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Date:	Fri, 14 Feb 2014 09:45:05 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Laszlo Papp <lpapp@....org>
Cc:	jdelvare@...e.de, lm-sensors@...sensors.org, lee.jones@...aro.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hwmon: (max6650) Convert to be a platform driver

On Fri, Feb 14, 2014 at 09:15:42AM +0000, Laszlo Papp wrote:
> The MFD driver has now been added, so this driver is now being adopted to be a
> subdevice driver on top of it. This means, the i2c driver usage is being
> converted to platform driver usage all around.
> 
> Signed-off-by: Laszlo Papp <lpapp@....org>
> ---
>  drivers/hwmon/Kconfig   |   2 +-
>  drivers/hwmon/max6650.c | 125 ++++++++++++++++++++++++------------------------
>  2 files changed, 63 insertions(+), 64 deletions(-)
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 7ed3aa6..fcfe484 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -962,7 +962,7 @@ config SENSORS_MAX6642
>  
>  config SENSORS_MAX6650
>  	tristate "Maxim MAX6650 sensor chip"
> -	depends on I2C
> +	depends on MFD_MAX665X
>  	help
>  	  If you say yes here you get support for the MAX6650 / MAX6651
>  	  sensor chips.
> diff --git a/drivers/hwmon/max6650.c b/drivers/hwmon/max6650.c
> index 162a520..4d79413 100644
> --- a/drivers/hwmon/max6650.c
> +++ b/drivers/hwmon/max6650.c
> @@ -39,6 +39,9 @@
>  #include <linux/hwmon.h>
>  #include <linux/hwmon-sysfs.h>
>  #include <linux/err.h>
> +#include <linux/platform_device.h>
> +
> +#include <linux/mfd/max665x-private.h>

'private' is a somewhat unusual file name in a global include file.
Why not just max665x.h ?

>  
>  /*
>   * Insmod parameters
> @@ -112,18 +115,19 @@ module_param(clock, int, S_IRUGO);
>  struct max6650_data {
>  	struct i2c_client *client;

client is no longer needed, and all other references to i2c
(such as include files) should be removed as well.

>  	const struct attribute_group *groups[3];
> +	struct max665x_dev *iodev;

The only use of this variable is to dereference map. 'struct regmap *map'
might thus make more sense here.

Also, iodev is not initialized. The first access to iodev->map will result
in a null pointer access.

