Taps are one frame at ~200 ms per frame just as they were at ~700, so the
polling cadence is what catches a tap once and the loop's cost is no longer the
limit. The remaining lever is the architecture stock uses: react to the touch
edge, then capture as fast as QTEE allows for the length of the press.
That rests on a prerequisite worth measuring before a line of it is written.
The IRQ line is requested with both edges enabled and an observer thread polls
it and logs every event with the kernel timestamp, the interval since the last,
and the pulse width. Pure observation -- the matching loop is untouched.
Two questions it answers. Whether edges are observable from userspace at all,
and how quiet the line is at idle under an armed session: the level poll caught
it high on 5 of 136 idle frames, so there are pulses at rest, and if they are
frequent a wake-on-edge is dead before it starts.
Jorijn van der Graaf
479f653e65