Re: [PATCH v2] drm: Check actual format for legacy pageflip.

[Alex Deucher <alexdeucher@gmail.com>]

On Sat, Jan 9, 2021 at 9:11 PM Bas Nieuwenhuizen
<bas@basnieuwenhuizen.nl> wrote:
>
> With modifiers one can actually have different format_info structs
> for the same format, which now matters for AMDGPU since we convert
> implicit modifiers to explicit modifiers with multiple planes.
>
> I checked other drivers and it doesn't look like they end up triggering
> this case so I think this is safe to relax.
>
> Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Reviewed-by: Zhan Liu <zhan.liu@amd.com>
> Acked-by: Christian König <christian.koenig@amd.com>
> Acked-by: Alex Deucher <alexander.deucher@amd.com>
> Fixes: 816853f9dc40 ("drm/amd/display: Set new format info for converted metadata.")

Do you have commit rights to drm-misc or do you need someone to commit
this for you?

Thanks!

Alex

> ---
>  drivers/gpu/drm/drm_plane.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index e6231947f987..a0cb746bcb0a 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -1163,7 +1163,14 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
>         if (ret)
>                 goto out;
>
> -       if (old_fb->format != fb->format) {
> +       /*
> +        * Only check the FOURCC format code, excluding modifiers. This is
> +        * enough for all legacy drivers. Atomic drivers have their own
> +        * checks in their ->atomic_check implementation, which will
> +        * return -EINVAL if any hw or driver constraint is violated due
> +        * to modifier changes.
> +        */
> +       if (old_fb->format->format != fb->format->format) {
>                 DRM_DEBUG_KMS("Page flip is not allowed to change frame buffer format.\n");
>                 ret = -EINVAL;
>                 goto out;
> --
> 2.29.2
>
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