drivers/leds/leds-is31fl319x.c - linux-mtk - Git at Google

 /*
  * Copyright 2015-16 Golden Delicious Computers
  *
  * Author: Nikolaus Schaller <hns@goldelico.com>
  *
  * This file is subject to the terms and conditions of version 2 of
  * the GNU General Public License.  See the file COPYING in the main
  * directory of this archive for more details.
  *
  * LED driver for the IS31FL319{0,1,3,6,9} to drive 1, 3, 6 or 9 light
  * effect LEDs.
  *
  */

 #include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/leds.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>

 /* register numbers */
 #define IS31FL319X_SHUTDOWN		0x00
 #define IS31FL319X_CTRL1		0x01
 #define IS31FL319X_CTRL2		0x02
 #define IS31FL319X_CONFIG1		0x03
 #define IS31FL319X_CONFIG2		0x04
 #define IS31FL319X_RAMP_MODE		0x05
 #define IS31FL319X_BREATH_MASK		0x06
 #define IS31FL319X_PWM(channel)		(0x07 + channel)
 #define IS31FL319X_DATA_UPDATE		0x10
 #define IS31FL319X_T0(channel)		(0x11 + channel)
 #define IS31FL319X_T123_1		0x1a
 #define IS31FL319X_T123_2		0x1b
 #define IS31FL319X_T123_3		0x1c
 #define IS31FL319X_T4(channel)		(0x1d + channel)
 #define IS31FL319X_TIME_UPDATE		0x26
 #define IS31FL319X_RESET		0xff

 #define IS31FL319X_REG_CNT		(IS31FL319X_RESET + 1)

 #define IS31FL319X_MAX_LEDS		9

 /* CS (Current Setting) in CONFIG2 register */
 #define IS31FL319X_CONFIG2_CS_SHIFT	4
 #define IS31FL319X_CONFIG2_CS_MASK	0x7
 #define IS31FL319X_CONFIG2_CS_STEP_REF	12

 #define IS31FL319X_CURRENT_MIN		((u32)5000)
 #define IS31FL319X_CURRENT_MAX		((u32)40000)
 #define IS31FL319X_CURRENT_STEP		((u32)5000)
 #define IS31FL319X_CURRENT_DEFAULT	((u32)20000)

 /* Audio gain in CONFIG2 register */
 #define IS31FL319X_AUDIO_GAIN_DB_MAX	((u32)21)
 #define IS31FL319X_AUDIO_GAIN_DB_STEP	((u32)3)

 /*
  * regmap is used as a cache of chip's register space,
  * to avoid reading back brightness values from chip,
  * which is known to hang.
  */
 struct is31fl319x_chip {
 	const struct is31fl319x_chipdef *cdef;
 	struct i2c_client               *client;
 	struct regmap                   *regmap;
 	struct mutex                    lock;
 	u32                             audio_gain_db;

 	struct is31fl319x_led {
 		struct is31fl319x_chip  *chip;
 		struct led_classdev     cdev;
 		u32                     max_microamp;
 		bool                    configured;
 	} leds[IS31FL319X_MAX_LEDS];
 };

 struct is31fl319x_chipdef {
 	int num_leds;
 };

 static const struct is31fl319x_chipdef is31fl3190_cdef = {
 	.num_leds = 1,
 };

 static const struct is31fl319x_chipdef is31fl3193_cdef = {
 	.num_leds = 3,
 };

 static const struct is31fl319x_chipdef is31fl3196_cdef = {
 	.num_leds = 6,
 };

 static const struct is31fl319x_chipdef is31fl3199_cdef = {
 	.num_leds = 9,
 };

 static const struct of_device_id of_is31fl319x_match[] = {
 	{ .compatible = "issi,is31fl3190", .data = &is31fl3190_cdef, },
 	{ .compatible = "issi,is31fl3191", .data = &is31fl3190_cdef, },
 	{ .compatible = "issi,is31fl3193", .data = &is31fl3193_cdef, },
 	{ .compatible = "issi,is31fl3196", .data = &is31fl3196_cdef, },
 	{ .compatible = "issi,is31fl3199", .data = &is31fl3199_cdef, },
 	{ .compatible = "si-en,sn3199",    .data = &is31fl3199_cdef, },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, of_is31fl319x_match);

