[Letux-kernel] evtest /dev/input/accel

Andreas Kemnade andreas at kemnade.info
Tue Apr 17 07:24:30 CEST 2018


Hi,

On Mon, 16 Apr 2018 12:26:23 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> I noticed a strange effect.
> 
> If I run
> 
> evtest /dev/input/accel | head -20
> 
> there is a report of the range and the current value of
> the accelerometer.
> 
> But it is "history". Which means that if I
> run this, then rotate the device and run again,
> I will get the old (unrotated) values. Only if
> I run once more, I get the new ones.
> 
> So this might also have an influence why QtMaze
> seems sluggish, i.e. has a noticeable delay.
> 
> It is unclear if this is an effect of the
> kernel input layer or the iio subsystem. Or
> the iio-bridge (maybe it gets buffered values
> where it should trigger a new read request).
> 
> Has anyone seen this as well?
> 

while true ; do echo X: $(<in_accel_x_raw ) Y: $(<in_accel_y_raw) Z: $(<in_accel_z_raw); done

does not work sluggish. So the accelerometer driver is not guilthy.

Regards,
Andreas
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