Hi Matt,

On Tue, 8 Jul 2014 16:51:24 -0700
Matt Roper [off-list ref] wrote:

Hi Boris.

I haven't really looked at any of your driver in depth, but from a quick
glance it looks like you're registering a cursor drm_plane (i.e., making
use of the new universal plane infrastructure), but you're also
providing an implementation of the legacy cursor ioctls (cursor_set and
cursor_move).  There's some patches working their way through the
pipeline that should make this unnecessary and hopefully simplify your
life a bit:

        http://cgit.freedesktop.org/drm-intel/commit/?h=drm-intel-nightly&id=c394c2b08e247c32ef292b75fd8b34312465f8ae
        http://cgit.freedesktop.org/drm-intel/commit/?h=drm-intel-nightly&id=b36552b32aa9c69e83a3a20bda56379fb9e52435
        http://cgit.freedesktop.org/drm-intel/commit/?h=drm-intel-nightly&id=161d0dc1dccb17ff7a38f462c7c0d4ef8bcc5662
        http://cgit.freedesktop.org/drm-intel/commit/?h=drm-intel-nightly&id=fc1d3e44ef7c1db93384150fdbf8948dcf949f15

The third patch there is the one that's really important for your work.
When a driver provides a cursor plane via the universal plane interface,
cursor_set and cursor_move are automatically implemented for you by
drm_mode_cursor_universal() in drivers/gpu/drm/drm_crtc.c and your
legacy handlers will never get called.  drm_mode_cursor_universal() will
take care of wrapping the bo's into a drm_framebuffer for you.

When I added the universal cursor stuff, I wanted to make sure that as
soon as a driver starts supporting universal planes it can stop
supporting the legacy ioctls directly; otherwise handling refcounting
when userspace switches back and forth between calling legacy ioctl's
and calling setplane() on a cursor plane would be a nightmare.

I think those patches are only available in drm-intel-nightly at the
moment and haven't moved on to drm-next and such yet, since i915 is the
only driver that currently has patches to make use of cursors via the
univeral plane interface (probably landing for kernel 3.17).

That's great news. I knew there were some work in progress on this
topic, but didn't know it was planned for 3.17. 

I'll move to this solution.

Thanks,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com