 static int is31fl319x_brightness_set(struct led_classdev *cdev,
 				     enum led_brightness brightness)
 {
 	struct is31fl319x_led *led = container_of(cdev, struct is31fl319x_led,
 						  cdev);
 	struct is31fl319x_chip *is31 = led->chip;
 	int chan = led - is31->leds;
 	int ret;
 	int i;
 	u8 ctrl1 = 0, ctrl2 = 0;

 	dev_dbg(&is31->client->dev, "%s %d: %d\n", __func__, chan, brightness);

 	mutex_lock(&is31->lock);

 	/* update PWM register */
 	ret = regmap_write(is31->regmap, IS31FL319X_PWM(chan), brightness);
 	if (ret < 0)
 		goto out;

 	/* read current brightness of all PWM channels */
 	for (i = 0; i < is31->cdef->num_leds; i++) {
 		unsigned int pwm_value;
 		bool on;

 		/*
 		 * since neither cdev nor the chip can provide
 		 * the current setting, we read from the regmap cache
 		 */

 		ret = regmap_read(is31->regmap, IS31FL319X_PWM(i), &pwm_value);
 		dev_dbg(&is31->client->dev, "%s read %d: ret=%d: %d\n",
 			__func__, i, ret, pwm_value);
 		on = ret >= 0 && pwm_value > LED_OFF;

 		if (i < 3)
 			ctrl1 |= on << i;       /* 0..2 => bit 0..2 */
 		else if (i < 6)
 			ctrl1 |= on << (i + 1); /* 3..5 => bit 4..6 */
 		else
 			ctrl2 |= on << (i - 6); /* 6..8 => bit 0..2 */
 	}

 	if (ctrl1 > 0 || ctrl2 > 0) {
 		dev_dbg(&is31->client->dev, "power up %02x %02x\n",
 			ctrl1, ctrl2);
 		regmap_write(is31->regmap, IS31FL319X_CTRL1, ctrl1);
 		regmap_write(is31->regmap, IS31FL319X_CTRL2, ctrl2);
 		/* update PWMs */
 		regmap_write(is31->regmap, IS31FL319X_DATA_UPDATE, 0x00);
 		/* enable chip from shut down */
 		ret = regmap_write(is31->regmap, IS31FL319X_SHUTDOWN, 0x01);
 	} else {
 		dev_dbg(&is31->client->dev, "power down\n");
 		/* shut down (no need to clear CTRL1/2) */
 		ret = regmap_write(is31->regmap, IS31FL319X_SHUTDOWN, 0x00);
 	}

 out:
 	mutex_unlock(&is31->lock);

 	return ret;
 }

 static int is31fl319x_parse_child_dt(const struct device *dev,
 				     const struct device_node *child,
 				     struct is31fl319x_led *led)
 {
 	struct led_classdev *cdev = &led->cdev;
 	int ret;

 	if (of_property_read_string(child, "label", &cdev->name))
 		cdev->name = child->name;

 	ret = of_property_read_string(child, "linux,default-trigger",
 				      &cdev->default_trigger);
 	if (ret < 0 && ret != -EINVAL) /* is optional */
 		return ret;

 	led->max_microamp = IS31FL319X_CURRENT_DEFAULT;
 	ret = of_property_read_u32(child, "led-max-microamp",
 				   &led->max_microamp);
 	if (!ret) {
 		if (led->max_microamp < IS31FL319X_CURRENT_MIN)
 			return -EINVAL;	/* not supported */
 		led->max_microamp = min(led->max_microamp,
 					  IS31FL319X_CURRENT_MAX);
 	}

 	return 0;
 }

 static int is31fl319x_parse_dt(struct device *dev,
 			       struct is31fl319x_chip *is31)
 {
 	struct device_node *np = dev->of_node, *child;
 	const struct of_device_id *of_dev_id;
 	int count;
 	int ret;

 	if (!np)
 		return -ENODEV;

