linux-imx

/*

 * Dallas Semiconductor DS1682 Elapsed Time Recorder device driver

 *

 * Written by: Grant Likely <grant.likely@secretlab.ca>

 *

 * 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/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);

    unsigned long long val, check;

    __le32 val_le = 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_le);

    if (rc < 0)

        return -EIO;

​

    val = le32_to_cpu(val_le);

​

    if (sattr->index == DS1682_REG_ELAPSED) {

        int retries = 5;

​

        /* Detect and retry when a tick occurs mid-read */

        do {

            rc = i2c_smbus_read_i2c_block_data(client, sattr->index,

                               sattr->nr,

                               (u8 *)&val_le);

            if (rc < 0 || retries <= 0)

                return -EIO;

​

            check = val;

            val = le32_to_cpu(val_le);

            retries--;

        } while (val != check && val != (check + 1));

    }

​