compal-laptop: Add charge control limit

Add charge control limit to the power supply subsystem of the Compal
platform driver.

This apparently was present in the original driver by Cezary Jackiewicz
at http://eko.one.pl/index.php?page=compal-laptop but it seems to have been
overlooked.

The Kconfig description is updated to reflect this addition. It now also
mentions the hwmon interface that was already present.
Signed-off-by: Roald Frederickx <roald.frederickx@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

drivers/platform/x86/Kconfig

@@ -309,8 +309,8 @@ config COMPAL_LAPTOP
 	  This is a driver for laptops built by Compal, and some models by
 	  other brands (e.g. Dell, Toshiba).
 
-	  It adds support for rfkill, Bluetooth, WLAN and LCD brightness
-	  control.
+	  It adds support for rfkill, Bluetooth, WLAN, LCD brightness, hwmon
+	  and battery charging level control.
 
 	  For a (possibly incomplete) list of supported laptops, please refer
 	  to: Documentation/platform/x86-laptop-drivers.txt

drivers/platform/x86/compal-laptop.c

@@ -151,6 +151,8 @@
 #define BAT_STATUS2			0xF1
 #define BAT_STOP_CHARGE1		0xF2
 #define BAT_STOP_CHARGE2		0xF3
+#define BAT_CHARGE_LIMIT		0x03
+#define BAT_CHARGE_LIMIT_MAX		100
 
 #define BAT_S0_DISCHARGE		(1 << 0)
 #define BAT_S0_DISCHRG_CRITICAL		(1 << 2)
@@ -601,6 +603,12 @@ static int bat_get_property(struct power_supply *psy,
 	case POWER_SUPPLY_PROP_CHARGE_NOW:
 		val->intval = ec_read_u16(BAT_CHARGE_NOW) * 1000;
 		break;
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT:
+		val->intval = ec_read_u8(BAT_CHARGE_LIMIT);
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX:
+		val->intval = BAT_CHARGE_LIMIT_MAX;
+		break;
 	case POWER_SUPPLY_PROP_CAPACITY:
 		val->intval = ec_read_u8(BAT_CAPACITY);
 		break;
@@ -634,6 +642,36 @@ static int bat_get_property(struct power_supply *psy,
 	return 0;
 }
 
+static int bat_set_property(struct power_supply *psy,
+				enum power_supply_property psp,
+				const union power_supply_propval *val)
+{
+	int level;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT:
+		level = val->intval;
+		if (level < 0 || level > BAT_CHARGE_LIMIT_MAX)
+			return -EINVAL;
+		if (ec_write(BAT_CHARGE_LIMIT, level) < 0)
+			return -EIO;
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+static int bat_writeable_property(struct power_supply *psy,
+				enum power_supply_property psp)
+{
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT:
+		return 1;
+	default:
+		return 0;
+	}
+}
 
 
 
@@ -726,6 +764,8 @@ static enum power_supply_property compal_bat_properties[] = {
 	POWER_SUPPLY_PROP_POWER_NOW,
 	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
 	POWER_SUPPLY_PROP_CHARGE_NOW,
+	POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT,
+	POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX,
 	POWER_SUPPLY_PROP_CAPACITY,
 	POWER_SUPPLY_PROP_CAPACITY_LEVEL,
 	POWER_SUPPLY_PROP_TEMP,
@@ -880,11 +920,12 @@ static const struct power_supply_desc psy_bat_desc = {
 	.properties	= compal_bat_properties,
 	.num_properties	= ARRAY_SIZE(compal_bat_properties),
 	.get_property	= bat_get_property,
+	.set_property	= bat_set_property,
+	.property_is_writeable = bat_writeable_property,
 };
 
 static void initialize_power_supply_data(struct compal_data *data)
 {
-
 	ec_read_sequence(BAT_MANUFACTURER_NAME_ADDR,
 					data->bat_manufacturer_name,
 					BAT_MANUFACTURER_NAME_LEN);