On Fri, May 10, 2019 at 1:57 AM Bastien Nocera [off-list ref] wrote:

On Sun, 2019-04-14 at 09:26 -0700, Roderick Colenbrander wrote:

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We at the time were one of the first to expose acceleration and gyro
data through /dev/input for DualShock 4 as supported by hid-sony. We
report acceleration in 'g' and angular velocity in 'degree / s'. We
set the resolution to respectively '1 g' and '1 degree / s'. The range
we set to the range of the device e.g. for DS4 -4g to +4g for
acceleration. I need to check though what coordinate system we use,
but I think it is right handed (gyro counter clockwise relative to
acceleration axes).

How do you export the gyro information through the input device?

For each DS4, there are multiple evdev devices for a DS4 for
respectively "gamepad", touchpad and motion sensors. The motion
sensors one, has INPUT_PROP_ACCELEROMETER set. ABS_X/_Y_Z provide
acceleration and ABS_RX/_RY/_RZ provide gyro. When we added this we
also updated the input documentation (event-codes.rst) to allow gyro
to use the rotational axes.

FWIW, we needed to do extra work in iio-sensor-proxy so that the
accelerometer in the Sixaxis/DS4 joypads (and uDraw tablet) didn't
appear as though they were accelerometer for the system:
https://github.com/hadess/iio-sensor-proxy/commit/401d59e54b3123860180d4401e09df8a1e1bc6c3

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The two other drivers using INPUT_PROC_ACCELEROMETER are hid-wacom and
hid-udraw-ps3 Wacom. Both seem to report resolution in 'g'  as well.

I wrote hid-udraw-ps3, and it's reporting accelerometer data through
input because the rest of the driver is input, and it didn't make much
sense to use another subsystem for just that small portion of the
events the device sends out.