emitted.     The message level is different for patch and file contexts.  For patches,   a WARNING is emitted.  While a milder CHECK is emitted for files.  So for   file contexts, the --strict flag must also be enabled.  - --min-conf-desc-length=n    Set the Kconfig entry minimum description length, if shorter, warn.  - --tab-size=n    Set the number of spaces for tab (default 8).  - --root=PATH    PATH to the kernel tree root.    This option must be specified when invoking checkpatch from outside   the kernel root.  - --no-summary    Suppress the per file summary.  - --mailback    Only produce a report in case of Warnings or Errors.  Milder Checks are   excluded from this.  - --summary-file    Include the filename in summary.  - --debug KEY=[0|1]    Turn on/off debugging of KEY, where KEY is one of 'values', 'possible',   'type', and 'attr' (default is all off).  - --fix    This is an EXPERIMENTAL feature.  If correctable errors exists, a file   <inputfile>.EXPERIMENTAL-checkpatch-fixes is created which has the   automatically fixable errors corrected.  - --fix-inplace    EXPERIMENTAL - Similar to --fix but input file is overwritten with fixes.    DO NOT USE this flag unless you are absolutely sure and you have a backup   in place.  - --ignore-perl-version    Override checking of perl version.  Runtime errors maybe encountered after   enabling this flag if the perl version does not meet the minimum specified.  - --codespell    Use the codespell dictionary for checking spelling errors.  - --codespellfile    Use the specified codespell file.   Default is '/usr/share/codespell/dictionary.txt'.  - --typedefsfile    Read additional types from this file.  - --color[=WHEN]    Use colors 'always', 'never', or only when output is a terminal ('auto').   Default is 'auto'.  - --kconfig-prefix=WORD    Use WORD as a prefix for Kconfig symbols (default is `CONFIG_`).  - -h, --help, --version    Display the help text. Message Levels============== Messages in checkpatch are divided into three levels. The levels of messagesin checkpatch denote the severity of the error. They are:  - ERROR    This is the most strict level.  Messages of type ERROR must be taken   seriously as they denote things that are very likely to be wrong.  - WARNING    This is the next stricter level.  Messages of type WARNING requires a   more careful review.  But it is milder than an ERROR.  - CHECK    This is the mildest level.  These are things which may require some thought. Type Descriptions================= This section contains a description of all the message types in checkpatch. .. Types in this section are also parsed by checkpatch... The types are grouped into subsections based on use.  Allocation style----------------   **ALLOC_ARRAY_ARGS**    The first argument for kcalloc or kmalloc_array should be the    number of elements.  sizeof() as the first argument is generally    wrong.    See: https://www.kernel.org/doc/html/latest/core-api/memory-allocation.html   **ALLOC_SIZEOF_STRUCT**    The allocation style is bad.  In general for family of    allocation functions using sizeof() to get memory size,    constructs like::       p = alloc(sizeof(struct foo), ...)     should be::       p = alloc(sizeof(*p), ...)     See: https://www.kernel.org/doc/html/latest/process/coding-style.html#allocating-memory   **ALLOC_WITH_MULTIPLY**    Prefer kmalloc_array/kcalloc over kmalloc/kzalloc with a    sizeof multiply.    See: https://www.kernel.org/doc/html/latest/core-api/memory-allocation.html  API usage---------   **ARCH_DEFINES**    Architecture specific defines should be avoided wherever    possible.   **ARCH_INCLUDE_LINUX**    Whenever asm/file.h is included and linux/file.h exists, a    conversion can be made when linux/file.h includes asm/file.h.    However this is not always the case (See signal.h).    This message type is emitted only for includes from arch/.   **AVOID_BUG**    BUG() or BUG_ON() should be avoided totally.    Use WARN() and WARN_ON() instead, and handle the "impossible"    error condition as gracefully as possible.    See: https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on   **CONSIDER_KSTRTO**    The simple_strtol(), simple_strtoll(), simple_strtoul(), and    simple_strtoull() functions explicitly ignore overflows, which    may lead to unexpected results in callers.  The respective kstrtol(),    kstrtoll(), kstrtoul(), and kstrtoull() functions tend to be the    correct replacements.    See: https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull   **LOCKDEP**    The lockdep_no_validate class was added as a temporary measure to    prevent warnings on conversion of device->sem to device->mutex.    It should not be used for any other purpose.    See: https://lore.kernel.org/lkml/1268959062.9440.467.camel@laptop/   **MALFORMED_INCLUDE**    The #include statement has a malformed path.  This has happened    because the author has included a double slash "//" in the pathname    accidentally.   **USE_LOCKDEP**    lockdep_assert_held() annotations should be preferred over    assertions based on spin_is_locked()    See: https://www.kernel.org/doc/html/latest/locking/lockdep-design.html#annotations   **UAPI_INCLUDE**    No #include statements in include/uapi should use a uapi/ path.  Comment style-------------   **BLOCK_COMMENT_STYLE**    The comment style is incorrect.  The preferred style for multi-    line comments is::       /*      * This is the preferred style      * for multi line comments.      */     The networking comment style is a bit different, with the first line    not empty like the former::       /* This is the preferred comment style      * for files in net/ and drivers/net/      */     See: https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting   **C99_COMMENTS**    C99 style single line comments (//) should not be used.    Prefer the block comment style instead.    See: https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting  Commit message--------------   **BAD_SIGN_OFF**    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   **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  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.  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 in include/linux/bitops.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

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