[PATCH -next v3] docs: document all error message types in checkpatch
Lukas Bulwahn
lukas.bulwahn at gmail.com
Mon Mar 22 07:33:00 UTC 2021
On Sun, Mar 21, 2021 at 12:26 PM Dwaipayan Ray <dwaipayanray1 at gmail.com> wrote:
>
> All the error message types now have a verbose description.
>
> Also there are two new groups of message types:
>
> - Macros, Attributes and Symbols
> - Functions and Variables
>
> Rearrange the message types to fit these new groups as needed.
>
> Signed-off-by: Dwaipayan Ray <dwaipayanray1 at gmail.com>
Let us go for a wider review on linux-doc and lkml...
Reviewed-by: Lukas Bulwahn <lukas.bulwahn at gmail.com>
> ---
>
> Changes in v3:
> - Add more explanation for LOCKDEP
> - Minor grammar fixes
>
> Changes in v2:
> - Replace 4.10 kernel doc links by latest
>
> Documentation/dev-tools/checkpatch.rst | 319 ++++++++++++++++++++++---
> 1 file changed, 281 insertions(+), 38 deletions(-)
>
> diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
> index 2671e54c8320..904fd5fe2484 100644
> --- a/Documentation/dev-tools/checkpatch.rst
> +++ b/Documentation/dev-tools/checkpatch.rst
> @@ -280,43 +280,12 @@ API usage
> However this is not always the case (See signal.h).
> This message type is emitted only for includes from arch/.
>
> - **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_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
>
> - **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))
> -
> **CONSIDER_KSTRTO**
> The simple_strtol(), simple_strtoll(), simple_strtoul(), and
> simple_strtoull() functions explicitly ignore overflows, which
> @@ -325,6 +294,25 @@ API usage
> 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
> -------------
> @@ -353,7 +341,6 @@ Comment style
> See: https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting
>
>
> -
> Commit message
> --------------
>
> @@ -397,6 +384,35 @@ Commit message
> 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 at 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
> ----------------
> @@ -426,6 +442,148 @@ Comparison style
> 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 or ARCH_HAVE_xyz patterns are totally 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 one
> + function at a time, we should either use weak functions (appropriate
> + for some cases), or the symbol that protects them should the
> + SAME SYMBOL WE USE.
Capital letter means SHOUTING. I do not see the need to shout here...
Maybe that was needed in the original mail... in the documentation, we
are happy that the reader reads it at all...
> + See: http://lkml.iu.edu/hypermail/linux/kernel/1309.3/01646.html
> +
> + **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)
> + {
> + ...
> + }
> +
> + **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
> +
> + **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
> +
> + **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.
> +
> + **RETURN_PARENTHESES**
> + return is not a function and as such doesn't need parentheses::
> +
> + return (bar);
> +
> + can simply be::
> +
> + return bar;
> +
> +
> Spacing and Brackets
> --------------------
>
> @@ -439,7 +597,7 @@ Spacing and Brackets
> and put the closing brace first::
>
> if (x is true) {
> - we do y
> + we do y
> }
>
> This applies for all non-functional blocks.
> @@ -448,7 +606,7 @@ Spacing and Brackets
>
> int function(int x)
> {
> - body of function
> + body of function
> }
>
> See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
> @@ -485,29 +643,114 @@ Spacing and Brackets
>
> printk(KERN_INFO "bar");
>
> + **ELSE_AFTER_BRACE**
> + `else {` should follow the closing block `}` on the same line.
> + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
> +
> **LINE_SPACING**
> Vertical space is wasted given the limited number of lines an
> editor window can display when multiple blank lines are used.
> See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
>
> + **OPEN_BRACE**
> + The opening brace should be following the function definitions on the
> + next line. For any non-functional block it should be on the same line
> + as the last construct.
> + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
> +
> + **POINTER_LOCATION**
> + When using pointer data or a function that returns a pointer type,
> + the preferred use of * is adjacent to the data name or function name
> + and not adjacent to the type name.
> + Examples::
> +
> + char *linux_banner;
> + unsigned long long memparse(char *ptr, char **retptr);
> + char *match_strdup(substring_t *s);
> +
> + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
> +
> **SPACING**
> Whitespace style used in the kernel sources is described in kernel docs.
> See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
>
> + **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;
> + /* fall through */
> + default:
> + break;
> + }
> +
> + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#indentation
> +
> **TRAILING_WHITESPACE**
> Trailing whitespace should always be removed.
> Some editors highlight the trailing whitespace and cause visual
> distractions when editing files.
> See: https://www.kernel.org/doc/html/latest/process/coding-style.html#spaces
>
> + **WHILE_AFTER_BRACE**
> + while should follow the closing bracket on the same line::
> +
> + do {
> + ...
> + } while(something);
> +
> + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
> +
>
> Others
> ------
>
> - **CAMELCASE**
> - Avoid CamelCase Identifiers.
> - See: https://www.kernel.org/doc/html/latest/process/coding-style.html#naming
> -
> **CONFIG_DESCRIPTION**
> Kconfig symbols should have a help text which fully describes
> it.
> +
> + **CORRUPTED_PATCH**
> + The patch seems to be corrupted or lines are wrapped.
> + Please regenerate the patch file before sending it to the maintainer.
> +
> + **DOS_LINE_ENDINGS**
> + For DOS-formatted patches, there are extra ^M symbols at the end of
> + the line. These should be removed.
> +
> + **EXECUTE_PERMISSIONS**
> + There is no reason for source files to be executable. The executable
> + bit can be removed safely.
> +
> + **NON_OCTAL_PERMISSIONS**
> + Permission bits should use 4 digit octal permissions (like 0700 or 0444).
> + Avoid using any other base like decimal.
> +
> + **NOT_UNIFIED_DIFF**
> + The patch file does not appear to be in unified-diff format. Please
> + regenerate the patch file before sending it to the maintainer.
> +
> + **PRINTF_0XDECIMAL**
> + Prefixing 0x with decimal output is defective and should be corrected.
> +
> + **TRAILING_STATEMENTS**
> + Trailing statements (for example after any conditional) should be
> + on the next line.
> + Like::
> +
> + if (x == y) break;
> +
> + should be::
> +
> + if (x == y)
> + break;
> --
> 2.30.0
>
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