User-space API for accelerometer(s)?

[Bastien Nocera <hadess@hadess.net>]

Hey,

I'm trying to integrate the accelerometer of the Lenovo Yoga into GNOME
and a modern desktop. The accelerometer is exported through an IIO
device as per:
https://github.com/pfps/yoga-laptop/blob/master/sensors/orientation.c

We already have some integration for accelerometers in udev/systemd and
GNOME, and they rely on the accelerometer being an input device, being
tagged with the ID_INPUT_ACCELEROMETER and sending out a kevent/uevent
when a major orientation change took place. This is handled by:
http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/accelerometer/accelerometer.c
for the WeTab/Pegatron devices for example.

So, my question regarding the IIO user-space API is:
is it possible to make the IIO accelerometer send out a kevent when the
orientation changes in a major way (using triggers?) or does user-space
need to poll the device instead?

If the former, I intend on writing a small helper to set up the
accelerometer, and a helper similar to the one already in the udev tree.

If the latter, I'll probably write a long-running helper, which would
offer the same interface as the one used by the Pegatron accelerometer
driver, so that we don't need to make any more changes to user-space.

Cheers