[media] tm6000: Add locking for USB transfers

This commit introduces the usb_lock mutex to ensure that a USB request
always gets the proper response. While this is currently not really
necessary it will become important as there are more users.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/tm6000/tm6000-cards.c

@@ -1168,6 +1168,7 @@ static int tm6000_usb_probe(struct usb_interface *interface,
 		return -ENOMEM;
 	}
 	spin_lock_init(&dev->slock);
+	mutex_init(&dev->usb_lock);
 
 	/* Increment usage count */
 	tm6000_devused |= 1<<nr;

drivers/staging/tm6000/tm6000-core.c

@@ -39,6 +39,8 @@ int tm6000_read_write_usb(struct tm6000_core *dev, u8 req_type, u8 req,
 	unsigned int pipe;
 	u8	     *data = NULL;
 
+	mutex_lock(&dev->usb_lock);
+
 	if (len)
 		data = kzalloc(len, GFP_KERNEL);
 
@@ -86,9 +88,9 @@ int tm6000_read_write_usb(struct tm6000_core *dev, u8 req_type, u8 req,
 	}
 
 	kfree(data);
-
 	msleep(5);
 
+	mutex_unlock(&dev->usb_lock);
 	return ret;
 }
 

drivers/staging/tm6000/tm6000.h

@@ -245,6 +245,7 @@ struct tm6000_core {
 
 	/* locks */
 	struct mutex			lock;
+	struct mutex			usb_lock;
 
 	/* usb transfer */
 	struct usb_device		*udev;		/* the usb device */