 	of_dev_id = of_match_device(of_is31fl319x_match, dev);
 	if (!of_dev_id) {
 		dev_err(dev, "Failed to match device with supported chips\n");
 		return -EINVAL;
 	}

 	is31->cdef = of_dev_id->data;

 	count = of_get_child_count(np);

 	dev_dbg(dev, "probe %s with %d leds defined in DT\n",
 		of_dev_id->compatible, count);

 	if (!count || count > is31->cdef->num_leds) {
 		dev_err(dev, "Number of leds defined must be between 1 and %u\n",
 			is31->cdef->num_leds);
 		return -ENODEV;
 	}

 	for_each_child_of_node(np, child) {
 		struct is31fl319x_led *led;
 		u32 reg;

 		ret = of_property_read_u32(child, "reg", &reg);
 		if (ret) {
 			dev_err(dev, "Failed to read led 'reg' property\n");
 			goto put_child_node;
 		}

 		if (reg < 1 || reg > is31->cdef->num_leds) {
 			dev_err(dev, "invalid led reg %u\n", reg);
 			ret = -EINVAL;
 			goto put_child_node;
 		}

 		led = &is31->leds[reg - 1];

 		if (led->configured) {
 			dev_err(dev, "led %u is already configured\n", reg);
 			ret = -EINVAL;
 			goto put_child_node;
 		}

 		ret = is31fl319x_parse_child_dt(dev, child, led);
 		if (ret) {
 			dev_err(dev, "led %u DT parsing failed\n", reg);
 			goto put_child_node;
 		}

 		led->configured = true;
 	}

 	is31->audio_gain_db = 0;
 	ret = of_property_read_u32(np, "audio-gain-db", &is31->audio_gain_db);
 	if (!ret)
 		is31->audio_gain_db = min(is31->audio_gain_db,
 					  IS31FL319X_AUDIO_GAIN_DB_MAX);

 	return 0;

 put_child_node:
 	of_node_put(child);
 	return ret;
 }

 static bool is31fl319x_readable_reg(struct device *dev, unsigned int reg)
 { /* we have no readable registers */
 	return false;
 }

 static bool is31fl319x_volatile_reg(struct device *dev, unsigned int reg)
 { /* volatile registers are not cached */
 	switch (reg) {
 	case IS31FL319X_DATA_UPDATE:
 	case IS31FL319X_TIME_UPDATE:
 	case IS31FL319X_RESET:
 		return true; /* always write-through */
 	default:
 		return false;
 	}
 }

 static const struct reg_default is31fl319x_reg_defaults[] = {
 	{ IS31FL319X_CONFIG1, 0x00},
 	{ IS31FL319X_CONFIG2, 0x00},
 	{ IS31FL319X_PWM(0), 0x00},
 	{ IS31FL319X_PWM(1), 0x00},
 	{ IS31FL319X_PWM(2), 0x00},
 	{ IS31FL319X_PWM(3), 0x00},
 	{ IS31FL319X_PWM(4), 0x00},
 	{ IS31FL319X_PWM(5), 0x00},
 	{ IS31FL319X_PWM(6), 0x00},
 	{ IS31FL319X_PWM(7), 0x00},
 	{ IS31FL319X_PWM(8), 0x00},
 };

 static struct regmap_config regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.max_register = IS31FL319X_REG_CNT,
 	.cache_type = REGCACHE_FLAT,
 	.readable_reg = is31fl319x_readable_reg,
 	.volatile_reg = is31fl319x_volatile_reg,
 	.reg_defaults = is31fl319x_reg_defaults,
 	.num_reg_defaults = ARRAY_SIZE(is31fl319x_reg_defaults),
 };

 static inline int is31fl319x_microamp_to_cs(struct device *dev, u32 microamp)
 { /* round down to nearest supported value (range check done by caller) */
 	u32 step = microamp / IS31FL319X_CURRENT_STEP;

 	return ((IS31FL319X_CONFIG2_CS_STEP_REF - step) &
 		IS31FL319X_CONFIG2_CS_MASK) <<
 		IS31FL319X_CONFIG2_CS_SHIFT; /* CS encoding */
 }

