[libcamera-devel] [PATCH v2] v4l2: V4L2CameraProxy: Add support for PREPARE_BUF as one of the supported ioctl

[Vedant Paranjape]

Sure, will do that.

On Sat, 15 Jan, 2022, 21:57 Laurent Pinchart, <
laurent.pinchart at ideasonboard.com> wrote:

> Hi Vedant,
>
> Thank you for the patch.
>
> On Wed, Jan 12, 2022 at 01:41:02AM +0530, Vedant Paranjape wrote:
> > Add support for PREPARE_BUF as one of the ioctl. Since this is a compat
> > layer, there doesn't seem to be an equivalent to the "transfer ownership
> > of the buffer to kernel driver" in V4L2Camera class.
> >
> > To match the error checks done by kernel implementation, we'd have to
> > check if dmabuf fd is valid and that the buffer size is large enough.
> > Doing so will not add any particular value to the program as
> > applications most likely don't depend on these conditions being
> > handled correctly.
> >
> > Signed-off-by: Vedant Paranjape <vedantparanjape160201 at gmail.com>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  src/v4l2/v4l2_camera_proxy.cpp | 32 ++++++++++++++++++++++++++++++++
> >  src/v4l2/v4l2_camera_proxy.h   |  1 +
> >  2 files changed, 33 insertions(+)
> >
> > diff --git a/src/v4l2/v4l2_camera_proxy.cpp
> b/src/v4l2/v4l2_camera_proxy.cpp
> > index 4d529bc29a4d..695af5be5c69 100644
> > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > @@ -544,6 +544,37 @@ int V4L2CameraProxy::vidioc_querybuf(V4L2CameraFile
> *file, struct v4l2_buffer *a
> >       return 0;
> >  }
> >
> > +int V4L2CameraProxy::vidioc_prepare_buf(V4L2CameraFile *file, struct
> v4l2_buffer *arg)
> > +{
> > +     LOG(V4L2Compat, Debug) << "Servicing vidioc_prepare_buf, index = "
> > +                            << arg->index << " fd = " << file->efd();
>
> We can replace this with
>
>         LOG(V4L2Compat, Debug)
>                 << "[" << file->description() << "] " << __func__
>                 << "(index=" << arg->index << ")";
>
> now that the V4L2 compat debugging improvements have been merged.
>
> > +
> > +     if (!hasOwnership(file))
> > +             return -EBUSY;
> > +
> > +     if (arg->index >= bufferCount_)
> > +             return -EINVAL;
> > +
> > +     if (arg->flags & V4L2_BUF_FLAG_REQUEST_FD)
> > +             return -EINVAL;
> > +
> > +     if (!validateBufferType(arg->type) ||
> > +         !validateMemoryType(arg->memory))
> > +             return -EINVAL;
> > +
> > +     struct v4l2_buffer &buffer = buffers_[arg->index];
> > +
> > +     if (buffer.flags & V4L2_BUF_FLAG_QUEUED ||
> > +         buffer.flags & V4L2_BUF_FLAG_PREPARED)
> > +             return -EINVAL;
> > +
> > +     buffer.flags |= V4L2_BUF_FLAG_PREPARED;
>
> This looks good, but there's one missing thing:
> V4L2CameraProxy::vidioc_dqbuf() should now clear the
> V4L2_BUF_FLAG_PREPARED flag. Can you send a v3 that addresses those two
> small issues ?
>
> > +
> > +     arg->flags = buffer.flags;
> > +
> > +     return 0;
> > +}
> > +
> >  int V4L2CameraProxy::vidioc_qbuf(V4L2CameraFile *file, struct
> v4l2_buffer *arg)
> >  {
> >       LOG(V4L2Compat, Debug) << "Servicing vidioc_qbuf, index = "
> > @@ -709,6 +740,7 @@ const std::set<unsigned long>
> V4L2CameraProxy::supportedIoctls_ = {
> >       VIDIOC_S_INPUT,
> >       VIDIOC_REQBUFS,
> >       VIDIOC_QUERYBUF,
> > +     VIDIOC_PREPARE_BUF,
> >       VIDIOC_QBUF,
> >       VIDIOC_DQBUF,
> >       VIDIOC_EXPBUF,
> > diff --git a/src/v4l2/v4l2_camera_proxy.h b/src/v4l2/v4l2_camera_proxy.h
> > index 14e027c3e7d1..6baba94262a9 100644
> > --- a/src/v4l2/v4l2_camera_proxy.h
> > +++ b/src/v4l2/v4l2_camera_proxy.h
> > @@ -57,6 +57,7 @@ private:
> >       int vidioc_s_input(V4L2CameraFile *file, int *arg);
> >       int vidioc_reqbufs(V4L2CameraFile *file, struct
> v4l2_requestbuffers *arg);
> >       int vidioc_querybuf(V4L2CameraFile *file, struct v4l2_buffer *arg);
> > +     int vidioc_prepare_buf(V4L2CameraFile *file, struct v4l2_buffer
> *arg);
> >       int vidioc_qbuf(V4L2CameraFile *file, struct v4l2_buffer *arg);
> >       int vidioc_dqbuf(V4L2CameraFile *file, struct v4l2_buffer *arg,
> >                        libcamera::Mutex *lock)
> LIBCAMERA_TSA_REQUIRES(*lock);
>
> --
> Regards,
>
> Laurent Pinchart
>
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