linux/drivers/hwmon/ads7828.c
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   1/*
   2 * ads7828.c - lm_sensors driver for ads7828 12-bit 8-channel ADC
   3 * (C) 2007 EADS Astrium
   4 *
   5 * This driver is based on the lm75 and other lm_sensors/hwmon drivers
   6 *
   7 * Written by Steve Hardy <shardy@redhat.com>
   8 *
   9 * Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads7828.pdf
  10 *
  11 * This program is free software; you can redistribute it and/or modify
  12 * it under the terms of the GNU General Public License as published by
  13 * the Free Software Foundation; either version 2 of the License, or
  14 * (at your option) any later version.
  15 *
  16 * This program is distributed in the hope that it will be useful,
  17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  19 * GNU General Public License for more details.
  20 *
  21 * You should have received a copy of the GNU General Public License
  22 * along with this program; if not, write to the Free Software
  23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  24 */
  25
  26#include <linux/module.h>
  27#include <linux/init.h>
  28#include <linux/slab.h>
  29#include <linux/jiffies.h>
  30#include <linux/i2c.h>
  31#include <linux/hwmon.h>
  32#include <linux/hwmon-sysfs.h>
  33#include <linux/err.h>
  34#include <linux/mutex.h>
  35
  36/* The ADS7828 registers */
  37#define ADS7828_NCH 8 /* 8 channels of 12-bit A-D supported */
  38#define ADS7828_CMD_SD_SE 0x80 /* Single ended inputs */
  39#define ADS7828_CMD_SD_DIFF 0x00 /* Differential inputs */
  40#define ADS7828_CMD_PD0 0x0 /* Power Down between A-D conversions */
  41#define ADS7828_CMD_PD1 0x04 /* Internal ref OFF && A-D ON */
  42#define ADS7828_CMD_PD2 0x08 /* Internal ref ON && A-D OFF */
  43#define ADS7828_CMD_PD3 0x0C /* Internal ref ON && A-D ON */
  44#define ADS7828_INT_VREF_MV 2500 /* Internal vref is 2.5V, 2500mV */
  45
  46/* Addresses to scan */
  47static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
  48        I2C_CLIENT_END };
  49
  50/* Module parameters */
  51static bool se_input = 1; /* Default is SE, 0 == diff */
  52static bool int_vref = 1; /* Default is internal ref ON */
  53static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
  54module_param(se_input, bool, S_IRUGO);
  55module_param(int_vref, bool, S_IRUGO);
  56module_param(vref_mv, int, S_IRUGO);
  57
  58/* Global Variables */
  59static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
  60static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
  61
  62/* Each client has this additional data */
  63struct ads7828_data {
  64        struct device *hwmon_dev;
  65        struct mutex update_lock; /* mutex protect updates */
  66        char valid; /* !=0 if following fields are valid */
  67        unsigned long last_updated; /* In jiffies */
  68        u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
  69};
  70
  71/* Function declaration - necessary due to function dependencies */
  72static int ads7828_detect(struct i2c_client *client,
  73                          struct i2c_board_info *info);
  74static int ads7828_probe(struct i2c_client *client,
  75                         const struct i2c_device_id *id);
  76
  77static inline u8 channel_cmd_byte(int ch)
  78{
  79        /* cmd byte C2,C1,C0 - see datasheet */
  80        u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
  81        cmd |= ads7828_cmd_byte;
  82        return cmd;
  83}
  84
  85/* Update data for the device (all 8 channels) */
  86static struct ads7828_data *ads7828_update_device(struct device *dev)
  87{
  88        struct i2c_client *client = to_i2c_client(dev);
  89        struct ads7828_data *data = i2c_get_clientdata(client);
  90
  91        mutex_lock(&data->update_lock);
  92
  93        if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
  94                        || !data->valid) {
  95                unsigned int ch;
  96                dev_dbg(&client->dev, "Starting ads7828 update\n");
  97
  98                for (ch = 0; ch < ADS7828_NCH; ch++) {
  99                        u8 cmd = channel_cmd_byte(ch);
 100                        data->adc_input[ch] =
 101                                i2c_smbus_read_word_swapped(client, cmd);
 102                }
 103                data->last_updated = jiffies;
 104                data->valid = 1;
 105        }
 106
 107        mutex_unlock(&data->update_lock);
 108
 109        return data;
 110}
 111
 112/* sysfs callback function */
 113static ssize_t show_in(struct device *dev, struct device_attribute *da,
 114        char *buf)
 115{
 116        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 117        struct ads7828_data *data = ads7828_update_device(dev);
 118        /* Print value (in mV as specified in sysfs-interface documentation) */
 119        return sprintf(buf, "%d\n", (data->adc_input[attr->index] *
 120                ads7828_lsb_resol)/1000);
 121}
 122
 123#define in_reg(offset)\