 static inline int is31fl319x_db_to_gain(u32 dezibel)
 { /* round down to nearest supported value (range check done by caller) */
 	return dezibel / IS31FL319X_AUDIO_GAIN_DB_STEP;
 }

 static int is31fl319x_probe(struct i2c_client *client,
 			    const struct i2c_device_id *id)
 {
 	struct is31fl319x_chip *is31;
 	struct device *dev = &client->dev;
 	struct i2c_adapter *adapter = to_i2c_adapter(dev->parent);
 	int err;
 	int i = 0;
 	u32 aggregated_led_microamp = IS31FL319X_CURRENT_MAX;

 	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
 		return -EIO;

 	is31 = devm_kzalloc(&client->dev, sizeof(*is31), GFP_KERNEL);
 	if (!is31)
 		return -ENOMEM;

 	mutex_init(&is31->lock);

 	err = is31fl319x_parse_dt(&client->dev, is31);
 	if (err)
 		goto free_mutex;

 	is31->client = client;
 	is31->regmap = devm_regmap_init_i2c(client, &regmap_config);
 	if (IS_ERR(is31->regmap)) {
 		dev_err(&client->dev, "failed to allocate register map\n");
 		err = PTR_ERR(is31->regmap);
 		goto free_mutex;
 	}

 	i2c_set_clientdata(client, is31);

 	/* check for write-reply from chip (we can't read any registers) */
 	err = regmap_write(is31->regmap, IS31FL319X_RESET, 0x00);
 	if (err < 0) {
 		dev_err(&client->dev, "no response from chip write: err = %d\n",
 			err);
 		err = -EIO; /* does not answer */
 		goto free_mutex;
 	}

 	/*
 	 * Kernel conventions require per-LED led-max-microamp property.
 	 * But the chip does not allow to limit individual LEDs.
 	 * So we take minimum from all subnodes for safety of hardware.
 	 */
 	for (i = 0; i < is31->cdef->num_leds; i++)
 		if (is31->leds[i].configured &&
 		    is31->leds[i].max_microamp < aggregated_led_microamp)
 			aggregated_led_microamp = is31->leds[i].max_microamp;

 	regmap_write(is31->regmap, IS31FL319X_CONFIG2,
 		     is31fl319x_microamp_to_cs(dev, aggregated_led_microamp) |
 		     is31fl319x_db_to_gain(is31->audio_gain_db));

 	for (i = 0; i < is31->cdef->num_leds; i++) {
 		struct is31fl319x_led *led = &is31->leds[i];

 		if (!led->configured)
 			continue;

 		led->chip = is31;
 		led->cdev.brightness_set_blocking = is31fl319x_brightness_set;

 		err = devm_led_classdev_register(&client->dev, &led->cdev);
 		if (err < 0)
 			goto free_mutex;
 	}

 	return 0;

 free_mutex:
 	mutex_destroy(&is31->lock);
 	return err;
 }

 static int is31fl319x_remove(struct i2c_client *client)
 {
 	struct is31fl319x_chip *is31 = i2c_get_clientdata(client);

 	mutex_destroy(&is31->lock);
 	return 0;
 }

 /*
  * i2c-core (and modalias) requires that id_table be properly filled,
  * even though it is not used for DeviceTree based instantiation.
  */
 static const struct i2c_device_id is31fl319x_id[] = {
 	{ "is31fl3190" },
 	{ "is31fl3191" },
 	{ "is31fl3193" },
 	{ "is31fl3196" },
 	{ "is31fl3199" },
 	{ "sn3199" },
 	{},
 };
 MODULE_DEVICE_TABLE(i2c, is31fl319x_id);

 static struct i2c_driver is31fl319x_driver = {
 	.driver   = {
 		.name           = "leds-is31fl319x",
 		.of_match_table = of_match_ptr(of_is31fl319x_match),
 	},
 	.probe    = is31fl319x_probe,
 	.remove   = is31fl319x_remove,
 	.id_table = is31fl319x_id,
 };

 module_i2c_driver(is31fl319x_driver);

