ds1682.c

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/*
 * Dallas Semiconductor DS1682 Elapsed Time Recorder device driver
 *
 * Written by: Grant Likely <[email protected]>
 *
 * Copyright (C) 2007 Secret Lab Technologies Ltd.
 *
 * 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.
 */

/*
 * The DS1682 elapsed timer recorder is a simple device that implements
 * one elapsed time counter, one event counter, an alarm signal and 10
 * bytes of general purpose EEPROM.
 *
 * This driver provides access to the DS1682 counters and user data via
 * the sysfs.  The following attributes are added to the device node:
 *     elapsed_time (u32): Total elapsed event time in ms resolution
 *     alarm_time (u32): When elapsed time exceeds the value in alarm_time,
 *                       then the alarm pin is asserted.
 *     event_count (u16): number of times the event pin has gone low.
 *     eeprom (u8[10]): general purpose EEPROM
 *
 * Counter registers and user data are both read/write unless the device
 * has been write protected.  This driver does not support turning off write
 * protection.  Once write protection is turned on, it is impossible to
 * turn it off again, so I have left the feature out of this driver to avoid
 * accidental enabling, but it is trivial to add write protect support.
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/sysfs.h>
#include <linux/ctype.h>
#include <linux/hwmon-sysfs.h>

/* Device registers */
#define DS1682_REG_CONFIG       0x00
#define DS1682_REG_ALARM        0x01
#define DS1682_REG_ELAPSED      0x05
#define DS1682_REG_EVT_CNTR     0x09
#define DS1682_REG_EEPROM       0x0b
#define DS1682_REG_RESET        0x1d
#define DS1682_REG_WRITE_DISABLE    0x1e
#define DS1682_REG_WRITE_MEM_DISABLE    0x1f

#define DS1682_EEPROM_SIZE      10

/*
 * Generic counter attributes
 */
static ssize_t ds1682_show(struct device *dev, struct device_attribute *attr,
               char *buf)
{
    struct sensor_device_attribute_2 *sattr = to_sensor_dev_attr_2(attr);
    struct i2c_client *client = to_i2c_client(dev);
    __le32 val = 0;
    int rc;

    dev_dbg(dev, "ds1682_show() called on %s\n", attr->attr.name);

    /* Read the register */
    rc = i2c_smbus_read_i2c_block_data(client, sattr->index, sattr->nr,
                       (u8 *) & val);
    if (rc < 0)
        return -EIO;

    /* Special case: the 32 bit regs are time values with 1/4s
     * resolution, scale them up to milliseconds */
    if (sattr->nr == 4)
        return sprintf(buf, "%llu\n",
            ((unsigned long long)le32_to_cpu(val)) * 250);

    /* Format the output string and return # of bytes */
    return sprintf(buf, "%li\n", (long)le32_to_cpu(val));
}

static ssize_t ds1682_store(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t count)
{
    struct sensor_device_attribute_2 *sattr = to_sensor_dev_attr_2(attr);
    struct i2c_client *client = to_i2c_client(dev);
    char *endp;
    u64 val;
    __le32 val_le;
    int rc;

    dev_dbg(dev, "ds1682_store() called on %s\n", attr->attr.name);

    /* Decode input */
    val = simple_strtoull(buf, &endp, 0);
    if (buf == endp) {
        dev_dbg(dev, "input string not a number\n");
        return -EINVAL;
    }

    /* Special case: the 32 bit regs are time values with 1/4s
     * resolution, scale input down to quarter-seconds */
    if (sattr->nr == 4)
        do_div(val, 250);

    /* write out the value */
    val_le = cpu_to_le32(val);
    rc = i2c_smbus_write_i2c_block_data(client, sattr->index, sattr->nr,
                        (u8 *) & val_le);
    if (rc < 0) {
        dev_err(dev, "register write failed; reg=0x%x, size=%i\n",
            sattr->index, sattr->nr);
        return -EIO;
    }

