Date:	Tue, 2 Oct 2012 17:28:40 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc:	lm-sensors@...sensors.org, Jean Delvare <khali@...ux-fr.org>,
	linux-kernel@...r.kernel.org, Steve Hardy <shardy@...hat.com>
Subject: Re: [PATCH v3 1/2] hwmon: (ads7828) driver cleanup

On Tue, Oct 02, 2012 at 06:10:02PM -0400, Vivien Didelot wrote:
> * Remove module parameters, add a ads7828_platform_data;
> * Move driver declaration to avoid adding function prototypes;
> * Remove unused macros;
> * Coding Style fixes.
> 
> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>

Hi Vivien,

nice cleanup. Couple of minor comments below.

> ---
>  Documentation/hwmon/ads7828           |  31 +++--
>  drivers/hwmon/ads7828.c               | 216 +++++++++++++++++-----------------
>  include/linux/platform_data/ads7828.h |  29 +++++
>  3 files changed, 155 insertions(+), 121 deletions(-)
>  create mode 100644 include/linux/platform_data/ads7828.h
> 
> diff --git a/Documentation/hwmon/ads7828 b/Documentation/hwmon/ads7828
> index 2bbebe6..b35668c 100644
> --- a/Documentation/hwmon/ads7828
> +++ b/Documentation/hwmon/ads7828
> @@ -5,21 +5,32 @@ Supported chips:
>    * Texas Instruments/Burr-Brown ADS7828
>      Prefix: 'ads7828'
>      Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4b
> -    Datasheet: Publicly available at the Texas Instruments website :
> +    Datasheet: Publicly available at the Texas Instruments website:
>                 http://focus.ti.com/lit/ds/symlink/ads7828.pdf
>  
>  Authors:
>          Steve Hardy <shardy@...hat.com>
>  
> -Module Parameters
> ------------------
> -
> -* se_input: bool (default Y)
> -  Single ended operation - set to N for differential mode
> -* int_vref: bool (default Y)
> -  Operate with the internal 2.5V reference - set to N for external reference
> -* vref_mv: int (default 2500)
> -  If using an external reference, set this to the reference voltage in mV
> +Platform data
> +-------------
> +
> +The ads7828 driver accepts an optional ads7828_platform_data structure (defined
> +in include/linux/platform_data/ads7828.h). If no structure is provided, the
> +configuration defaults to single ended operation and internal vref (2.5V).
> +
> +The structure fields are:
> +
> +* diff_input: bool
> +  Differential operation - set to true for differential mode,
> +  false for default single ended mode.
> +* ext_vref: bool
> +  External reference - set to true if it operates with an external reference,
> +  false for default internal reference.
> +* vref_mv: int
> +  Voltage reference - if using an external reference, set this to the reference
> +  voltage in mV, otherwise, it will default to the internal value (2500mV).
> +  This value will be bounded with limits accepted by the chip, described in the
> +  datasheet.
>  
>  Description
>  -----------
> diff --git a/drivers/hwmon/ads7828.c b/drivers/hwmon/ads7828.c
> index bf3fdf4..0a13bf8 100644
> --- a/drivers/hwmon/ads7828.c
> +++ b/drivers/hwmon/ads7828.c
> @@ -6,7 +6,7 @@
>   *
>   * Written by Steve Hardy <shardy@...hat.com>
>   *
> - * Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads7828.pdf
> + * For further information, see the Documentation/hwmon/ads7828 file.
>   *
>   * This program is free software; you can redistribute it and/or modify
>   * it under the terms of the GNU General Public License as published by
> @@ -23,63 +23,48 @@
>   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>   */
>  
> -#include <linux/module.h>
> -#include <linux/init.h>
> -#include <linux/slab.h>
> -#include <linux/jiffies.h>
> -#include <linux/i2c.h>
> +#include <linux/err.h>
>  #include <linux/hwmon.h>
>  #include <linux/hwmon-sysfs.h>
> -#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/jiffies.h>
> +#include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <linux/platform_data/ads7828.h>
> +#include <linux/slab.h>
>  
>  /* The ADS7828 registers */
> -#define ADS7828_NCH 8 /* 8 channels of 12-bit A-D supported */
> -#define ADS7828_CMD_SD_SE 0x80 /* Single ended inputs */
> -#define ADS7828_CMD_SD_DIFF 0x00 /* Differential inputs */
> -#define ADS7828_CMD_PD0 0x0 /* Power Down between A-D conversions */
> -#define ADS7828_CMD_PD1 0x04 /* Internal ref OFF && A-D ON */
> -#define ADS7828_CMD_PD2 0x08 /* Internal ref ON && A-D OFF */
> -#define ADS7828_CMD_PD3 0x0C /* Internal ref ON && A-D ON */
> -#define ADS7828_INT_VREF_MV 2500 /* Internal vref is 2.5V, 2500mV */
> +#define ADS7828_NCH		8	/* 8 channels supported */
> +#define ADS7828_CMD_SD_SE	0x80	/* Single ended inputs */
> +#define ADS7828_CMD_PD1		0x04	/* Internal vref OFF && A/D ON */
> +#define ADS7828_CMD_PD3		0x0C	/* Internal vref ON && A/D ON */
> +#define ADS7828_INT_VREF_MV	2500	/* Internal vref is 2.5V, 2500mV */
> +#define ADS7828_EXT_VREF_MV_MIN	50	/* External vref min value 0.05V */
> +#define ADS7828_EXT_VREF_MV_MAX	5250	/* External vref max value 5.25V */
