On Wed, Sep 30, 2009 at 6:38 PM, Denis Borisevich <dennisfen@xxxxxxxxx> wrote:
Hi!
I want to use poll() functionality (to properly handle select() and
poll() syscalls) in my char-device driver. The code for my kernel-side
poll() function is (a little bit simplified):
unsigned int my_poll(struct file *filp, struct poll_table_struct *wait)
{
unsigned int mask=0;
unsigned long flags;
poll_wait(filp, my_wait_queue, wait);
if ( any_data_available > 0)
mask |= POLLIN | POLLRDNORM;
return mask;
}
Where "my_wait_queue" is of "wait_queue_head_t" type,
"any_data_available" if the flag which tells if any data is available
within internal buffer.
When you are setting 'any_data_available' variable to some positive values at the same place you have to wakeup process that is waiting in wait-queue.
May be this part is missing in your current code and because of that select is not retuning before timeout.
May be this part is missing in your current code and because of that select is not retuning before timeout.
When I load this driver and start user-space application wich calls
select() with 5 seconds timeout the select() returns after waiting
this timeout no matter when the data comes into the port (1,2,3
seconds). The return value is positive when the data available and 0
when no data comes, as it should be. The question is why select()
waits for the timeout even when data is available?
--
Denis
Thanks,
Chetan Nanda
Chetan Nanda
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