Linux Device Drivers Development

The poll method

If you need to implement a passive wait (not wasting CPU cycles while sensing the character device), you must implement the poll() function, which will be called whenever a user space program performs select() or poll() system calls on the file associated with the device:

unsigned int (*poll) (struct file *, struct poll_table_struct *); 

The kernel function at the heart of this method is poll_wait(), defined in <linux/poll.h>, which is the header you should include in driver code:

void poll_wait(struct file * filp, wait_queue_head_t * wait_address, 
poll_table *p) 

poll_wait() adds the device associated with a struct file structure (given as the first parameter) to a list of those that can wake up processes (which have been ...