>  
>  /* Addresses to scan */
>  static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
>  	I2C_CLIENT_END };
>  
> -/* Module parameters */
> -static bool se_input = 1; /* Default is SE, 0 == diff */
> -static bool int_vref = 1; /* Default is internal ref ON */
> -static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
> -module_param(se_input, bool, S_IRUGO);
> -module_param(int_vref, bool, S_IRUGO);
> -module_param(vref_mv, int, S_IRUGO);
> -
> -/* Global Variables */
> -static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
> -static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
> -
> -/* Each client has this additional data */
> +/* Client specific data */
>  struct ads7828_data {
>  	struct device *hwmon_dev;
> -	struct mutex update_lock; /* mutex protect updates */
> -	char valid; /* !=0 if following fields are valid */
> -	unsigned long last_updated; /* In jiffies */
> -	u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
> +	struct mutex update_lock;	/* Mutex protecting updates */
> +	unsigned long last_updated;	/* Last updated time (in jiffies) */
> +	u16 adc_input[ADS7828_NCH];	/* ADS7828_NCH samples */
> +	bool valid;			/* Validity flag */
> +	bool diff_input;		/* Differential input */
> +	bool ext_vref;			/* External voltage reference */
> +	unsigned int vref_mv;		/* voltage reference value */
> +	u8 cmd_byte;			/* Command byte without channel bits */
> +	unsigned int lsb_resol;		/* Resolution of the ADC sample LSB */
>  };
>  
> -/* Function declaration - necessary due to function dependencies */
> -static int ads7828_detect(struct i2c_client *client,
> -			  struct i2c_board_info *info);
> -static int ads7828_probe(struct i2c_client *client,
> -			 const struct i2c_device_id *id);
> -
> -static inline u8 channel_cmd_byte(int ch)
> +/* Command byte C2,C1,C0 - see datasheet */
> +static inline u8 ads7828_cmd_byte(u8 cmd, int ch)
>  {
> -	/* cmd byte C2,C1,C0 - see datasheet */
> -	u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
> -	cmd |= ads7828_cmd_byte;
> -	return cmd;
> +	return cmd | (((ch >> 1) | (ch & 0x01) << 2) << 4);
>  }
>  
>  /* Update data for the device (all 8 channels) */
> @@ -96,12 +81,12 @@ static struct ads7828_data *ads7828_update_device(struct device *dev)
>  		dev_dbg(&client->dev, "Starting ads7828 update\n");
>  
>  		for (ch = 0; ch < ADS7828_NCH; ch++) {
> -			u8 cmd = channel_cmd_byte(ch);
> +			u8 cmd = ads7828_cmd_byte(data->cmd_byte, ch);
>  			data->adc_input[ch] =
>  				i2c_smbus_read_word_swapped(client, cmd);
>  		}
>  		data->last_updated = jiffies;
> -		data->valid = 1;
> +		data->valid = true;
>  	}
>  
>  	mutex_unlock(&data->update_lock);
> @@ -110,28 +95,25 @@ static struct ads7828_data *ads7828_update_device(struct device *dev)
>  }
>  
>  /* sysfs callback function */
> -static ssize_t show_in(struct device *dev, struct device_attribute *da,
> -	char *buf)
> +static ssize_t ads7828_show_in(struct device *dev, struct device_attribute *da,
> +			       char *buf)
>  {
>  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
>  	struct ads7828_data *data = ads7828_update_device(dev);
> -	/* Print value (in mV as specified in sysfs-interface documentation) */
> -	return sprintf(buf, "%d\n", (data->adc_input[attr->index] *
> -		ads7828_lsb_resol)/1000);
> -}
> +	unsigned int value = DIV_ROUND_CLOSEST(data->adc_input[attr->index] *
> +					       data->lsb_resol, 1000);
>  
> -#define in_reg(offset)\
> -static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
> -	NULL, offset)
> +	return sprintf(buf, "%d\n", value);
> +}
>  
> -in_reg(0);
> -in_reg(1);
> -in_reg(2);
> -in_reg(3);
> -in_reg(4);
> -in_reg(5);
> -in_reg(6);
> -in_reg(7);
> +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ads7828_show_in, NULL, 0);
> +static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ads7828_show_in, NULL, 1);
> +static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ads7828_show_in, NULL, 2);
> +static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, ads7828_show_in, NULL, 3);
> +static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, ads7828_show_in, NULL, 4);
> +static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, ads7828_show_in, NULL, 5);
> +static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, ads7828_show_in, NULL, 6);
> +static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, ads7828_show_in, NULL, 7);
>  
>  static struct attribute *ads7828_attributes[] = {
>  	&sensor_dev_attr_in0_input.dev_attr.attr,
> @@ -152,36 +134,20 @@ static const struct attribute_group ads7828_group = {
>  static int ads7828_remove(struct i2c_client *client)
>  {
>  	struct ads7828_data *data = i2c_get_clientdata(client);
> +
>  	hwmon_device_unregister(data->hwmon_dev);
>  	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
> -	kfree(i2c_get_clientdata(client));
> +	i2c_set_clientdata(client, NULL);

