thinkpad_acpi: add support for force_discharge

index b8b74889..28a87640 100644
@@ -9236,7 +9236,11 @@ static struct ibm_struct mute_led_driver_data = {
 #define SET_INHIBIT	"BICS"
 #define GET_INHIBIT	"BICG"
 
+#define GET_DISCHARGE	"BDSG"
+#define SET_DISCHARGE	"PSBS"
+
 #define INHIBIT_ATTR	"inhibit_charge"
+#define DISCHARGE_ATTR	"force_discharge"
 
 #define START_ATTR "charge_start_threshold"
 #define STOP_ATTR  "charge_stop_threshold"

@@ -9256,7 +9260,8 @@ enum {
 	/* This is used in the get/set helpers */
 	THRESHOLD_START,
 	THRESHOLD_STOP,
-	INHIBIT_CHARGE
+	INHIBIT_CHARGE,
+	FORCE_DISCHARGE
 };
 
 struct tpacpi_battery_data {

@@ -9265,6 +9270,7 @@ struct tpacpi_battery_data {
 	int charge_stop;
 	int stop_support;
 	int inhibit_support;
+	int discharge_support;
 };
 
 struct tpacpi_battery_driver_data {

@@ -9329,6 +9335,12 @@ static int tpacpi_battery_get(int what, int battery, int *ret)
 		/* The inhibit charge status is in the first bit */
 		*ret = *ret & 0x01;
 		return 0;
+	case FORCE_DISCHARGE:
+		if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_DISCHARGE, ret, battery))
+			return -ENODEV;
+		/* The force discharge status is in the first bit */
+		*ret = *ret & 0x01;
+		return 0;
 	default:
 		pr_crit("wrong parameter: %d", what);
 		return -EINVAL;

@@ -9372,6 +9384,14 @@ static int tpacpi_battery_set(int what, int battery, int value)
 			return -ENODEV;
 		}
 		return 0;
+	case FORCE_DISCHARGE:
+		param = battery;
+		param |= value << 8;
+		if ACPI_FAILURE(tpacpi_battery_acpi_eval(SET_DISCHARGE, &ret, param)) {
+			pr_err("failed to set force dischrage on %d", battery);
+			return -ENODEV;
+		}
+		return 0;
 	default:
 		pr_crit("wrong parameter: %d", what);
 		return -EINVAL;

@@ -9431,11 +9451,16 @@ static int tpacpi_battery_probe(int battery)
 			/* Support is marked in bit 5 */
 			battery_info.batteries[battery].inhibit_support = ret & BIT(5);
 
-	pr_info("battery %d registered (start %d, stop %d, inhibit: %d)",
+	if (acpi_has_method(hkey_handle, GET_DISCHARGE))
+		if (!ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_DISCHARGE, &ret, battery)))
+			battery_info.batteries[battery].discharge_support = ret & BIT(8);
+
+	pr_info("battery %d registered (start %d, stop %d, inhibit: %d, force: %d)",
 			battery,
 			battery_info.batteries[battery].charge_start,
 			battery_info.batteries[battery].charge_stop,
-			battery_info.batteries[battery].inhibit_support);
+			battery_info.batteries[battery].inhibit_support,
+			battery_info.batteries[battery].discharge_support);
 
 	return 0;
 }

@@ -9530,6 +9555,15 @@ static ssize_t tpacpi_battery_store(int what,
 		if (tpacpi_battery_set(INHIBIT_CHARGE, battery, value))
 			return -ENODEV;
 		return count;
+	case FORCE_DISCHARGE:
+		if (!battery_info.batteries[battery].discharge_support)
+			return -ENODEV;
+		/* The only valid values are 1 and 0 */
+		if (value != 0 && value != 1)
+			return -EINVAL;
+		if (tpacpi_battery_set(FORCE_DISCHARGE, battery, value))
+			return -ENODEV;
+		return count;
 	default:
 		pr_crit("Wrong parameter: %d", what);
 		return -EINVAL;

@@ -9606,14 +9640,30 @@ static ssize_t inhibit_charge_show(struct device *device,
 	return tpacpi_battery_show(INHIBIT_CHARGE, device, buf);
 }
 
+static ssize_t force_discharge_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	return tpacpi_battery_store(FORCE_DISCHARGE, dev, buf, count);
+}
+
+static ssize_t force_discharge_show(struct device *device,
+				struct device_attribute *attr,
+				char *buf)
+{
+	return tpacpi_battery_show(FORCE_DISCHARGE, device, buf);
+}
+
 static DEVICE_ATTR_RW(charge_start_threshold);
 static DEVICE_ATTR_RW(charge_stop_threshold);
 static DEVICE_ATTR_RW(inhibit_charge);
+static DEVICE_ATTR_RW(force_discharge);
 
 static struct attribute *tpacpi_battery_attrs[] = {
 	&dev_attr_charge_start_threshold.attr,
 	&dev_attr_charge_stop_threshold.attr,
 	&dev_attr_inhibit_charge.attr,
+	&dev_attr_force_discharge.attr,
 	NULL,
 };