[PATCH] drm: rework SET_MASTER and DROP_MASTER perm handling

[Emil Velikov]

On Mon, 9 Mar 2020 at 13:13, Emil Velikov <emil.l.velikov at gmail.com> wrote:

> > OTOH, if applications exist that rely on drop-master failing in this
> > specific case, making drop-master succeed would break them. That might
> > include a buggy set-master path that was written, but does not actually
> > work because it was never tested since drop-master never worked.
> >
> > So I do not fully buy this argument yet, but I also cannot name any
> > explicit examples that would break.
> >
> >
> I've ventured for a while in the X (Xorg + drivers), Weston,
> sway/wlroots and Mesa's codebase.
> There were zero instances of such misuse. If other projects come to
> mind - I'll gladly take a look.
>
Just checked a few other projects with git pickaxe* - zero cases of
mentioned (mis)use. In particular:
 - qtbase + qtwayland + gtk
Never used the wrappers or ioctls

 - kwin + plasmashell
Never used the wrappers or ioctls

 - mutter + gnome-shell
Briefly used the wrappers. Sane codepath

 - igt-gpu-tools ... just because I had it open
Sane use both wrappers and ioctls.

Any other projects I should check?

-Emil

* Both via libdrm and directly calling the ioctl
git log -p -S DROP_MASTER
git log -p -S drmDropMaster