From 7c0940e431c33ca13e9fde57ea0ad56da6529c56 Mon Sep 17 00:00:00 2001 From: Itay Shem-tov Date: Thu, 3 Sep 2026 13:42:44 +0300 Subject: [PATCH] ACPI: SBS: report relative state of charge as CAPACITY acpi_sbs reads SBS command 0x0e (AbsoluteStateOfCharge) into battery->state_of_charge, which is exported unmodified as POWER_SUPPLY_PROP_CAPACITY. Per the Smart Battery Data Specification 1.1, 0x0e is expressed as a percentage of DesignCapacity and is explicitly permitted to exceed 100%. Documentation/ABI/testing/sysfs-class-power specifies the capacity attribute as "Valid values: 0 - 100 (percent)", so any pack whose FullChargeCapacity exceeds its DesignCapacity - the normal state of a new or recently replaced battery - makes the driver report out of range. The correct source is 0x0d (RelativeStateOfCharge), a percentage of FullChargeCapacity, which the specification bounds to 0..100. This is the same defect that was fixed in the i2c SBS driver by commit b1f092f6480e ("sbs-battery.c: Capacity attr = remaining relative capacity"), whose reasoning applies verbatim here; drivers/acpi/sbs.c was not updated at the time. drivers/power/supply/sbs-battery.c has used 0x0d since, so the two SBS drivers currently disagree about what CAPACITY means. Observed on a MacBookPro11,1 with an SMP/bq20z451 pack (FullChargeCapacity 6775 mAh, DesignCapacity 6400 mAh). Both registers read back-to-back from the pack at a full charge: 0x0d RelativeStateOfCharge = 100 % 0x0e AbsoluteStateOfCharge = 106 % /sys/class/power_supply/BAT0/capacity reported 106 while upower, which computes charge_now/charge_full itself rather than trusting the driver, reported 100. battery->state_of_charge has no other consumer, so no other property changes behaviour. Signed-off-by: Itay Shem-tov Reviewed-by: Sebastian Reichel Link: https://patch.msgid.link/20260903104244.25556-1-itayst@gmail.com Signed-off-by: Rafael J. Wysocki --- drivers/acpi/sbs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/sbs.c b/drivers/acpi/sbs.c index 86b7c7975852..862cb94a8b43 100644 --- a/drivers/acpi/sbs.c +++ b/drivers/acpi/sbs.c @@ -318,7 +318,7 @@ static struct acpi_battery_reader state_readers[] = { {0x0a, SMBUS_READ_WORD, offsetof(struct acpi_battery, rate_now)}, {0x0b, SMBUS_READ_WORD, offsetof(struct acpi_battery, rate_avg)}, {0x0f, SMBUS_READ_WORD, offsetof(struct acpi_battery, capacity_now)}, - {0x0e, SMBUS_READ_WORD, offsetof(struct acpi_battery, state_of_charge)}, + {0x0d, SMBUS_READ_WORD, offsetof(struct acpi_battery, state_of_charge)}, {0x16, SMBUS_READ_WORD, offsetof(struct acpi_battery, state)}, };