Re: [PATCH libdrm] libdrm: update drm/drm_fourcc.h from kernel to add multi plane formats

Hello,

On 04/06/2012 11:22 AM, Kyungmin Park wrote:

• V4L2 develper

Sylwester, please give your opinions? How to handle it at v4l2 side.

Thank you, Kyungmin Park

On Apr 6, 2012 12:44 AM, "Ville Syrjälä" <syrjala@sci.fi mailto:syrjala@sci.fi> wrote:

On Fri, Apr 06, 2012 at 03:05:36PM +0900, Inki Dae wrote:
> Hi Ville,
>
> > -----Original Message-----
> > From: Ville Syrjälä [mailto:ville.syrjala@linux.intel.com
<mailto:ville.syrjala@linux.intel.com>]
> > Sent: Friday, April 06, 2012 3:14 AM
> > To: airlied@redhat.com <mailto:airlied@redhat.com>
> > Cc: inki.dae@samsung.com <mailto:inki.dae@samsung.com>;
kyungmin.park@samsung.com <mailto:kyungmin.park@samsung.com>; dri-
> > devel@lists.freedesktop.org <mailto:devel@lists.freedesktop.org>;
Seung-Woo Kim
> > Subject: Re: [PATCH libdrm] libdrm: update drm/drm_fourcc.h from kernel to
> > add multi plane formats
> >
> > On Fri, Mar 30, 2012 at 01:12:58PM +0300, Ville Syrjälä wrote:
> > > On Fri, Mar 30, 2012 at 11:54:50AM +0900, Seung-Woo Kim wrote:
> > > > Multi buffer plane pixel formats are added as like kernel header.
> > > >
> > > > Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com
<mailto:sw0312.kim@samsung.com>>
> > > > ---
> > > >  include/drm/drm_fourcc.h |    7 +++++++
> > > >  1 files changed, 7 insertions(+), 0 deletions(-)
> > > >
> > > > diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
> > > > index 85facb0..7cfd95a 100644
> > > > --- a/include/drm/drm_fourcc.h
> > > > +++ b/include/drm/drm_fourcc.h
> > > > @@ -107,6 +107,10 @@
> > > >  #define DRM_FORMAT_NV16                fourcc_code('N', 'V', '1',
'6') /*
> > 2x1 subsampled Cr:Cb plane */
> > > >  #define DRM_FORMAT_NV61                fourcc_code('N', 'V', '6',
'1') /*
> > 2x1 subsampled Cb:Cr plane */
> > > >
> > > > +/* 2 non contiguous plane YCbCr */
> > > > +#define DRM_FORMAT_NV12M       fourcc_code('N', 'M', '1', '2') /* 2x2
> > subsampled Cr:Cb plane */
> > >
> > > NAK. DRM_FORMAT_NV12 handles this just fine.
> >
> > And I just realized that I was already too late with my NAK since this a
> > libdrm patch. Apparently the kernel drm_fourcc.h changes were snuck in
> > via some backdoor without review. Sigh.
> >
>
> We had already requested review for it. for this you can refer to link
> below:
>
> http://lists.freedesktop.org/archives/dri-devel/2011-December/017654.html

I see. I couldn't find it in my work mailbox for some reason, and I
don't remember having seen the patch before. I suppose I just missed it
due to Christmas vacations, and was too blind to see it in my mailbox.
Also google decicded to filter my search results too much, so I didn't
spot it via the web archives either. I'm sorry for the false accusation.

> > So they're now in Linus's tree. But looks like format_check() was never
> > updated to accept them, so there's no way anyone could actually be using
> > them. So Dave, can we still remove them from the kernel header?
> >
>
> Yes, right. these formats aren't used for any SoCs except Exynos series yet
> but just we are first. I think they should be added because anyone may use
> them someday at least possible.

Since DRM_FORMAT_NV12M is _identical_ to DRM_FORMAT_NV12, I see no point
in adding it (similarly for YUV420M vs. YUV420).

In V4L2 the fourcc also determines the number of memory planes in the frame buffer. The multi-planar API has been added to support devices with odd alignment requirements (image components, like Y/CbCr in separate physical memory buffers) for which it was difficult to map whole frame into contiguous user memory region.

Here is some excample: http://linuxtv.org/downloads/v4l-dvb-apis/V4L2-PIX-FMT-NV12M.html

I'm not terribly familiar with the buffer structure in DRM, maybe there are better ways to handle something like this in DRI.

--
Ville Syrjälä
syrjala@sci.fi <mailto:syrjala@sci.fi>
http://www.sci.fi/~syrjala/

Regards,