linux-kernel - Re: [PATCH v2 3/3] media: uvcvideo: Remove stream->is

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Message-ID: <CANiDSCttXAu0bJHG7L=Y4Y0LqfRQa=Y-wC8PKr1Pv7Hwpq6Txg@mail.gmail.com>
Date: Mon, 2 Jun 2025 15:33:18 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: Hans Verkuil <hans@...erkuil.nl>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, Hans de Goede <hdegoede@...hat.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] media: uvcvideo: Remove stream->is_streaming field

Hi Hans

On Mon, 2 Jun 2025 at 15:23, Hans Verkuil <hans@...erkuil.nl> wrote:
>
> On 02/06/2025 14:59, Ricardo Ribalda wrote:
> > The is_streaming field is used by modular PM to know if the device is
> > currently streaming or not.
> >
> > With the transition to vb2 and fop helpers, we can use vb2 functions for
> > the same functionality. The great benefit is that vb2 already takes
> > track of the streaming state for us.
> >
> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_queue.c | 11 ++++++++-
> >  drivers/media/usb/uvc/uvc_v4l2.c  | 51 ++-------------------------------------
> >  drivers/media/usb/uvc/uvcvideo.h  |  1 -
> >  3 files changed, 12 insertions(+), 51 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
> > index 72c5494dee9f46ff61072e7d293bfaddda40e615..dff93bec204428b8aebc09332e0322fa68823fa4 100644
> > --- a/drivers/media/usb/uvc/uvc_queue.c
> > +++ b/drivers/media/usb/uvc/uvc_queue.c
> > @@ -165,12 +165,18 @@ static int uvc_start_streaming(struct vb2_queue *vq, unsigned int count)
> >
> >       lockdep_assert_irqs_enabled();
> >
> > +     ret = uvc_pm_get(stream->dev);
> > +     if (ret)
> > +             return ret;
> > +
> >       queue->buf_used = 0;
> >
> >       ret = uvc_video_start_streaming(stream);
>
> I'm not sure this is correct. See comments below.
>
> >       if (ret == 0)
> >               return 0;
> >
> > +     uvc_pm_put(stream->dev);
> > +
> >       spin_lock_irq(&queue->irqlock);
> >       uvc_queue_return_buffers(queue, UVC_BUF_STATE_QUEUED);
> >       spin_unlock_irq(&queue->irqlock);
> > @@ -181,11 +187,14 @@ static int uvc_start_streaming(struct vb2_queue *vq, unsigned int count)
> >  static void uvc_stop_streaming(struct vb2_queue *vq)
> >  {
> >       struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
> > +     struct uvc_streaming *stream = uvc_queue_to_stream(queue);
> >
> >       lockdep_assert_irqs_enabled();
> >
> > -     if (vq->type != V4L2_BUF_TYPE_META_CAPTURE)
> > +     if (vq->type != V4L2_BUF_TYPE_META_CAPTURE) {
> > +             uvc_pm_put(stream->dev);
>
> This doesn't look right, for both video and metadata uvc_pm_get is called,
> but only for video is put called.

Please take a look at
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/usb/uvc/uvc_queue.c#n195

start_streaming is not called for metadata nodes, only for video nodes.



>
> >               uvc_video_stop_streaming(uvc_queue_to_stream(queue));
>
> And this is odd too.
>
> > +     }
>
> My assumption is that uvc_video_start_streaming and uvc_video_stop_streaming
> are valid for both video and meta: i.e. the first time you start streaming
> (either video or meta) you call uvc_video_start_streaming. If you were already
> streaming for e.g. video, then start streaming metadata (or vice versa), then
> you don't need to do anything in start_streaming.
>
> Same for stop_streaming: only if both video and metadata stopped streaming
> is uvc_video_stop_streaming called.
>
> Please correct me if I am wrong.
>
> In any case, if I am right, then you have to rework this code accordingly.
>
> Regardless, you need to test various sequences of streaming video and metadata
> in different orders and make sure this is handled correctly.

