Commit d14f0c20 authored by José Expósito's avatar José Expósito Committed by Simon Ser
Browse files

drm/plane: Make format_mod_supported truly optional 

The documentation for "drm_plane_funcs.format_mod_supported" reads:

  This *optional* hook is used for the DRM to determine if the given
  format/modifier combination is valid for the plane. This allows the
  DRM to generate the correct format bitmask (which formats apply to
  which modifier), and to validate modifiers at atomic_check time.

  *If not present*, then any modifier in the plane's modifier
  list is allowed with any of the plane's formats.

However, where the function is not present, an invalid IN_FORMATS blob
property with modifiers but no formats is exposed to user-space.

This breaks the latest Weston [1]. For testing purposes, I extracted the
affected code to a standalone program [2].

Make "create_in_format_blob" behave as documented.

[1] https://gitlab.freedesktop.org/wayland/weston/-/blob/9.0/libweston/backend-drm/kms.c#L431
[2] https://github.com/JoseExposito/drm-sandbox/blob/main/in_formats.c



Signed-off-by: default avatarJosé Expósito <jose.exposito89@gmail.com>
Reviewed-by: default avatarSimon Ser <contact@emersion.fr>
Signed-off-by: default avatarSimon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20211226112503.31771-2-jose.exposito89@gmail.com
parent b146e343

drivers/gpu/drm/drm_plane.c

+2 −7
Original line number Diff line number Diff line
@@ -202,17 +202,13 @@ static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane 


	memcpy(formats_ptr(blob_data), plane->format_types, formats_size);



	/* If we can't determine support, just bail */

	if (!plane->funcs->format_mod_supported)

		goto done;



	mod = modifiers_ptr(blob_data);

	for (i = 0; i < plane->modifier_count; i++) {

		for (j = 0; j < plane->format_count; j++) {

			if (plane->funcs->format_mod_supported(plane,

			if (!plane->funcs->format_mod_supported ||

			    plane->funcs->format_mod_supported(plane,

							       plane->format_types[j],

							       plane->modifiers[i])) {



				mod->formats |= 1ULL << j;

			}

		}
@@ -223,7 +219,6 @@ static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane 
		mod++;

	}



done:

	drm_object_attach_property(&plane->base, config->modifiers_property,

				   blob->base.id);