s found, even if that is reported as a feature
  (as it was meant to be but only the MagicTrackpad does)
- when upower or someone access /sys/class/power_supply/hid-*/capacity it
  will probe the device and return it's status.

It works great for both devices, but I have two concerns:
- the report_features function has a duplicated code
- it would be nice if it was possible for specific drivers to provide their own
  probe as there might be some strange devices... (but maybe it's
already possible)

I've talked to the upower dev and he fixed it to be able to show the
right percentage.

Here how the uevent file (in /sys/class/power_supply/hid-*/) looks like:
POWER_SUPPLY_NAME=hid-00:22:41:D9:18:E7-battery
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_ONLINE=1
POWER_SUPPLY_CAPACITY=66
POWER_SUPPLY_MODEL_NAME=MacAdmin’s keyboard
POWER_SUPPLY_STATUS=Discharging

POWER_SUPPLY_NAME=hid-70:CD:60:F5:FF:3F-battery
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_ONLINE=1
POWER_SUPPLY_CAPACITY=62
POWER_SUPPLY_MODEL_NAME=nexx’s Trackpad
POWER_SUPPLY_STATUS=Discharging

Signed-off-by: Daniel Nicoletti <dantti12@gmail.com>
YùÛ"’&x