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    SubjectRe: [PATCH v3 2/3] media: uvcvideo: Do not halt the device after disconnect
    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@iki.fi> 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@chromium.org>
    > > > ---
    > > > 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

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