Linux内核代码格式审查

前言

Linux内核代码有一套自己的代码格式规范，相关的规范说明在内核代码树目录：Documentation/CodingStyle或Documentation/process/coding-style.rst。
具体细节大家可以自己去看，这里就不贴了。

以前提交内核补丁，一直用scripts/checkpatch.pl来过一遍代码格式，没怎么去研究。
最近刚好检查格式报了个错，以前没怎么遇到，于是就去看了下。

报错信息：

ERROR: do not set execute permissions for source files

从提示上看很明显是源码文件权限问题。

Checkpatch 介绍

内核官方与它相关的文档：https://www.kernel.org/doc/html/latest/dev-tools/checkpatch.html
下面是它的介绍（保持原汁原味）：

Checkpatch (scripts/checkpatch.pl) is a perl script which checks for trivial style violations in patches and optionally corrects them. Checkpatch can also be run on file contexts and without the kernel tree.

Checkpatch is not always right. Your judgement takes precedence over checkpatch messages. If your code looks better with the violations, then its probably best left alone.

重点：Checkpatch不仅可以检查格式，也可以修正格式。它检查和修正不一定总是对的！只能作为参考，以自己的判断为准！

Checkpatch 使用方式

scripts/checkpatch.pl脚本的帮助信息，使用方式：

Usage: ./scripts/checkpatch.pl [OPTION]... [FILE]...
Version: 0.32

Options:
  -q, --quiet                quiet
  -v, --verbose              verbose mode
  --no-tree                  run without a kernel tree
  --no-signoff               do not check for 'Signed-off-by' line
  --patch                    treat FILE as patchfile (default)
  --emacs                    emacs compile window format
  --terse                    one line per report
  --showfile                 emit diffed file position, not input file position
  -g, --git                  treat FILE as a single commit or git revision range
                             single git commit with:
                               <rev>
                               <rev>^
                               <rev>~n
                             multiple git commits with:
                               <rev1>..<rev2>
                               <rev1>...<rev2>
                               <rev>-<count>
                             git merges are ignored
  -f, --file                 treat FILE as regular source file
  --subjective, --strict     enable more subjective tests
  --list-types               list the possible message types
  --types TYPE(,TYPE2...)    show only these comma separated message types
  --ignore TYPE(,TYPE2...)   ignore various comma separated message types
  --show-types               show the specific message type in the output
  --max-line-length=n        set the maximum line length, (default 100)
                             if exceeded, warn on patches
                             requires --strict for use with --file
  --min-conf-desc-length=n   set the min 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
  --no-summary               suppress the per-file summary
  --mailback                 only produce a report in case of warnings/errors
  --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)
  --test-only=WORD           report only warnings/errors containing WORD
                             literally
  --fix                      EXPERIMENTAL - may create horrible results
                             If correctable single-line errors exist, create
                             "<inputfile>.EXPERIMENTAL-checkpatch-fixes"
                             with potential errors corrected to the preferred
                             checkpatch style
  --fix-inplace              EXPERIMENTAL - may create horrible results
                             Is the same as --fix, but overwrites the input
                             file.  It's your fault if there's no backup or git
  --ignore-perl-version      override checking of perl version.  expect
                             runtime errors.
  --codespell                Use the codespell dictionary for spelling/typos
                             (default:/usr/share/codespell/dictionary.txt)
  --codespellfile            Use this codespell dictionary
  --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
                             CONFIG_)
  -h, --help, --version      display this help and exit

When FILE is - read standard input.

说明：

--fix: 可以使用该选项去尝试修复格式问题。
-g, --git: 后面跟commit id可以直接去检查git提交，默认输入是补丁文件
--subjective, --strict: 执行更严格的格式审查

Checkpatch 审查输出等级

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.