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

[Mario Kleiner]

On Sat, Jan 2, 2021 at 3:02 PM Bas Nieuwenhuizen
<bas at 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 at basnieuwenhuizen.nl>
> Fixes: 816853f9dc40 ("drm/amd/display: Set new format info for converted metadata.")
> ---
>  drivers/gpu/drm/drm_plane.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index e6231947f987..f5085990cfac 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -1163,7 +1163,7 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
>         if (ret)
>                 goto out;
>
> -       if (old_fb->format != fb->format) {
> +       if (old_fb->format->format != fb->format->format) {

This was btw. the original way before Ville made it more strict about
4 years ago, to catch issues related to tiling, and more complex
layouts, like the dcc tiling/retiling introduced by your modifier
patches. That's why I hope my alternative patch is a good solution for
atomic drivers while keeping the strictness for potential legacy
drivers.

-mario

>                 DRM_DEBUG_KMS("Page flip is not allowed to change frame buffer format.\n");
>                 ret = -EINVAL;
>                 goto out;
> --
> 2.29.2
>