Re: [PATCH] ACPI: full battery charge cannot exceed current one

Jan Včelák
2013-12-09T22:25:22Z

>> Some degraded batteries report maximal capacity to be smaller than
>> current charge of the battery. This can confuse some user space
>> applications (like upower).
>
> Can't we just fix upower?

It looks like upower already resolved that:

http://cgit.freedesktop.org/upower/tree/src/linux/up-device-supply.c#n652

If the purpose of sysfs is to provide raw values retrieved from battery,
then I agree that this should not be handled in kernel.
Otherwise I would expect semantically correct data there.

>> + /* Some degraded batteries report lower full charge than current one. */
>> + if (battery->capacity_now > battery->full_charge_capacity)
>> + battery->full_charge_capacity = battery->capacity_now;
>> +
>
> Does upower read *_full on every read of the value? How do we guarantee
> that it won't read energy_now without updating energy_full and still
> come up with an incorrect calculation?

That's a good point. I'm not sure about other applications, but upower
always refreshes all values. Function up_device_supply_refresh_battery
seems to be the only place where 'charge_now' is being read: