/*
 * adcxx.c
 *
 * The adcxx4s is an AD converter family from National Semiconductor (NS).
 *
 * Copyright (c) 2008 Marc Pignat <marc.pignat@hevs.ch>
 *
 * The adcxx4s communicates with a host processor via an SPI/Microwire Bus
 * interface. This driver supports the whole family of devices with name
 * ADC<bb><c>S<sss>, where
 * * bb is the resolution in number of bits (8, 10, 12)
 * * c is the number of channels (1, 2, 4, 8)
 * * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
 *   and 101 for 1 MSPS)
 *
 * Complete datasheets are available at National's website here:
 * http://www.national.com/ds/DC/ADC<bb><c>S<sss>.pdf
 *
 * Handling of 8, 10 and 12 bits converters are the same, the
 * unavailable bits are 0 :)
 *
 * 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.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/sysfs.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/mutex.h>
#include <linux/mod_devicetable.h>
#include <linux/spi/spi.h>

#define DRVNAME         "adcxx"

struct adcxx {
        struct device *hwmon_dev;
        struct mutex lock;
        u32 channels;
        u32 reference; /* in millivolts */
};

/* sysfs hook function */
static ssize_t adcxx_read(struct device *dev,
                struct device_attribute *devattr, char *buf)
{
        struct spi_device *spi = to_spi_device(dev);
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct adcxx *adc = dev_get_drvdata(&spi->dev);
        u8 tx_buf[2];
        u8 rx_buf[2];
        int status;
        u32 value;

        if (mutex_lock_interruptible(&adc->lock))
                return -ERESTARTSYS;

        if (adc->channels == 1) {
                status = spi_read(spi, rx_buf, sizeof(rx_buf));
        } else {
                tx_buf[0] = attr->index << 3; /* other bits are don't care */
                status = spi_write_then_read(spi, tx_buf, sizeof(tx_buf),
                                                rx_buf, sizeof(rx_buf));
        }
        if (status < 0) {
                dev_warn(dev, "SPI synch. transfer failed with status %d\n",
                                status);
                goto out;
        }

        value = (rx_buf[0] << 8) + rx_buf[1];
        dev_dbg(dev, "raw value = 0x%x\n", value);

        value = value * adc->reference >> 12;
        status = sprintf(buf, "%d\n", value);
out:
        mutex_unlock(&adc->lock);
        return status;
}

static ssize_t adcxx_show_min(struct device *dev,
                struct device_attribute *devattr, char *buf)
{
        /* The minimum reference is 0 for this chip family */
        return sprintf(buf, "0\n");
}

static ssize_t adcxx_show_max(struct device *dev,
                struct device_attribute *devattr, char *buf)
{
        struct spi_device *spi = to_spi_device(dev);
        struct adcxx *adc = dev_get_drvdata(&spi->dev);
        u32 reference;

        if (mutex_lock_interruptible(&adc->lock))
                return -ERESTARTSYS;

        reference = adc->reference;

        mutex_unlock(&adc->lock);

        return sprintf(buf, "%d\n", reference);
}

static ssize_t adcxx_set_max(struct device *dev,
        struct device_attribute *devattr, const char *buf, size_t count)
{
        struct spi_device *spi = to_spi_device(dev);
        struct adcxx *adc = dev_get_drvdata(&spi->dev);
        unsigned long value;

        if (strict_strtoul(buf, 10, &value))
                return -EINVAL;

        if (mutex_lock_interruptible(&adc->lock))
                return -ERESTARTSYS;

        adc->reference = value;

        mutex_unlock(&adc->lock);

        return count;
}

static ssize_t adcxx_show_name(struct device *dev, struct device_attribute
                              *devattr, char *buf)
{
        struct spi_device *spi = to_spi_device(dev);
        struct adcxx *adc = dev_get_drvdata(&spi->dev);

