Hi,
poll system call has to return -1 on some error occurance on the device. In its
normal working condition it returns the state of the device whether its readble
or writable...
When the device is disconnected here again i am checking whether device is
present or not..
struct scanner_dev *dev;
dev = (struct scanner_dev *)file->private_data;
if(!dev) // or if(!dev->device_present)
return -EBADF;
irrespective of what error value i return, poll at the application is returning
1(that is, there is some activity on one file descriptor) After this,
application is trying to read/ write on device which is gonna fail again. I
tried returning POLLERR if device is not present but no effect...
I tried searching other standard USB driver , they do the same as i have done..
But not getting why poll is always returning positive number or timeout to
application.
here is poll implementation...
static unsigned int scanner_poll (struct file *file,
struct poll_table_struct *wait)
{
struct scanner_dev *dev;
unsigned int mask = 0;
dev = (struct scanner_dev *)file->private_data;
if(!dev->device_present)
return -EBADF;
if (NULL != wait)
poll_wait (file, &dev->read_q, wait);
// If data is present , say its readable(POLLIN)
if (dev->read_data_present)
{
#ifdef DEBUG
printk ("Read data present \n");
#endif
mask |= POLLIN | POLLRDNORM;
}
// Scanner device is always writtable (POLLOUT)
mask |= POLLOUT | POLLWRNORM;
return mask;
}
Thanks for ur inputs in advance
Savita
-------------------------------------------------------
This SF.Net email is sponsored by the JBoss Inc.
Get Certified Today * Register for a JBoss Training Course
Free Certification Exam for All Training Attendees Through End of 2005
Visit http://www.jboss.com/services/certification for more information
_______________________________________________
[email protected]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
