I have no idea about the exact rules, but this angered Dave's 32bit
rhel gcc.
Reported-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

Starting with SKL display engine can scan out Y, and newly introduced Yf
tiling formats so add the latter to the frame buffer modifier space.

v2: Definitions moved to drm_fourcc.h.
v3: Try to document the format better.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

To be used from the new addfb2 extension.

v2:
- Drop Intel-specific untiled modfier.
- Move to drm_fourcc.h.
- Document layouts a bit and denote them as platform-specific and not
  useable for cross-driver sharing.
- Add Y-tiling for completeness.
- Drop special docstring markers to avoid confusing kerneldoc.

v3: Give Y-tiling a unique idea, noticed by Tvrtko.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> (v1)
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

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: NRob Clark <robdclark@gmail.com>
Reviewed-by: NDaniel Stone <daniels@collabora.com>
Acked-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

So this has been merged originally in

commit 83052d4d
Author: Seung-Woo Kim <sw0312.kim@samsung.com>
Date:   Thu Dec 15 15:40:55 2011 +0900

    drm: Add multi buffer plane pixel formats

which hasn't seen a lot of review really. The problem is that it's not
a real pixel format, but just a different way to lay out NV12 pixels
in macroblocks, i.e. a tiling format.

The new way of doing this is with the soon-to-be-merged fb modifiers.

This was brough up in some long irc discussion around the entire
topic, as an example of where things have gone wrong. Luckily we can
correct the mistake:
- The kms side support for NV12MT is all dead code because
  format_check in drm_crtc.c never accepted NV12MT.
- The gem side for the gsc support doesn't look better: The code
  forgets to set the pixel format and makes a big mess with the tiling
  mode bits, inadvertedly setting them all.

Conclusion: This never really worked (at least not in upstream) and
hence we can safely correct our mistake here.

Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Rob Clark <robclark@freedesktop.org>
Cc: Daniel Stone <daniel@fooishbar.org>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NRob Clark <robclark@freedesktop.org>
Reviewed-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>
Acked-by: NJoonyoung Shim <jy0922.shim@samsung.com>
Acked-by: NSeung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NMichael Kerrisk <mtk.manpages@gmail.com>
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NDave Jones <davej@redhat.com>

Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

The NV12M/YUV420M formats are identical to the NV12/YUV420 formats.
So just remove these duplicated format names.

This might look like breaking the ABI, but the code has never actually
accepted these formats, so nothing can be using them.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

Multi buffer plane pixel format has seperated memory spaces for each
plane. For example, NV12M has Y plane and CbCr plane and these are in
non contiguous memory region. Compared with NV12, NV12M's memory shape
is like following.
NV12  : ______(Y)(CbCr)_______
NV12M : __(Y)_ ..... _(CbCr)__
Signed-off-by: NSeung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

drm_fourcc.h can be included from user space so use the appropriate types.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Name the formats as DRM_FORMAT_X instead of DRM_FOURCC_X. Use consistent
names, especially for the RGB formats. Component order and byte order are
now strictly specified for each format.

The RGB format naming follows a convention where the components names
and sizes are listed from left to right, matching the order within a
single pixel from most significant bit to least significant bit.

The YUV format names vary more. For the 4:2:2 packed formats and 2
plane formats use the fourcc. For the three plane formats the
name includes the plane order and subsampling information using the
standard subsampling notation. Some of those also happen to match
the official fourcc definition.

The fourccs for for all the RGB formats and some of the YUV formats
I invented myself. The idea was that looking at just the fourcc you
get some idea what the format is about without having to decode it
using some external reference.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

To properly support the various plane formats supported by different
hardware, the kernel must know the pixel format of a framebuffer object.
So add a new ioctl taking a format argument corresponding to a fourcc
name from the new drm_fourcc.h header file.  Implement the fb creation
hooks in terms of the new mode_fb_cmd2 using helpers where the old
bpp/depth values are needed.

v2: create DRM specific fourcc header file for sharing with libdrm etc
v3: fix rebase failure and use DRM fourcc codes in intel_display.c and
    update commit message
v4: make fb_cmd2 handle field into an array for multi-object formats
    pull in Ville's fix for the memcpy in drm_plane_init
    apply Ville's cleanup to zero out fb_cmd2 arg in drm_mode_addfb
v5: add 'flags' field for interlaced support (from Ville)
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: NAlan Cox <alan@lxorguk.ukuu.org.uk>
Reviewed-by: NRob Clark <rob.clark@linaro.org>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>