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.
Signed-off-by: Simon Ser contact@emersion.fr Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Cc: Pekka Paalanen pekka.paalanen@collabora.com Cc: Daniel Stone daniels@collabora.com --- include/uapi/drm/drm_mode.h | 88 +++++++++++++++++++++++++------------ 1 file changed, 60 insertions(+), 28 deletions(-)
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h index e1e351682872..a345404dd315 100644 --- a/include/uapi/drm/drm_mode.h +++ b/include/uapi/drm/drm_mode.h @@ -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. */ __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), one per plane. */ + __u32 pitches[4]; + /** @offsets: Offset into the buffer, 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