Why do we need to call poll_wait in poll?

Question

In LDD3, i saw such codes

static unsigned int scull_p_poll(struct file *filp, poll_table *wait)
{
    struct scull_pipe *dev = filp->private_data;
    uns         


        

Answer 1

poll_wait triggers when there is an expected event occurred on any of the fd's it is waiting on OR it hits timeout.

Check the mask to know which event triggered poll_wait. If you don't want poll_wait to trigger on such event, you can configure it while registering file descriptor to poll fd.