On Tue, Oct 25, 2011 at 11:43:09AM -0500, Rob Clark wrote:
> On Tue, Oct 25, 2011 at 9:09 AM, Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> wrote:
> > diff --git a/include/drm/drm_mode.h b/include/drm/drm_mode.h
> > index 34a0d22..dafe8df 100644
> > --- a/include/drm/drm_mode.h
> > +++ b/include/drm/drm_mode.h
> > @@ -272,8 +272,9 @@ struct drm_mode_fb_cmd2 {
> > __u32 bpp;
> > __u32 depth;
> > __u32 pixel_format; /* fourcc code from videodev2.h */
> > - /* driver specific handle */
> > - __u32 handle;
> > + __u32 handle_count;
> > + /* driver specific buffer object handle array */
> > + __u64 handles;
> > };
>
>
> Ok, after a bit of discussion with Jakob on IRC, this is what we arrived at:
>
> 1) It would be nice to have the option for multi-planar formats to be
> able to use one single buffer object, or one buffer object per plane.
> In the case of one buffer per plane, the order is dictated by the
> fourcc.
>
> 2) We do need per-plane stride for some formats, in particular I420
> which is a bit ambiguous otherwise (ie. is the stride of the U and V
> planes half the stride as the Y plane, or the same?)
>
> 3) Maybe we need per-plane offsets, but I think this case could be
> handled by just using one bo per plane, so left it out
>
> 4) bpp/depth are redundant w/ the pixel_format. Just in case, as a
> future placeholder, and inspired by 'struct v4l2_pix_format', add a
> priv field. Although making the field big enough to hold a pointer if
> absolutely really needed.
>
> struct drm_mode_fb_cmd2 {
> __u32 fb_id;
> __u32 width, height;
> __u32 pixel_format; /* fourcc code from videodev2.h */
> __u64 priv; /* private data, depends on pixelformat */
>
> /* in case of planar formats, either one buffer object,
> * or one buffer object per plane, is allowed. In the
> * case per-plane bo's, the order is dictated by the
> * fourcc.. ie. NV12 (http://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 first buffer and UV as
> * second buffer. In the case that only a single bo
> * is used then buffer[1].handle should be zero. (But
> * a plane specific pitch could still be specified.)
> */
> struct {
> __u32 pitch;
> /* driver specific handle */
> __u32 handle;
Why not just add a
__u32 offset;
__u32 rsvd;
and call it a day. This thing is pretty big already, so that bloat doesn't
matter that much. Maybe spec that buffer[0].offset must be zero. With that
you can also do I420 with the following layout
+-------+
|YYYYYYY|
|YYYYYYY|
|YYYYYYY|
|YYYYYYY|
+---+---+
|UUU|VVV|
|UUU|VVV|
+---+---+
i.e. stride_U == stride_V, with their lines meshed into one line.
-Daniel
> } buffer[16];
> };
>
>
> BR,
> -R
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--
Daniel Vetter
Mail: daniel@xxxxxxxx
Mobile: +41 (0)79 365 57 48
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