Message-ID: <20161118184058.GC19884@dell.home>
Date:   Fri, 18 Nov 2016 18:40:58 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Olimpiu Dejeu <olimpiu@...ticsand.com>
Cc:     robh@...nel.org, linux-kernel@...r.kernel.org,
        linux-fbdev@...r.kernel.org, devicetree@...r.kernel.org,
        jingoohan1@...il.com
Subject: Re: [PATCH 1/2] backlight: arcxcnn: add support for ArticSand devices

I'll give this a quick once over, but Jingoo will also need to review.

On Thu, 10 Nov 2016, Olimpiu Dejeu wrote:

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

This is not a commit log.  It's a changelog which lives at <####>.

> Signed-off-by: Olimpiu Dejeu <olimpiu@...ticsand.com>
> 
> ---

<####>

>  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.

As far as I'm aware, this does not constitude as a proper GPL licence
statement.

> + */
> +
> +#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>

Alphabetical.

> +#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)

No need for simple defines to be place inside parenthesis.

> +#define DEFAULT_BL_NAME		"arctic_bl"

Don't do this.  Just use the name in the place you need to use it.

> +#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;

Why?

> +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;

You only need one of 'bl', 'dev' and 'client'.

> +	struct arcxcnn_platform_data *pdata;

pdata should not be stored in ddata.

> +	struct pwm_device *pwm;
> +	struct regulator *supply;	/* regulator for VDD input */
> +};

Document using kerneldoc.

> +static int arcxcnn_write_byte(struct arcxcnn *lp, u8 reg, u8 data)
> +{
> +	s32 ret = -1;
> +	int att;
> +
> +	for (att = 0; att < s_retries; att++) {

This is non-standard.

Why would it fail on first attempt and succeed on the next?

> +		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);
> +}

I'd really rather you didn't role your own read/write/update API!

> +static int arcxcnn_set_brightness(struct arcxcnn *lp, u32 brightness)
> +{
> +	int ret;
> +	u8 val;
> +
> +	val = (brightness & 0xF) << 4;

Define the shift value.

> +	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);

'\n' here.

> +	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 */

Replace this with a comment.

> +	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
> +		 */

This is not a valid multi-line kernel comment.

See: Documentation/CodingStyle

> +		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;

This variable seems pretty redundant.

> +	struct backlight_properties props;

Dynamically request memory for this.

> +	struct arcxcnn_platform_data *pdata = lp->pdata;
> +	const char *name = pdata->name ? : DEFAULT_BL_NAME;

Why do you need to set a name different from the device 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,

This should be arcxcnn_chip_id_show()

> +		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);

This is not pdata.

What is led_str anyway?  It looks like an int, not a string.

> +}
> +
> +static ssize_t arcxcnn_set_led_str(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t len)
> +{

arcxcnn_led_str_store()

> +	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;

Shouldn't you be return -EINVAL if 0 is not valid?

> +		lp->pdata->led_str = ledstr & 0x3F;
> +		arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
> +			ARCXCNN_LEDEN_MASK, lp->pdata->led_str);

What are you lining up against here?

> +	}

'\n'

> +	return len;
> +}
> +
> +static ssize_t arcxcnn_get_bl_ctl_mode(struct device *dev,
> +	     struct device_attribute *attr, char *buf)
> +{

arcxcnn_bl_ctl_mode_show()

> +	struct arcxcnn *lp = dev_get_drvdata(dev);
> +	char *strmode = NULL;

Why are you pre-initialising here?

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

Remove "based" and place it in scnprintf instead.

> +	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

No ifdefery please.

Use if (IS_ENABLED(CONFIG_OF)) before calling arcxcnn_parse_dt()
instead.

> +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");

That's not what this means is it?

> +		return -EINVAL;
> +	}

'\n'

> +	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;

These are already 0.

And you need to take these 'out' of pdata.

Create a config struct to place them all in and add it to ddata.

> +	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;
> +	}

You need to get these signed off by the DT folk.

> +	ret = of_property_count_u32_elems(node, "led-sources");
> +	if (ret < 0)
> +		lp->pdata->led_str = 0x3F;

What is 3F?  Please define it.

> +	else {
> +		num_entry = ret;
> +		if (num_entry > 6)
> +			num_entry = 6;

What is 6?  No magic numbers.

> +		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]);

This is not good code.  Please make it easier to read.

> +	}
> +	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;

You don't need both of these.

> +	lp->chip_id = id->driver_data;

What are you going to use this for?

> +	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
> +		 */

Not a valid multi-line comment.

> +		ret = arcxcnn_parse_dt(lp);
> +		if (ret < 0) {
> +			/* no device tree, use defaults based on module params
> +			 */

Not a valid single-line comment.

> +			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;

These are already 0.

> +			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;

Define all magic numbers.

> +	/* make sure it belongs to this driver
> +	 * TODO - handle specific ids
> +	 */
> +	if (chipid != 0x02A5) {
> +		#if 1

What on earth is this?

> +		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 */

Spelling.

> +	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);

More magic numbers.

> +	/* 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);

What are the default values of these registers?

If 0, then just write them without the checks.

> +	/* set initial LED Strings */

What is 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);

'\n'

> +	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);
> +	}

'\n'

> +	lp->bl->props.brightness = 0;

'\n'

> +	backlight_update_status(lp->bl);

'\n'

> +	if (lp->supply)
> +		regulator_disable(lp->supply);

'\n'

> +	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

Then why supply it here at all?

> + */
> +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),
> +		   },

Tabbing.

> +	.probe = arcxcnn_probe,
> +	.remove = arcxcnn_remove,
> +	.id_table = arcxcnn_ids,
> +};
> +

Superfluous '\n'

> +module_i2c_driver(arcxcnn_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Brian Dodge <bdodge09@...look.com>");

Who?

> +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

Tab out the ':'s.

This is only platform data if it's set by the platform.

Otherwise it's just a config or bitfields.

> + * 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

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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