[PATCH 1/2] backlight: arcxcnn: add support for ArticSand devices

[Olimpiu Dejeu]

Resubmition of arcxcnn backlight driver addressing the naming convention
 concerns raised by Rob H.

Signed-off-by: Olimpiu Dejeu <olimpiu@xxxxxxxxxxxxxx>

---
 drivers/video/backlight/Kconfig      |   7 +
 drivers/video/backlight/Makefile     |   1 +
 drivers/video/backlight/arcxcnn_bl.c | 541 +++++++++++++++++++++++++++++++++++
 include/linux/i2c/arcxcnn.h          |  67 +++++
 4 files changed, 616 insertions(+)
 create mode 100644 drivers/video/backlight/arcxcnn_bl.c
 create mode 100644 include/linux/i2c/arcxcnn.h

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 5ffa4b4..4e1d2ad 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -460,6 +460,13 @@ config BACKLIGHT_BD6107
 	help
 	  If you have a Rohm BD6107 say Y to enable the backlight driver.
 
+config BACKLIGHT_ARCXCNN
+	tristate "Backlight driver for the Arctic Sands ARCxCnnnn family"
+	depends on I2C
+	help
+	  If you have an ARCxCnnnn family backlight say Y to enable
+	  the backlight driver.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endif # BACKLIGHT_LCD_SUPPORT
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 16ec534..8905129 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -55,3 +55,4 @@ obj-$(CONFIG_BACKLIGHT_SKY81452)	+= sky81452-backlight.o
 obj-$(CONFIG_BACKLIGHT_TOSA)		+= tosa_bl.o
 obj-$(CONFIG_BACKLIGHT_TPS65217)	+= tps65217_bl.o
 obj-$(CONFIG_BACKLIGHT_WM831X)		+= wm831x_bl.o
+obj-$(CONFIG_BACKLIGHT_ARCXCNN) 	+= arcxcnn_bl.o
diff --git a/drivers/video/backlight/arcxcnn_bl.c b/drivers/video/backlight/arcxcnn_bl.c
new file mode 100644
index 0000000..1dad680
--- /dev/null
+++ b/drivers/video/backlight/arcxcnn_bl.c
@@ -0,0 +1,541 @@
+/*
+ * Backlight driver for ArcticSand ARC_X_C_0N_0N Devices
+ *
+ * Copyright 2016 ArcticSand, Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/pwm.h>
+#include <linux/regulator/consumer.h>
+
+#include "linux/i2c/arcxcnn.h"
+
+#define ARCXCNN_CMD		(0x00)  /* Command Register */
+#define ARCXCNN_CMD_STDBY	(0x80)	/* I2C Standby */
+#define ARCXCNN_CMD_RESET	(0x40)	/* Reset */
+#define ARCXCNN_CMD_BOOST	(0x10)	/* Boost */
+#define ARCXCNN_CMD_OVP_MASK	(0x0C)	/* --- Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_XXV	(0x0C)	/* <rsvrd> Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_20V	(0x08)	/* 20v Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_24V	(0x04)	/* 24v Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_31V	(0x00)	/* 31.4v Over Voltage Threshold */
+#define ARCXCNN_CMD_EXT_COMP	(0x01)	/* part (0) or full (1) external comp */
+
+#define ARCXCNN_CONFIG	(0x01)  /* Configuration */
+#define ARCXCNN_STATUS1	(0x02)  /* Status 1 */
+#define ARCXCNN_STATUS2	(0x03)  /* Status 2 */
+#define ARCXCNN_FADECTRL	(0x04)  /* Fading Control */
+#define ARCXCNN_ILED_CONFIG	(0x05)  /* ILED Configuration */
+
+#define ARCXCNN_LEDEN		(0x06)  /* LED Enable Register */
