Re: [PATCH] Input: evdev - use monotonic clock for event timestamps

From: Henrik Rydberg
Date: Wed Oct 05 2011 - 05:17:38 EST

> I understand your concern about breaking random drivers, and am hoping
> that someon on this list could indicate whether this is a real concern
> or not. To get a better feeling for possible regressions, I checked
> xf86-input-evdev & -synaptics, and neither uses the evdev timestamp in
> their current incarnations. Any idea what else might be a good place
> to check?

The input system is used for all sorts of events - switches, for
instance. The point is that it is nearly impossible to know if
something will break or not, hence the reluctance to modify interfaces.

> One option is to make the evdev timestamp clock source a per-driver
> configuration option (controllable from userspace?). This sounds like
> it is doable, but would be significantly more complicated.
> Another option would be to timestamp with monotonicraw + boottime +
> sleeptime. This would be approximately wall clock time, but without
> ntp and slew adjustments. But, I fear this would just make the rare
> driver issue less obvious, since it would only become obvious when the
> two clock sources started drifting apart.

I agree, the problem is not really solvable. Dmitry?

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