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From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Tue, 9 Jan 2024 16:46:54 +0100
Message-ID: <CAKMK7uGQqH7Y7bnNb=zeKkLyavtoJBpGJxwptBBUSqsYGdFEtA@mail.gmail.com>
Subject: Re: [PATCH v2] doc-guide: kernel-doc: tell about object-like macros
To: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-kernel@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org
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On Sun, 7 Jan 2024 at 02:24, Randy Dunlap <rdunlap@infradead.org> wrote:
>
> Since 2014 kernel-doc has supported describing object-like macros
> but it is not documented anywhere. I should have required some
> documentation for it when I merged the patch. :(
>
> There are currently only 3 uses of this (all in DRM headers, in
> include/drm/*.h).
>
> Add object-like macro kernel-doc documentation now so that more may
> know about it and use it.
>
> Fixes: cbb4d3e6510b ("scripts/kernel-doc: handle object-like macros")
> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: linux-doc@vger.kernel.org
> ---
> v2: Previous attempts to use kernel-doc were for data definitions,
>     not macros, so remove that comment.
>     Remove a duplicate word in the patch description.
>     Add examples.

Randy pointed to this in another thread and also mentioned that
function-like macros are already documented, so this also has my

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>


>
>  Documentation/doc-guide/kernel-doc.rst |   45 +++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
>
> diff -- a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst
> --- a/Documentation/doc-guide/kernel-doc.rst
> +++ b/Documentation/doc-guide/kernel-doc.rst
> @@ -341,6 +341,51 @@ Typedefs with function prototypes can al
>     */
>     typedef void (*type_name)(struct v4l2_ctrl *arg1, void *arg2);
>
> +Object-like macro documentation
> +-------------------------------
> +
> +Object-like macros are distinct from function-like macros. They are
> +differentiated by whether the macro name is immediately followed by a
> +left parenthesis ('(') for function-like macros or not followed by one
> +for object-like macros.
> +
> +Function-like macros are handled like functions by ``scripts/kernel-doc``.
> +They may have a parameter list. Object-like macros have do not have a
> +parameter list.
> +
> +The general format of an object-like macro kernel-doc comment is::
> +
> +  /**
> +   * define object_name - Brief description.
> +   *
> +   * Description of the object.
> +   */
> +
> +Example::
> +
> +  /**
> +   * define MAX_ERRNO - maximum errno value that is supported
> +   *
> +   * Kernel pointers have redundant information, so we can use a
> +   * scheme where we can return either an error code or a normal
> +   * pointer with the same return value.
> +   */
> +  #define MAX_ERRNO    4095
> +
> +Example::
> +
> +  /**
> +   * define DRM_GEM_VRAM_PLANE_HELPER_FUNCS - \
> +   *   Initializes struct drm_plane_helper_funcs for VRAM handling
> +   *
> +   * This macro initializes struct drm_plane_helper_funcs to use the
> +   * respective helper functions.
> +   */
> +  #define DRM_GEM_VRAM_PLANE_HELPER_FUNCS \
> +       .prepare_fb = drm_gem_vram_plane_helper_prepare_fb, \
> +       .cleanup_fb = drm_gem_vram_plane_helper_cleanup_fb
> +
> +
>  Highlights and cross-references
>  -------------------------------
>
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch