diff mbox series

drm/modifiers: Enforce consistency between the cap an IN_FORMATS

Message ID 20210414090815.453744-1-daniel.vetter@ffwll.ch (mailing list archive)
State New
Headers show
Series drm/modifiers: Enforce consistency between the cap an IN_FORMATS | expand

Commit Message

Daniel Vetter April 14, 2021, 9:08 a.m. UTC
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.

Acked-by: Maxime Ripard <maxime@cerno.tech>
Cc: Simon Ser <contact@emersion.fr>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
---
 drivers/gpu/drm/drm_plane.c   | 18 +++++++++++++++++-
 include/drm/drm_mode_config.h |  2 ++
 2 files changed, 19 insertions(+), 1 deletion(-)

Comments

Pekka Paalanen April 14, 2021, 12:14 p.m. UTC | #1
On Wed, 14 Apr 2021 11:08:15 +0200
Daniel Vetter <daniel.vetter@ffwll.ch> 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.
> 
> Acked-by: Maxime Ripard <maxime@cerno.tech>
> Cc: Simon Ser <contact@emersion.fr>
> Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
> Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> ---
>  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..20c7a1665414 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) {
> +		WARN_ON(!config->allow_fb_modifiers &&
> +			!list_empty(&config->plane_list));
>  		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 +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:
>  	 *

Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>


Thanks,
pq
Simon Ser April 16, 2021, 6:30 a.m. UTC | #2
Reviewed-by: Simon Ser <contact@emersion.fr>
diff mbox series

Patch

diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 0dd43882fe7c..20c7a1665414 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) {
+		WARN_ON(!config->allow_fb_modifiers &&
+			!list_empty(&config->plane_list));
 		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 +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:
 	 *