[PATCH 1/3] drm: change DROP_MASTER permissions to allow DRM_MASTER

[Emil Velikov]

On Wed, 19 Dec 2018 at 20:36, Daniel Vetter <daniel at ffwll.ch> wrote:
>
> On Wed, Dec 19, 2018 at 07:22:45PM +0000, Emil Velikov wrote:
> > From: Emil Velikov <emil.velikov at collabora.com>
> >
> > Currently only DRM_ROOT_ONLY is allowed to call the ioctl.
> >
> > Change that to DRM_MASTER, which means that only a process that is the
> > current DRM master can drop it. Which makes sense, the process should
> > be able to opt-out without any specific requirements.
> >
> > Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
>
> I guess this makes sense, but then you already need someone else to do the
> setmaster for you if you want to run as non-root and be able to switch
> between compositors. So no idea where this will be useful.
>
X, Weston and the Gnome/KDE wayland compositors use logind for managing that.
Some have codepaths to manage drm{Set,Drop}Master manually, although
they don't seems to bother adjusting privileges, I'd imagine due to VT
switching.

If ones has CONFIG_VT=n system, then it should be a matter of once-off
drmSetMaster + lower priv.

> Either way: New uapi -> needs the userspace patches to exist.

Slightly confused - apps already use the uapi, what do you mean with
"new uapi" here?
I'm OK with adding an IGT, although beyond that I'm not sure what
other userspace patches I could provide.

Thanks
Emil