drivers/video/backlight/lp855x_bl.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * TI LP855x Backlight Driver
  *
  *			Copyright (C) 2011 Texas Instruments
  */

 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/backlight.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/of.h>
 #include <linux/platform_data/lp855x.h>
 #include <linux/pwm.h>
 #include <linux/regulator/consumer.h>

 /* LP8550/1/2/3/6 Registers */
 #define LP855X_BRIGHTNESS_CTRL		0x00
 #define LP855X_DEVICE_CTRL		0x01
 #define LP855X_EEPROM_START		0xA0
 #define LP855X_EEPROM_END		0xA7
 #define LP8556_EPROM_START		0xA0
 #define LP8556_EPROM_END		0xAF

 /* LP8555/7 Registers */
 #define LP8557_BL_CMD			0x00
 #define LP8557_BL_MASK			0x01
 #define LP8557_BL_ON			0x01
 #define LP8557_BL_OFF			0x00
 #define LP8557_BRIGHTNESS_CTRL		0x04
 #define LP8557_CONFIG			0x10
 #define LP8555_EPROM_START		0x10
 #define LP8555_EPROM_END		0x7A
 #define LP8557_EPROM_START		0x10
 #define LP8557_EPROM_END		0x1E

 #define DEFAULT_BL_NAME		"lcd-backlight"
 #define MAX_BRIGHTNESS		255

 enum lp855x_brightness_ctrl_mode {
 	PWM_BASED = 1,
 	REGISTER_BASED,
 };

 struct lp855x;

 /*
  * struct lp855x_device_config
  * @pre_init_device: init device function call before updating the brightness
  * @reg_brightness: register address for brigthenss control
  * @reg_devicectrl: register address for device control
  * @post_init_device: late init device function call
  */
 struct lp855x_device_config {
 	int (*pre_init_device)(struct lp855x *);
 	u8 reg_brightness;
 	u8 reg_devicectrl;
 	int (*post_init_device)(struct lp855x *);
 };

 struct lp855x {
 	const char *chipname;
 	enum lp855x_chip_id chip_id;
 	enum lp855x_brightness_ctrl_mode mode;
 	struct lp855x_device_config *cfg;
 	struct i2c_client *client;
 	struct backlight_device *bl;
 	struct device *dev;
 	struct lp855x_platform_data *pdata;
 	struct pwm_device *pwm;
 	struct regulator *supply;	/* regulator for VDD input */
 	struct regulator *enable;	/* regulator for EN/VDDIO input */
 };

 static int lp855x_write_byte(struct lp855x *lp, u8 reg, u8 data)
 {
 	return i2c_smbus_write_byte_data(lp->client, reg, data);
 }

 static int lp855x_update_bit(struct lp855x *lp, u8 reg, u8 mask, u8 data)
 {
 	int ret;
 	u8 tmp;

 	ret = i2c_smbus_read_byte_data(lp->client, reg);
 	if (ret < 0) {
 		dev_err(lp->dev, "failed to read 0x%.2x\n", reg);
 		return ret;
 	}

 	tmp = (u8)ret;
 	tmp &= ~mask;
 	tmp |= data & mask;

 	return lp855x_write_byte(lp, reg, tmp);
 }

 static bool lp855x_is_valid_rom_area(struct lp855x *lp, u8 addr)
 {
 	u8 start, end;

 	switch (lp->chip_id) {
 	case LP8550:
 	case LP8551:
 	case LP8552:
 	case LP8553:
 		start = LP855X_EEPROM_START;
 		end = LP855X_EEPROM_END;
 		break;
 	case LP8556:
 		start = LP8556_EPROM_START;
 		end = LP8556_EPROM_END;
 		break;
 	case LP8555:
 		start = LP8555_EPROM_START;
 		end = LP8555_EPROM_END;
 		break;
 	case LP8557:
 		start = LP8557_EPROM_START;
 		end = LP8557_EPROM_END;
 		break;
 	default:
 		return false;
 	}

 	return addr >= start && addr <= end;
 }

 static int lp8557_bl_off(struct lp855x *lp)
 {
 	/* BL_ON = 0 before updating EPROM settings */
 	return lp855x_update_bit(lp, LP8557_BL_CMD, LP8557_BL_MASK,
 				LP8557_BL_OFF);
 }

