Re: [PATCH v5 3/5] media: uvcvideo: Increase/decrease the PM counter per IOCTL

[Laurent Pinchart]

On Thu, Mar 27, 2025 at 07:52:27PM +0200, Laurent Pinchart wrote:
> Hi Ricardo,
> 
> Thank you for the patch.
> 
> On Mon, Mar 03, 2025 at 07:13:40PM +0000, Ricardo Ribalda wrote:
> > Now we call uvc_pm_get/put from the device open/close. This low
> > level of granularity might leave the camera powered on in situations
> > where it is not needed.
> > 
> > Increase the granularity by increasing and decreasing the Power
> 
> You're decreasing the granularity, not increasing it.
> 
> > Management counter per ioctl. There are two special cases where the
> > power management outlives the ioctl: async controls and streamon. Handle
> > those cases as well.
> > 
> > In a future patch, we will remove the uvc_pm_get/put from open/close.
> > 
> > Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c | 13 +++++++++++--
> >  drivers/media/usb/uvc/uvc_v4l2.c | 23 +++++++++++++++++++++--
> >  drivers/media/usb/uvc/uvcvideo.h |  1 +
> >  3 files changed, 33 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 4e58476d305e..47188c7f96c7 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -1594,12 +1594,15 @@ static void uvc_ctrl_set_handle(struct uvc_fh *handle, struct uvc_control *ctrl,
> >  
> >  		if (ctrl->handle) {
> >  			WARN_ON(!ctrl->handle->pending_async_ctrls);
> > -			if (ctrl->handle->pending_async_ctrls)
> > +			if (ctrl->handle->pending_async_ctrls) {
> >  				ctrl->handle->pending_async_ctrls--;
> > +				uvc_pm_put(handle->chain->dev);
> 
> Shouldn't this be
> 
> 				uvc_pm_put(ctrl->handle->chain->dev);
> 
> ? In practice it won't make a difference as dev will be the same for
> both, but it seems clearer.
> 
> > +			}
> >  		}
> >  
> >  		ctrl->handle = new_handle;
> >  		handle->pending_async_ctrls++;
> > +		uvc_pm_get(handle->chain->dev);
> 
> Similarly, we should use ctrl->handle here too (including for the
> pending_async_ctrls++).
> 
> >  		return;
> >  	}
> >  
> > @@ -1611,6 +1614,7 @@ static void uvc_ctrl_set_handle(struct uvc_fh *handle, struct uvc_control *ctrl,
> >  	if (WARN_ON(!handle->pending_async_ctrls))
> >  		return;
> >  	handle->pending_async_ctrls--;
> > +	uvc_pm_put(handle->chain->dev);
> >  }
> >  
> >  void uvc_ctrl_status_event(struct uvc_video_chain *chain,
> > @@ -2815,6 +2819,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
> >  void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >  {
> >  	struct uvc_entity *entity;
> > +	int i;
> >  
> >  	guard(mutex)(&handle->chain->ctrl_mutex);
> >  
> > @@ -2829,7 +2834,11 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
> >  		}
> >  	}
> >  
> > -	WARN_ON(handle->pending_async_ctrls);
> > +	if (!WARN_ON(handle->pending_async_ctrls))
> > +		return;
> > +
> > +	for (i = 0; i < handle->pending_async_ctrls; i++)
> > +		uvc_pm_put(handle->stream->dev);
> >  }
> >  
> >  /*
> > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > index de1e105f7263..1c9ac72be58a 100644
> > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > @@ -691,6 +691,9 @@ static int uvc_v4l2_release(struct file *file)
> >  	if (uvc_has_privileges(handle))
> >  		uvc_queue_release(&stream->queue);
> >  
> > +	if (handle->is_streaming)
> > +		uvc_pm_put(stream->dev);
> > +
> >  	/* Release the file handle. */
> >  	uvc_dismiss_privileges(handle);
> >  	v4l2_fh_del(&handle->vfh);
> > @@ -857,6 +860,7 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
> >  		return ret;
> >  
> >  	handle->is_streaming = true;
> > +	uvc_pm_get(stream->dev);

Another comment: shouldn't you handle the return value (here and
elsewhere, including where you use guards) ?

> >  
> >  	return 0;
> >  }
> > @@ -873,7 +877,10 @@ static int uvc_ioctl_streamoff(struct file *file, void *fh,
> >  	guard(mutex)(&stream->mutex);
> >  
> >  	uvc_queue_streamoff(&stream->queue, type);
> > -	handle->is_streaming = false;
> > +	if (handle->is_streaming) {
> > +		handle->is_streaming = false;
> > +		uvc_pm_put(stream->dev);
> > +	}
> >  
> >  	return 0;
> >  }
> > @@ -1410,6 +1417,8 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
> >  	void __user *up = compat_ptr(arg);
> >  	long ret;
> >  
> > +	guard(uvc_pm)(handle->stream->dev);
> > +
> >  	switch (cmd) {
> >  	case UVCIOC_CTRL_MAP32:
> >  		ret = uvc_v4l2_get_xu_mapping(&karg.xmap, up);
> > @@ -1444,6 +1453,16 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
> >  }
> >  #endif
> >  
> > +static long uvc_v4l2_video_ioctl2(struct file *file,
> > +				  unsigned int cmd, unsigned long arg)
> > +{
> > +	struct uvc_fh *handle = file->private_data;
> > +
> > +	guard(uvc_pm)(handle->stream->dev);
> > +
> > +	return video_ioctl2(file, cmd, arg);
> > +}
> > +
> >  static ssize_t uvc_v4l2_read(struct file *file, char __user *data,
> >  		    size_t count, loff_t *ppos)
> >  {
> > @@ -1529,7 +1548,7 @@ const struct v4l2_file_operations uvc_fops = {
> >  	.owner		= THIS_MODULE,
> >  	.open		= uvc_v4l2_open,
> >  	.release	= uvc_v4l2_release,
> > -	.unlocked_ioctl	= video_ioctl2,
> > +	.unlocked_ioctl	= uvc_v4l2_video_ioctl2,
> 
> I'd have named this uvc_v4l2_unlocked_ioctl.
> 
> >  #ifdef CONFIG_COMPAT
> >  	.compat_ioctl32	= uvc_v4l2_compat_ioctl32,
> >  #endif
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index fbe3649c7cd6..eb8e374fa4c5 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -766,6 +766,7 @@ void uvc_status_put(struct uvc_device *dev);
> >  /* PM */
> >  int uvc_pm_get(struct uvc_device *dev);
> >  void uvc_pm_put(struct uvc_device *dev);
> > +DEFINE_GUARD(uvc_pm, struct uvc_device *, uvc_pm_get(_T), uvc_pm_put(_T))
> >  
> >  /* Controls */
> >  extern const struct v4l2_subscribed_event_ops uvc_ctrl_sub_ev_ops;

-- 
Regards,

Laurent Pinchart