/*
 * Copyright (C) 2001-2004 Aurelien Jarno <aurelien@aurel32.net>
 * Ported to Linux 2.6 by Aurelien Jarno <aurelien@aurel32.net> with
 * the help of Jean Delvare <khali@linux-fr.org>
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
#include <linux/err.h>
#include <linux/hwmon.h>

/* Insmod parameters */

static int input_mode;
module_param(input_mode, int, 0);
MODULE_PARM_DESC(input_mode,
        "Analog input mode:\n"
        " 0 = four single ended inputs\n"
        " 1 = three differential inputs\n"
        " 2 = single ended and differential mixed\n"
        " 3 = two differential inputs\n");

/*
 * The PCF8591 control byte
 *      7    6    5    4    3    2    1    0
 *   |  0 |AOEF|   AIP   |  0 |AINC|  AICH   |
 */

/* Analog Output Enable Flag (analog output active if 1) */
#define PCF8591_CONTROL_AOEF            0x40

/*
 * Analog Input Programming
 * 0x00 = four single ended inputs
 * 0x10 = three differential inputs
 * 0x20 = single ended and differential mixed
 * 0x30 = two differential inputs
 */
#define PCF8591_CONTROL_AIP_MASK        0x30

/* Autoincrement Flag (switch on if 1) */
#define PCF8591_CONTROL_AINC            0x04

/*
 * Channel selection
 * 0x00 = channel 0
 * 0x01 = channel 1
 * 0x02 = channel 2
 * 0x03 = channel 3
 */
#define PCF8591_CONTROL_AICH_MASK       0x03

/* Initial values */
#define PCF8591_INIT_CONTROL    ((input_mode << 4) | PCF8591_CONTROL_AOEF)
#define PCF8591_INIT_AOUT       0       /* DAC out = 0 */

/* Conversions */
#define REG_TO_SIGNED(reg)      (((reg) & 0x80) ? ((reg) - 256) : (reg))

struct pcf8591_data {
        struct device *hwmon_dev;
        struct mutex update_lock;

        u8 control;
        u8 aout;
};

static void pcf8591_init_client(struct i2c_client *client);
static int pcf8591_read_channel(struct device *dev, int channel);

/* following are the sysfs callback functions */
#define show_in_channel(channel)                                        \
static ssize_t show_in##channel##_input(struct device *dev,             \
                                        struct device_attribute *attr,  \
                                        char *buf)                      \
{                                                                       \
        return sprintf(buf, "%d\n", pcf8591_read_channel(dev, channel));\
}                                                                       \
static DEVICE_ATTR(in##channel##_input, S_IRUGO,                        \
                   show_in##channel##_input, NULL);

show_in_channel(0);
show_in_channel(1);
show_in_channel(2);
show_in_channel(3);

static ssize_t show_out0_ouput(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
        return sprintf(buf, "%d\n", data->aout * 10);
}

static ssize_t set_out0_output(struct device *dev,
                               struct device_attribute *attr,
                               const char *buf, size_t count)
{
        unsigned long val;
        struct i2c_client *client = to_i2c_client(dev);
        struct pcf8591_data *data = i2c_get_clientdata(client);
        int err;

        err = kstrtoul(buf, 10, &val);
        if (err)
                return err;

        val /= 10;
        if (val > 255)
                return -EINVAL;

        data->aout = val;
        i2c_smbus_write_byte_data(client, data->control, data->aout);
        return count;
}

static DEVICE_ATTR(out0_output, S_IWUSR | S_IRUGO,
                   show_out0_ouput, set_out0_output);

static ssize_t show_out0_enable(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
        return sprintf(buf, "%u\n", !(!(data->control & PCF8591_CONTROL_AOEF)));
}

static ssize_t set_out0_enable(struct device *dev,
                               struct device_attribute *attr,
                               const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct pcf8591_data *data = i2c_get_clientdata(client);
        unsigned long val;
        int err;

        err = kstrtoul(buf, 10, &val);
        if (err)
                return err;

        mutex_lock(&data->update_lock);
        if (val)
                data->control |= PCF8591_CONTROL_AOEF;
        else
                data->control &= ~PCF8591_CONTROL_AOEF;
        i2c_smbus_write_byte(client, data->control);
        mutex_unlock(&data->update_lock);
        return count;
}

static DEVICE_ATTR(out0_enable, S_IWUSR | S_IRUGO,
                   show_out0_enable, set_out0_enable);

static struct attribute *pcf8591_attributes[] = {
        &dev_attr_out0_enable.attr,
        &dev_attr_out0_output.attr,
        &dev_attr_in0_input.attr,
        &dev_attr_in1_input.attr,
        NULL
};

static const struct attribute_group pcf8591_attr_group = {
        .attrs = pcf8591_attributes,
};

static struct attribute *pcf8591_attributes_opt[] = {
        &dev_attr_in2_input.attr,
        &dev_attr_in3_input.attr,
        NULL
};

static const struct attribute_group pcf8591_attr_group_opt = {
        .attrs = pcf8591_attributes_opt,
};

