Re: [PATCH v3 2/3] media: uvcvideo: Do not halt the device after disconnect

[Ricardo Ribalda]

Hi Sakari

On Wed, 22 Nov 2023 at 11:25, Sakari Ailus <sakari.ailus@xxxxxx> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Tue, Nov 21, 2023 at 07:53:49PM +0000, Ricardo Ribalda wrote:
> > usb drivers should not call to any usb_() function after the
> > .disconnect() callback has been triggered.
> >
> > If the camera is streaming, the uvc driver will call usb_set_interface or
> > usb_clear_halt once the device is being released. Let's fix this issue.
> >
> > This is probably not the only driver affected with this kind of bug, but
> > until there is a better way to do it in the core this is the way to
> > solve this issue.
> >
> > When/if a different mechanism is implemented in the core to solve the
> > lifetime of devices we will adopt it in uvc.
> >
> > Trace:
> > [ 1065.389723] drivers/media/usb/uvc/uvc_driver.c:2248 uvc_disconnect enter
> > [ 1065.390160] drivers/media/usb/uvc/uvc_driver.c:2264 uvc_disconnect exit
> > [ 1065.433956] drivers/media/usb/uvc/uvc_v4l2.c:659 uvc_v4l2_release enter
> > [ 1065.433973] drivers/media/usb/uvc/uvc_video.c:2274 uvc_video_stop_streaming enter
> > [ 1065.434560] drivers/media/usb/uvc/uvc_video.c:2285 uvc_video_stop_streaming exit
> > [ 1065.435154] drivers/media/usb/uvc/uvc_v4l2.c:680 uvc_v4l2_release exit
> > [ 1065.435188] drivers/media/usb/uvc/uvc_driver.c:2248 uvc_disconnect enter
> >
> > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> > ---
> >  drivers/media/usb/uvc/uvc_driver.c |  2 ++
> >  drivers/media/usb/uvc/uvc_video.c  | 45 ++++++++++++++++++++++++--------------
> >  drivers/media/usb/uvc/uvcvideo.h   |  2 ++
> >  3 files changed, 32 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > index 08fcd2ffa727..413c32867617 100644
> > --- a/drivers/media/usb/uvc/uvc_driver.c
> > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > @@ -2257,6 +2257,8 @@ static void uvc_disconnect(struct usb_interface *intf)
> >               return;
> >
> >       uvc_unregister_video(dev);
> > +     /* Barrier needed to synchronize with uvc_video_stop_streaming(). */
> > +     smp_store_release(&dev->disconnected, true);
> >       kref_put(&dev->ref, uvc_delete);
> >  }
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index 28dde08ec6c5..032b44e45b22 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -2243,28 +2243,39 @@ int uvc_video_start_streaming(struct uvc_streaming *stream)
> >       return ret;
> >  }
> >
> > -void uvc_video_stop_streaming(struct uvc_streaming *stream)
> > +static void uvc_video_halt(struct uvc_streaming *stream)
> >  {
> > -     uvc_video_stop_transfer(stream, 1);
> > +     unsigned int epnum;
> > +     unsigned int pipe;
> > +     unsigned int dir;
> >
> >       if (stream->intf->num_altsetting > 1) {
>
> Doesn't this imply the device is using isochronous mode?

I haven't changed the behaviour for halt, it is just that git diff is
being a bit too creative here:

Basically it is doing:

void video_halt() {
   if (is_isoc()) {
     usb_set_interface(stream->dev->udev, stream->intfnum, 0);
     return;
   }
   usb_clear_halt();
}

instead of the old:

void video_halt() {
   if (is_isoc()) {
     usb_set_interface(stream->dev->udev, stream->intfnum, 0);
   }  else {
      usb_clear_halt();
   }
}

Thanks!
>
> >               usb_set_interface(stream->dev->udev, stream->intfnum, 0);
> > -     } else {
> > -             /*
> > -              * UVC doesn't specify how to inform a bulk-based device
> > -              * when the video stream is stopped. Windows sends a
> > -              * CLEAR_FEATURE(HALT) request to the video streaming
> > -              * bulk endpoint, mimic the same behaviour.
> > -              */
> > -             unsigned int epnum = stream->header.bEndpointAddress
> > -                                & USB_ENDPOINT_NUMBER_MASK;
> > -             unsigned int dir = stream->header.bEndpointAddress
> > -                              & USB_ENDPOINT_DIR_MASK;
> > -             unsigned int pipe;
> > -
> > -             pipe = usb_sndbulkpipe(stream->dev->udev, epnum) | dir;
> > -             usb_clear_halt(stream->dev->udev, pipe);
> > +             return;
> >       }
> >
> > +     /*
> > +      * UVC doesn't specify how to inform a bulk-based device
>
> Then this comment doesn't look right. What about the code? This isn't
> mentioned in the commit message either.
>
> > +      * when the video stream is stopped. Windows sends a
> > +      * CLEAR_FEATURE(HALT) request to the video streaming
> > +      * bulk endpoint, mimic the same behaviour.
> > +      */
> > +     epnum = stream->header.bEndpointAddress & USB_ENDPOINT_NUMBER_MASK;
> > +     dir = stream->header.bEndpointAddress & USB_ENDPOINT_DIR_MASK;
> > +     pipe = usb_sndbulkpipe(stream->dev->udev, epnum) | dir;
> > +     usb_clear_halt(stream->dev->udev, pipe);
> > +}
> > +
> > +void uvc_video_stop_streaming(struct uvc_streaming *stream)
> > +{
> > +     uvc_video_stop_transfer(stream, 1);
> > +
> > +     /*
> > +      * Barrier needed to synchronize with uvc_disconnect().
> > +      * We cannot call usb_* functions on a disconnected USB device.
> > +      */
> > +     if (!smp_load_acquire(&stream->dev->disconnected))
> > +             uvc_video_halt(stream);
> > +
> >       uvc_video_clock_cleanup(stream);
> >  }
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index 6fb0a78b1b00..4318ce8e31db 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -559,6 +559,8 @@ struct uvc_device {
> >       unsigned int users;
> >       atomic_t nmappings;
> >
> > +     bool disconnected;
> > +
> >       /* Video control interface */
> >  #ifdef CONFIG_MEDIA_CONTROLLER
> >       struct media_device mdev;
> >
>
> --
> Kind regards,
>
> Sakari Ailus



-- 
Ricardo Ribalda