 MODULE_AUTHOR("H. Nikolaus Schaller <hns@goldelico.com>");
 MODULE_AUTHOR("Andrey Utkin <andrey_utkin@fastmail.com>");
 MODULE_DESCRIPTION("IS31FL319X LED driver");
 MODULE_LICENSE("GPL v2");
	/*
	* Copyright 2015-16 Golden Delicious Computers
	*
	* Author: Nikolaus Schaller <hns@goldelico.com>
	*
	* This file is subject to the terms and conditions of version 2 of
	* the GNU General Public License. See the file COPYING in the main
	* directory of this archive for more details.
	*
	* LED driver for the IS31FL319{0,1,3,6,9} to drive 1, 3, 6 or 9 light
	* effect LEDs.
	*
	*/

	#include <linux/err.h>
	#include <linux/i2c.h>
	#include <linux/leds.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_device.h>
	#include <linux/regmap.h>
	#include <linux/slab.h>

	/* register numbers */
	#define IS31FL319X_SHUTDOWN 0x00
	#define IS31FL319X_CTRL1 0x01
	#define IS31FL319X_CTRL2 0x02
	#define IS31FL319X_CONFIG1 0x03
	#define IS31FL319X_CONFIG2 0x04
	#define IS31FL319X_RAMP_MODE 0x05
	#define IS31FL319X_BREATH_MASK 0x06
	#define IS31FL319X_PWM(channel) (0x07 + channel)
	#define IS31FL319X_DATA_UPDATE 0x10
	#define IS31FL319X_T0(channel) (0x11 + channel)
	#define IS31FL319X_T123_1 0x1a
	#define IS31FL319X_T123_2 0x1b
	#define IS31FL319X_T123_3 0x1c
	#define IS31FL319X_T4(channel) (0x1d + channel)
	#define IS31FL319X_TIME_UPDATE 0x26
	#define IS31FL319X_RESET 0xff

	#define IS31FL319X_REG_CNT (IS31FL319X_RESET + 1)

	#define IS31FL319X_MAX_LEDS 9

	/* CS (Current Setting) in CONFIG2 register */
	#define IS31FL319X_CONFIG2_CS_SHIFT 4
	#define IS31FL319X_CONFIG2_CS_MASK 0x7
	#define IS31FL319X_CONFIG2_CS_STEP_REF 12

	#define IS31FL319X_CURRENT_MIN ((u32)5000)
	#define IS31FL319X_CURRENT_MAX ((u32)40000)
	#define IS31FL319X_CURRENT_STEP ((u32)5000)
	#define IS31FL319X_CURRENT_DEFAULT ((u32)20000)

	/* Audio gain in CONFIG2 register */
	#define IS31FL319X_AUDIO_GAIN_DB_MAX ((u32)21)
	#define IS31FL319X_AUDIO_GAIN_DB_STEP ((u32)3)

	/*
	* regmap is used as a cache of chip's register space,
	* to avoid reading back brightness values from chip,
	* which is known to hang.
	*/
	struct is31fl319x_chip {
	const struct is31fl319x_chipdef *cdef;
	struct i2c_client *client;
	struct regmap *regmap;
	struct mutex lock;
	u32 audio_gain_db;

	struct is31fl319x_led {
	struct is31fl319x_chip *chip;
	struct led_classdev cdev;
	u32 max_microamp;
	bool configured;
	} leds[IS31FL319X_MAX_LEDS];
	};

	struct is31fl319x_chipdef {
	int num_leds;
	};

	static const struct is31fl319x_chipdef is31fl3190_cdef = {
	.num_leds = 1,
	};

	static const struct is31fl319x_chipdef is31fl3193_cdef = {
	.num_leds = 3,
	};

	static const struct is31fl319x_chipdef is31fl3196_cdef = {
	.num_leds = 6,
	};

	static const struct is31fl319x_chipdef is31fl3199_cdef = {
	.num_leds = 9,
	};