        return sprintf(buf, "adcxx%ds\n", adc->channels);
}

static struct sensor_device_attribute ad_input[] = {
        SENSOR_ATTR(name, S_IRUGO, adcxx_show_name, NULL, 0),
        SENSOR_ATTR(in_min, S_IRUGO, adcxx_show_min, NULL, 0),
        SENSOR_ATTR(in_max, S_IWUSR | S_IRUGO, adcxx_show_max,
                                        adcxx_set_max, 0),
        SENSOR_ATTR(in0_input, S_IRUGO, adcxx_read, NULL, 0),
        SENSOR_ATTR(in1_input, S_IRUGO, adcxx_read, NULL, 1),
        SENSOR_ATTR(in2_input, S_IRUGO, adcxx_read, NULL, 2),
        SENSOR_ATTR(in3_input, S_IRUGO, adcxx_read, NULL, 3),
        SENSOR_ATTR(in4_input, S_IRUGO, adcxx_read, NULL, 4),
        SENSOR_ATTR(in5_input, S_IRUGO, adcxx_read, NULL, 5),
        SENSOR_ATTR(in6_input, S_IRUGO, adcxx_read, NULL, 6),
        SENSOR_ATTR(in7_input, S_IRUGO, adcxx_read, NULL, 7),
};

/*----------------------------------------------------------------------*/

static int __devinit adcxx_probe(struct spi_device *spi)
{
        int channels = spi_get_device_id(spi)->driver_data;
        struct adcxx *adc;
        int status;
        int i;

        adc = kzalloc(sizeof *adc, GFP_KERNEL);
        if (!adc)
                return -ENOMEM;

        /* set a default value for the reference */
        adc->reference = 3300;
        adc->channels = channels;
        mutex_init(&adc->lock);

        mutex_lock(&adc->lock);

        dev_set_drvdata(&spi->dev, adc);

        for (i = 0; i < 3 + adc->channels; i++) {
                status = device_create_file(&spi->dev, &ad_input[i].dev_attr);
                if (status) {
                        dev_err(&spi->dev, "device_create_file failed.\n");
                        goto out_err;
                }
        }

        adc->hwmon_dev = hwmon_device_register(&spi->dev);
        if (IS_ERR(adc->hwmon_dev)) {
                dev_err(&spi->dev, "hwmon_device_register failed.\n");
                status = PTR_ERR(adc->hwmon_dev);
                goto out_err;
        }

        mutex_unlock(&adc->lock);
        return 0;

out_err:
        for (i--; i >= 0; i--)
                device_remove_file(&spi->dev, &ad_input[i].dev_attr);

        dev_set_drvdata(&spi->dev, NULL);
        mutex_unlock(&adc->lock);
        kfree(adc);
        return status;
}

static int __devexit adcxx_remove(struct spi_device *spi)
{
        struct adcxx *adc = dev_get_drvdata(&spi->dev);
        int i;

        mutex_lock(&adc->lock);
        hwmon_device_unregister(adc->hwmon_dev);
        for (i = 0; i < 3 + adc->channels; i++)
                device_remove_file(&spi->dev, &ad_input[i].dev_attr);

        dev_set_drvdata(&spi->dev, NULL);
        mutex_unlock(&adc->lock);
        kfree(adc);

        return 0;
}

static const struct spi_device_id adcxx_ids[] = {
        { "adcxx1s", 1 },
        { "adcxx2s", 2 },
        { "adcxx4s", 4 },
        { "adcxx8s", 8 },
        { },
};
MODULE_DEVICE_TABLE(spi, adcxx_ids);

static struct spi_driver adcxx_driver = {
        .driver = {
                .name   = "adcxx",
                .owner  = THIS_MODULE,
        },
        .id_table = adcxx_ids,
        .probe  = adcxx_probe,
        .remove = __devexit_p(adcxx_remove),
};

static int __init init_adcxx(void)
{
        return spi_register_driver(&adcxx_driver);
}

static void __exit exit_adcxx(void)
{
        spi_unregister_driver(&adcxx_driver);
}

module_init(init_adcxx);
module_exit(exit_adcxx);

MODULE_AUTHOR("Marc Pignat");
MODULE_DESCRIPTION("National Semiconductor adcxx8sxxx Linux driver");
MODULE_LICENSE("GPL");