 static int lp8557_bl_on(struct lp855x *lp)
 {
 	/* BL_ON = 1 after updating EPROM settings */
 	return lp855x_update_bit(lp, LP8557_BL_CMD, LP8557_BL_MASK,
 				LP8557_BL_ON);
 }

 static struct lp855x_device_config lp855x_dev_cfg = {
 	.reg_brightness = LP855X_BRIGHTNESS_CTRL,
 	.reg_devicectrl = LP855X_DEVICE_CTRL,
 };

 static struct lp855x_device_config lp8557_dev_cfg = {
 	.reg_brightness = LP8557_BRIGHTNESS_CTRL,
 	.reg_devicectrl = LP8557_CONFIG,
 	.pre_init_device = lp8557_bl_off,
 	.post_init_device = lp8557_bl_on,
 };

 /*
  * Device specific configuration flow
  *
  *    a) pre_init_device(optional)
  *    b) update the brightness register
  *    c) update device control register
  *    d) update ROM area(optional)
  *    e) post_init_device(optional)
  *
  */
 static int lp855x_configure(struct lp855x *lp)
 {
 	u8 val, addr;
 	int i, ret;
 	struct lp855x_platform_data *pd = lp->pdata;

 	switch (lp->chip_id) {
 	case LP8550:
 	case LP8551:
 	case LP8552:
 	case LP8553:
 	case LP8556:
 		lp->cfg = &lp855x_dev_cfg;
 		break;
 	case LP8555:
 	case LP8557:
 		lp->cfg = &lp8557_dev_cfg;
 		break;
 	default:
 		return -EINVAL;
 	}

 	if (lp->cfg->pre_init_device) {
 		ret = lp->cfg->pre_init_device(lp);
 		if (ret) {
 			dev_err(lp->dev, "pre init device err: %d\n", ret);
 			goto err;
 		}
 	}

 	val = pd->initial_brightness;
 	ret = lp855x_write_byte(lp, lp->cfg->reg_brightness, val);
 	if (ret)
 		goto err;

 	val = pd->device_control;
 	ret = lp855x_write_byte(lp, lp->cfg->reg_devicectrl, val);
 	if (ret)
 		goto err;

 	if (pd->size_program > 0) {
 		for (i = 0; i < pd->size_program; i++) {
 			addr = pd->rom_data[i].addr;
 			val = pd->rom_data[i].val;
 			if (!lp855x_is_valid_rom_area(lp, addr))
 				continue;

 			ret = lp855x_write_byte(lp, addr, val);
 			if (ret)
 				goto err;
 		}
 	}

 	if (lp->cfg->post_init_device) {
 		ret = lp->cfg->post_init_device(lp);
 		if (ret) {
 			dev_err(lp->dev, "post init device err: %d\n", ret);
 			goto err;
 		}
 	}

 	return 0;

 err:
 	return ret;
 }

 static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 {
 	unsigned int period = lp->pdata->period_ns;
 	unsigned int duty = br * period / max_br;
 	struct pwm_device *pwm;

 	/* request pwm device with the consumer name */
 	if (!lp->pwm) {
 		pwm = devm_pwm_get(lp->dev, lp->chipname);
 		if (IS_ERR(pwm))
 			return;

 		lp->pwm = pwm;

 		/*
 		 * FIXME: pwm_apply_args() should be removed when switching to
 		 * the atomic PWM API.
 		 */
 		pwm_apply_args(pwm);
 	}

 	pwm_config(lp->pwm, duty, period);
 	if (duty)
 		pwm_enable(lp->pwm);
 	else
 		pwm_disable(lp->pwm);
 }

 static int lp855x_bl_update_status(struct backlight_device *bl)
 {
 	struct lp855x *lp = bl_get_data(bl);
 	int brightness = bl->props.brightness;

 	if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
 		brightness = 0;

 	if (lp->mode == PWM_BASED)
 		lp855x_pwm_ctrl(lp, brightness, bl->props.max_brightness);
 	else if (lp->mode == REGISTER_BASED)
 		lp855x_write_byte(lp, lp->cfg->reg_brightness, (u8)brightness);

