The previous wording could be understood by user-space evelopers as "a primary/cursor plane is only compatible with a single CRTC" [1].
Reword the planes description to make it clear the DRM-internal drm_crtc.primary and drm_crtc.cursor planes are for legacy uAPI.
[1]: https://github.com/swaywm/wlroots/pull/2333#discussion_r456788057
Signed-off-by: Simon Ser contact@emersion.fr Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Cc: Pekka Paalanen ppaalanen@gmail.com --- drivers/gpu/drm/drm_crtc.c | 3 +++ drivers/gpu/drm/drm_plane.c | 16 +++++++++------- 2 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index 8d19d258547f..a6336c7154d6 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -256,6 +256,9 @@ struct dma_fence *drm_crtc_create_fence(struct drm_crtc *crtc) * planes). For really simple hardware which has only 1 plane look at * drm_simple_display_pipe_init() instead. * + * The @primary and @cursor planes are only relevant for legacy uAPI, see + * &drm_crtc.primary and &drm_crtc.cursor. + * * Returns: * Zero on success, error code on failure. */ diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index 385801dd21f9..5d33ca9f0032 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -49,14 +49,16 @@ * &struct drm_plane (possibly as part of a larger structure) and registers it * with a call to drm_universal_plane_init(). * - * Cursor and overlay planes are optional. All drivers should provide one - * primary plane per CRTC to avoid surprising userspace too much. See enum - * drm_plane_type for a more in-depth discussion of these special uapi-relevant - * plane types. Special planes are associated with their CRTC by calling - * drm_crtc_init_with_planes(). - * * The type of a plane is exposed in the immutable "type" enumeration property, - * which has one of the following values: "Overlay", "Primary", "Cursor". + * which has one of the following values: "Overlay", "Primary", "Cursor" (see + * enum drm_plane_type). A plane can be compatible with multiple CRTCs, see + * &drm_plane.possible_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 + * drivers should provide one primary plane per CRTC to avoid surprising legacy + * userspace too much. */
static unsigned int drm_num_planes(struct drm_device *dev)