+#define ARCXCNN_LEDEN_ISETEXT	(0x80)	/* Full-scale current set externally */
+#define ARCXCNN_LEDEN_MASK	(0x3F)	/* LED string enables */
+#define ARCXCNN_LEDEN_LED1	(0x01)
+#define ARCXCNN_LEDEN_LED2	(0x02)
+#define ARCXCNN_LEDEN_LED3	(0x04)
+#define ARCXCNN_LEDEN_LED4	(0x08)
+#define ARCXCNN_LEDEN_LED5	(0x10)
+#define ARCXCNN_LEDEN_LED6	(0x20)
+
+#define ARCXCNN_WLED_ISET_LSB	(0x07)  /* LED ISET LSB (in upper nibble) */
+#define ARCXCNN_WLED_ISET_MSB	(0x08)  /* LED ISET MSB (8 bits) */
+
+#define ARCXCNN_DIMFREQ		(0x09)
+#define ARCXCNN_COMP_CONFIG	(0x0A)
+#define ARCXCNN_FILT_CONFIG	(0x0B)
+#define ARCXCNN_IMAXTUNE	(0x0C)
+
+#define DEFAULT_BL_NAME		"arctic_bl"
+#define MAX_BRIGHTNESS		4095
+
+static int s_no_reset_on_remove;
+module_param_named(noreset, s_no_reset_on_remove, int, 0644);
+MODULE_PARM_DESC(noreset, "No reset on module removal");
+
+static int s_ibright = 60;
+module_param_named(ibright, s_ibright, int, 0644);
+MODULE_PARM_DESC(ibright, "Initial brightness (when no plat data)");
+
+static int s_iledstr = 0x3F;
+module_param_named(iledstr, s_iledstr, int, 0644);
+MODULE_PARM_DESC(iledstr, "Initial LED String (when no plat data)");
+
+static int s_retries = 2; /* 1 == only one try */
+module_param_named(retries, s_retries, int, 0644);
+MODULE_PARM_DESC(retries, "I2C retries attempted");
+
+enum arcxcnn_brightness_ctrl_mode {
+	PWM_BASED = 1,
+	REGISTER_BASED,
+};
+
+struct arcxcnn;
+
+struct arcxcnn {
+	char chipname[64];
+	enum arcxcnn_chip_id chip_id;
+	enum arcxcnn_brightness_ctrl_mode mode;
+	struct i2c_client *client;
+	struct backlight_device *bl;
+	struct device *dev;
+	struct arcxcnn_platform_data *pdata;
+	struct pwm_device *pwm;
+	struct regulator *supply;	/* regulator for VDD input */
+};
+
+static int arcxcnn_write_byte(struct arcxcnn *lp, u8 reg, u8 data)
+{
+	s32 ret = -1;
+	int att;
+
+	for (att = 0; att < s_retries; att++) {
+		ret = i2c_smbus_write_byte_data(lp->client, reg, data);
+		if (ret >= 0)
+			return 0;
+	}
+	return ret;
+}
+
+static u8 arcxcnn_read_byte(struct arcxcnn *lp, u8 reg)
+{
+	int val;
+	int att;
+
+	for (att = 0; att < s_retries; att++) {
+		val = i2c_smbus_read_byte_data(lp->client, reg);
+		if (val >= 0)
+			return (u8)val;
+	}
+	return 0;
+}
+
+static int arcxcnn_update_bit(struct arcxcnn *lp, u8 reg, u8 mask, u8 data)
+{
+	int ret, att;
+	u8 tmp;
+
+	for (att = 0, ret = -1; att < s_retries; att++) {
+		ret = i2c_smbus_read_byte_data(lp->client, reg);
+		if (ret >= 0)
+			break;
+	}
+	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 arcxcnn_write_byte(lp, reg, tmp);
+}
+
+static int arcxcnn_set_brightness(struct arcxcnn *lp, u32 brightness)
+{
+	int ret;
+	u8 val;
+
+	val = (brightness & 0xF) << 4;
+	ret = arcxcnn_write_byte(lp, ARCXCNN_WLED_ISET_LSB, val);
+	if (ret < 0)
+		return ret;
+	val = (brightness >> 4);
+	ret = arcxcnn_write_byte(lp, ARCXCNN_WLED_ISET_MSB, val);
+	return ret;
+}
+
+static int arcxcnn_bl_update_status(struct backlight_device *bl)
+{
+	struct arcxcnn *lp = bl_get_data(bl);