	static const struct of_device_id of_is31fl319x_match[] = {
	{ .compatible = "issi,is31fl3190", .data = &is31fl3190_cdef, },
	{ .compatible = "issi,is31fl3191", .data = &is31fl3190_cdef, },
	{ .compatible = "issi,is31fl3193", .data = &is31fl3193_cdef, },
	{ .compatible = "issi,is31fl3196", .data = &is31fl3196_cdef, },
	{ .compatible = "issi,is31fl3199", .data = &is31fl3199_cdef, },
	{ .compatible = "si-en,sn3199", .data = &is31fl3199_cdef, },
	{ }
	};
	MODULE_DEVICE_TABLE(of, of_is31fl319x_match);

	static int is31fl319x_brightness_set(struct led_classdev *cdev,
	enum led_brightness brightness)
	{
	struct is31fl319x_led *led = container_of(cdev, struct is31fl319x_led,
	cdev);
	struct is31fl319x_chip *is31 = led->chip;
	int chan = led - is31->leds;
	int ret;
	int i;
	u8 ctrl1 = 0, ctrl2 = 0;

	dev_dbg(&is31->client->dev, "%s %d: %d\n", __func__, chan, brightness);

	mutex_lock(&is31->lock);

	/* update PWM register */
	ret = regmap_write(is31->regmap, IS31FL319X_PWM(chan), brightness);
	if (ret < 0)
	goto out;

	/* read current brightness of all PWM channels */
	for (i = 0; i < is31->cdef->num_leds; i++) {
	unsigned int pwm_value;
	bool on;

	/*
	* since neither cdev nor the chip can provide
	* the current setting, we read from the regmap cache
	*/

	ret = regmap_read(is31->regmap, IS31FL319X_PWM(i), &pwm_value);
	dev_dbg(&is31->client->dev, "%s read %d: ret=%d: %d\n",
	__func__, i, ret, pwm_value);
	on = ret >= 0 && pwm_value > LED_OFF;

	if (i < 3)
	ctrl1 \|= on << i; /* 0..2 => bit 0..2 */
	else if (i < 6)
	ctrl1 \|= on << (i + 1); /* 3..5 => bit 4..6 */
	else
	ctrl2 \|= on << (i - 6); /* 6..8 => bit 0..2 */
	}

	if (ctrl1 > 0 \|\| ctrl2 > 0) {
	dev_dbg(&is31->client->dev, "power up %02x %02x\n",
	ctrl1, ctrl2);
	regmap_write(is31->regmap, IS31FL319X_CTRL1, ctrl1);
	regmap_write(is31->regmap, IS31FL319X_CTRL2, ctrl2);
	/* update PWMs */
	regmap_write(is31->regmap, IS31FL319X_DATA_UPDATE, 0x00);
	/* enable chip from shut down */
	ret = regmap_write(is31->regmap, IS31FL319X_SHUTDOWN, 0x01);
	} else {
	dev_dbg(&is31->client->dev, "power down\n");
	/* shut down (no need to clear CTRL1/2) */
	ret = regmap_write(is31->regmap, IS31FL319X_SHUTDOWN, 0x00);
	}

	out:
	mutex_unlock(&is31->lock);

	return ret;
	}

	static int is31fl319x_parse_child_dt(const struct device *dev,
	const struct device_node *child,
	struct is31fl319x_led *led)
	{
	struct led_classdev *cdev = &led->cdev;
	int ret;

	if (of_property_read_string(child, "label", &cdev->name))
	cdev->name = child->name;

	ret = of_property_read_string(child, "linux,default-trigger",
	&cdev->default_trigger);
	if (ret < 0 && ret != -EINVAL) /* is optional */
	return ret;

	led->max_microamp = IS31FL319X_CURRENT_DEFAULT;
	ret = of_property_read_u32(child, "led-max-microamp",
	&led->max_microamp);
	if (!ret) {
	if (led->max_microamp < IS31FL319X_CURRENT_MIN)
	return -EINVAL; /* not supported */
	led->max_microamp = min(led->max_microamp,
	IS31FL319X_CURRENT_MAX);
	}

	return 0;
	}

	static int is31fl319x_parse_dt(struct device *dev,
	struct is31fl319x_chip *is31)
	{
	struct device_node np = dev->of_node, child;
	const struct of_device_id *of_dev_id;
	int count;
	int ret;

