Re: [Bugme-new] [Bug 8297] New: ldusb returns bad data on subsequent reads if no data is available.

> > Problem Description:
> > Using my Go!Temp temperature probe with the ldusb driver I decided to cat the
> > device file /dev/ldusb0 to see what it would return.  Bad idea, I was presented
> > with an endless spewing of crap.
> > 
> > After a little debugging it seems the problem is that in ld_usb_open
> > dev->interrupt_in_done is set to 0, and the URB is submitted.  When ld_usb_read
> > is called if no data is in the buffer it waits for ld_usb_interrupt_in_callback
> > to complete by checking if dev->interrupt_in_done has been set to 1.  That works
> > fine if you only read once after calling open however, if you happen to read
> > more than once dev->interrupt_in_done is never reset so you read from the empty
> > buffer even though no data has arrived.

Does this patch work?

	Regards
		Oliver
Signed-off-by: Oliver Neukum <[email protected]>
---------
--- a/drivers/usb/misc/ldusb.c	2007-04-04 09:33:16.000000000 +0200
+++ b/drivers/usb/misc/ldusb.c	2007-04-04 09:33:22.000000000 +0200
@@ -162,6 +162,8 @@
 	size_t			interrupt_in_endpoint_size;
 	int			interrupt_in_running;
 	int			interrupt_in_done;
+	int			buffer_overflow;
+	spinlock_t		rbsl;
 
 	char*			interrupt_out_buffer;
 	struct usb_endpoint_descriptor* interrupt_out_endpoint;
@@ -227,10 +229,12 @@
 		} else {
 			dbg_info(&dev->intf->dev, "%s: nonzero status received: %d\n",
 				 __FUNCTION__, urb->status);
+			spin_lock(&dev->rbsl);
 			goto resubmit; /* maybe we can recover */
 		}
 	}
 
+	spin_lock(&dev->rbsl);
 	if (urb->actual_length > 0) {
 		next_ring_head = (dev->ring_head+1) % ring_buffer_size;
 		if (next_ring_head != dev->ring_tail) {
@@ -245,17 +249,20 @@
 			dev_warn(&dev->intf->dev,
 				 "Ring buffer overflow, %d bytes dropped\n",
 				 urb->actual_length);
+			dev->buffer_overflow = 1;
 	}
 
 resubmit:
 	/* resubmit if we're still running */
-	if (dev->interrupt_in_running && dev->intf) {
+	if (dev->interrupt_in_running && !dev->buffer_overflow && dev->intf) {
 		retval = usb_submit_urb(dev->interrupt_in_urb, GFP_ATOMIC);
-		if (retval)
+		if (retval) {
 			dev_err(&dev->intf->dev,
 				"usb_submit_urb failed (%d)\n", retval);
+			dev->buffer_overflow = 1;
+		}
 	}
-
+	spin_unlock(&dev->rbsl);
 exit:
 	dev->interrupt_in_done = 1;
 	wake_up_interruptible(&dev->read_wait);
@@ -327,6 +334,7 @@
 	/* initialize in direction */
 	dev->ring_head = 0;
 	dev->ring_tail = 0;
+	dev->buffer_overflow = 0;
 	usb_fill_int_urb(dev->interrupt_in_urb,
 			 interface_to_usbdev(interface),
 			 usb_rcvintpipe(interface_to_usbdev(interface),
@@ -436,6 +444,7 @@
 	size_t *actual_buffer;
 	size_t bytes_to_read;
 	int retval = 0;
+	int rv;
 
 	dev = file->private_data;
 
@@ -457,7 +466,10 @@
 	}
 
 	/* wait for data */
+	spin_lock_irq(&dev->rbsl);
 	if (dev->ring_head == dev->ring_tail) {
+		dev->interrupt_in_done = 0;
+		spin_unlock_irq(&dev->rbsl);
 		if (file->f_flags & O_NONBLOCK) {
 			retval = -EAGAIN;
 			goto unlock_exit;
@@ -465,6 +477,8 @@
 		retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done);
 		if (retval < 0)
 			goto unlock_exit;
+	} else {
+		spin_unlock_irq(&dev->rbsl);
 	}
 
 	/* actual_buffer contains actual_length + interrupt_in_buffer */
@@ -483,6 +497,17 @@
 
 	retval = bytes_to_read;
 
+	spin_lock_irq(&dev->rbsl);
+	if (dev->buffer_overflow) {
+		dev->buffer_overflow = 0;
+		spin_unlock_irq(&dev->rbsl);
+		rv = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
+		if (rv < 0)
+			dev->buffer_overflow = 1;
+	} else {
+		spin_unlock_irq(&dev->rbsl);
+	}
+
 unlock_exit:
 	/* unlock the device */
 	up(&dev->sem);
@@ -632,6 +657,7 @@
 		goto exit;
 	}
 	init_MUTEX(&dev->sem);
+	spin_lock_init(&dev->rbsl);
 	dev->intf = intf;
 	init_waitqueue_head(&dev->read_wait);
 	init_waitqueue_head(&dev->write_wait);

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