 	return 0;
 }

 static const struct backlight_ops lp855x_bl_ops = {
 	.options = BL_CORE_SUSPENDRESUME,
 	.update_status = lp855x_bl_update_status,
 };

 static int lp855x_backlight_register(struct lp855x *lp)
 {
 	struct backlight_device *bl;
 	struct backlight_properties props;
 	struct lp855x_platform_data *pdata = lp->pdata;
 	const char *name = pdata->name ? : DEFAULT_BL_NAME;

 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_PLATFORM;
 	props.max_brightness = MAX_BRIGHTNESS;

 	if (pdata->initial_brightness > props.max_brightness)
 		pdata->initial_brightness = props.max_brightness;

 	props.brightness = pdata->initial_brightness;

 	bl = devm_backlight_device_register(lp->dev, name, lp->dev, lp,
 				       &lp855x_bl_ops, &props);
 	if (IS_ERR(bl))
 		return PTR_ERR(bl);

 	lp->bl = bl;

 	return 0;
 }

 static ssize_t lp855x_get_chip_id(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
 	struct lp855x *lp = dev_get_drvdata(dev);

 	return scnprintf(buf, PAGE_SIZE, "%s\n", lp->chipname);
 }

 static ssize_t lp855x_get_bl_ctl_mode(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
 	struct lp855x *lp = dev_get_drvdata(dev);
 	char *strmode = NULL;

 	if (lp->mode == PWM_BASED)
 		strmode = "pwm based";
 	else if (lp->mode == REGISTER_BASED)
 		strmode = "register based";

 	return scnprintf(buf, PAGE_SIZE, "%s\n", strmode);
 }

 static DEVICE_ATTR(chip_id, S_IRUGO, lp855x_get_chip_id, NULL);
 static DEVICE_ATTR(bl_ctl_mode, S_IRUGO, lp855x_get_bl_ctl_mode, NULL);

 static struct attribute *lp855x_attributes[] = {
 	&dev_attr_chip_id.attr,
 	&dev_attr_bl_ctl_mode.attr,
 	NULL,
 };

 static const struct attribute_group lp855x_attr_group = {
 	.attrs = lp855x_attributes,
 };

 #ifdef CONFIG_OF
 static int lp855x_parse_dt(struct lp855x *lp)
 {
 	struct device *dev = lp->dev;
 	struct device_node *node = dev->of_node;
 	struct lp855x_platform_data *pdata;
 	int rom_length;

 	if (!node) {
 		dev_err(dev, "no platform data\n");
 		return -EINVAL;
 	}

 	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
 	if (!pdata)
 		return -ENOMEM;

 	of_property_read_string(node, "bl-name", &pdata->name);
 	of_property_read_u8(node, "dev-ctrl", &pdata->device_control);
 	of_property_read_u8(node, "init-brt", &pdata->initial_brightness);
 	of_property_read_u32(node, "pwm-period", &pdata->period_ns);

 	/* Fill ROM platform data if defined */
 	rom_length = of_get_child_count(node);
 	if (rom_length > 0) {
 		struct lp855x_rom_data *rom;
 		struct device_node *child;
 		int i = 0;

 		rom = devm_kcalloc(dev, rom_length, sizeof(*rom), GFP_KERNEL);
 		if (!rom)
 			return -ENOMEM;

 		for_each_child_of_node(node, child) {
 			of_property_read_u8(child, "rom-addr", &rom[i].addr);
 			of_property_read_u8(child, "rom-val", &rom[i].val);
 			i++;
 		}

 		pdata->size_program = rom_length;
 		pdata->rom_data = &rom[0];
 	}

 	lp->pdata = pdata;

 	return 0;
 }
 #else
 static int lp855x_parse_dt(struct lp855x *lp)
 {
 	return -EINVAL;
 }
 #endif

 static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
 {
 	struct lp855x *lp;
 	int ret;

 	if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
 		return -EIO;

 	lp = devm_kzalloc(&cl->dev, sizeof(struct lp855x), GFP_KERNEL);
 	if (!lp)
 		return -ENOMEM;

