ads7828.c

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/*
 * ads7828.c - lm_sensors driver for ads7828 12-bit 8-channel ADC
 * (C) 2007 EADS Astrium
 *
 * This driver is based on the lm75 and other lm_sensors/hwmon drivers
 *
 * Written by Steve Hardy <[email protected]>
 *
 * Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads7828.pdf
 *
 * 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
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * 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/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/mutex.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 */

/* 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 */
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 */
};

/* 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)
{
    /* cmd byte C2,C1,C0 - see datasheet */
    u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
    cmd |= ads7828_cmd_byte;
    return cmd;
}

/* Update data for the device (all 8 channels) */
static struct ads7828_data *ads7828_update_device(struct device *dev)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ads7828_data *data = i2c_get_clientdata(client);

    mutex_lock(&data->update_lock);

    if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
            || !data->valid) {
        unsigned int ch;
        dev_dbg(&client->dev, "Starting ads7828 update\n");

        for (ch = 0; ch < ADS7828_NCH; ch++) {
            u8 cmd = channel_cmd_byte(ch);
            data->adc_input[ch] =
                i2c_smbus_read_word_swapped(client, cmd);
        }
        data->last_updated = jiffies;
        data->valid = 1;
    }

    mutex_unlock(&data->update_lock);

    return data;
}

/* sysfs callback function */
static ssize_t 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);
}

#define in_reg(offset)\
static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
    NULL, offset)

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 struct attribute *ads7828_attributes[] = {
    &sensor_dev_attr_in0_input.dev_attr.attr,
    &sensor_dev_attr_in1_input.dev_attr.attr,
    &sensor_dev_attr_in2_input.dev_attr.attr,
    &sensor_dev_attr_in3_input.dev_attr.attr,
    &sensor_dev_attr_in4_input.dev_attr.attr,
    &sensor_dev_attr_in5_input.dev_attr.attr,
    &sensor_dev_attr_in6_input.dev_attr.attr,
    &sensor_dev_attr_in7_input.dev_attr.attr,
    NULL
};

static const struct attribute_group ads7828_group = {
    .attrs = ads7828_attributes,
};

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);
    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;
    int ch;

    /* Check we have a valid client */
    if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))
        return -ENODEV;

    /*
     * Now, we do the remaining detection. There is no identification
     * dedicated register so attempt to sanity check using knowledge of
     * the chip
     * - Read from the 8 channel addresses
     * - 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);
        if (in_data & 0xF000) {
            pr_debug("%s : Doesn't look like an ads7828 device\n",
                 __func__);
            return -ENODEV;
        }
    }

    strlcpy(info->type, "ads7828", I2C_NAME_SIZE);

    return 0;
}

static int ads7828_probe(struct i2c_client *client,
             const struct i2c_device_id *id)
{
    struct ads7828_data *data;
    int err;

    data = devm_kzalloc(&client->dev, sizeof(struct ads7828_data),
                GFP_KERNEL);
    if (!data)
        return -ENOMEM;

    i2c_set_clientdata(client, data);
    mutex_init(&data->update_lock);

    /* Register sysfs hooks */
    err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
    if (err)
        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;
    }

    return 0;

exit_remove:
    sysfs_remove_group(&client->dev.kobj, &ads7828_group);
    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;

    /* Calculate the LSB resolution */
    ads7828_lsb_resol = (vref_mv*1000)/4096;

    return i2c_add_driver(&ads7828_driver);
}

static void __exit sensors_ads7828_exit(void)
{
    i2c_del_driver(&ads7828_driver);
}

MODULE_AUTHOR("Steve Hardy <[email protected]>");
MODULE_DESCRIPTION("ADS7828 driver");
MODULE_LICENSE("GPL");

module_init(sensors_ads7828_init);
module_exit(sensors_ads7828_exit);