/*
 * Real code
 */

static int pcf8591_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
{
        struct pcf8591_data *data;
        int err;

        data = devm_kzalloc(&client->dev, sizeof(struct pcf8591_data),
                            GFP_KERNEL);
        if (!data)
                return -ENOMEM;

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

        /* Initialize the PCF8591 chip */
        pcf8591_init_client(client);

        /* Register sysfs hooks */
        err = sysfs_create_group(&client->dev.kobj, &pcf8591_attr_group);
        if (err)
                return err;

        /* Register input2 if not in "two differential inputs" mode */
        if (input_mode != 3) {
                err = device_create_file(&client->dev, &dev_attr_in2_input);
                if (err)
                        goto exit_sysfs_remove;
        }

        /* Register input3 only in "four single ended inputs" mode */
        if (input_mode == 0) {
                err = device_create_file(&client->dev, &dev_attr_in3_input);
                if (err)
                        goto exit_sysfs_remove;
        }

        data->hwmon_dev = hwmon_device_register(&client->dev);
        if (IS_ERR(data->hwmon_dev)) {
                err = PTR_ERR(data->hwmon_dev);
                goto exit_sysfs_remove;
        }

        return 0;

exit_sysfs_remove:
        sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
        sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
        return err;
}

static int pcf8591_remove(struct i2c_client *client)
{
        struct pcf8591_data *data = i2c_get_clientdata(client);

        hwmon_device_unregister(data->hwmon_dev);
        sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
        sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
        return 0;
}

/* Called when we have found a new PCF8591. */
static void pcf8591_init_client(struct i2c_client *client)
{
        struct pcf8591_data *data = i2c_get_clientdata(client);
        data->control = PCF8591_INIT_CONTROL;
        data->aout = PCF8591_INIT_AOUT;

        i2c_smbus_write_byte_data(client, data->control, data->aout);

        /*
         * The first byte transmitted contains the conversion code of the
         * previous read cycle. FLUSH IT!
         */
        i2c_smbus_read_byte(client);
}

static int pcf8591_read_channel(struct device *dev, int channel)
{
        u8 value;
        struct i2c_client *client = to_i2c_client(dev);
        struct pcf8591_data *data = i2c_get_clientdata(client);

        mutex_lock(&data->update_lock);

        if ((data->control & PCF8591_CONTROL_AICH_MASK) != channel) {
                data->control = (data->control & ~PCF8591_CONTROL_AICH_MASK)
                              | channel;
                i2c_smbus_write_byte(client, data->control);

                /*
                 * The first byte transmitted contains the conversion code of
                 * the previous read cycle. FLUSH IT!
                 */
                i2c_smbus_read_byte(client);
        }
        value = i2c_smbus_read_byte(client);

        mutex_unlock(&data->update_lock);

        if ((channel == 2 && input_mode == 2) ||
            (channel != 3 && (input_mode == 1 || input_mode == 3)))
                return 10 * REG_TO_SIGNED(value);
        else
                return 10 * value;
}

static const struct i2c_device_id pcf8591_id[] = {
        { "pcf8591", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, pcf8591_id);

static struct i2c_driver pcf8591_driver = {
        .driver = {
                .name   = "pcf8591",
        },
        .probe          = pcf8591_probe,
        .remove         = pcf8591_remove,
        .id_table       = pcf8591_id,
};

static int __init pcf8591_init(void)
{
        if (input_mode < 0 || input_mode > 3) {
                pr_warn("invalid input_mode (%d)\n", input_mode);
                input_mode = 0;
        }
        return i2c_add_driver(&pcf8591_driver);
}

static void __exit pcf8591_exit(void)
{
        i2c_del_driver(&pcf8591_driver);
}

MODULE_AUTHOR("Aurelien Jarno <aurelien@aurel32.net>");
MODULE_DESCRIPTION("PCF8591 driver");
MODULE_LICENSE("GPL");

module_init(pcf8591_init);
module_exit(pcf8591_exit);