/*
 * lm70.c
 *
 * The LM70 is a temperature sensor chip from National Semiconductor (NS).
 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
 *
 * The LM70 communicates with a host processor via an SPI/Microwire Bus
 * interface. The complete datasheet is available at National's website
 * here:
 * http://www.national.com/pf/LM/LM70.html
 *
 * 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/device.h>
#include <linux/err.h>
#include <linux/sysfs.h>
#include <linux/hwmon.h>
#include <linux/mutex.h>
#include <linux/mod_devicetable.h>
#include <linux/spi/spi.h>


#define DRVNAME         "lm70"

#define LM70_CHIP_LM70          0       /* original NS LM70 */
#define LM70_CHIP_TMP121        1       /* TI TMP121/TMP123 */

struct lm70 {
        struct device *hwmon_dev;
        struct mutex lock;
        unsigned int chip;
};

/* sysfs hook function */
static ssize_t lm70_sense_temp(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct spi_device *spi = to_spi_device(dev);
        int status, val = 0;
        u8 rxbuf[2];
        s16 raw=0;
        struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);

        if (mutex_lock_interruptible(&p_lm70->lock))
                return -ERESTARTSYS;

        /*
         * spi_read() requires a DMA-safe buffer; so we use
         * spi_write_then_read(), transmitting 0 bytes.
         */
        status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
        if (status < 0) {
                printk(KERN_WARNING
                "spi_write_then_read failed with status %d\n", status);
                goto out;
        }
        raw = (rxbuf[0] << 8) + rxbuf[1];
        dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
                rxbuf[0], rxbuf[1], raw);

        /*
         * LM70:
         * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
         * complement value. Only the MSB 11 bits (1 sign + 10 temperature
         * bits) are meaningful; the LSB 5 bits are to be discarded.
         * See the datasheet.
         *
         * Further, each bit represents 0.25 degrees Celsius; so, multiply
         * by 0.25. Also multiply by 1000 to represent in millidegrees
         * Celsius.
         * So it's equivalent to multiplying by 0.25 * 1000 = 250.
         *
         * TMP121/TMP123:
         * 13 bits of 2's complement data, discard LSB 3 bits,
         * resolution 0.0625 degrees celsius.
         */
        switch (p_lm70->chip) {
        case LM70_CHIP_LM70:
                val = ((int)raw / 32) * 250;
                break;

        case LM70_CHIP_TMP121:
                val = ((int)raw / 8) * 625 / 10;
                break;
        }

        status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
out:
        mutex_unlock(&p_lm70->lock);
        return status;
}

static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);

static ssize_t lm70_show_name(struct device *dev, struct device_attribute
                              *devattr, char *buf)
{
        struct lm70 *p_lm70 = dev_get_drvdata(dev);
        int ret;

        switch (p_lm70->chip) {
        case LM70_CHIP_LM70:
                ret = sprintf(buf, "lm70\n");
                break;
        case LM70_CHIP_TMP121:
                ret = sprintf(buf, "tmp121\n");
                break;
        default:
                ret = -EINVAL;
        }
        return ret;
}

static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);

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

static int __devinit lm70_probe(struct spi_device *spi)
{
        int chip = spi_get_device_id(spi)->driver_data;
        struct lm70 *p_lm70;
        int status;

        /* signaling is SPI_MODE_0 for both LM70 and TMP121 */
        if (spi->mode & (SPI_CPOL | SPI_CPHA))
                return -EINVAL;

        /* 3-wire link (shared SI/SO) for LM70 */
        if (chip == LM70_CHIP_LM70 && !(spi->mode & SPI_3WIRE))
                return -EINVAL;

        /* NOTE:  we assume 8-bit words, and convert to 16 bits manually */

        p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
        if (!p_lm70)
                return -ENOMEM;

        mutex_init(&p_lm70->lock);
        p_lm70->chip = chip;

        /* sysfs hook */
        p_lm70->hwmon_dev = hwmon_device_register(&spi->dev);
        if (IS_ERR(p_lm70->hwmon_dev)) {
                dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
                status = PTR_ERR(p_lm70->hwmon_dev);
                goto out_dev_reg_failed;
        }
        dev_set_drvdata(&spi->dev, p_lm70);

        if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))
         || (status = device_create_file(&spi->dev, &dev_attr_name))) {
                dev_dbg(&spi->dev, "device_create_file failure.\n");
                goto out_dev_create_file_failed;
        }

        return 0;

out_dev_create_file_failed:
        device_remove_file(&spi->dev, &dev_attr_temp1_input);
        hwmon_device_unregister(p_lm70->hwmon_dev);
out_dev_reg_failed:
        dev_set_drvdata(&spi->dev, NULL);
        kfree(p_lm70);
        return status;
}

static int __devexit lm70_remove(struct spi_device *spi)
{
        struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);

        device_remove_file(&spi->dev, &dev_attr_temp1_input);
        device_remove_file(&spi->dev, &dev_attr_name);
        hwmon_device_unregister(p_lm70->hwmon_dev);
        dev_set_drvdata(&spi->dev, NULL);
        kfree(p_lm70);

        return 0;
}


static const struct spi_device_id lm70_ids[] = {
        { "lm70",   LM70_CHIP_LM70 },
        { "tmp121", LM70_CHIP_TMP121 },
        { },
};
MODULE_DEVICE_TABLE(spi, lm70_ids);

static struct spi_driver lm70_driver = {
        .driver = {
                .name   = "lm70",
                .owner  = THIS_MODULE,
        },
        .id_table = lm70_ids,
        .probe  = lm70_probe,
        .remove = __devexit_p(lm70_remove),
};

static int __init init_lm70(void)
{
        return spi_register_driver(&lm70_driver);
}

static void __exit cleanup_lm70(void)
{
        spi_unregister_driver(&lm70_driver);
}

module_init(init_lm70);
module_exit(cleanup_lm70);

MODULE_AUTHOR("Kaiwan N Billimoria");
MODULE_DESCRIPTION("NS LM70 / TI TMP121/TMP123 Linux driver");
MODULE_LICENSE("GPL");