 	lp->client = cl;
 	lp->dev = &cl->dev;
 	lp->chipname = id->name;
 	lp->chip_id = id->driver_data;
 	lp->pdata = dev_get_platdata(&cl->dev);

 	if (!lp->pdata) {
 		ret = lp855x_parse_dt(lp);
 		if (ret < 0)
 			return ret;
 	}

 	if (lp->pdata->period_ns > 0)
 		lp->mode = PWM_BASED;
 	else
 		lp->mode = REGISTER_BASED;

 	lp->supply = devm_regulator_get(lp->dev, "power");
 	if (IS_ERR(lp->supply)) {
 		if (PTR_ERR(lp->supply) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;
 		lp->supply = NULL;
 	}

 	lp->enable = devm_regulator_get_optional(lp->dev, "enable");
 	if (IS_ERR(lp->enable)) {
 		ret = PTR_ERR(lp->enable);
 		if (ret == -ENODEV) {
 			lp->enable = NULL;
 		} else {
 			if (ret != -EPROBE_DEFER)
 				dev_err(lp->dev, "error getting enable regulator: %d\n",
 					ret);
 			return ret;
 		}
 	}

 	if (lp->supply) {
 		ret = regulator_enable(lp->supply);
 		if (ret < 0) {
 			dev_err(&cl->dev, "failed to enable supply: %d\n", ret);
 			return ret;
 		}
 	}

 	if (lp->enable) {
 		ret = regulator_enable(lp->enable);
 		if (ret < 0) {
 			dev_err(lp->dev, "failed to enable vddio: %d\n", ret);
 			return ret;
 		}

 		/*
 		 * LP8555 datasheet says t_RESPONSE (time between VDDIO and
 		 * I2C) is 1ms.
 		 */
 		usleep_range(1000, 2000);
 	}

 	i2c_set_clientdata(cl, lp);

 	ret = lp855x_configure(lp);
 	if (ret) {
 		dev_err(lp->dev, "device config err: %d", ret);
 		return ret;
 	}

 	ret = lp855x_backlight_register(lp);
 	if (ret) {
 		dev_err(lp->dev,
 			"failed to register backlight. err: %d\n", ret);
 		return ret;
 	}

 	ret = sysfs_create_group(&lp->dev->kobj, &lp855x_attr_group);
 	if (ret) {
 		dev_err(lp->dev, "failed to register sysfs. err: %d\n", ret);
 		return ret;
 	}

 	backlight_update_status(lp->bl);
 	return 0;
 }

 static int lp855x_remove(struct i2c_client *cl)
 {
 	struct lp855x *lp = i2c_get_clientdata(cl);

 	lp->bl->props.brightness = 0;
 	backlight_update_status(lp->bl);
 	if (lp->supply)
 		regulator_disable(lp->supply);
 	sysfs_remove_group(&lp->dev->kobj, &lp855x_attr_group);

 	return 0;
 }

 static const struct of_device_id lp855x_dt_ids[] = {
 	{ .compatible = "ti,lp8550", },
 	{ .compatible = "ti,lp8551", },
 	{ .compatible = "ti,lp8552", },
 	{ .compatible = "ti,lp8553", },
 	{ .compatible = "ti,lp8555", },
 	{ .compatible = "ti,lp8556", },
 	{ .compatible = "ti,lp8557", },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, lp855x_dt_ids);

 static const struct i2c_device_id lp855x_ids[] = {
 	{"lp8550", LP8550},
 	{"lp8551", LP8551},
 	{"lp8552", LP8552},
 	{"lp8553", LP8553},
 	{"lp8555", LP8555},
 	{"lp8556", LP8556},
 	{"lp8557", LP8557},
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, lp855x_ids);

 static struct i2c_driver lp855x_driver = {
 	.driver = {
 		   .name = "lp855x",
 		   .of_match_table = of_match_ptr(lp855x_dt_ids),
 		   },
 	.probe = lp855x_probe,
 	.remove = lp855x_remove,
 	.id_table = lp855x_ids,
 };

 module_i2c_driver(lp855x_driver);

