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

[Laurent Pinchart]

On Thu, Mar 27, 2025 at 10:05:19PM +0100, Ricardo Ribalda wrote:
> On Thu, 27 Mar 2025 at 18:57, Laurent Pinchart wrote:
> > On Thu, Mar 27, 2025 at 07:52:27PM +0200, Laurent Pinchart wrote:
> > > 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) ?
> 
> Good point... I guess I got excited trying to use the guards :)

I like them too :-)

> > > >
> > > >     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