Re: [PATCH v3 1/1] coding-style: recommend split headers instead of kernel.h

Randy Dunlap
2024-01-28T06:26:47Z

On 1/8/24 12:22, Yueh-Shun Li wrote:
> In section "18) Don't re-invent the kernel macros" in "Linux kernel
> coding style":
>
> Recommend reusing macros from headers inside include/linux, instead of
> the obsolete include/linux/kernel.h
>
> Change wording
>
> - "The header file contains macros" -> "the header files provide macros"
> Some macros are intended to use inside the header file only, or are
> considered the implementation detail of other facilities. Developers
> are expected to determine if a macro is meant to be used outside the
> header file.
>
> Signed-off-by: Yueh-Shun Li <shamrocklee@posteo.net>

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Thanks.

> ---
> Documentation/process/coding-style.rst | 24 +++++++++++++-----------
> 1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
> index 6db37a46d305..2a5c4f4c568c 100644
> --- a/Documentation/process/coding-style.rst
> +++ b/Documentation/process/coding-style.rst
> @@ -1048,27 +1048,29 @@ readable alternative if the call-sites have naked true/false constants.
> Otherwise limited use of bool in structures and arguments can improve
> readability.
>
> +
> 18) Don't re-invent the kernel macros
> -------------------------------------
>
> -The header file include/linux/kernel.h contains a number of macros that
> -you should use, rather than explicitly coding some variant of them yourself.
> +The header files in the ``include/linux`` directory provide a number of macros
> +that you should use, rather than explicitly coding some variant of them
> +yourself.
> +
> For example, if you need to calculate the length of an array, take advantage
> -of the macro
> +of the macro ``ARRAY_SIZE()`` from ``include/linux/array_size.h`` by
>
> .. code-block:: c
>
> - #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> + #include <linux/array_size.h>
> + ARRAY_SIZE(x) // The size of array x
>
> Similarly, if you need to calculate the size of some structure member, use
> +``sizeof_field()`` from ``include/linux/stddef.h``.
>
> -.. code-block:: c
> -
> - #define sizeof_field(t, f) (sizeof(((t*)0)->f))
> -
> -There are also min() and max() macros that do strict type checking if you
> -need them. Feel free to peruse that header file to see what else is already
> -defined that you shouldn't reproduce in your code.
> +There are also ``min()`` and ``max()`` macros in ``include/linux/minmax.h``
> +that do strict type checking if you need them. Feel free to search across and
> +peruse the header files to see what else is already defined that you shouldn't
> +reproduce in your code.
>
>
> 19) Editor modelines and other cruft

--
#Randy