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/*
* 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/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,
};

static int __init ds1682_init(void)
{
return i2c_add_driver(&ds1682_driver);
}

static void __exit ds1682_exit(void)
{
i2c_del_driver(&ds1682_driver);
}

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

module_init(ds1682_init);
module_exit(ds1682_exit);
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