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/*

 * 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/spi/spi.h>

#define DRVNAME         "lm70"

struct lm70 {

        struct device *hwmon_dev;

        struct mutex lock;

};

/* 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;

        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;

        }

        dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]);

        raw = (rxbuf[1] << 8) + rxbuf[0];

        dev_dbg(dev, "raw=0x%x\n", raw);

        /*

         * 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.

         */

        val = ((int)raw/32) * 250;

        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)

{

        return sprintf(buf, "lm70\n");

}

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

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

static int __devinit lm70_probe(struct spi_device *spi)

{

        struct lm70 *p_lm70;

        int status;

        /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */

        if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE))

                return -EINVAL;

        p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);

        if (!p_lm70)

                return -ENOMEM;

        mutex_init(&p_lm70->lock);

        /* 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 struct spi_driver lm70_driver = {

        .driver = {

                .name   = "lm70",

                .owner  = THIS_MODULE,

        },

        .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("National Semiconductor LM70 Linux driver");

MODULE_LICENSE("GPL");