Re: [PATCH] drm: check_pixel_format() should return true if no modifiers are passed for a supported pixel format

[Brian Starkey]

Hi Ayan,

On Fri, May 25, 2018 at 04:35:41PM +0100, Ayan Kumar Halder wrote:
> If a plane supports a pixel format and the framebuffer does not pass any
> modifiers, then drm_plane_check_pixel_format() should always return true
> for the given format regardless of whether the plane supports any
> modifiers or not.
>
> Signed-off-by: Ayan Kumar Halder <ayan.halder@xxxxxxx>
> ---
> drivers/gpu/drm/drm_plane.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 6d2a6e4..873c084 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -564,6 +564,9 @@ int drm_plane_check_pixel_format(struct drm_plane *plane,
> 	if (!plane->modifier_count)
> 		return 0;
>
> +	if (modifier == DRM_FORMAT_MOD_NONE)
> +		return 0;
> +

There can be drivers which have formats which are only supported when
a modifier is used - so I don't think this check is right to have in
the core.

Drivers need to check if they support the format with no modifier
(same as DRM_FORMAT_MOD_LINEAR) in their format_mod_supported()
callback.

Thanks,
-Brian

> 	for (i = 0; i < plane->modifier_count; i++) {
> 		if (modifier == plane->modifiers[i])
> 			break;
> --
> 2.7.4