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ACPI: battery: negate current when discharging

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The ACPI specification requires that battery rate is always positive,
but the kernel ABI for POWER_SUPPLY_PROP_CURRENT_NOW
(Documentation/ABI/testing/sysfs-class-power) specifies that it should
be negative when a battery is discharging. When reporting CURRENT_NOW,
massage the value to match the documented ABI.

This only changes the sign of `current_now` and not `power_now` because
documentation doesn't describe any particular meaning for `power_now` so
leaving `power_now` unchanged is less likely to confuse userspace
unnecessarily, whereas becoming consistent with the documented ABI is
worth potentially confusing clients that read `current_now`.

Signed-off-by: Peter Marheine <pmarheine@chromium.org>
Link: https://patch.msgid.link/20250508024146.1436129-1-pmarheine@chromium.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Peter Marheine 2025-05-08 12:41:45 +10:00 • committed by Rafael J. Wysocki
parent 46d839adcc
commit 234f715550
1 changed files with 16 additions and 3 deletions
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19
drivers/acpi/battery.c
View file

@ -243,10 +243,23 @@ static int acpi_battery_get_property(struct power_supply *psy,
break;
case POWER_SUPPLY_PROP_CURRENT_NOW:
case POWER_SUPPLY_PROP_POWER_NOW:
if (battery->rate_now == ACPI_BATTERY_VALUE_UNKNOWN)
if (battery->rate_now == ACPI_BATTERY_VALUE_UNKNOWN) {
ret = -ENODEV;
else
val->intval = battery->rate_now * 1000;
break;
}
val->intval = battery->rate_now * 1000;
/*
* When discharging, the current should be reported as a
* negative number as per the power supply class interface
* definition.
*/
if (psp == POWER_SUPPLY_PROP_CURRENT_NOW &&
(battery->state & ACPI_BATTERY_STATE_DISCHARGING) &&
acpi_battery_handle_discharging(battery)
== POWER_SUPPLY_STATUS_DISCHARGING)
val->intval = -val->intval;
break;
case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN: