Re: [PATCH] ACPI / Battery: Return -ENODATA for unknown values in get_property()

[Sitsofe Wheeler <sitsofe@yahoo.com>]

On Sat, Oct 23, 2010 at 12:19:13AM +0200, Rafael J. Wysocki wrote:
> 
> OK, so can you test the patch below, please?

The latest patch seems to fix/workaround the problem. upower now reports
0 as the energy rate, there are no warnings in dmesg and battery hotplug
works. Looks good and there's the option for a future upower to
interpret the missing sysfs as meaning "unknown".

Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>

> The function acpi_battery_get_property() is called by the
> power supply framework's function power_supply_show_property()
> implementing the sysfs interface for power supply devices as the
> ACPI battery driver's ->get_property() callback.  Thus it is supposed
> to return error code if the value of the given property is unknown.
> Unfortunately, however, it returns 0 in those cases and puts a
> wrong (negative) value into the intval field of the
> union power_supply_propval object provided by
> power_supply_show_property().  In consequence, wron negative

wron -> wrong?

> Fix this by making acpi_battery_get_property() return -ENODEV
> for properties with unknown values (-ENODEV is returned, because
> power_supply_uevent() returns with error for any other error code
> returned by power_supply_show_property()).

OK that's sneaky and clever - technically power_supply_uevent should be
more robust but presumably things are already prepared to handle -ENODEV
so overloading the meaning leads to the smallest change.

-- 
Sitsofe | http://sucs.org/~sits/