On Tue, 21 Dec 2021 at 13:13, José Expósito jose.exposito89@gmail.com wrote:
Adding format modifiers without implementing the function "drm_plane_funcs.format_mod_supported" exposes an invalid IN_FORMATS blob with modifiers but no formats to user-space.
I think the fix should be applied to the generic code. The docs at drm_plane.h clearly state that this callback is optional:
* 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 valdiate 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.
So, one should fix the core code in create_in_format_blob() to include all combinations.
This breaks the latest Weston [1]. For testing purposes, I extracted the affected code to a standalone program [2].
Make clear in the IN_FORMATS documentation that implementing "format_mod_supported" is mandatory.
format_mod_supported() being optional or mandatory should be documented in the format_mod_supported() docs, not in the IN_FORMAT docs.
[1] https://gitlab.freedesktop.org/wayland/weston/-/blob/9.0/libweston/backend-d... [2] https://github.com/JoseExposito/drm-sandbox/blob/main/in_formats.c
Signed-off-by: José Expósito jose.exposito89@gmail.com
drivers/gpu/drm/drm_plane.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index 82afb854141b..347571f8909a 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -126,8 +126,11 @@
- IN_FORMATS:
Blob property which contains the set of buffer format and modifierpairs supported by this plane. The blob is a struct
drm_format_modifier_blob. Without this property the plane doesn't
support buffers with modifiers. Userspace cannot change this property.
drm_format_modifier_blob and the drm_plane_funcs.format_mod_supported
function must be implemented by the driver to determine if the given
format/modifier combination is valid for the plane. Without this property
the plane doesn't support buffers with modifiers. Userspace cannot change
this property.Note that userspace can check the &DRM_CAP_ADDFB2_MODIFIERS drivercapability for general modifier support. If this flag is set then every-- 2.25.1