Re: [PATCH v3 2/3] media: uvcvideo: Do not halt the device after disconnect
From: Sakari Ailus
Date: Wed Nov 22 2023 - 06:04:45 EST
Hi Ricardo,
On Wed, Nov 22, 2023 at 11:32:16AM +0100, Ricardo Ribalda wrote:
> 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!
Oops. I missed the removal of the else branch altogether while reading the
patch.
Shouldn't you also ensure the disconnect callback won't return until the
streaming has been stopped here?
> >
> > > 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