+	u32 brightness = bl->props.brightness;
+
+	if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+		brightness = 0;
+
+	/* set brightness */
+	if (lp->mode == PWM_BASED)
+		; /* via pwm */
+	else if (lp->mode == REGISTER_BASED)
+		arcxcnn_set_brightness(lp, brightness);
+
+	/* set power-on/off/save modes */
+	if (bl->props.power == 0)
+		/* take out of standby */
+		arcxcnn_update_bit(lp, ARCXCNN_CMD, ARCXCNN_CMD_STDBY, 0);
+	else
+		/* 1-3 == power save, 4 = off
+		 * place in low-power standby mode
+		 */
+		arcxcnn_update_bit(lp, ARCXCNN_CMD,
+				ARCXCNN_CMD_STDBY, ARCXCNN_CMD_STDBY);
+	return 0;
+}
+
+static const struct backlight_ops arcxcnn_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = arcxcnn_bl_update_status,
+};
+
+static int arcxcnn_backlight_register(struct arcxcnn *lp)
+{
+	struct backlight_device *bl;
+	struct backlight_properties props;
+	struct arcxcnn_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,
+				       &arcxcnn_bl_ops, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	lp->bl = bl;
+
+	return 0;
+}
+
+static ssize_t arcxcnn_get_chip_id(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct arcxcnn *lp = dev_get_drvdata(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", lp->chipname);
+}
+
+static ssize_t arcxcnn_get_led_str(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct arcxcnn *lp = dev_get_drvdata(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%02X\n", lp->pdata->led_str);
+}
+
+static ssize_t arcxcnn_set_led_str(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct arcxcnn *lp = dev_get_drvdata(dev);
+	unsigned long ledstr;
+
+	if (kstrtoul(buf, 0, &ledstr))
+		return 0;
+
+	if (ledstr != lp->pdata->led_str) {
+		/* don't allow 0 for ledstr, use power to turn all off */
+		if (ledstr == 0)
+			return 0;
+		lp->pdata->led_str = ledstr & 0x3F;
+		arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
+			ARCXCNN_LEDEN_MASK, lp->pdata->led_str);
+	}
+	return len;
+}
+
+static ssize_t arcxcnn_get_bl_ctl_mode(struct device *dev,
+	     struct device_attribute *attr, char *buf)
+{
+	struct arcxcnn *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, 0444, arcxcnn_get_chip_id, NULL);
+static DEVICE_ATTR(led_str, 0664, arcxcnn_get_led_str, arcxcnn_set_led_str);
+static DEVICE_ATTR(bl_ctl_mode, 0444, arcxcnn_get_bl_ctl_mode, NULL);
+
+static struct attribute *arcxcnn_attributes[] = {
+	&dev_attr_chip_id.attr,
+	&dev_attr_led_str.attr,
+	&dev_attr_bl_ctl_mode.attr,
+	NULL,
+};
+
+static const struct attribute_group arcxcnn_attr_group = {
+	.attrs = arcxcnn_attributes,
+};
+
+#ifdef CONFIG_OF
+static int arcxcnn_parse_dt(struct arcxcnn *lp)
+{
+	struct device *dev = lp->dev;
+	struct device_node *node = dev->of_node;
+	u32 prog_val, num_entry, sources[6];
+	int ret;
+
+	if (!node) {
+		dev_err(dev, "no platform data.\n");
+		return -EINVAL;
+	}
+	lp->pdata->led_config_0_set = false;
+	lp->pdata->led_config_1_set = false;