i2c_set_clientdata(client, NULL) is not necessary. The framework does that for you.

> +
>  	return 0;
>  }
>  
> -static const struct i2c_device_id ads7828_id[] = {
> -	{ "ads7828", 0 },
> -	{ }
> -};
> -MODULE_DEVICE_TABLE(i2c, ads7828_id);
> -
> -/* This is the driver that will be inserted */
> -static struct i2c_driver ads7828_driver = {
> -	.class = I2C_CLASS_HWMON,
> -	.driver = {
> -		.name = "ads7828",
> -	},
> -	.probe = ads7828_probe,
> -	.remove = ads7828_remove,
> -	.id_table = ads7828_id,
> -	.detect = ads7828_detect,
> -	.address_list = normal_i2c,
> -};
> -
>  /* Return 0 if detection is successful, -ENODEV otherwise */
>  static int ads7828_detect(struct i2c_client *client,
>  			  struct i2c_board_info *info)
>  {
>  	struct i2c_adapter *adapter = client->adapter;
> +	u8 default_cmd_byte = ADS7828_CMD_SD_SE | ADS7828_CMD_PD3;
>  	int ch;
>  
>  	/* Check we have a valid client */
> @@ -196,9 +162,12 @@ static int ads7828_detect(struct i2c_client *client,
>  	 * - Check the top 4 bits of each result are not set (12 data bits)
>  	 */
>  	for (ch = 0; ch < ADS7828_NCH; ch++) {
> -		u16 in_data;
> -		u8 cmd = channel_cmd_byte(ch);
> -		in_data = i2c_smbus_read_word_swapped(client, cmd);
> +		u8 cmd = ads7828_cmd_byte(default_cmd_byte, ch);
> +		u16 in_data = i2c_smbus_read_word_swapped(client, cmd);
> +
> +		if (in_data < 0)
> +			return -ENODEV;
> +
>  		if (in_data & 0xF000) {
>  			pr_debug("%s : Doesn't look like an ads7828 device\n",
>  				 __func__);
> @@ -214,61 +183,86 @@ static int ads7828_detect(struct i2c_client *client,
>  static int ads7828_probe(struct i2c_client *client,
>  			 const struct i2c_device_id *id)
>  {
> -	struct ads7828_data *data;
>  	int err;
> -
> -	data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
> -	if (!data) {
> -		err = -ENOMEM;
> -		goto exit;
> +	struct ads7828_data *data;
> +	struct ads7828_platform_data *pdata = client->dev.platform_data;
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct ads7828_data),
> +			    GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
The above change (use of devm_kzalloc) is in the latest upstream code already.
Please reparent.