 MODULE_DESCRIPTION("Texas Instruments LP855x Backlight driver");
 MODULE_AUTHOR("Milo Kim <milo.kim@ti.com>");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* TI LP855x Backlight Driver
	*
	* Copyright (C) 2011 Texas Instruments
	*/

	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/i2c.h>
	#include <linux/backlight.h>
	#include <linux/delay.h>
	#include <linux/err.h>
	#include <linux/of.h>
	#include <linux/platform_data/lp855x.h>
	#include <linux/pwm.h>
	#include <linux/regulator/consumer.h>

	/* LP8550/1/2/3/6 Registers */
	#define LP855X_BRIGHTNESS_CTRL 0x00
	#define LP855X_DEVICE_CTRL 0x01
	#define LP855X_EEPROM_START 0xA0
	#define LP855X_EEPROM_END 0xA7
	#define LP8556_EPROM_START 0xA0
	#define LP8556_EPROM_END 0xAF

	/* LP8555/7 Registers */
	#define LP8557_BL_CMD 0x00
	#define LP8557_BL_MASK 0x01
	#define LP8557_BL_ON 0x01
	#define LP8557_BL_OFF 0x00
	#define LP8557_BRIGHTNESS_CTRL 0x04
	#define LP8557_CONFIG 0x10
	#define LP8555_EPROM_START 0x10
	#define LP8555_EPROM_END 0x7A
	#define LP8557_EPROM_START 0x10
	#define LP8557_EPROM_END 0x1E

	#define DEFAULT_BL_NAME "lcd-backlight"
	#define MAX_BRIGHTNESS 255

	enum lp855x_brightness_ctrl_mode {
	PWM_BASED = 1,
	REGISTER_BASED,
	};

	struct lp855x;

	/*
	* struct lp855x_device_config
	* @pre_init_device: init device function call before updating the brightness
	* @reg_brightness: register address for brigthenss control
	* @reg_devicectrl: register address for device control
	* @post_init_device: late init device function call
	*/
	struct lp855x_device_config {
	int (pre_init_device)(struct lp855x );
	u8 reg_brightness;
	u8 reg_devicectrl;
	int (post_init_device)(struct lp855x );
	};

	struct lp855x {
	const char *chipname;
	enum lp855x_chip_id chip_id;
	enum lp855x_brightness_ctrl_mode mode;
	struct lp855x_device_config *cfg;
	struct i2c_client *client;
	struct backlight_device *bl;
	struct device *dev;
	struct lp855x_platform_data *pdata;
	struct pwm_device *pwm;
	struct regulator supply; / regulator for VDD input */
	struct regulator enable; / regulator for EN/VDDIO input */
	};

	static int lp855x_write_byte(struct lp855x *lp, u8 reg, u8 data)
	{
	return i2c_smbus_write_byte_data(lp->client, reg, data);
	}

	static int lp855x_update_bit(struct lp855x *lp, u8 reg, u8 mask, u8 data)
	{
	int ret;
	u8 tmp;

	ret = i2c_smbus_read_byte_data(lp->client, reg);
	if (ret < 0) {
	dev_err(lp->dev, "failed to read 0x%.2x\n", reg);
	return ret;
	}

	tmp = (u8)ret;
	tmp &= ~mask;
	tmp \|= data & mask;

	return lp855x_write_byte(lp, reg, tmp);
	}

	static bool lp855x_is_valid_rom_area(struct lp855x *lp, u8 addr)
	{
	u8 start, end;

	switch (lp->chip_id) {
	case LP8550:
	case LP8551:
	case LP8552:
	case LP8553:
	start = LP855X_EEPROM_START;
	end = LP855X_EEPROM_END;
	break;
	case LP8556:
	start = LP8556_EPROM_START;
	end = LP8556_EPROM_END;
	break;
	case LP8555:
	start = LP8555_EPROM_START;
	end = LP8555_EPROM_END;
	break;
	case LP8557:
	start = LP8557_EPROM_START;
	end = LP8557_EPROM_END;
	break;
	default:
	return false;
	}

