[libcamera-devel] [PATCH v4] v4l2: V4L2CameraProxy: Add EXPBUF as one of the supported ioctl

[Vedant Paranjape]

Hi Laurent,

On Sat, 8 Jan, 2022, 19:22 Laurent Pinchart, <
laurent.pinchart at ideasonboard.com> wrote:

> Hi Vedant,
>
> On Sat, Jan 08, 2022 at 03:10:15AM +0530, Vedant Paranjape wrote:
> > Hello Laurent,
> > I have been able to get v4l2-ctl working to stream using dmabuf, here
> > are the steps I followed:
> >
> > 1) Apply the patch in the trailing email (v4) on the latest branch of
> libcamera
> > 2) Clone master of v4l-utils and apply this patch
> >
> https://patchwork.kernel.org/project/linux-media/patch/20220104130708.166638-1-vedantparanjape160201@gmail.com/
> > 3) Compile v4l-utils
> > 4) give alias v4l2-ctl-edge=<PATH OF COMPILED V4l2-ctl>
> > 5) run the following command in libcamera root directory:
> >      LD_PRELOAD=./build/src/v4l2/v4l2-compat.so v4l2-ctl-edge -d0
> > --set-fmt-video=pixelformat='YUYV' --stream-mmap --out-device
> > /dev/video3 --stream-out-dmabuf --get-fmt-video --get-fmt-video-out
>
> You can drop the last two arguments.
>
> While this show that the EXPBUF implementation works, in a real use case
> you would still potentially have different formats on the capture and
> output side, which would lead to garbled output. You should specify the
> format and resolution explicitly on both the capture and output side.
>

Makes sense, I'll keep this in mind.

I'll merge the patch.
>
> > I have attached the output of lsv4l2 here as well:
> >
> > video0: HD WebCam: HD WebCam
> > video1: HD WebCam: HD WebCam
> > video2: vivid-000-vid-cap
> > video3: vivid-000-vid-out
> >
> > Here's the terminal output: https://paste.debian.net/1226342/
> >
> > Regards,
> > Vedant Paranjape
> >
> > On Thu, Dec 30, 2021 at 4:06 AM Laurent Pinchart wrote:
> > > On Wed, Dec 29, 2021 at 12:20:14AM +0530, Vedant Paranjape wrote:
> > > > To support DMABUF as one of the memory buffer, we need to implement
> > > > EXPBUF in the v4l2 compat layer.
> > > >
> > > > This patch implements vidioc_expbuf as one of the supported ioctls.
> > > >
> > > > Bug: https://bugs.libcamera.org/show_bug.cgi?id=89
> > > >
> > > > Signed-off-by: Vedant Paranjape <vedantparanjape160201 at gmail.com>
> > >
> > > This looks fine. As soon as you can test it with v4l2-ctl and capture
> > > images, I think it can be merged.
> > >
> > > I've sent a patch for v4l2-ctl (which has been merged in the master
> > > branch already) that should help with testing.
> > >
> > > > ---
> > > >  src/v4l2/v4l2_camera_proxy.cpp | 30 ++++++++++++++++++++++++++++++
> > > >  src/v4l2/v4l2_camera_proxy.h   |  1 +
> > > >  2 files changed, 31 insertions(+)
> > > >
> > > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp
> b/src/v4l2/v4l2_camera_proxy.cpp
> > > > index c1375777c185..4d529bc29a4d 100644
> > > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > > @@ -624,6 +624,32 @@ int
> V4L2CameraProxy::vidioc_dqbuf(V4L2CameraFile *file, struct v4l2_buffer *arg,
> > > >       return 0;
> > > >  }
> > > >
> > > > +int V4L2CameraProxy::vidioc_expbuf(V4L2CameraFile *file, struct
> v4l2_exportbuffer *arg)
> > > > +{
> > > > +     LOG(V4L2Compat, Debug) << "Servicing vidioc_expbuf fd = " <<
> file->efd();
> > > > +
> > > > +     if (!hasOwnership(file))
> > > > +             return -EBUSY;
> > > > +
> > > > +     /* \todo Verify that the memory type is MMAP when adding
> DMABUF support */
> > > > +     if (!validateBufferType(arg->type))
> > > > +             return -EINVAL;
> > > > +
> > > > +     if (arg->index >= bufferCount_)
> > > > +             return -EINVAL;
> > > > +
> > > > +     if (arg->flags & ~(O_CLOEXEC | O_ACCMODE))
> > > > +             return -EINVAL;
> > > > +
> > > > +     memset(arg->reserved, 0, sizeof(arg->reserved));
> > > > +
> > > > +     /* \todo honor the O_ACCMODE flags passed to this function */
> > > > +     arg->fd = fcntl(vcam_->getBufferFd(arg->index),
> > > > +                     arg->flags & O_CLOEXEC ? F_DUPFD_CLOEXEC :
> F_DUPFD, 0);
> > > > +
> > > > +     return 0;
> > > > +}
> > > > +
> > > >  int V4L2CameraProxy::vidioc_streamon(V4L2CameraFile *file, int *arg)
> > > >  {
> > > >       LOG(V4L2Compat, Debug) << "Servicing vidioc_streamon fd = " <<
> file->efd();
> > > > @@ -685,6 +711,7 @@ const std::set<unsigned long>
> V4L2CameraProxy::supportedIoctls_ = {
> > > >       VIDIOC_QUERYBUF,
> > > >       VIDIOC_QBUF,
> > > >       VIDIOC_DQBUF,
> > > > +     VIDIOC_EXPBUF,
> > > >       VIDIOC_STREAMON,
> > > >       VIDIOC_STREAMOFF,
> > > >  };
> > > > @@ -755,6 +782,9 @@ int V4L2CameraProxy::ioctl(V4L2CameraFile *file,
> unsigned long request, void *ar
> > > >       case VIDIOC_DQBUF:
> > > >               ret = vidioc_dqbuf(file, static_cast<struct
> v4l2_buffer *>(arg), &proxyMutex_);
> > > >               break;
> > > > +     case VIDIOC_EXPBUF:
> > > > +             ret = vidioc_expbuf(file, static_cast<struct
> v4l2_exportbuffer *>(arg));
> > > > +             break;
> > > >       case VIDIOC_STREAMON:
> > > >               ret = vidioc_streamon(file, static_cast<int *>(arg));
> > > >               break;
> > > > diff --git a/src/v4l2/v4l2_camera_proxy.h
> b/src/v4l2/v4l2_camera_proxy.h
> > > > index fa0a49e0439b..14e027c3e7d1 100644
> > > > --- a/src/v4l2/v4l2_camera_proxy.h
> > > > +++ b/src/v4l2/v4l2_camera_proxy.h
> > > > @@ -60,6 +60,7 @@ private:
> > > >       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);
> > > > +     int vidioc_expbuf(V4L2CameraFile *file, struct
> v4l2_exportbuffer *arg);
> > > >       int vidioc_streamon(V4L2CameraFile *file, int *arg);
> > > >       int vidioc_streamoff(V4L2CameraFile *file, int *arg);
> > > >
>
> --
> Regards,
>
> Laurent Pinchart


>
Regards,
Vedant Paranjape
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