Multiple HW plane enable BKM in open source Weston

Marius Vlad marius.vlad at
Mon Dec 30 09:29:02 UTC 2019


Yes, overlays are supported in weston but do note that this mailing list
is also about other compositors and the protocol itself.

Clients do not specify where to "place" the surfaces, the compositor
back-end is the only one who can make those decisions based on what HW
is capable of, what is currently in use, and what other surfaces are
currently being displayed. The back-end, in weston, got a new face lift,
and exposes a little bit better the conditions in which a view can make
it to a HW plane: is a (HW) plane available, is the pixel format
suitable, etc. If you feel  adventurous that should be place to learn more.

Together with this face lift weston can now place an AR24 type of pixel
buffer on the overlay plane, so if HW capable of using that pixel format
should be able to place the view into an overlay plane. I'm mentioning
this because `weston-simple-egl` will default to that when started, and
a fairly recent i915 driver should have an overlay supporting that.

We have in weston debug scopes capable of displaying large amounts of
debug information. Start weston with with `--debug`  and use the client
`weston-debug` with `-a` to list all current debug scopes. `drm-backend'
is the one useful in this case. It will display which views made to it a
HW plane, or why was the reasons for not doing so. Should be able to
correlate a bit this information with decision tree currently done in

Hope this helps.

On 12/30/19 4:05 AM, Tang, Jun wrote:
> Hi Wayland Experts,
> I checked the open source version of Weston code, seems there is atomic mode setting API to add new plane properties. I believe overlay HW plane should be supported by Weston. But as a newbie for Wayland. Still not sure how application can put their surface on specified HW plane. Could you please share me some BKM on Wayland client side? Any quick ideas would be appreciated!
> -James
> _______________________________________________
> wayland-devel mailing list
> wayland-devel at

Marius Vlad

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