Re: [PATCH v19 0/9] Add DELETE_BUF ioctl

[Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>]

Le 07/02/2024 à 12:20, Hans Verkuil a écrit :
> On 07/02/2024 12:15, Benjamin Gaignard wrote:
> > Le 07/02/2024 à 10:12, Hans Verkuil a écrit :
> > > Hi Benjamin,
> > >
> > > On 06/02/2024 09:58, Hans Verkuil wrote:
> > > > On 06/02/2024 09:02, Benjamin Gaignard wrote:
> > > > > Unlike when resolution change on keyframes, dynamic resolution change
> > > > > on inter frames doesn't allow to do a stream off/on sequence because
> > > > > it is need to keep all previous references alive to decode inter frames.
> > > > > This constraint have two main problems:
> > > > > - more memory consumption.
> > > > > - more buffers in use.
> > > > > To solve these issue this series introduce DELETE_BUFS ioctl and remove
> > > > > the 32 buffers limit per queue.
> > > > This v19 looks good. There are three outstanding issues that I need to take a
> > > > look at:
> > > >
> > > > 1) Can we still signal support for DELETE_BUFS in the V4L2_BUF_CAP_ caps?
> > > >      It would be nice to have, but I'm not sure if and how that can be done.
> > > So, I came up with the following patch to add back the V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS
> > > capability. If the DELETE_BUFS ioctl is valid, then it sets this capability
> > > before calling vidioc_reqbufs or vidioc_create_bufs. So right now it will set
> > > this for any queue. If we ever want to disable this for a specific queue, then
> > > either the driver has to override these two ops and clear the flag, or a new
> > > vb2_queue flag (e.g. disable_delete_bufs) is added and vb2_set_flags_and_caps()
> > > will clear that capability based on that flag.
> > >
> > > In any case, for now just set it for both queues by default.
> > >
> > > If you agree that this is a good way to proceed, then can you incorporate this
> > > into a v20? You can add the documentation for this cap from the v17 version.
> > Do you want it to be a separate patch or included in the patch introducing DELETE_BUFS ioctl ?
> Up to you, whatever makes the most sense.

I will include it in DELETE_BUFS patch because it is strongly related to it.

Regards,
Benjamin

> Regards,
>
> 	Hans
>
> > > Regards,
> > >
> > >      Hans
> > >
> > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> > > ---
> > > diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > > index 8e437104f9c1..64f2d662d068 100644
> > > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > > @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
> > >            *flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
> > >        }
> > >
> > > -    *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> > > +    *caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> > >        if (q->io_modes & VB2_MMAP)
> > >            *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
> > >        if (q->io_modes & VB2_USERPTR)
> > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> > > index a172d33edd19..45bc705e171e 100644
> > > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > > @@ -2100,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
> > >    static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> > >                    struct file *file, void *fh, void *arg)
> > >    {
> > > +    struct video_device *vfd = video_devdata(file);
> > >        struct v4l2_requestbuffers *p = arg;
> > >        int ret = check_fmt(file, p->type);
> > >
> > > @@ -2108,6 +2109,9 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> > >
> > >        memset_after(p, 0, flags);
> > >
> > > +    if (is_valid_ioctl(vfd, VIDIOC_DELETE_BUFS))
> > > +        p->capabilities = V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS;
> > > +
> > >        return ops->vidioc_reqbufs(file, fh, p);
> > >    }
> > >
> > > @@ -2141,6 +2145,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
> > >    static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> > >                    struct file *file, void *fh, void *arg)
> > >    {
> > > +    struct video_device *vfd = video_devdata(file);
> > >        struct v4l2_create_buffers *create = arg;
> > >        int ret = check_fmt(file, create->format.type);
> > >
> > > @@ -2151,6 +2156,9 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> > >
> > >        v4l_sanitize_format(&create->format);
> > >
> > > +    if (is_valid_ioctl(vfd, VIDIOC_DELETE_BUFS))
> > > +        create->capabilities = V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS;
> > > +
> > >        ret = ops->vidioc_create_bufs(file, fh, create);
> > >
> > >        if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
> > > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > > index 03443833aaaa..da307f46f903 100644
> > > --- a/include/uapi/linux/videodev2.h
> > > +++ b/include/uapi/linux/videodev2.h
> > > @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
> > >    #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF    (1 << 5)
> > >    #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS        (1 << 6)
> > >    #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS        (1 << 7)
> > > +#define V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS        (1 << 8)
> > >
> > >    /**
> > >     * struct v4l2_plane - plane info for multi-planar buffers