samsung-laptop: add battery life extender support

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

Documentation/ABI/testing/sysfs-driver-samsung-laptop

@@ -17,3 +17,13 @@ Description:	Some Samsung laptops have different "performance levels"
 		Specifically, not all support the "overclock" option,
 		and it's still unknown if this value even changes
 		anything, other than making the user feel a bit better.
+
+What:		/sys/devices/platform/samsung/battery_life_extender
+Date:		December 1, 2011
+KernelVersion:	3.3
+Contact:	Corentin Chary <corentin.chary@gmail.com>
+Description:	Max battery charge level can be modified, battery cycle
+		life can be extended by reducing the max battery charge
+		level.
+		0 means normal battery mode (100% charge)
+		1 means battery life extender mode (80% charge)

drivers/platform/x86/samsung-laptop.c

@@ -104,6 +104,10 @@ struct sabi_commands {
 	u16 get_performance_level;
 	u16 set_performance_level;
 
+	/* 0x80 is off, 0x81 is on */
+	u16 get_battery_life_extender;
+	u16 set_battery_life_extender;
+
 	/*
 	 * Tell the BIOS that Linux is running on this machine.
 	 * 81 is on, 80 is off
@@ -157,6 +161,9 @@ static const struct sabi_config sabi_configs[] = {
 			.get_performance_level = 0x08,
 			.set_performance_level = 0x09,
 
+			.get_battery_life_extender = 0xFFFF,
+			.set_battery_life_extender = 0xFFFF,
+
 			.set_linux = 0x0a,
 		},
 
@@ -204,6 +211,9 @@ static const struct sabi_config sabi_configs[] = {
 			.get_performance_level = 0x31,
 			.set_performance_level = 0x32,
 
+			.get_battery_life_extender = 0x65,
+			.set_battery_life_extender = 0x66,
+
 			.set_linux = 0xff,
 		},
 
@@ -543,8 +553,78 @@ static ssize_t set_performance_level(struct device *dev,
 static DEVICE_ATTR(performance_level, S_IWUSR | S_IRUGO,
 		   get_performance_level, set_performance_level);
 
+static int read_battery_life_extender(struct samsung_laptop *samsung)
+{
+	const struct sabi_commands *commands = &samsung->config->commands;
+	struct sabi_data data;
+	int retval;
+
+	if (commands->get_battery_life_extender == 0xFFFF)
+		return -ENODEV;
+
+	memset(&data, 0, sizeof(data));
+	data.data[0] = 0x80;
+	retval = sabi_command(samsung, commands->get_battery_life_extender,
+			      &data, &data);
+
+	if (retval)
+		return retval;
+
+	if (data.data[0] != 0 && data.data[0] != 1)
+		return -ENODEV;
+
+	return data.data[0];
+}
+
+static int write_battery_life_extender(struct samsung_laptop *samsung,
+				       int enabled)
+{
+	const struct sabi_commands *commands = &samsung->config->commands;
+	struct sabi_data data;
+
+	memset(&data, 0, sizeof(data));
+	data.data[0] = 0x80 | enabled;
+	return sabi_command(samsung, commands->set_battery_life_extender,
+			    &data, NULL);
+}
+
+static ssize_t get_battery_life_extender(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct samsung_laptop *samsung = dev_get_drvdata(dev);
+	int ret;
+
+	ret = read_battery_life_extender(samsung);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%d\n", ret);
+}
+
+static ssize_t set_battery_life_extender(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct samsung_laptop *samsung = dev_get_drvdata(dev);
+	int ret, value;
+
+	if (!count || sscanf(buf, "%i", &value) != 1)
+		return -EINVAL;
+
+	ret = write_battery_life_extender(samsung, !!value);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR(battery_life_extender, S_IWUSR | S_IRUGO,
+		   get_battery_life_extender, set_battery_life_extender);
+
 static struct attribute *platform_attributes[] = {
 	&dev_attr_performance_level.attr,
+	&dev_attr_battery_life_extender.attr,
 	NULL
 };
 
@@ -643,6 +723,8 @@ static mode_t samsung_sysfs_is_visible(struct kobject *kobj,
 
 	if (attr == &dev_attr_performance_level.attr)
 		ok = !!samsung->config->performance_levels[0].name;
+	if (attr == &dev_attr_battery_life_extender.attr)
+		ok = !!(read_battery_life_extender(samsung) >= 0);
 
 	return ok ? attr->mode : 0;
 }