Commit a3574119 authored by Simon Ser's avatar Simon Ser

drm: document struct drm_mode_fb_cmd2

Follow-up for the DRM_IOCTL_MODE_GETFB2 docs.

v2: (Daniel Stone)
- Replace fourcc.org with drm_fourcc.h because this is the
  authoritative source and the website may have mismatches.
- Drop assumption that offsets will generally be 0.
- Mention that unused entries must be zero'ed out.

v3: (Pekka)
- Mention that a handle can be re-used
- Add unit for pitches/offsets
Signed-off-by: default avatarSimon Ser <contact@emersion.fr>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: default avatarPekka Paalanen <pekka.paalanen@collabora.com>
Cc: Daniel Stone <daniels@collabora.com>
Reviewed-by: default avatarDaniel Stone <daniels@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220203133753.261507-1-contact@emersion.fr
parent eea89dff
......@@ -663,41 +663,73 @@ struct drm_mode_fb_cmd {
#define DRM_MODE_FB_INTERLACED (1<<0) /* for interlaced framebuffers */
#define DRM_MODE_FB_MODIFIERS (1<<1) /* enables ->modifer[] */
/**
* struct drm_mode_fb_cmd2 - Frame-buffer metadata.
*
* This struct holds frame-buffer metadata. There are two ways to use it:
*
* - User-space can fill this struct and perform a &DRM_IOCTL_MODE_ADDFB2
* ioctl to register a new frame-buffer. The new frame-buffer object ID will
* be set by the kernel in @fb_id.
* - User-space can set @fb_id and perform a &DRM_IOCTL_MODE_GETFB2 ioctl to
* fetch metadata about an existing frame-buffer.
*
* In case of planar formats, this struct allows up to 4 buffer objects with
* offsets and pitches per plane. The pitch and offset order is dictated by the
* format FourCC as defined by ``drm_fourcc.h``, e.g. NV12 is described as:
*
* YUV 4:2:0 image with a plane of 8 bit Y samples followed by an
* interleaved U/V plane containing 8 bit 2x2 subsampled colour difference
* samples.
*
* So it would consist of a Y plane at ``offsets[0]`` and a UV plane at
* ``offsets[1]``.
*
* To accommodate tiled, compressed, etc formats, a modifier can be specified.
* For more information see the "Format Modifiers" section. Note that even
* though it looks like we have a modifier per-plane, we in fact do not. The
* modifier for each plane must be identical. Thus all combinations of
* different data layouts for multi-plane formats must be enumerated as
* separate modifiers.
*
* All of the entries in @handles, @pitches, @offsets and @modifier must be
* zero when unused. Warning, for @offsets and @modifier zero can't be used to
* figure out whether the entry is used or not since it's a valid value (a zero
* offset is common, and a zero modifier is &DRM_FORMAT_MOD_LINEAR).
*/
struct drm_mode_fb_cmd2 {
/** @fb_id: Object ID of the frame-buffer. */
__u32 fb_id;
/** @width: Width of the frame-buffer. */
__u32 width;
/** @height: Height of the frame-buffer. */
__u32 height;
__u32 pixel_format; /* fourcc code from drm_fourcc.h */
__u32 flags; /* see above flags */
/**
* @pixel_format: FourCC format code, see ``DRM_FORMAT_*`` constants in
* ``drm_fourcc.h``.
*/
__u32 pixel_format;
/**
* @flags: Frame-buffer flags (see &DRM_MODE_FB_INTERLACED and
* &DRM_MODE_FB_MODIFIERS).
*/
__u32 flags;
/*
* In case of planar formats, this ioctl allows up to 4
* buffer objects with offsets and pitches per plane.
* The pitch and offset order is dictated by the fourcc,
* e.g. NV12 (https://fourcc.org/yuv.php#NV12) is described as:
*
* YUV 4:2:0 image with a plane of 8 bit Y samples
* followed by an interleaved U/V plane containing
* 8 bit 2x2 subsampled colour difference samples.
*
* So it would consist of Y as offsets[0] and UV as
* offsets[1]. Note that offsets[0] will generally
* be 0 (but this is not required).
*
* To accommodate tiled, compressed, etc formats, a
* modifier can be specified. The default value of zero
* indicates "native" format as specified by the fourcc.
* Vendor specific modifier token. Note that even though
* it looks like we have a modifier per-plane, we in fact
* do not. The modifier for each plane must be identical.
* Thus all combinations of different data layouts for
* multi plane formats must be enumerated as separate
* modifiers.
/**
* @handles: GEM buffer handle, one per plane. Set to 0 if the plane is
* unused. The same handle can be used for multiple planes.
*/
__u32 handles[4];
__u32 pitches[4]; /* pitch for each plane */
__u32 offsets[4]; /* offset of each plane */
__u64 modifier[4]; /* ie, tiling, compress */
/** @pitches: Pitch (aka. stride) in bytes, one per plane. */
__u32 pitches[4];
/** @offsets: Offset into the buffer in bytes, one per plane. */
__u32 offsets[4];
/**
* @modifier: Format modifier, one per plane. See ``DRM_FORMAT_MOD_*``
* constants in ``drm_fourcc.h``. All planes must use the same
* modifier. Ignored unless &DRM_MODE_FB_MODIFIERS is set in @flags.
*/
__u64 modifier[4];
};
#define DRM_MODE_FB_DIRTY_ANNOTATE_COPY 0x01
......
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