>  	struct mutex update_lock;
>  	int nr_fans;
>  	char valid; /* zero until following fields are valid */
>  	unsigned long last_updated; /* in jiffies */
>  
>  	/* register values */
> -	u8 speed;
> -	u8 config;
> -	u8 tach[4];
> -	u8 count;
> -	u8 dac;
> -	u8 alarm;
> +	int speed;
> +	int config;
> +	int tach[4];
> +	int count;
> +	int dac;
> +	int alarm;
>  };
>  
>  static const u8 tach_reg[] = {
> @@ -136,31 +140,29 @@ static const u8 tach_reg[] = {
>  static struct max6650_data *max6650_update_device(struct device *dev)
>  {
>  	struct max6650_data *data = dev_get_drvdata(dev);
> -	struct i2c_client *client = data->client;
> +	struct regmap *map = data->iodev->map;
>  	int i;
> +	int alarm;
>  
>  	mutex_lock(&data->update_lock);
>  
>  	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
> -		data->speed = i2c_smbus_read_byte_data(client,
> -						       MAX6650_REG_SPEED);
> -		data->config = i2c_smbus_read_byte_data(client,
> -							MAX6650_REG_CONFIG);
> +		regmap_read(map, MAX6650_REG_SPEED, &data->speed);
> +		regmap_read(map, MAX6650_REG_CONFIG, &data->config);
>  		for (i = 0; i < data->nr_fans; i++) {
> -			data->tach[i] = i2c_smbus_read_byte_data(client,
> -								 tach_reg[i]);
> +			data->tach[i] = regmap_read(map, tach_reg[i],
> +							&data->tach[i]);
>  		}
> -		data->count = i2c_smbus_read_byte_data(client,
> -							MAX6650_REG_COUNT);
> -		data->dac = i2c_smbus_read_byte_data(client, MAX6650_REG_DAC);
> +		regmap_read(map, MAX6650_REG_COUNT, &data->count);
> +		regmap_read(map, MAX6650_REG_DAC, &data->dac);
>  
>  		/*
>  		 * Alarms are cleared on read in case the condition that
>  		 * caused the alarm is removed. Keep the value latched here
>  		 * for providing the register through different alarm files.
>  		 */
> -		data->alarm |= i2c_smbus_read_byte_data(client,
> -							MAX6650_REG_ALARM);
> +		regmap_read(map, MAX6650_REG_ALARM, &alarm);
> +		data->alarm |= alarm;
>  
>  		data->last_updated = jiffies;
>  		data->valid = 1;
> @@ -256,7 +258,6 @@ static ssize_t set_target(struct device *dev, struct device_attribute *devattr,
>  			 const char *buf, size_t count)
>  {
>  	struct max6650_data *data = dev_get_drvdata(dev);
> -	struct i2c_client *client = data->client;
>  	int kscale, ktach;
>  	unsigned long rpm;
>  	int err;
> @@ -284,7 +285,7 @@ static ssize_t set_target(struct device *dev, struct device_attribute *devattr,
>  		ktach = 255;
>  	data->speed = ktach;
>  
> -	i2c_smbus_write_byte_data(client, MAX6650_REG_SPEED, data->speed);
> +	regmap_write(data->iodev->map, MAX6650_REG_SPEED, data->speed);
>  
>  	mutex_unlock(&data->update_lock);
>  
> @@ -325,7 +326,6 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *devattr,
>  			const char *buf, size_t count)
>  {
>  	struct max6650_data *data = dev_get_drvdata(dev);
> -	struct i2c_client *client = data->client;
>  	unsigned long pwm;
>  	int err;
>  
> @@ -342,7 +342,7 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *devattr,
>  	else
>  		data->dac = 76 - (76 * pwm)/255;
>  
> -	i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);
> +	regmap_write(data->iodev->map, MAX6650_REG_DAC, data->dac);
>  
>  	mutex_unlock(&data->update_lock);
>  
> @@ -371,7 +371,7 @@ static ssize_t set_enable(struct device *dev, struct device_attribute *devattr,
>  			  const char *buf, size_t count)
>  {
>  	struct max6650_data *data = dev_get_drvdata(dev);
> -	struct i2c_client *client = data->client;
> +	struct regmap *map = data->iodev->map;
>  	int max6650_modes[3] = {0, 3, 2};
>  	unsigned long mode;
>  	int err;
> @@ -385,11 +385,11 @@ static ssize_t set_enable(struct device *dev, struct device_attribute *devattr,
>  
>  	mutex_lock(&data->update_lock);
>  
> -	data->config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
> +	regmap_read(map, MAX6650_REG_CONFIG, &data->config);
>  	data->config = (data->config & ~MAX6650_CFG_MODE_MASK)
>  		       | (max6650_modes[mode] << 4);
>  
> -	i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, data->config);
> +	regmap_write(map, MAX6650_REG_CONFIG, data->config);
>  
>  	mutex_unlock(&data->update_lock);
>  
> @@ -421,7 +421,6 @@ static ssize_t set_div(struct device *dev, struct device_attribute *devattr,
>  		       const char *buf, size_t count)
>  {
>  	struct max6650_data *data = dev_get_drvdata(dev);
> -	struct i2c_client *client = data->client;
>  	unsigned long div;
>  	int err;
>  
> @@ -448,7 +447,7 @@ static ssize_t set_div(struct device *dev, struct device_attribute *devattr,
>  		return -EINVAL;
>  	}
>  
> -	i2c_smbus_write_byte_data(client, MAX6650_REG_COUNT, data->count);
> +	regmap_write(data->iodev->map, MAX6650_REG_COUNT, data->count);
>  	mutex_unlock(&data->update_lock);
>  
>  	return count;
> @@ -465,16 +464,15 @@ static ssize_t get_alarm(struct device *dev, struct device_attribute *devattr,
>  			 char *buf)
>  {
>  	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> -	struct max6650_data *data = max6650_update_device(dev);
> -	struct i2c_client *client = data->client;
> +	struct max6650_data *data = dev_get_drvdata(dev);
>  	int alarm = 0;
>  
>  	if (data->alarm & attr->index) {
>  		mutex_lock(&data->update_lock);
> -		alarm = 1;
>  		data->alarm &= ~attr->index;
> -		data->alarm |= i2c_smbus_read_byte_data(client,
> -							MAX6650_REG_ALARM);
> +		regmap_read(data->iodev->map, MAX6650_REG_ALARM, &alarm);
> +		data->alarm |= alarm;
> +		alarm = 1;
>  		mutex_unlock(&data->update_lock);
>  	}
>  
> @@ -505,10 +503,11 @@ static umode_t max6650_attrs_visible(struct kobject *kobj, struct attribute *a,
>  {
>  	struct device *dev = container_of(kobj, struct device, kobj);
>  	struct max6650_data *data = dev_get_drvdata(dev);
> -	struct i2c_client *client = data->client;
> -	u8 alarm_en = i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN);
> +	int alarm_en;
>  	struct device_attribute *devattr;
>  
> +	regmap_read(data->iodev->map, MAX6650_REG_ALARM_EN, &alarm_en);
> +