> +	if (pdata) {
> +		data->diff_input = pdata->diff_input;
> +		data->ext_vref = pdata->ext_vref;
> +		if (data->ext_vref)
> +			data->vref_mv = pdata->vref_mv;
>  	}
>  
> +	/* Bound Vref with min/max values if it was provided */
> +	if (data->vref_mv)
> +		data->vref_mv = SENSORS_LIMIT(data->vref_mv,
> +					      ADS7828_EXT_VREF_MV_MIN,
> +					      ADS7828_EXT_VREF_MV_MAX);
> +	else
> +		data->vref_mv = ADS7828_INT_VREF_MV;
> +
> +	data->lsb_resol = DIV_ROUND_CLOSEST(data->vref_mv * 1000, 4096);
> +
> +	data->cmd_byte = data->ext_vref ? ADS7828_CMD_PD1 : ADS7828_CMD_PD3;
> +	if (!data->diff_input)
> +		data->cmd_byte |= ADS7828_CMD_SD_SE;
> +
>  	i2c_set_clientdata(client, data);
>  	mutex_init(&data->update_lock);
>  
> -	/* Register sysfs hooks */
>  	err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
>  	if (err)
> -		goto exit_free;
> +		return err;
>  
>  	data->hwmon_dev = hwmon_device_register(&client->dev);
>  	if (IS_ERR(data->hwmon_dev)) {
>  		err = PTR_ERR(data->hwmon_dev);
> -		goto exit_remove;
> +		goto error;
>  	}
>  
>  	return 0;
>  
> -exit_remove:
> +error:
>  	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
> -exit_free:
> -	kfree(data);
> -exit:
>  	return err;
>  }
>  
> -static int __init sensors_ads7828_init(void)
> -{
> -	/* Initialize the command byte according to module parameters */
> -	ads7828_cmd_byte = se_input ?
> -		ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
> -	ads7828_cmd_byte |= int_vref ?
> -		ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
> +static const struct i2c_device_id ads7828_ids[] = {
> +	{ "ads7828", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ads7828_ids);
>  
> -	/* Calculate the LSB resolution */
> -	ads7828_lsb_resol = (vref_mv*1000)/4096;
> +static struct i2c_driver ads7828_driver = {
> +	.class = I2C_CLASS_HWMON,
> +	.driver = {
> +		.name = "ads7828",
> +	},
> +	.address_list = normal_i2c,
> +	.detect = ads7828_detect,
> +	.probe = ads7828_probe,
> +	.remove = ads7828_remove,
> +	.id_table = ads7828_ids,
> +};
>  
> +static int __init sensors_ads7828_init(void)
> +{
>  	return i2c_add_driver(&ads7828_driver);
>  }
> +module_init(sensors_ads7828_init);
>  
>  static void __exit sensors_ads7828_exit(void)
>  {
>  	i2c_del_driver(&ads7828_driver);
>  }
> +module_exit(sensors_ads7828_exit);
>  
With the cleanup, you can now use the module_i2c_driver macro.

>  MODULE_AUTHOR("Steve Hardy <shardy@...hat.com>");
> -MODULE_DESCRIPTION("ADS7828 driver");
> +MODULE_DESCRIPTION("Driver for TI ADS7828 A/D converter");
>  MODULE_LICENSE("GPL");
> -
> -module_init(sensors_ads7828_init);
> -module_exit(sensors_ads7828_exit);
> diff --git a/include/linux/platform_data/ads7828.h b/include/linux/platform_data/ads7828.h
> new file mode 100644
> index 0000000..3245f45
> --- /dev/null
> +++ b/include/linux/platform_data/ads7828.h
> @@ -0,0 +1,29 @@
> +/*
> + * TI ADS7828 A/D Converter platform data definition
> + *
> + * Copyright (c) 2012 Savoir-faire Linux Inc.
> + *          Vivien Didelot <vivien.didelot@...oirfairelinux.com>
> + *
> + * For further information, see the Documentation/hwmon/ads7828 file.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef _PDATA_ADS7828_H
> +#define _PDATA_ADS7828_H
> +
> +/**
> + * struct ads7828_platform_data - optional ADS7828 connectivity info
> + * @diff_input:		Differential input mode.
> + * @ext_vref:		Use an external voltage reference.
> + * @vref_mv:		Voltage reference value, if external.
> + */
> +struct ads7828_platform_data {
> +	bool diff_input;
> +	bool ext_vref;
> +	unsigned int vref_mv;
> +};
> +
> +#endif /* _PDATA_ADS7828_H */
> -- 
> 1.7.11.4
> 
> 
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