[PATCH] acpi/battery: fix wrong value of capacity_now reported by few battery types when fully charged

[Josef Gajdusek]

It seems that some batteries (noticed on DELL JYPJ136) assume 
capacity_now = design_capacity when fully charged. This causes 
reported capacity to suddenly jump to >full_charge_capacity (and that 
means capacity reported to userspace is >100% and incorrect) 
values after 99%. This patch attempts to detect this bug and trims 
capacity_now properly.

---
diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index e48fc98..3338dd5 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -532,6 +532,14 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
 			" invalid.\n");
 	}
 
+	/* When fully charged, some batteries wrongly report
+	 * capacity_now = design_capacity instead of = full_charge_capacity
+	 */
+	if (battery->capacity_now == battery->design_capacity &&
+	    battery->full_charge_capacity != ACPI_BATTERY_VALUE_UNKNOWN)
+		battery->capacity_now = battery->full_charge_capacity;
+
+
 	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags)
 	    && battery->capacity_now >= 0 && battery->capacity_now <= 100)
 		battery->capacity_now = (battery->capacity_now *

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