There is now a difference in handline alarm_en and in general
return values from i2c_smbus_read_byte_data vs. regmap_read.
alarm_en is no longer initialized if regmap_read() returns an error.
It will therefore be necessary to check the return values or pre-initialize
the variable. The same applies to all other places where the reeturn value of
regmap_read is not checked.

>  	/*
>  	 * Hide the alarms that have not been enabled by the firmware
>  	 */
> @@ -560,17 +559,17 @@ static const struct attribute_group max6651_group = {
>   * Real code
>   */
>  
> -static int max6650_init_client(struct max6650_data *data,
> -			       struct i2c_client *client)
> +static int max6650_init_client(struct platform_device *pdev)
>  {
> -	struct device *dev = &client->dev;

I had a reason for introducing this variable here and in the probe function.
Please don't remove it.

> +	struct max6650_data *data = platform_get_drvdata(pdev);
> +	struct regmap *map = data->iodev->map;
>  	int config;
>  	int err = -EIO;
>  
> -	config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
> +	regmap_read(map, MAX6650_REG_CONFIG, &config);
>  
>  	if (config < 0) {
> -		dev_err(dev, "Error reading config, aborting.\n");
> +		dev_err(&pdev->dev, "Error reading config, aborting.\n");
>  		return err;
>  	}
>  
> @@ -584,11 +583,11 @@ static int max6650_init_client(struct max6650_data *data,
>  		config |= MAX6650_CFG_V12;
>  		break;
>  	default:
> -		dev_err(dev, "illegal value for fan_voltage (%d)\n",
> +		dev_err(&pdev->dev, "illegal value for fan_voltage (%d)\n",
>  			fan_voltage);
>  	}
>  
> -	dev_info(dev, "Fan voltage is set to %dV.\n",
> +	dev_info(&pdev->dev, "Fan voltage is set to %dV.\n",
>  		 (config & MAX6650_CFG_V12) ? 12 : 5);
>  
>  	switch (prescaler) {
> @@ -614,10 +613,11 @@ static int max6650_init_client(struct max6650_data *data,
>  			 | MAX6650_CFG_PRESCALER_16;
>  		break;
>  	default:
> -		dev_err(dev, "illegal value for prescaler (%d)\n", prescaler);
> +		dev_err(&pdev->dev, "illegal value for prescaler (%d)\n",
> +			prescaler);
>  	}
>  
> -	dev_info(dev, "Prescaler is set to %d.\n",
> +	dev_info(&pdev->dev, "Prescaler is set to %d.\n",
>  		 1 << (config & MAX6650_CFG_PRESCALER_MASK));
>  
>  	/*
> @@ -627,46 +627,45 @@ static int max6650_init_client(struct max6650_data *data,
>  	 */
>  
>  	if ((config & MAX6650_CFG_MODE_MASK) == MAX6650_CFG_MODE_OFF) {
> -		dev_dbg(dev, "Change mode to open loop, full off.\n");
> +		dev_dbg(&pdev->dev, "Change mode to open loop, full off.\n");
>  		config = (config & ~MAX6650_CFG_MODE_MASK)
>  			 | MAX6650_CFG_MODE_OPEN_LOOP;
> -		if (i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, 255)) {
> -			dev_err(dev, "DAC write error, aborting.\n");
> +		if (regmap_write(data->iodev->map, MAX6650_REG_DAC, 255) < 0) {
> +			dev_err(&pdev->dev, "DAC write error, aborting.\n");
>  			return err;
>  		}
>  	}
>  
> -	if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
> -		dev_err(dev, "Config write error, aborting.\n");
> +	if (regmap_write(map, MAX6650_REG_CONFIG, config) < 0) {
> +		dev_err(&pdev->dev, "Config write error, aborting.\n");
>  		return err;
>  	}
>  
>  	data->config = config;
> -	data->count = i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT);
> +	regmap_read(map, MAX6650_REG_COUNT, &data->count);
>  
>  	return 0;
>  }
>  
> -static int max6650_probe(struct i2c_client *client,
> -			 const struct i2c_device_id *id)
> +static int max6650_probe(struct platform_device *pdev)
>  {
> -	struct device *dev = &client->dev;
> -	struct max6650_data *data;
> +	struct max6650_data *data = platform_get_drvdata(pdev);

