Am Mittwoch, 31. Januar 2007 20:25 schrieb Alan Stern:
> > How do I find out whether the device is idle?
> > The mouse is not idle if it has been moved (or buttons clicked)
> > To find out whether it has been moved the device must not be suspended.
> > At which point in time then should I check? Are you saying that the
> > timer should be started and suspend() should fail if the devices hasn't
> > been idle?
>
> Logically speaking, the computer doesn't and can't know if the device is
> currently idle. After all, it takes several milliseconds for the HID
> reports indicating any activity to be transferred from the device to the
> computer, so the computer's knowledge is always at least a little bit out
> of date.
Yes, this race condition is unavoidable.
> So you shouldn't base any decisions on whether the device is currently
> idle. Instead, you have to check whether the device has been idle for a
> sufficiently long time. That's what the timer is for: You restart the
Yes, that's the way I currently do it.
> timer whenever there is any activity, and when the timer expires you know
> the device has been idle long enough that you should suspend it. That's
> exactly how the autosuspend infrastructure works.
This would call mod_timer() for every completed in-URB. Are you
sure this is better than an approach maintaining a periodical timer
and check for IO in the meantime?
Regards
Oliver
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