[PATCH] drm/fourcc: Document open source user waiver

[Daniel Vetter]

On Wed, Nov 23, 2022 at 08:24:37PM +0100, Daniel Vetter wrote:
> It's a bit a FAQ, and we really can't claim to be the authoritative
> source for allocating these numbers used in many standard extensions
> if we tell closed source or vendor stacks in general to go away.
> 
> Iirc this was already clarified in some vulkan discussions, but I
> can't find that anywhere anymore. At least not in a public link.
> 
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: David Airlie <airlied at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Alex Deucher <alexdeucher at gmail.com>
> Cc: Daniel Stone <daniel at fooishbar.org>
> Cc: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
> Cc: Jason Ekstrand <jason at jlekstrand.net>
> Cc: Neil Trevett <ntrevett at nvidia.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

>From irc:

<airlied> danvet: ack from me

> ---
>  include/uapi/drm/drm_fourcc.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index bc056f2d537d..de703c6be969 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -88,6 +88,18 @@ extern "C" {
>   *
>   * The authoritative list of format modifier codes is found in
>   * `include/uapi/drm/drm_fourcc.h`
> + *
> + * Open Source User Waiver
> + * -----------------------
> + *
> + * Because this is the authoritative source for pixel formats and modifiers
> + * referenced by GL, Vulkan extensions and other standards and hence used both
> + * by open source and closed source driver stacks, the usual requirement for an
> + * upstream in-kernel or open source userspace user does not apply.
> + *
> + * To ensure, as much as feasible, compatibility across stacks and avoid
> + * confusion with incompatible enumerations stakeholders for all relevant driver
> + * stacks should approve additions.
>   */
>  
>  #define fourcc_code(a, b, c, d) ((__u32)(a) | ((__u32)(b) << 8) | \
> -- 
> 2.37.2
> 

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