driver data points to struct max665x_dev *.

This should probably be something like
	struct max665x_dev *iodev = platform_get_drvdata(pdev);
as a separate variable. It also needs to be validated to ensure
that it is not NULL.

> +	const struct platform_device_id *id = platform_get_device_id(pdev);
>  	struct device *hwmon_dev;
>  	int err;
>  
> -	data = devm_kzalloc(dev, sizeof(struct max6650_data), GFP_KERNEL);
> +	data = devm_kzalloc(&pdev->dev, sizeof(struct max6650_data),
> +							GFP_KERNEL);
>  	if (!data)
>  		return -ENOMEM;
>  
> -	data->client = client;

	data->iodev = iodev;
or better
	data->map = iodev->map;

is missing.

>  	mutex_init(&data->update_lock);
>  	data->nr_fans = id->driver_data;
>  
>  	/*
>  	 * Initialize the max6650 chip
>  	 */
> -	err = max6650_init_client(data, client);
> +	err = max6650_init_client(pdev);
>  	if (err)
>  		return err;
>  
> @@ -675,20 +674,20 @@ static int max6650_probe(struct i2c_client *client,
>  	if (data->nr_fans == 4)
>  		data->groups[1] = &max6651_group;
>  
> -	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
> -							   client->name, data,
> -							   data->groups);
> +	hwmon_dev = devm_hwmon_device_register_with_groups(&pdev->dev,
> +							   data->client->name,

This will crash (client is NULL).

You'll have to come up with a scheme to pass the device type from the mfd driver
to this one, and use "max6650" and "max6651" as names here.

> +							   data, data->groups);
>  	return PTR_ERR_OR_ZERO(hwmon_dev);
>  }
>  
> -static const struct i2c_device_id max6650_id[] = {
> +static const struct platform_device_id max6650_id[] = {
>  	{ "max6650", 1 },
>  	{ "max6651", 4 },
>  	{ }
>  };
> -MODULE_DEVICE_TABLE(i2c, max6650_id);
> +MODULE_DEVICE_TABLE(platform, max6650_id);
>  
> -static struct i2c_driver max6650_driver = {
> +static struct platform_driver max6650_driver = {
>  	.driver = {
>  		.name	= "max6650",
>  	},
> @@ -696,7 +695,7 @@ static struct i2c_driver max6650_driver = {
>  	.id_table	= max6650_id,
>  };
>  
> -module_i2c_driver(max6650_driver);
> +module_platform_driver(max6650_driver);
>  
>  MODULE_AUTHOR("Hans J. Koch");
>  MODULE_DESCRIPTION("MAX6650 sensor driver");
> -- 
> 1.8.5.4
> 
> 
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