	return addr >= start && addr <= end;
	}

	static int lp8557_bl_off(struct lp855x *lp)
	{
	/* BL_ON = 0 before updating EPROM settings */
	return lp855x_update_bit(lp, LP8557_BL_CMD, LP8557_BL_MASK,
	LP8557_BL_OFF);
	}

	static int lp8557_bl_on(struct lp855x *lp)
	{
	/* BL_ON = 1 after updating EPROM settings */
	return lp855x_update_bit(lp, LP8557_BL_CMD, LP8557_BL_MASK,
	LP8557_BL_ON);
	}

	static struct lp855x_device_config lp855x_dev_cfg = {
	.reg_brightness = LP855X_BRIGHTNESS_CTRL,
	.reg_devicectrl = LP855X_DEVICE_CTRL,
	};

	static struct lp855x_device_config lp8557_dev_cfg = {
	.reg_brightness = LP8557_BRIGHTNESS_CTRL,
	.reg_devicectrl = LP8557_CONFIG,
	.pre_init_device = lp8557_bl_off,
	.post_init_device = lp8557_bl_on,
	};

	/*
	* Device specific configuration flow
	*
	* a) pre_init_device(optional)
	* b) update the brightness register
	* c) update device control register
	* d) update ROM area(optional)
	* e) post_init_device(optional)
	*
	*/
	static int lp855x_configure(struct lp855x *lp)
	{
	u8 val, addr;
	int i, ret;
	struct lp855x_platform_data *pd = lp->pdata;

	switch (lp->chip_id) {
	case LP8550:
	case LP8551:
	case LP8552:
	case LP8553:
	case LP8556:
	lp->cfg = &lp855x_dev_cfg;
	break;
	case LP8555:
	case LP8557:
	lp->cfg = &lp8557_dev_cfg;
	break;
	default:
	return -EINVAL;
	}

	if (lp->cfg->pre_init_device) {
	ret = lp->cfg->pre_init_device(lp);
	if (ret) {
	dev_err(lp->dev, "pre init device err: %d\n", ret);
	goto err;
	}
	}

	val = pd->initial_brightness;
	ret = lp855x_write_byte(lp, lp->cfg->reg_brightness, val);
	if (ret)
	goto err;

	val = pd->device_control;
	ret = lp855x_write_byte(lp, lp->cfg->reg_devicectrl, val);
	if (ret)
	goto err;

	if (pd->size_program > 0) {
	for (i = 0; i < pd->size_program; i++) {
	addr = pd->rom_data[i].addr;
	val = pd->rom_data[i].val;
	if (!lp855x_is_valid_rom_area(lp, addr))
	continue;

	ret = lp855x_write_byte(lp, addr, val);
	if (ret)
	goto err;
	}
	}

	if (lp->cfg->post_init_device) {
	ret = lp->cfg->post_init_device(lp);
	if (ret) {
	dev_err(lp->dev, "post init device err: %d\n", ret);
	goto err;
	}
	}

	return 0;

	err:
	return ret;
	}

	static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
	{
	unsigned int period = lp->pdata->period_ns;
	unsigned int duty = br * period / max_br;
	struct pwm_device *pwm;

	/* request pwm device with the consumer name */
	if (!lp->pwm) {
	pwm = devm_pwm_get(lp->dev, lp->chipname);
	if (IS_ERR(pwm))
	return;

	lp->pwm = pwm;

	/*
	* FIXME: pwm_apply_args() should be removed when switching to
	* the atomic PWM API.
	*/
	pwm_apply_args(pwm);
	}

	pwm_config(lp->pwm, duty, period);
	if (duty)
	pwm_enable(lp->pwm);
	else
	pwm_disable(lp->pwm);
	}

	static int lp855x_bl_update_status(struct backlight_device *bl)
	{
	struct lp855x *lp = bl_get_data(bl);
	int brightness = bl->props.brightness;

	if (bl->props.state & (BL_CORE_SUSPENDED \| BL_CORE_FBBLANK))
	brightness = 0;

	if (lp->mode == PWM_BASED)
	lp855x_pwm_ctrl(lp, brightness, bl->props.max_brightness);
	else if (lp->mode == REGISTER_BASED)
	lp855x_write_byte(lp, lp->cfg->reg_brightness, (u8)brightness);

