add poll_event*() interface

Hi,

The following patches, including the one below, attempt to create a new sleep interface.

In reviewing the remaining schedule_timeout() callers in the kernel, I noticed that a number of usages of this function obey this model:

/* sleep at most this long */
timeout = jiffies + some_time;
/* every interval of time, check some_event's state */

while (some_event) {
	/* state to sleep in depends on the intent */
	set_current_state(TASK_{UN,}INTERRUPTIBLE);
	/* each iteration sleep for some_other_time */
	schedule_timeout(some_other_time);
}

Now, I thought to myself, this is very similar to wait_event() and co., but without wait-queues. And, thus, instead of a wait-queue being the trigger to check a condition, the some_other_time sleep going by is.

Thus, it seemed logical to add an interface to do exactly this in a nice compact way, but using msleep() and msleep_interruptible().

Patch 1/5: Adds the poll_event(), poll_event_timeout(), poll_event_interruptible() and poll_event_interruptible_timeout() interfaces.

Patch {2,3,4,5}/5: Demonstrates the utitlity of poll_event*() in various drivers.

I am more than happy to change the names of these macros, change the names of the variables, or whatever other suggestions you may have. I closely modelled the macros after wait_event*(), which should be apparently.

If this code has a decent response from KJML, I will go ahead and push it to LKML.

Thanks,
Nish

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