	if (!np)
	return -ENODEV;

	of_dev_id = of_match_device(of_is31fl319x_match, dev);
	if (!of_dev_id) {
	dev_err(dev, "Failed to match device with supported chips\n");
	return -EINVAL;
	}

	is31->cdef = of_dev_id->data;

	count = of_get_child_count(np);

	dev_dbg(dev, "probe %s with %d leds defined in DT\n",
	of_dev_id->compatible, count);

	if (!count \|\| count > is31->cdef->num_leds) {
	dev_err(dev, "Number of leds defined must be between 1 and %u\n",
	is31->cdef->num_leds);
	return -ENODEV;
	}

	for_each_child_of_node(np, child) {
	struct is31fl319x_led *led;
	u32 reg;

	ret = of_property_read_u32(child, "reg", &reg);
	if (ret) {
	dev_err(dev, "Failed to read led 'reg' property\n");
	goto put_child_node;
	}

	if (reg < 1 \|\| reg > is31->cdef->num_leds) {
	dev_err(dev, "invalid led reg %u\n", reg);
	ret = -EINVAL;
	goto put_child_node;
	}

	led = &is31->leds[reg - 1];

	if (led->configured) {
	dev_err(dev, "led %u is already configured\n", reg);
	ret = -EINVAL;
	goto put_child_node;
	}

	ret = is31fl319x_parse_child_dt(dev, child, led);
	if (ret) {
	dev_err(dev, "led %u DT parsing failed\n", reg);
	goto put_child_node;
	}

	led->configured = true;
	}

	is31->audio_gain_db = 0;
	ret = of_property_read_u32(np, "audio-gain-db", &is31->audio_gain_db);
	if (!ret)
	is31->audio_gain_db = min(is31->audio_gain_db,
	IS31FL319X_AUDIO_GAIN_DB_MAX);

	return 0;

	put_child_node:
	of_node_put(child);
	return ret;
	}

	static bool is31fl319x_readable_reg(struct device *dev, unsigned int reg)
	{ /* we have no readable registers */
	return false;
	}

	static bool is31fl319x_volatile_reg(struct device *dev, unsigned int reg)
	{ /* volatile registers are not cached */
	switch (reg) {
	case IS31FL319X_DATA_UPDATE:
	case IS31FL319X_TIME_UPDATE:
	case IS31FL319X_RESET:
	return true; /* always write-through */
	default:
	return false;
	}
	}

	static const struct reg_default is31fl319x_reg_defaults[] = {
	{ IS31FL319X_CONFIG1, 0x00},
	{ IS31FL319X_CONFIG2, 0x00},
	{ IS31FL319X_PWM(0), 0x00},
	{ IS31FL319X_PWM(1), 0x00},
	{ IS31FL319X_PWM(2), 0x00},
	{ IS31FL319X_PWM(3), 0x00},
	{ IS31FL319X_PWM(4), 0x00},
	{ IS31FL319X_PWM(5), 0x00},
	{ IS31FL319X_PWM(6), 0x00},
	{ IS31FL319X_PWM(7), 0x00},
	{ IS31FL319X_PWM(8), 0x00},
	};

	static struct regmap_config regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.max_register = IS31FL319X_REG_CNT,
	.cache_type = REGCACHE_FLAT,
	.readable_reg = is31fl319x_readable_reg,
	.volatile_reg = is31fl319x_volatile_reg,
	.reg_defaults = is31fl319x_reg_defaults,
	.num_reg_defaults = ARRAY_SIZE(is31fl319x_reg_defaults),
	};

	static inline int is31fl319x_microamp_to_cs(struct device *dev, u32 microamp)
	{ /* round down to nearest supported value (range check done by caller) */
	u32 step = microamp / IS31FL319X_CURRENT_STEP;

	return ((IS31FL319X_CONFIG2_CS_STEP_REF - step) &
	IS31FL319X_CONFIG2_CS_MASK) <<
	IS31FL319X_CONFIG2_CS_SHIFT; /* CS encoding */
	}

	static inline int is31fl319x_db_to_gain(u32 dezibel)
	{ /* round down to nearest supported value (range check done by caller) */
	return dezibel / IS31FL319X_AUDIO_GAIN_DB_STEP;
	}

	static int is31fl319x_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct is31fl319x_chip *is31;
	struct device *dev = &client->dev;
	struct i2c_adapter *adapter = to_i2c_adapter(dev->parent);
	int err;
	int i = 0;
	u32 aggregated_led_microamp = IS31FL319X_CURRENT_MAX;

