Hi,
I am writing a device driver based on usb-skeleton.c. I want to use the
select() system call in user space and therefore I am trying to implement
the device driver method poll().
I found code for implementing the driver method poll in Linux Device
Drivers 3, chapter 6.
I simply added the following code to the driver:
// ------------------------------------------
static unsigned int skel_poll(struct file *filp, poll_table *wait)
{
struct usb_skel *dev = filp->private_data;
unsigned int mask = 0;
printk(KERN_INFO "*** skel_poll\n");
down(&dev->sem);
poll_wait(filp, &dev->inq, wait);
poll_wait(filp, &dev->outq, wait);
if(dev->rp != dev->wp)
mask |= POLLIN | POLLRDNORM; /* readable */
if(spacefree(dev))
mask |= POLLOUT | POLLWRNORM; /* writable */
up(&dev->sem);
return mask;
}
static int spacefree(struct usb_skel *dev)
{
if(dev->rp == dev->wp)
return dev->bulk_in_size - 1;
return (( dev->rp + dev->bulk_in_size - dev->wp) % dev->bulk_in_size)
-1;
}
// ------------------------------------------
Now, when I am testing the driver with select() in user space, the
computer hangs. The driver without the poll code above works normally and
prints out the KERN_INFO printouts as it uses the read() and write()
system calls.
How shall I modify the code to make the poll() implementation work?
Thanks in advance.
/ Moge
-If you want the whole device driver code attached, just ask me and I'll
send it.
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