/*
 * 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));
        }

        /* Format the output string and return # of bytes
         * Special case: the 32 bit regs are time values with 1/4s
         * resolution, scale them up to milliseconds
         */
        return sprintf(buf, "%llu\n", (sattr->nr == 4) ? (val * 250) : 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);
        u64 val;
        __le32 val_le;
        int rc;

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

        /* Decode input */
        rc = kstrtoull(buf, 0, &val);
        if (rc < 0) {
                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);

        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);

        /* 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 const 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 const struct of_device_id ds1682_of_match[] = {
        { .compatible = "dallas,ds1682", },
        {}
};
MODULE_DEVICE_TABLE(of, ds1682_of_match);

static struct i2c_driver ds1682_driver = {
        .driver = {
                .name = "ds1682",
                .of_match_table = ds1682_of_match,
        },
        .probe = ds1682_probe,
        .remove = ds1682_remove,
        .id_table = ds1682_id,
};

module_i2c_driver(ds1682_driver);

MODULE_AUTHOR("Grant Likely <grant.likely@secretlab.ca>");
MODULE_DESCRIPTION("DS1682 Elapsed Time Indicator driver");
MODULE_LICENSE("GPL");