[libcamera-devel] [PATCH v2 11/27] libcamera: v4l2_videodevice: Document plane handling in createBuffer()

[Hirokazu Honda]

Hi Laurent,

On Mon, Sep 6, 2021 at 4:11 PM Jean-Michel Hautbois
<jeanmichel.hautbois at ideasonboard.com> wrote:
>
> Hi Laurent,
>
> On 06/09/2021 04:00, Laurent Pinchart wrote:
> > The V4L2VideoDevice::createBuffer() calculates offsets manually when
> > using a multi-planar pixel format and a single-planar V4L2 format. The
> > process isn't trivial, document it.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>

Reviewed-by: Hirokazu Honda <hiroh at chromium.org>

> > ---
> >  src/libcamera/v4l2_videodevice.cpp | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> > index 1483181a0856..88535f5a07c7 100644
> > --- a/src/libcamera/v4l2_videodevice.cpp
> > +++ b/src/libcamera/v4l2_videodevice.cpp
> > @@ -1334,10 +1334,19 @@ std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
> >       }
> >
> >       /*
> > +      * If we have a multi-planar format with a V4L2 single-planar buffer,
> > +      * split the single V4L2 plane into multiple FrameBuffer planes by
> > +      * computing the offsets manually.
> > +      *
> >        * The format info is not guaranteed to be valid, as there are no
> >        * PixelFormatInfo for metadata formats, so check it first.
> >        */
> >       if (formatInfo_->isValid() && formatInfo_->numPlanes() != numPlanes) {
> > +             /*
> > +              * There's no valid situation where the number of colour planes
> > +              * differs from the number of V4L2 planes and the V4L2 buffer
> > +              * has more than one plane.
> > +              */
> >               ASSERT(numPlanes == 1u);
> >
> >               planes.resize(formatInfo_->numPlanes());
> >