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drm/plane: Make format_mod_supported truly optional

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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: José Expósito <jose.exposito89@gmail.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20211226112503.31771-2-jose.exposito89@gmail.com
This commit is contained in:
José Expósito 2021-12-26 12:24:58 +01:00 committed by Simon Ser
parent b146e343a9
commit d14f0c2053
1 changed files with 2 additions and 7 deletions
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9
drivers/gpu/drm/drm_plane.c
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@ -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);