+	lp->pdata->dim_freq_set = false;
+	lp->pdata->comp_config_set = false;
+	lp->pdata->filter_config_set = false;
+	lp->pdata->trim_config_set = false;
+
+	ret = of_property_read_string(node, "label", &lp->pdata->name);
+	if (ret < 0)
+		lp->pdata->name = NULL;
+
+	ret = of_property_read_u32(node, "default-brightness", &prog_val);
+	if (ret < 0)
+		prog_val = s_ibright;
+	lp->pdata->initial_brightness = prog_val;
+	if (lp->pdata->initial_brightness > MAX_BRIGHTNESS)
+		lp->pdata->initial_brightness = MAX_BRIGHTNESS;
+
+	ret = of_property_read_u32(node, "arc,led-config-0", &prog_val);
+	if (ret == 0) {
+		lp->pdata->led_config_0 = (u8)prog_val;
+		lp->pdata->led_config_0_set = true;
+	}
+	ret = of_property_read_u32(node, "arc,led-config-1", &prog_val);
+	if (ret == 0) {
+		lp->pdata->led_config_1 = (u8)prog_val;
+		lp->pdata->led_config_1_set = true;
+	}
+	ret = of_property_read_u32(node, "arc,dim-freq", &prog_val);
+	if (ret == 0) {
+		lp->pdata->dim_freq = (u8)prog_val;
+		lp->pdata->dim_freq_set = true;
+	}
+	ret = of_property_read_u32(node, "arc,comp-config", &prog_val);
+	if (ret == 0) {
+		lp->pdata->comp_config = (u8)prog_val;
+		lp->pdata->comp_config_set = true;
+	}
+	ret = of_property_read_u32(node, "arc,filter-config", &prog_val);
+	if (ret == 0) {
+		lp->pdata->filter_config = (u8)prog_val;
+		lp->pdata->filter_config_set = true;
+	}
+	ret = of_property_read_u32(node, "arc,trim-config", &prog_val);
+	if (ret == 0) {
+		lp->pdata->trim_config = (u8)prog_val;
+		lp->pdata->trim_config_set = true;
+	}
+	ret = of_property_count_u32_elems(node, "led-sources");
+	if (ret < 0)
+		lp->pdata->led_str = 0x3F;
+	else {
+		num_entry = ret;
+		if (num_entry > 6)
+			num_entry = 6;
+
+		ret = of_property_read_u32_array(node, "led-sources", sources,
+					num_entry);
+		if (ret < 0) {
+			dev_err(dev, "led-sources node is invalid.\n");
+			return -EINVAL;
+		}
+
+		lp->pdata->led_str = 0;
+		while (num_entry > 0)
+			lp->pdata->led_str |= (1 << sources[--num_entry]);
+	}
+	return 0;
+}
+#else
+static int arcxcnn_parse_dt(struct arcxcnn *lp)
+{
+	return -EINVAL;
+}
+#endif
+
+static int arcxcnn_probe(struct i2c_client *cl, const struct i2c_device_id *id)
+{
+	struct arcxcnn *lp;
+	int ret;
+	u8 regval;
+	u16 chipid;
+
+	if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	lp = devm_kzalloc(&cl->dev, sizeof(*lp), GFP_KERNEL);
+	if (!lp)
+		return -ENOMEM;
+
+	lp->client = cl;
+	lp->dev = &cl->dev;
+	lp->chip_id = id->driver_data;
+	lp->pdata = dev_get_platdata(&cl->dev);
+
+	if (!lp->pdata) {
+		lp->pdata = devm_kzalloc(lp->dev,
+				sizeof(*lp->pdata), GFP_KERNEL);
+		if (!lp->pdata)
+			return -ENOMEM;
+
+		/* no platform data, parse the device-tree for info.  if there
+		 * is no device tree entry, we are being told we exist because
+		 * user-land said so, so make up the info we need
+		 */
+		ret = arcxcnn_parse_dt(lp);
+		if (ret < 0) {
+			/* no device tree, use defaults based on module params
+			 */