	return 0;
	}

	static const struct backlight_ops lp855x_bl_ops = {
	.options = BL_CORE_SUSPENDRESUME,
	.update_status = lp855x_bl_update_status,
	};

	static int lp855x_backlight_register(struct lp855x *lp)
	{
	struct backlight_device *bl;
	struct backlight_properties props;
	struct lp855x_platform_data *pdata = lp->pdata;
	const char *name = pdata->name ? : DEFAULT_BL_NAME;

	memset(&props, 0, sizeof(props));
	props.type = BACKLIGHT_PLATFORM;
	props.max_brightness = MAX_BRIGHTNESS;

	if (pdata->initial_brightness > props.max_brightness)
	pdata->initial_brightness = props.max_brightness;

	props.brightness = pdata->initial_brightness;

	bl = devm_backlight_device_register(lp->dev, name, lp->dev, lp,
	&lp855x_bl_ops, &props);
	if (IS_ERR(bl))
	return PTR_ERR(bl);

	lp->bl = bl;

	return 0;
	}

	static ssize_t lp855x_get_chip_id(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct lp855x *lp = dev_get_drvdata(dev);

	return scnprintf(buf, PAGE_SIZE, "%s\n", lp->chipname);
	}

	static ssize_t lp855x_get_bl_ctl_mode(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct lp855x *lp = dev_get_drvdata(dev);
	char *strmode = NULL;

	if (lp->mode == PWM_BASED)
	strmode = "pwm based";
	else if (lp->mode == REGISTER_BASED)
	strmode = "register based";

	return scnprintf(buf, PAGE_SIZE, "%s\n", strmode);
	}

	static DEVICE_ATTR(chip_id, S_IRUGO, lp855x_get_chip_id, NULL);
	static DEVICE_ATTR(bl_ctl_mode, S_IRUGO, lp855x_get_bl_ctl_mode, NULL);

	static struct attribute *lp855x_attributes[] = {
	&dev_attr_chip_id.attr,
	&dev_attr_bl_ctl_mode.attr,
	NULL,
	};

	static const struct attribute_group lp855x_attr_group = {
	.attrs = lp855x_attributes,
	};

	#ifdef CONFIG_OF
	static int lp855x_parse_dt(struct lp855x *lp)
	{
	struct device *dev = lp->dev;
	struct device_node *node = dev->of_node;
	struct lp855x_platform_data *pdata;
	int rom_length;

	if (!node) {
	dev_err(dev, "no platform data\n");
	return -EINVAL;
	}

	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
	if (!pdata)
	return -ENOMEM;

	of_property_read_string(node, "bl-name", &pdata->name);
	of_property_read_u8(node, "dev-ctrl", &pdata->device_control);
	of_property_read_u8(node, "init-brt", &pdata->initial_brightness);
	of_property_read_u32(node, "pwm-period", &pdata->period_ns);

	/* Fill ROM platform data if defined */
	rom_length = of_get_child_count(node);
	if (rom_length > 0) {
	struct lp855x_rom_data *rom;
	struct device_node *child;
	int i = 0;

	rom = devm_kcalloc(dev, rom_length, sizeof(*rom), GFP_KERNEL);
	if (!rom)
	return -ENOMEM;

	for_each_child_of_node(node, child) {
	of_property_read_u8(child, "rom-addr", &rom[i].addr);
	of_property_read_u8(child, "rom-val", &rom[i].val);
	i++;
	}

	pdata->size_program = rom_length;
	pdata->rom_data = &rom[0];
	}

	lp->pdata = pdata;

	return 0;
	}
	#else
	static int lp855x_parse_dt(struct lp855x *lp)
	{
	return -EINVAL;
	}
	#endif

	static int lp855x_probe(struct i2c_client cl, const struct i2c_device_id id)
	{
	struct lp855x *lp;
	int ret;

	if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
	return -EIO;

	lp = devm_kzalloc(&cl->dev, sizeof(struct lp855x), GFP_KERNEL);
	if (!lp)
	return -ENOMEM;

