On Tue, 13 Apr 2021 11:49:03 +0200
Daniel Vetter <daniel.vetter@xxxxxxxx> wrote:
> It's very confusing for userspace to have to deal with inconsistencies
> here, and some drivers screwed this up a bit. Most just ommitted the
> format list when they meant to say that only linear modifier is
> allowed, but some also meant that only implied modifiers are
> acceptable (because actually none of the planes registered supported
> modifiers).
>
> Now that this is all done consistently across all drivers, document
> the rules and enforce it in the drm core.
>
> Cc: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: Maxime Ripard <mripard@xxxxxxxxxx>
> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> ---
> drivers/gpu/drm/drm_plane.c | 16 +++++++++++++++-
> include/drm/drm_mode_config.h | 2 ++
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 0dd43882fe7c..16a7e3e57f7f 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -128,6 +128,11 @@
> * pairs 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.
> + *
> + * Note that userspace can check the DRM_CAP_ADDFB2_MODIFIERS driver
> + * capability for general modifier support. If this flag is set then every
> + * plane will have the IN_FORMATS property, even when it only supports
> + * DRM_FORMAT_MOD_LINEAR.
Ooh, that's even better. But isn't that changing the meaning of the
cap? Isn't the cap older than IN_FORMATS?
What about the opposite? Is it allowed to have even a single IN_FORMATS
if you don't have the cap?
> */
>
> static unsigned int drm_num_planes(struct drm_device *dev)
> @@ -277,8 +282,14 @@ static int __drm_universal_plane_init(struct drm_device *dev,
> format_modifier_count++;
> }
>
> - if (format_modifier_count)
> + /* autoset the cap and check for consistency across all planes */
> + if (format_modifier_count) {
> + WARN_ON(!config->allow_fb_modifiers &&
> + !list_empty(&config->plane_list));
What does this mean?
> config->allow_fb_modifiers = true;
> + } else {
> + WARN_ON(config->allow_fb_modifiers);
> + }
>
> plane->modifier_count = format_modifier_count;
> plane->modifiers = kmalloc_array(format_modifier_count,
> @@ -360,6 +371,9 @@ static int __drm_universal_plane_init(struct drm_device *dev,
> * drm_universal_plane_init() to let the DRM managed resource infrastructure
> * take care of cleanup and deallocation.
> *
> + * Drivers supporting modifiers must set @format_modifiers on all their planes,
> + * even those that only support DRM_FORMAT_MOD_LINEAR.
Good.
> + *
> * Returns:
> * Zero on success, error code on failure.
> */
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index ab424ddd7665..1ddf7783fdf7 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -909,6 +909,8 @@ struct drm_mode_config {
> * @allow_fb_modifiers:
> *
> * Whether the driver supports fb modifiers in the ADDFB2.1 ioctl call.
> + * Note that drivers should not set this directly, it is automatically
> + * set in drm_universal_plane_init().
> *
> * IMPORTANT:
> *
Thanks,
pq
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