+			lp->pdata->led_config_0_set = false;
+			lp->pdata->led_config_1_set = false;
+			lp->pdata->dim_freq_set = false;
+			lp->pdata->comp_config_set = false;
+			lp->pdata->filter_config_set = false;
+			lp->pdata->trim_config_set = false;
+
+			lp->pdata->name = NULL;
+			lp->pdata->initial_brightness = s_ibright;
+			lp->pdata->led_str = s_iledstr;
+		}
+	}
+
+	if (lp->pdata->dim_freq_set)
+		lp->mode = PWM_BASED;
+	else
+		lp->mode = REGISTER_BASED;
+
+	i2c_set_clientdata(cl, lp);
+
+	/* read device ID */
+	regval = arcxcnn_read_byte(lp, 0x1E);
+	chipid = regval;
+	chipid <<= 8;
+	regval = arcxcnn_read_byte(lp, 0x1F);
+	chipid |= regval;
+
+	/* make sure it belongs to this driver
+	 * TODO - handle specific ids
+	 */
+	if (chipid != 0x02A5) {
+		#if 1
+		dev_info(&cl->dev, "Chip Id is %04X\n", chipid);
+		#else
+		dev_err(&cl->dev, "%04X is not ARC2C\n", chipid);
+		return -ENODEV;
+		#endif
+	}
+	/* reset the device */
+	arcxcnn_write_byte(lp, ARCXCNN_CMD, ARCXCNN_CMD_RESET);
+
+	/* set initial brightness */
+	arcxcnn_set_brightness(lp, lp->pdata->initial_brightness);
+
+	/* if fadectrl set in DT, set the value directly, else leave default */
+	if (lp->pdata->led_config_0_set)
+		arcxcnn_write_byte(lp, ARCXCNN_FADECTRL,
+			lp->pdata->led_config_0);
+
+	/* if iled config set in DT, set the value, else internal mode */
+	if (lp->pdata->led_config_1_set)
+		arcxcnn_write_byte(lp, ARCXCNN_ILED_CONFIG,
+			lp->pdata->led_config_1);
+	else
+		arcxcnn_write_byte(lp, ARCXCNN_ILED_CONFIG, 0x57);
+
+	/* other misc DT settings */
+	if (lp->pdata->dim_freq_set)
+		arcxcnn_write_byte(lp, ARCXCNN_FADECTRL, lp->pdata->dim_freq);
+	if (lp->pdata->comp_config_set)
+		arcxcnn_write_byte(lp, ARCXCNN_COMP_CONFIG,
+			lp->pdata->comp_config);
+	if (lp->pdata->filter_config_set)
+		arcxcnn_write_byte(lp, ARCXCNN_FILT_CONFIG,
+			lp->pdata->filter_config);
+	if (lp->pdata->trim_config_set)
+		arcxcnn_write_byte(lp, ARCXCNN_IMAXTUNE,
+			lp->pdata->trim_config);
+
+	/* set initial LED Strings */
+	arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
+		ARCXCNN_LEDEN_MASK, lp->pdata->led_str);
+
+	snprintf(lp->chipname, sizeof(lp->chipname),
+		"%s-%04X", id->name, chipid);
+
+	ret = arcxcnn_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, &arcxcnn_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 arcxcnn_remove(struct i2c_client *cl)
+{
+	struct arcxcnn *lp = i2c_get_clientdata(cl);
+
+	if (!s_no_reset_on_remove) {
+		/* disable all strings */
+		arcxcnn_write_byte(lp, ARCXCNN_LEDEN, 0x00);
+		/* reset the device */
+		arcxcnn_write_byte(lp, ARCXCNN_CMD, ARCXCNN_CMD_RESET);
+	}
+	lp->bl->props.brightness = 0;
+	backlight_update_status(lp->bl);
+	if (lp->supply)
+		regulator_disable(lp->supply);
+	sysfs_remove_group(&lp->dev->kobj, &arcxcnn_attr_group);
+
+	return 0;
+}
+
+static const struct of_device_id arcxcnn_dt_ids[] = {
+	{ .compatible = "arc,arc2c0608" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, arcxcnn_dt_ids);
+
