Re: [PATCH v3 4/4] drm: require each CRTC to have a unique primary plane

On Fri, Dec 11, 2020 at 2:08 PM Simon Ser contact@emersion.fr wrote:

User-space expects to be able to pick a primary plane for each CRTC exposed by the driver. Make sure this assumption holds in drm_mode_config_validate.

Use the legacy drm_crtc.primary field to check this, because it's simpler and we require drivers to set it anyways. Accumulate a set of primary planes which are already used for a CRTC in a bitmask. Error out if a primary plane is re-used.

v2: new patch

v3:

• Use u64 instead of __u64 (Jani)
• Use `unsigned int` instead of `unsigned` (Jani)

Signed-off-by: Simon Ser contact@emersion.fr Cc: Daniel Vetter daniel@ffwll.ch Cc: Pekka Paalanen ppaalanen@gmail.com Cc: Jani Nikula jani.nikula@linux.intel.com

Yeah makes sense to also check this.

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

---

drivers/gpu/drm/drm_mode_config.c | 21 +++++++++++++++++++++ drivers/gpu/drm/drm_plane.c | 6 ++++++ 2 files changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c index fbe680035129..c5cf5624c106 100644 --- a/drivers/gpu/drm/drm_mode_config.c +++ b/drivers/gpu/drm/drm_mode_config.c @@ -626,6 +626,9 @@ void drm_mode_config_validate(struct drm_device *dev) { struct drm_encoder *encoder; struct drm_crtc *crtc;

•   struct drm_plane *plane;
  

•   u64 primary_with_crtc = 0, cursor_with_crtc = 0;
  

•   unsigned int num_primary = 0;
  
    if (!drm_core_check_feature(dev, DRIVER_MODESET))
            return;
  

@@ -647,12 +650,30 @@ void drm_mode_config_validate(struct drm_device *dev) "Bogus primary plane possible_crtcs: [PLANE:%d:%s] must be compatible with [CRTC:%d:%s]\n", crtc->primary->base.id, crtc->primary->name, crtc->base.id, crtc->name);

•                   WARN(primary_with_crtc & BIT(crtc->primary->index),
  

•                        "Primary plane [PLANE:%d:%s] used for two CRTCs",
  

•                        crtc->primary->base.id, crtc->primary->name);
  

•                   primary_with_crtc |= BIT(crtc->primary->index);
            }
            if (crtc->cursor) {
                    WARN(!(crtc->cursor->possible_crtcs & BIT(crtc->index)),
                         "Bogus cursor plane possible_crtcs: [PLANE:%d:%s] must be compatible with [CRTC:%d:%s]\n",
                         crtc->cursor->base.id, crtc->cursor->name,
                         crtc->base.id, crtc->name);
  

•                   WARN(cursor_with_crtc & BIT(crtc->cursor->index),
  

•                        "Primary plane [PLANE:%d:%s] used for two CRTCs",
  

•                        crtc->cursor->base.id, crtc->cursor->name);
  

•                   cursor_with_crtc |= BIT(crtc->cursor->index);
            }
    }
  

•   drm_for_each_plane(plane, dev) {
  

•           if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
  

•                   num_primary++;
  

•           }
  

•   }
  

•   WARN(num_primary != dev->mode_config.num_crtc,
  

•        "Must have as many primary planes as there are CRTCs, but have %u primary planes and %u CRTCs",
  

•        num_primary, dev->mode_config.num_crtc);
  

} diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index 49b0a8b9ac02..a1f4510efa83 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -54,6 +54,12 @@

• enum drm_plane_type). A plane can be compatible with multiple CRTCs, see
• &drm_plane.possible_crtcs.

• • Each CRTC must have a unique primary plane userspace can attach to enable
• • the CRTC. In other words, userspace must be able to attach a different
• • primary plane to each CRTC at the same time. Primary planes can still be
• • compatible with multiple CRTCs. There must be exactly as many primary planes
• • as there are CRTCs.
• • Legacy uAPI doesn't expose the primary and cursor planes directly. DRM core
  • relies on the driver to set the primary and optionally the cursor plane used
  • for legacy IOCTLs. This is done by calling drm_crtc_init_with_planes(). All

-- 2.29.2