Weston default pixel format

[Daniel Stone]

Hi Santiago,

On Fri, 3 Aug 2018 at 09:28, Santiago Otero <sotero at gsertel.com> wrote:
> El 03/08/18 a las 09:35, Pekka Paalanen escribió:
>> No, you cannot use another KMS application at the same time as Weston
>> is active. The kernel DRM core will forbid access (denies DRM Master
>> status) if there is already something using KMS, so at any time you can
>> only run either Weston or some other DRM KMS app.
>>
>> The fact that you think it is possible suggests that you are using a
>> deliberately broken downstream kernel. A normal upstream kernel would
>> deny this.
>
> I think there's no need to get DRM Master if you only want to use another different  plane for drawing (/dev/dri/controlD64). I've got it working this way.

Control nodes have been removed from upstream kernels a couple of years ago:
https://cgit.freedesktop.org/drm/drm-tip/commit/?id=8a357d10043c75e980e7fcdb60d2b913491564af

>From the commit message, it sounds like your downstream kernel tree
has some changes to allow control nodes to be used in this way, since
they did not work out of the box. It will also not work with modern
atomic drivers anymore.

>> My recommendation instead is to rearchitect your software stack so that
>> Weston will be the only KMS app in the system, and video players push
>> their content via Wayland through Weston, using e.g. the Wayland dmabuf
>> extension and Weston's support for overlays (and underlays, if someone
>> implements them).
>
> I've tried to make it work with Wayland dmabuf with little success. The performance was bad, there was tearing and it didn't work for HDR video due to some KMS/DRM properties that I need to set. Using patched Weston and my player with KMS, now it's working right.

We've had good success with this in the past: the performance has been
completely fine, and tearing is just a result of missing
synchronisation, which at a guess could be improper handling of buffer
release events. GStreamer's waylandsink is a good example of how to
correctly use the interface if that helps.

Colour management is not yet supported in Weston, but a topic we are working on.

Cheers,
Daniel