+/* Note that the device/chip ID is not fixed in silicon so
+ * auto-probing of these devices on the bus is most likely
+ * not possible, use device tree to set i2c bus address
+ */
+static const struct i2c_device_id arcxcnn_ids[] = {
+	{"arc2c0608", ARC2C0608},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, arcxcnn_ids);
+
+static struct i2c_driver arcxcnn_driver = {
+	.driver = {
+		   .name = "arcxcnn_bl",
+		   .of_match_table = of_match_ptr(arcxcnn_dt_ids),
+		   },
+	.probe = arcxcnn_probe,
+	.remove = arcxcnn_remove,
+	.id_table = arcxcnn_ids,
+};
+
+module_i2c_driver(arcxcnn_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Brian Dodge <bdodge09@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("ARCXCNN Backlight driver");
diff --git a/include/linux/i2c/arcxcnn.h b/include/linux/i2c/arcxcnn.h
new file mode 100644
index 0000000..1c681dd
--- /dev/null
+++ b/include/linux/i2c/arcxcnn.h
@@ -0,0 +1,67 @@
+/*
+ * Backlight driver for ArcticSand ARC2C0608 Backlight Devices
+ *
+ * Copyright 2016 ArcticSand, Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#ifndef _ARCXCNN_H
+#define _ARCXCNN_H
+
+enum arcxcnn_chip_id {
+	ARC2C0608
+};
+
+enum arcxcnn_brightness_source {
+	ARCXCNN_PWM_ONLY,
+	ARCXCNN_I2C_ONLY = 2,
+};
+
+#define ARCXCNN_MAX_PROGENTRIES	48	/* max a/v pairs for custom */
+
+/**
+ * struct arcxcnn_platform_data
+ * @name : Backlight driver name. If it is not defined, default name is set.
+ * @initial_brightness : initial value of backlight brightness
+ * @led_str	 : initial LED string enables, upper bit is global on/off
+ * @led_config_0 : fading speed (period between intensity steps)
+ * @led_config_1 : misc settings, see datasheet
+ * @dim_freq	 : pwm dimming frequency if in pwm mode
+ * @comp_config	 : misc config, see datasheet
+ * @filter_config: RC/PWM filter config, see datasheet
+ * @trim_config	 : full scale current trim, see datasheet
+ * @led_config_0_set	: the value in led_config_0 is valid
+ * @led_config_1_set	: the value in led_config_1 is valid
+ * @dim_freq_set	: the value in dim_freq is valid
+ * @comp_config_set	: the value in comp_config is valid
+ * @filter_config_set	: the value in filter_config is valid
+ * @trim_config_set	: the value in trim_config is valid
+ *
+ * the _set flags are used to indicate that the value was explicitly set
+ * in the device tree or platform data. settings not set are left as default
+ * power-on default values of the chip except for led_str and led_config_1
+ * which are set by the driver (led_str is specified indirectly in the
+ * device tree via "led-sources")
+ */
+struct arcxcnn_platform_data {
+	const char *name;
+	u16 initial_brightness;
+	u8	led_str;
+
+	u8	led_config_0;
+	u8	led_config_1;
+	u8	dim_freq;
+	u8	comp_config;
+	u8	filter_config;
+	u8	trim_config;
+
+	bool	led_config_0_set;
+	bool	led_config_1_set;
+	bool	dim_freq_set;
+	bool	comp_config_set;
+	bool	filter_config_set;
+	bool	trim_config_set;
+};
+
+#endif
-- 
2.7.4