[PATCH weston v5 00/36] Head-based output configuration API a.k.a clone mode infrastructure

[Pekka Paalanen]

On Thu, 14 Dec 2017 10:11:32 -0500
Alex Deucher <alexdeucher at gmail.com> wrote:

> On Thu, Dec 14, 2017 at 6:40 AM, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> > From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> >
> > Hi all,
> >
> > this is v5 (to match the numbering of my public branches) of the libweston user
> > facing API and infrastructure for supporting shared-CRTC clone mode.
> >
> > Previous submission with rationale:
> > https://lists.freedesktop.org/archives/wayland-devel/2017-October/035604.html
> >
> > Design document:
> > https://phabricator.freedesktop.org/w/wayland/weston/atomic-output-config/
> >
> > The goal:
> > https://phabricator.freedesktop.org/T7727  
> 
> FWIW, at least with the DC modesetting code in amdgpu, we can
> synchronize multiple crtcs to the same timing when the monitors all
> support the same mode timing or with monitors that have different
> timings using variable length blanking periods on freesync capable
> monitors.

Hi Alex,

that's cool. How does userspace take advantage of that, how do you
configure KMS/atomic to make use of that? Is it supported through
legacy KMS (non-atomic) as well?

Does it involve things like the driver stealing an unused CRTC for each
additional clone?

The feature would fit perfectly under the "shared-CRTC clone mode" from
libweston API point of view, even though it's not actually a single
shared CRTC.


Thanks,
pq

> 
> 
> Alex
> 
> >
> > Changes in v5 compared to v3 are minor:
> > - "libweston: properly orphan wl_output resources" is new.
> > - Removal of wl_output global, when a head is detached from an enabled output.
> > - Print "Detected a monitor change" only for enabled heads.
> >
> > You can find this series in the branch:
> > https://gitlab.collabora.com/pq/weston/commits/clonemode-user-API-5
> >
> > I went through the same testing procedure as with v3, the previous submission.
> >
> >
> > However, the interesting bits are in the branch:
> > https://gitlab.collabora.com/pq/weston/commits/clonemode-4
> >
> > As new things compared to clonemode-user-API-2, that one contains:
> > - support for configuring clone mode in weston.ini
> > - main.c implementation to configure a clode using the new API
> > - desktop-shell enhancements to avoid redundant panel and background surfaces
> >   in clone mode
> > - hooking up custom data to weston_output via a new user-side destroy signal
> > - naming outputs freely
> > - DRM-backend support for shared-CRTC clone mode
> > - video mode list merging in the DRM-backend
> >
> > The shared-CRTC clone mode has been tested to work on an i.MX6 device.
> > Unfortunately it seems that PC hardware that would support it is becoming
> > scarce AFAIU.
> >
> > Most of the patches in clonemode-4 depend on the atomic modesetting series and
> > can therefore be submitted only after that one.
> >
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