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@xxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
Cc: Daniel Stone <daniels@xxxxxxxxxxxxx>
---
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
--
2.35.1
