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, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index b1979e7bdc88..3053aab968f9 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -837,6 +837,7 @@ void drm_helper_mode_fill_fb_struct(struct drm_framebuffer *fb,
 	for (i = 0; i < 4; i++) {
 		fb->pitches[i] = mode_cmd->pitches[i];
 		fb->offsets[i] = mode_cmd->offsets[i];
+		fb->modifier[i] = mode_cmd->modifier[i];
 	}
 	drm_fb_get_bpp_depth(mode_cmd->pixel_format, &fb->depth,
 				    &fb->bits_per_pixel);