ACPI battery: support percentage battery remaining capacity

According to the ACPI spec, some kinds of primary battery can
report percentage battery remaining capacity directly to OS.

In this case, it reports the LastFullChargedCapacity == 100,
BatteryPresentRate = 0xFFFFFFFF, and BatteryRemaingCapacity a
percentage value, which actually means RemainingBatteryPercentage.

Now we found some battery follows this rule even if it's a rechargeable.
https://bugzilla.kernel.org/show_bug.cgi?id=15979

Handle these batteries correctly in ACPI battery driver
so that they won't break userspace.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/battery.c

@@ -95,6 +95,7 @@ enum {
 	 * due to bad math.
 	 */
 	ACPI_BATTERY_QUIRK_SIGNED16_CURRENT,
+	ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY,
 };
 
 struct acpi_battery {
@@ -405,6 +406,8 @@ static int acpi_battery_get_info(struct acpi_battery *battery)
 		result = extract_package(battery, buffer.pointer,
 				info_offsets, ARRAY_SIZE(info_offsets));
 	kfree(buffer.pointer);
+	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags))
+		battery->full_charge_capacity = battery->design_capacity;
 	return result;
 }
 
@@ -441,6 +444,10 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
 	    battery->rate_now != -1)
 		battery->rate_now = abs((s16)battery->rate_now);
 
+	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags)
+	    && battery->capacity_now >= 0 && battery->capacity_now <= 100)
+		battery->capacity_now = (battery->capacity_now *
+				battery->full_charge_capacity) / 100;
 	return result;
 }
 
@@ -552,6 +559,33 @@ static void acpi_battery_quirks(struct acpi_battery *battery)
 	}
 }
 
+/*
+ * According to the ACPI spec, some kinds of primary batteries can
+ * report percentage battery remaining capacity directly to OS.
+ * In this case, it reports the Last Full Charged Capacity == 100
+ * and BatteryPresentRate == 0xFFFFFFFF.
+ *
+ * Now we found some battery reports percentage remaining capacity
+ * even if it's rechargeable.
+ * https://bugzilla.kernel.org/show_bug.cgi?id=15979
+ *
+ * Handle this correctly so that they won't break userspace.
+ */
+static void acpi_battery_quirks2(struct acpi_battery *battery)
+{
+	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags))
+		return ;
+
+        if (battery->full_charge_capacity == 100 &&
+            battery->rate_now == ACPI_BATTERY_VALUE_UNKNOWN &&
+            battery->capacity_now >=0 && battery->capacity_now <= 100) {
+		set_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags);
+		battery->full_charge_capacity = battery->design_capacity;
+		battery->capacity_now = (battery->capacity_now *
+				battery->full_charge_capacity) / 100;
+	}
+}
+
 static int acpi_battery_update(struct acpi_battery *battery)
 {
 	int result, old_present = acpi_battery_present(battery);
@@ -573,7 +607,9 @@ static int acpi_battery_update(struct acpi_battery *battery)
 	}
 	if (!battery->bat.dev)
 		sysfs_add_battery(battery);
-	return acpi_battery_get_state(battery);
+	result = acpi_battery_get_state(battery);
+	acpi_battery_quirks2(battery);
+	return result;
 }
 
 /* --------------------------------------------------------------------------