On Thu, May 06, 2021 at 03:23:43PM +0200, Daniel Vetter 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.
>
> v2:
> - Make the capability a link (Simon)
> - Note that all is lost before 5.1.
>
> v3:
> - Use drm_WARN_ON (Lyude)
>
> Acked-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
> Reviewed-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
> Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
> Acked-by: Maxime Ripard <maxime@xxxxxxxxxx>
> Cc: Simon Ser <contact@xxxxxxxxxxx>
> Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> 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>
Pushed to drm-misc-next after another round of intel-gfx CI testing.
-Daniel
> ---
> drivers/gpu/drm/drm_plane.c | 18 +++++++++++++++++-
> include/drm/drm_mode_config.h | 2 ++
> 2 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 0dd43882fe7c..b373958ecb30 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -128,6 +128,13 @@
> * 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. Before linux kernel release v5.1 there have been
> + * various bugs in this area with inconsistencies between the capability
> + * flag and per-plane properties.
> */
>
> static unsigned int drm_num_planes(struct drm_device *dev)
> @@ -277,8 +284,14 @@ 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) {
> + drm_WARN_ON(dev, !config->allow_fb_modifiers &&
> + !list_empty(&config->plane_list));
> config->allow_fb_modifiers = true;
> + } else {
> + drm_WARN_ON(dev, config->allow_fb_modifiers);
> + }
>
> plane->modifier_count = format_modifier_count;
> plane->modifiers = kmalloc_array(format_modifier_count,
> @@ -360,6 +373,9 @@ 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.
> + *
> * 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:
> *
> --
> 2.31.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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