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Date: Wed, 22 Nov 2023 11:32:16 +0100
From: Ricardo Ribalda <ribalda@...omium.org>
To: Sakari Ailus <sakari.ailus@....fi>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
Guenter Roeck <linux@...ck-us.net>,
Tomasz Figa <tfiga@...omium.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Alan Stern <stern@...land.harvard.edu>,
Hans Verkuil <hverkuil-cisco@...all.nl>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
Sean Paul <seanpaul@...omium.org>,
Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v3 2/3] media: uvcvideo: Do not halt the device after disconnect
Hi Sakari
On Wed, 22 Nov 2023 at 11:25, Sakari Ailus <sakari.ailus@....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@...omium.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!
>
> > 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
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