	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
	return -EIO;

	is31 = devm_kzalloc(&client->dev, sizeof(*is31), GFP_KERNEL);
	if (!is31)
	return -ENOMEM;

	mutex_init(&is31->lock);

	err = is31fl319x_parse_dt(&client->dev, is31);
	if (err)
	goto free_mutex;

	is31->client = client;
	is31->regmap = devm_regmap_init_i2c(client, &regmap_config);
	if (IS_ERR(is31->regmap)) {
	dev_err(&client->dev, "failed to allocate register map\n");
	err = PTR_ERR(is31->regmap);
	goto free_mutex;
	}

	i2c_set_clientdata(client, is31);

	/* check for write-reply from chip (we can't read any registers) */
	err = regmap_write(is31->regmap, IS31FL319X_RESET, 0x00);
	if (err < 0) {
	dev_err(&client->dev, "no response from chip write: err = %d\n",
	err);
	err = -EIO; /* does not answer */
	goto free_mutex;
	}

	/*
	* Kernel conventions require per-LED led-max-microamp property.
	* But the chip does not allow to limit individual LEDs.
	* So we take minimum from all subnodes for safety of hardware.
	*/
	for (i = 0; i < is31->cdef->num_leds; i++)
	if (is31->leds[i].configured &&
	is31->leds[i].max_microamp < aggregated_led_microamp)
	aggregated_led_microamp = is31->leds[i].max_microamp;

	regmap_write(is31->regmap, IS31FL319X_CONFIG2,
	is31fl319x_microamp_to_cs(dev, aggregated_led_microamp) \|
	is31fl319x_db_to_gain(is31->audio_gain_db));

	for (i = 0; i < is31->cdef->num_leds; i++) {
	struct is31fl319x_led *led = &is31->leds[i];

	if (!led->configured)
	continue;

	led->chip = is31;
	led->cdev.brightness_set_blocking = is31fl319x_brightness_set;

	err = devm_led_classdev_register(&client->dev, &led->cdev);
	if (err < 0)
	goto free_mutex;
	}

	return 0;

	free_mutex:
	mutex_destroy(&is31->lock);
	return err;
	}

	static int is31fl319x_remove(struct i2c_client *client)
	{
	struct is31fl319x_chip *is31 = i2c_get_clientdata(client);

	mutex_destroy(&is31->lock);
	return 0;
	}

	/*
	* i2c-core (and modalias) requires that id_table be properly filled,
	* even though it is not used for DeviceTree based instantiation.
	*/
	static const struct i2c_device_id is31fl319x_id[] = {
	{ "is31fl3190" },
	{ "is31fl3191" },
	{ "is31fl3193" },
	{ "is31fl3196" },
	{ "is31fl3199" },
	{ "sn3199" },
	{},
	};
	MODULE_DEVICE_TABLE(i2c, is31fl319x_id);

	static struct i2c_driver is31fl319x_driver = {
	.driver = {
	.name = "leds-is31fl319x",
	.of_match_table = of_match_ptr(of_is31fl319x_match),
	},
	.probe = is31fl319x_probe,
	.remove = is31fl319x_remove,
	.id_table = is31fl319x_id,
	};

	module_i2c_driver(is31fl319x_driver);

	MODULE_AUTHOR("H. Nikolaus Schaller <hns@goldelico.com>");
	MODULE_AUTHOR("Andrey Utkin <andrey_utkin@fastmail.com>");
	MODULE_DESCRIPTION("IS31FL319X LED driver");
	MODULE_LICENSE("GPL v2");