> > 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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