	lp->client = cl;
	lp->dev = &cl->dev;
	lp->chipname = id->name;
	lp->chip_id = id->driver_data;
	lp->pdata = dev_get_platdata(&cl->dev);

	if (!lp->pdata) {
	ret = lp855x_parse_dt(lp);
	if (ret < 0)
	return ret;
	}

	if (lp->pdata->period_ns > 0)
	lp->mode = PWM_BASED;
	else
	lp->mode = REGISTER_BASED;

	lp->supply = devm_regulator_get(lp->dev, "power");
	if (IS_ERR(lp->supply)) {
	if (PTR_ERR(lp->supply) == -EPROBE_DEFER)
	return -EPROBE_DEFER;
	lp->supply = NULL;
	}

	lp->enable = devm_regulator_get_optional(lp->dev, "enable");
	if (IS_ERR(lp->enable)) {
	ret = PTR_ERR(lp->enable);
	if (ret == -ENODEV) {
	lp->enable = NULL;
	} else {
	if (ret != -EPROBE_DEFER)
	dev_err(lp->dev, "error getting enable regulator: %d\n",
	ret);
	return ret;
	}
	}

	if (lp->supply) {
	ret = regulator_enable(lp->supply);
	if (ret < 0) {
	dev_err(&cl->dev, "failed to enable supply: %d\n", ret);
	return ret;
	}
	}

	if (lp->enable) {
	ret = regulator_enable(lp->enable);
	if (ret < 0) {
	dev_err(lp->dev, "failed to enable vddio: %d\n", ret);
	return ret;
	}

	/*
	* LP8555 datasheet says t_RESPONSE (time between VDDIO and
	* I2C) is 1ms.
	*/
	usleep_range(1000, 2000);
	}

	i2c_set_clientdata(cl, lp);

	ret = lp855x_configure(lp);
	if (ret) {
	dev_err(lp->dev, "device config err: %d", ret);
	return ret;
	}

	ret = lp855x_backlight_register(lp);
	if (ret) {
	dev_err(lp->dev,
	"failed to register backlight. err: %d\n", ret);
	return ret;
	}

	ret = sysfs_create_group(&lp->dev->kobj, &lp855x_attr_group);
	if (ret) {
	dev_err(lp->dev, "failed to register sysfs. err: %d\n", ret);
	return ret;
	}

	backlight_update_status(lp->bl);
	return 0;
	}

	static int lp855x_remove(struct i2c_client *cl)
	{
	struct lp855x *lp = i2c_get_clientdata(cl);

	lp->bl->props.brightness = 0;
	backlight_update_status(lp->bl);
	if (lp->supply)
	regulator_disable(lp->supply);
	sysfs_remove_group(&lp->dev->kobj, &lp855x_attr_group);

	return 0;
	}

	static const struct of_device_id lp855x_dt_ids[] = {
	{ .compatible = "ti,lp8550", },
	{ .compatible = "ti,lp8551", },
	{ .compatible = "ti,lp8552", },
	{ .compatible = "ti,lp8553", },
	{ .compatible = "ti,lp8555", },
	{ .compatible = "ti,lp8556", },
	{ .compatible = "ti,lp8557", },
	{ }
	};
	MODULE_DEVICE_TABLE(of, lp855x_dt_ids);

	static const struct i2c_device_id lp855x_ids[] = {
	{"lp8550", LP8550},
	{"lp8551", LP8551},
	{"lp8552", LP8552},
	{"lp8553", LP8553},
	{"lp8555", LP8555},
	{"lp8556", LP8556},
	{"lp8557", LP8557},
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, lp855x_ids);

	static struct i2c_driver lp855x_driver = {
	.driver = {
	.name = "lp855x",
	.of_match_table = of_match_ptr(lp855x_dt_ids),
	},
	.probe = lp855x_probe,
	.remove = lp855x_remove,
	.id_table = lp855x_ids,
	};

	module_i2c_driver(lp855x_driver);

	MODULE_DESCRIPTION("Texas Instruments LP855x Backlight driver");
	MODULE_AUTHOR("Milo Kim <milo.kim@ti.com>");
	MODULE_LICENSE("GPL");