drm: add support for tiled/compressed/etc modifier in addfb2

In DRM/KMS we are lacking a good way to deal with tiled/compressed
formats.  Especially in the case of dmabuf/prime buffer sharing, where
we cannot always rely on under-the-hood flags passed to driver specific
gem-create ioctl to pass around these extra flags.

The proposal is to add a per-plane format modifier.  This allows to, if
necessary, use different tiling patters for sub-sampled planes, etc.
The format modifiers are added at the end of the ioctl struct, so for
legacy userspace it will be zero padded.

v1: original
v1.5: increase modifier to 64b

v2: Incorporate review comments from the big thread, plus a few more.

- Add a getcap so that userspace doesn't have to jump through hoops.
- Allow modifiers only when a flag is set. That way drivers know when
  they're dealing with old userspace and need to fish out e.g. tiling
  from other information.
- After rolling out checks for ->modifier to all drivers I've decided
  that this is way too fragile and needs an explicit opt-in flag. So
  do that instead.
- Add a define (just for documentation really) for the "NONE"
  modifier. Imo we don't need to add mask #defines since drivers
  really should only do exact matches against values defined with
  fourcc_mod_code.
- Drop the Samsung tiling modifier on Rob's request since he's not yet
  sure whether that one is accurate.

v3:
- Also add a new ->modifier[] array to struct drm_framebuffer and fill
  it in drm_helper_mode_fill_fb_struct. Requested by Tvrkto Uruslin.
- Remove TODO in comment and add code comment that modifiers should be
  properly documented, requested by Rob.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Stone <daniel@fooishbar.org>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Michel Dänzer <michel@daenzer.net>
Signed-off-by: Rob Clark <robdclark@gmail.com> (v1.5)
Reviewed-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 0ebd9286b332..cee54c45eba9 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -202,6 +202,7 @@ struct drm_framebuffer {
         const struct drm_framebuffer_funcs *funcs;
         unsigned int pitches[4];
         unsigned int offsets[4];
+        uint64_t modifier[4];
         unsigned int width;
         unsigned int height;
         /* depth can be 15 or 16 */
@@ -1152,6 +1153,9 @@ struct drm_mode_config {
         /* whether async page flip is supported or not */
         bool async_page_flip;
 
+        /* whether the driver supports fb modifiers */
+        bool allow_fb_modifiers;
+
         /* cursor size */
         uint32_t cursor_width, cursor_height;
 };