 124static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
 125        NULL, offset)
 126
 127in_reg(0);
 128in_reg(1);
 129in_reg(2);
 130in_reg(3);
 131in_reg(4);
 132in_reg(5);
 133in_reg(6);
 134in_reg(7);
 135
 136static struct attribute *ads7828_attributes[] = {
 137        &sensor_dev_attr_in0_input.dev_attr.attr,
 138        &sensor_dev_attr_in1_input.dev_attr.attr,
 139        &sensor_dev_attr_in2_input.dev_attr.attr,
 140        &sensor_dev_attr_in3_input.dev_attr.attr,
 141        &sensor_dev_attr_in4_input.dev_attr.attr,
 142        &sensor_dev_attr_in5_input.dev_attr.attr,
 143        &sensor_dev_attr_in6_input.dev_attr.attr,
 144        &sensor_dev_attr_in7_input.dev_attr.attr,
 145        NULL
 146};
 147
 148static const struct attribute_group ads7828_group = {
 149        .attrs = ads7828_attributes,
 150};
 151
 152static int ads7828_remove(struct i2c_client *client)
 153{
 154        struct ads7828_data *data = i2c_get_clientdata(client);
 155        hwmon_device_unregister(data->hwmon_dev);
 156        sysfs_remove_group(&client->dev.kobj, &ads7828_group);
 157        kfree(i2c_get_clientdata(client));
 158        return 0;
 159}
 160
 161static const struct i2c_device_id ads7828_id[] = {
 162        { "ads7828", 0 },
 163        { }
 164};
 165MODULE_DEVICE_TABLE(i2c, ads7828_id);
 166
 167/* This is the driver that will be inserted */
 168static struct i2c_driver ads7828_driver = {
 169        .class = I2C_CLASS_HWMON,
 170        .driver = {
 171                .name = "ads7828",
 172        },
 173        .probe = ads7828_probe,
 174        .remove = ads7828_remove,
 175        .id_table = ads7828_id,
 176        .detect = ads7828_detect,
 177        .address_list = normal_i2c,
 178};
 179
 180/* Return 0 if detection is successful, -ENODEV otherwise */
 181static int ads7828_detect(struct i2c_client *client,
 182                          struct i2c_board_info *info)
 183{
 184        struct i2c_adapter *adapter = client->adapter;
 185        int ch;
 186
 187        /* Check we have a valid client */
 188        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))
 189                return -ENODEV;
 190
 191        /*
 192         * Now, we do the remaining detection. There is no identification
 193         * dedicated register so attempt to sanity check using knowledge of
 194         * the chip
 195         * - Read from the 8 channel addresses
 196         * - Check the top 4 bits of each result are not set (12 data bits)
 197         */
 198        for (ch = 0; ch < ADS7828_NCH; ch++) {
 199                u16 in_data;
 200                u8 cmd = channel_cmd_byte(ch);
 201                in_data = i2c_smbus_read_word_swapped(client, cmd);
 202                if (in_data & 0xF000) {
 203                        pr_debug("%s : Doesn't look like an ads7828 device\n",
 204                                 __func__);
 205                        return -ENODEV;
 206                }
 207        }
 208
 209        strlcpy(info->type, "ads7828", I2C_NAME_SIZE);
 210
 211        return 0;
 212}
 213
 214static int ads7828_probe(struct i2c_client *client,
 215                         const struct i2c_device_id *id)
 216{
 217        struct ads7828_data *data;
 218        int err;
 219
 220        data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
 221        if (!data) {
 222                err = -ENOMEM;
 223                goto exit;
 224        }
 225
 226        i2c_set_clientdata(client, data);
 227        mutex_init(&data->update_lock);
 228
 229        /* Register sysfs hooks */
 230        err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
 231        if (err)
 232                goto exit_free;
 233
 234        data->hwmon_dev = hwmon_device_register(&client->dev);
 235        if (IS_ERR(data->hwmon_dev)) {
 236                err = PTR_ERR(data->hwmon_dev);
 237                goto exit_remove;
 238        }
 239
 240        return 0;
 241
 242exit_remove:
 243        sysfs_remove_group(&client->dev.kobj, &ads7828_group);
 244exit_free:
 245        kfree(data);
 246exit:
 247        return err;
 248}
 249
 250static int __init sensors_ads7828_init(void)
 251{
 252        /* Initialize the command byte according to module parameters */
 253        ads7828_cmd_byte = se_input ?
 254                ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
 255        ads7828_cmd_byte |= int_vref ?
 256                ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
 257
 258        /* Calculate the LSB resolution */
 259        ads7828_lsb_resol = (vref_mv*1000)/4096;
 260
 261        return i2c_add_driver(&ads7828_driver);
 262}
 263
 264static void __exit sensors_ads7828_exit(void)
 265{
 266        i2c_del_driver(&ads7828_driver);
 267}
 268
 269MODULE_AUTHOR("Steve Hardy <shardy@redhat.com>");
 270MODULE_DESCRIPTION("ADS7828 driver");
 271MODULE_LICENSE("GPL");
 272
 273module_init(sensors_ads7828_init);
 274module_exit(sensors_ads7828_exit);
 275
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