I have tried streaming and getting frames. After some seconds the
device turns off as expected.

>
> Regards,
>
>         Hans
>
> >
> >       spin_lock_irq(&queue->irqlock);
> >       uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
> > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > index 7a5ecbefa32c0a6b74c85d7f77a25b433598471e..d4bee0d4334b764c0cf02363b573b55fb44eb228 100644
> > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > @@ -617,9 +617,6 @@ static int uvc_v4l2_release(struct file *file)
> >
> >       uvc_ctrl_cleanup_fh(handle);
> >
> > -     if (handle->is_streaming)
> > -             uvc_pm_put(stream->dev);
> > -
> >       /* Release the file handle. */
> >       vb2_fop_release(file);
> >       file->private_data = NULL;
> > @@ -677,50 +674,6 @@ static int uvc_ioctl_try_fmt(struct file *file, void *fh,
> >       return uvc_v4l2_try_format(stream, fmt, &probe, NULL, NULL);
> >  }
> >
> > -static int uvc_ioctl_streamon(struct file *file, void *fh,
> > -                           enum v4l2_buf_type type)
> > -{
> > -     struct uvc_fh *handle = fh;
> > -     struct uvc_streaming *stream = handle->stream;
> > -     int ret;
> > -
> > -     if (handle->is_streaming)
> > -             return 0;
> > -
> > -     ret = uvc_pm_get(stream->dev);
> > -     if (ret)
> > -             return ret;
> > -
> > -     ret = vb2_ioctl_streamon(file, fh, type);
> > -     if (ret) {
> > -             uvc_pm_put(stream->dev);
> > -             return ret;
> > -     }
> > -
> > -     handle->is_streaming = true;
> > -
> > -     return 0;
> > -}
> > -
> > -static int uvc_ioctl_streamoff(struct file *file, void *fh,
> > -                            enum v4l2_buf_type type)
> > -{
> > -     struct uvc_fh *handle = fh;
> > -     struct uvc_streaming *stream = handle->stream;
> > -     int ret;
> > -
> > -     ret = vb2_ioctl_streamoff(file, fh, type);
> > -     if (ret)
> > -             return ret;
> > -
> > -     if (handle->is_streaming) {
> > -             handle->is_streaming = false;
> > -             uvc_pm_put(stream->dev);
> > -     }
> > -
> > -     return 0;
> > -}
> > -
> >  static int uvc_ioctl_enum_input(struct file *file, void *fh,
> >                               struct v4l2_input *input)
> >  {
> > @@ -1323,8 +1276,8 @@ const struct v4l2_ioctl_ops uvc_ioctl_ops = {
> >       .vidioc_expbuf = vb2_ioctl_expbuf,
> >       .vidioc_dqbuf = vb2_ioctl_dqbuf,
> >       .vidioc_create_bufs = vb2_ioctl_create_bufs,
> > -     .vidioc_streamon = uvc_ioctl_streamon,
> > -     .vidioc_streamoff = uvc_ioctl_streamoff,
> > +     .vidioc_streamon = vb2_ioctl_streamon,
> > +     .vidioc_streamoff = vb2_ioctl_streamoff,
> >       .vidioc_enum_input = uvc_ioctl_enum_input,
> >       .vidioc_g_input = uvc_ioctl_g_input,
> >       .vidioc_s_input = uvc_ioctl_s_input,
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index 3ddbf065a2cbae40ee48cb06f84ca8f0052990c4..f895f690f7cdc1af942d5f3a5f10e9dd1c956a35 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -626,7 +626,6 @@ struct uvc_fh {
> >       struct uvc_video_chain *chain;
> >       struct uvc_streaming *stream;
> >       unsigned int pending_async_ctrls;
> > -     bool is_streaming;
> >  };
> >
> >  /* ------------------------------------------------------------------------
> >
>


-- 
Ricardo Ribalda