It's duplicating (without using some of the helpers) drm_gem_mmap with
the addition that it can redirect to drm-buf mmap support. But prime
import/export was dropped in

commit 990ed2720717173bbdea4cfb2bad37cc7aa91495
Author: Rob Clark <robdclark@gmail.com>
Date:   Thu May 21 11:58:30 2015 -0400

    drm/vgem: drop DRIVER_PRIME (v2)

for now, so this is dead code. And since I want to rework the locking
for drm_gem_mmap it seems simpler to de-dupe this code for now and
then start over with the reworked one again, if we want to resurrect
this all indeed.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://mid.gmane.org/1444894601-5200-8-git-send-email-daniel.vetter@ffwll.ch
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

With two exceptions (drm/qxl and drm/radeon) all vm_operations_struct
structs should be constant.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Since there's only one global instance ever we don't need to have
anything fancy. Stops a WARNING in the get_unique ioctl that the
unique name isn't set.

Cc: <stable@vger.kernel.org> # 4.1+ only
Reportedy-and-tested-by: Fabio Coatti <fabio.coatti@gmail.com>
Cc: Fabio Coatti <fabio.coatti@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

For actual sharing of buffers with other drivers (ie. actual hardware)
we'll need to pimp things out a bit better to deal w/ caching, multiple
memory domains, etc.  See thread:

  http://lists.freedesktop.org/archives/dri-devel/2015-May/083160.html

But for the llvmpipe use-case this isn't a problem.  Nor do we really
need prime/dri3 (dri2 is sufficient).  So until the other issues are
sorted lets remove DRIVER_PRIME.

v2: also drop the dead code

[airlied:
 Okay I'm convinced this API could have a lot of use cases
 that are really really bad, yes the upload use case is valid
 however that isn't the only use case enabled, and if we allow
 all the other use cases, people will start to (ab)use them,
 and then they'll be ABI and my life will get worse, so disable
 PRIME for now]

Acked-by: Thomas Hellstrom <thellstrom@vmware.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

This patch implements the virtual GEM driver with PRIME sharing which
allows vgem to import a gem object from other drivers for the purpose
of mmap-ing them to userspace. The mmap is done using the mmap
operation exported by other drivers.

v2: remove platform_device and do not attach to dma bufs
v3: use drm helpers for get/put pages
v4: correct dumb create pitch

Reviewed-by: Rob Clark <robdclark@gmail.com> (v3)
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org> (v3)
Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Zach Reizner <zachr@google.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>