"light" channel not working in hid-sensor-hub

Hey,

It seems that the "light" channel that's available in hid-sensor-hub
stopped working quite some time ago. I've tested this on a ColorHug ALS
light sensor, as well as on the light sensor part of the HID sensor hub
on a Surface 3.

The accelerometer and the gyro work fine on the Surface 3, but the
light sensor only ever returns zeros when iio-sensor-proxy or the
iio_generic_buffer tools are used:

$ sudo iio_generic_buffer -A -N 0
iio device number being used is 0
iio trigger number being used is 0
Enabling all channels
Enabling: in_intensity_both_en
Enabling: in_illuminance_en
/sys/bus/iio/devices/iio:device0 als-dev0
0.000000 0.000000 
0.000000 0.000000 
0.000000 0.000000 
0.000000 0.000000 
0.000000 0.000000 
Disabling: in_intensity_both_en
Disabling: in_illuminance_en

I believe this has been broken for at least a year. Does anyone know
what the problem could be, or how to get started debugging the
problem? 

I'll probably try checking whether the problem is with the user-space
parsing of the data, rather than the kernel driver.

Cheers