On 17/09/19 7:38 pm, zou lan wrote:
Hi Daniel & all
I find the function drm_output_prepare_overlay_view() only use the plane
type of WDRM_PLANE_TYPE_OVERLAY. it could be a waste for some planes of
type WDRM_PLANE_TYPE_PRIMARY if the universal planes is enable.
For example, the kernel define 6 crtcs, and each crtc will have one
primary type plane, but not all of the crtcs are used by weston_output.
Some crtcs may never used, if we reserve all the primary type planes as
scanout plane, that could waste some of them.
Could the open source drm backend modify the logic of judge the overlay
plane? let the primary plane equal to overlay plane or judge in
drm_output_prepare_overlay_view(), if the plane is not used by outputs,
it could be used by overlay?
Thank you!
Best regards
Nancy
Hi,
As far as I'm aware, the kernel never advertises more than one primary
plane per CRTC and they're never possible to be used with multiple
CRTCs:
https://www.kernel.org/doc/html/latest/gpu/drm-kms.html#plane-abstraction
>All drivers should provide one primary plane per CRTC to avoid
surprising userspace too much
Perhaps that restriction is not as strict as I interpret it to be, but
I'm not aware of anything which does not have a one-to-one relationship
between primary planes and CRTCs.
Scott
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