sbs-battery: Reading CHARGE in uAh

[Michael Heinemann <posted@heine.so>]

Hi,

I got an INSPIRED ENERGY NH2057 Battery which is compliant to SBS 
Specification Version 1.1.

The Battery is generally working but I noticed that the values I get 
from sysfs for the CHARGE values
are identical to the values I get as ENERGY and they are in uWh. 
According to the power_supply_class
documentation CHARGE should be in uAh and ENERGY in uWh.

So I took a look into the drivers/power/supply/sbs-battery.c and noticed 
a possible bug in the code
when switching from BATTERY_MODE_WATTS to BATTERY_MODE_AMPS:

The configuration bit, according to the SBS Spec, is bit 15 of the 
BatteryMode Register.

These two modes are reflected in the code as:

enum sbs_battery_mode {
	BATTERY_MODE_AMPS,
	BATTERY_MODE_WATTS
};

When I look into the 'sbs_set_battery_mode' function I don't see any 
point where these mode bits are
shifted to bit 15. When I debug I only see the register being changed 
from 0x8000 to 0x8001 and back.

So I'm a bit confused, is this actually working for somebody? I see in 
the 'for-next' branch [1] that
there is currently work done to add a mutex to the mode switch. So at 
least it seems to be working for
some people. But I don't see why. Am I missing something?


Regards,
Michael

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply.git/log/drivers/power/supply/sbs-battery.c?h=for-next