    return count;
}

/*
 * Simple register attributes
 */
static SENSOR_DEVICE_ATTR_2(elapsed_time, S_IRUGO | S_IWUSR, ds1682_show,
                ds1682_store, 4, DS1682_REG_ELAPSED);
static SENSOR_DEVICE_ATTR_2(alarm_time, S_IRUGO | S_IWUSR, ds1682_show,
                ds1682_store, 4, DS1682_REG_ALARM);
static SENSOR_DEVICE_ATTR_2(event_count, S_IRUGO | S_IWUSR, ds1682_show,
                ds1682_store, 2, DS1682_REG_EVT_CNTR);

static const struct attribute_group ds1682_group = {
    .attrs = (struct attribute *[]) {
        &sensor_dev_attr_elapsed_time.dev_attr.attr,
        &sensor_dev_attr_alarm_time.dev_attr.attr,
        &sensor_dev_attr_event_count.dev_attr.attr,
        NULL,
    },
};

/*
 * User data attribute
 */
static ssize_t ds1682_eeprom_read(struct file *filp, struct kobject *kobj,
                  struct bin_attribute *attr,
                  char *buf, loff_t off, size_t count)
{
    struct i2c_client *client = kobj_to_i2c_client(kobj);
    int rc;

    dev_dbg(&client->dev, "ds1682_eeprom_read(p=%p, off=%lli, c=%zi)\n",
        buf, off, count);

    if (off >= DS1682_EEPROM_SIZE)
        return 0;

    if (off + count > DS1682_EEPROM_SIZE)
        count = DS1682_EEPROM_SIZE - off;

    rc = i2c_smbus_read_i2c_block_data(client, DS1682_REG_EEPROM + off,
                       count, buf);
    if (rc < 0)
        return -EIO;

    return count;
}

static ssize_t ds1682_eeprom_write(struct file *filp, struct kobject *kobj,
                   struct bin_attribute *attr,
                   char *buf, loff_t off, size_t count)
{
    struct i2c_client *client = kobj_to_i2c_client(kobj);

    dev_dbg(&client->dev, "ds1682_eeprom_write(p=%p, off=%lli, c=%zi)\n",
        buf, off, count);

    if (off >= DS1682_EEPROM_SIZE)
        return -ENOSPC;

    if (off + count > DS1682_EEPROM_SIZE)
        count = DS1682_EEPROM_SIZE - off;

    /* Write out to the device */
    if (i2c_smbus_write_i2c_block_data(client, DS1682_REG_EEPROM + off,
                       count, buf) < 0)
        return -EIO;

    return count;
}

static struct bin_attribute ds1682_eeprom_attr = {
    .attr = {
        .name = "eeprom",
        .mode = S_IRUGO | S_IWUSR,
    },
    .size = DS1682_EEPROM_SIZE,
    .read = ds1682_eeprom_read,
    .write = ds1682_eeprom_write,
};

/*
 * Called when a ds1682 device is matched with this driver
 */
static int ds1682_probe(struct i2c_client *client,
            const struct i2c_device_id *id)
{
    int rc;

    if (!i2c_check_functionality(client->adapter,
                     I2C_FUNC_SMBUS_I2C_BLOCK)) {
        dev_err(&client->dev, "i2c bus does not support the ds1682\n");
        rc = -ENODEV;
        goto exit;
    }

    rc = sysfs_create_group(&client->dev.kobj, &ds1682_group);
    if (rc)
        goto exit;

    rc = sysfs_create_bin_file(&client->dev.kobj, &ds1682_eeprom_attr);
    if (rc)
        goto exit_bin_attr;

    return 0;

 exit_bin_attr:
    sysfs_remove_group(&client->dev.kobj, &ds1682_group);
 exit:
    return rc;
}

static int ds1682_remove(struct i2c_client *client)
{
    sysfs_remove_bin_file(&client->dev.kobj, &ds1682_eeprom_attr);
    sysfs_remove_group(&client->dev.kobj, &ds1682_group);
    return 0;
}

static const struct i2c_device_id ds1682_id[] = {
    { "ds1682", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, ds1682_id);

static struct i2c_driver ds1682_driver = {
    .driver = {
        .name = "ds1682",
    },
    .probe = ds1682_probe,
    .remove = ds1682_remove,
    .id_table = ds1682_id,
};

module_i2c_driver(ds1682_driver);

MODULE_AUTHOR("Grant Likely <[email protected]>");
MODULE_DESCRIPTION("DS1682 Elapsed Time Indicator driver");
MODULE_LICENSE("GPL");