[Intel-gfx] [PATCH] drm: Documentation style guide

Thierry Reding thierry.reding at gmail.com
Mon Dec 14 07:39:06 PST 2015

On Wed, Dec 09, 2015 at 05:08:02PM +0100, Daniel Vetter wrote:
> Every time I type or review docs this seems a bit different. Try to
> document the common style so we can try to unify at least new docs.
> v2: Spelling fixes from Pierre, Laurent and Jani.
> v3: More spelling fixes from Lukas.
> Cc: Pierre Moreau <pierre.morrow at free.fr>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Cc: Lukas Wunner <lukas at wunner.de>
> Acked-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Link: http://patchwork.freedesktop.org/patch/msgid/1449564561-3896-1-git-send-email-daniel.vetter@ffwll.ch
> ---
>  Documentation/DocBook/gpu.tmpl | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> index 749b8e2f2113..c66d6412f573 100644
> --- a/Documentation/DocBook/gpu.tmpl
> +++ b/Documentation/DocBook/gpu.tmpl
> @@ -124,6 +124,43 @@
>      <para>
>        [Insert diagram of typical DRM stack here]
>      </para>
> +  <sect1>
> +    <title>Style Guidelines</title>
> +    <para>
> +      For consistency this documentation uses American English. Abbreviations
> +      are written as all-uppercase, for example: DRM, KMS, IOCTL, CRTC, and so
> +      on. To aid in reading, documentations make full use of the markup

"..., the documentation makes full use of..." and perhaps "makes use of
the full set of markup characters that kerneldoc provides".

> +      characters kerneldoc provides: @parameter for function parameters, @member
> +      for structure members, &structure to reference structures and
> +      function() for functions. These all get automatically hyperlinked if
> +      kerneldoc for the referenced objects exists. When referencing entries in
> +      function vtables please use ->vfunc(). Note that kerneldoc does
> +      not support referencing struct members directly, so please add a reference
> +      to the vtable struct somewhere in the same paragraph or at least section.
> +    </para>
> +    <para>
> +      Except in special situations (to separate locked from unlocked variants)
> +      locking requirements for functions aren't documented in the kerneldoc.
> +      Instead locking should be check at runtime using e.g.

"should be checked"

> +      <code>WARN_ON(!mutex_is_locked(...));</code>. Since it's much easier to
> +      ignore documentation than runtime noise this provides more value. And on
> +      top of that runtime checks do need to be updated when the locking rules
> +      change, increasing the chances that they're correct. Within the
> +      documentation the locking rules should be explained in the relevant
> +      structures: Either in the comment for the lock explaining what it
> +      protects, or data fields need a note about which lock protects them, or
> +      both.

I think you're supposed to have the "or" only in the final subsentence:

	"either ... protects, data fields need ..., or both."

> +    </para>
> +    <para>
> +      Functions which have a non-<code>void</code> return value should have a
> +      section called "Returns" explaining the expected return values in
> +      different cases and their meanings. Currently there's no consensus whether
> +      that section name should be all upper-case or not, and whether it should
> +      end in a colon or not. Go with the file-local style. Other common section

I thought the colon was necessary for kerneldoc to turn it into a

Overall, long overdue, so thanks for writing it up:

Acked-by: Thierry Reding <treding at nvidia.com>
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