Re: [PATCH 07/19] Input: evdev - Add the events() callback

Reading the time just once and applying it as the timestamp to an
entire frame is very nice.
However, is it ever possible for the SYN_REPORT to get delayed until
the next batch of input_values, therefore breaking the assumption that
the SYN_REPORT timestamp applies to the rest of the input_values for
its frame?

Yes, but see reply to previous patch.

Also, bonus points if the input driver could set this input frame
timestamp based on when it first saw a hardware interrupt rather then
when evdev gets around to sending the frame to userspace.  This could
potentially remove a lot of the timing jitter userspace sees when
computing ballistics based on input event timestamps.

In principle, yes (it has been discussed before), but in practise some
devices provide timestamps and some not, and the scale and granularity
may vary. In addition, desktop userland (read X input) does not even
use the kernel timestamp, so the effect would not even be seen without
a synchronized effort. I am not saying it is a bad idea, but it has
some details to get straight before it becomes useful.

Thanks,
Henrik