Stereo 3D v3

Damien Lespiau damien.lespiau at
Sun Sep 8 08:03:52 PDT 2013

On Sun, Sep 08, 2013 at 03:46:43PM +0200, David Herrmann wrote:
> The series implements SET_CAP as a per _file_ capability set, not per
> master. I like it this way. Note that with SET_VERSION, we already
> have a per _master_ capability set. Compared to SET_CAP it only allows
> incremental capability changes, but that's fine I think.
> However, the problem with per-master capabilities (SET_VERSION) is
> that we currently have no way to control which master a
> graphics-server gets assigned to. If it's started in background, it
> will get the same master as the foreground compositor. Therefore, we
> don't want per-master client-capabilities. It's wrong and breaks
> existing setups (same as SET_VERSION, and everyone knows that). I also
> don't see a reason to bind capabilities to a master object.
> SET_CAP describes what the *calling client* understands and can work
> with. And this is logically bound to drm_file (as it represents a
> client). On the other hand, GET_CAP describes what the *device*
> understands and provides. This is obviously bound to a "drm_device". A
> "drm_master" object allows to split GET_CAP capabilities and resources
> across multiple logical master objects. But these resemble a
> drm_device much more than a drm_file.
> So no, this capability is not dropped with a change in master. It's
> independent of the active/bound master. It just describes what a
> client sees or not sees.

Right, that sums it up. Note that while I've made stereo_allowed a per
fd thing (which is what I wanted in that case, alter the reality viewed
by the process opening the file), SET_CAP itself it marked as master
only. This can be changed in the future to provide per-cap access
restrictions if needed.


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