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

[Ricardo Ribalda]

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) {
 		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
+	 * 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;

-- 
2.43.0.rc1.413.gea7ed67945-goog