/*
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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>
#include <linux/slab.h>
#include <linux/of_device.h>


#define DRVNAME         "lm70"

#define LM70_CHIP_LM70          0       /* original NS LM70 */
#define LM70_CHIP_TMP121        1       /* TI TMP121/TMP123 */
#define LM70_CHIP_LM71          2       /* NS LM71 */
#define LM70_CHIP_LM74          3       /* NS LM74 */
#define LM70_CHIP_TMP122        4       /* TI TMP122/TMP124 */

struct lm70 {
        struct spi_device *spi;
        struct mutex lock;
        unsigned int chip;
};

/* sysfs hook function */
static ssize_t temp1_input_show(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct lm70 *p_lm70 = dev_get_drvdata(dev);
        struct spi_device *spi = p_lm70->spi;
        int status, val = 0;
        u8 rxbuf[2];
        s16 raw = 0;

        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) {
                dev_warn(dev, "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.
         *
         * LM74 and TMP121/TMP122/TMP123/TMP124:
         * 13 bits of 2's complement data, discard LSB 3 bits,
         * resolution 0.0625 degrees celsius.
         *
         * LM71:
         * 14 bits of 2's complement data, discard LSB 2 bits,
         * resolution 0.0312 degrees celsius.
         */
        switch (p_lm70->chip) {
        case LM70_CHIP_LM70:
                val = ((int)raw / 32) * 250;
                break;

        case LM70_CHIP_TMP121:
        case LM70_CHIP_TMP122:
        case LM70_CHIP_LM74:
                val = ((int)raw / 8) * 625 / 10;
                break;

        case LM70_CHIP_LM71:
                val = ((int)raw / 4) * 3125 / 100;
                break;
        }

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

static DEVICE_ATTR_RO(temp1_input);

static struct attribute *lm70_attrs[] = {
        &dev_attr_temp1_input.attr,
        NULL
};

ATTRIBUTE_GROUPS(lm70);

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

#ifdef CONFIG_OF
static const struct of_device_id lm70_of_ids[] = {
        {
                .compatible = "ti,lm70",
                .data = (void *) LM70_CHIP_LM70,
        },
        {
                .compatible = "ti,tmp121",
                .data = (void *) LM70_CHIP_TMP121,
        },
        {
                .compatible = "ti,tmp122",
                .data = (void *) LM70_CHIP_TMP122,
        },
        {
                .compatible = "ti,lm71",
                .data = (void *) LM70_CHIP_LM71,
        },
        {
                .compatible = "ti,lm74",
                .data = (void *) LM70_CHIP_LM74,
        },
        {},
};
MODULE_DEVICE_TABLE(of, lm70_of_ids);
#endif

static int lm70_probe(struct spi_device *spi)
{
        const struct of_device_id *match;
        struct device *hwmon_dev;
        struct lm70 *p_lm70;
        int chip;

        match = of_match_device(lm70_of_ids, &spi->dev);
        if (match)
                chip = (int)(uintptr_t)match->data;
        else
                chip = spi_get_device_id(spi)->driver_data;

        /* signaling is SPI_MODE_0 */
        if (spi->mode & (SPI_CPOL | SPI_CPHA))
                return -EINVAL;

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

        p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL);
        if (!p_lm70)
                return -ENOMEM;

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

        hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev,
                                                           spi->modalias,
                                                           p_lm70, lm70_groups);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct spi_device_id lm70_ids[] = {
        { "lm70",   LM70_CHIP_LM70 },
        { "tmp121", LM70_CHIP_TMP121 },
        { "tmp122", LM70_CHIP_TMP122 },
        { "lm71",   LM70_CHIP_LM71 },
        { "lm74",   LM70_CHIP_LM74 },
        { },
};
MODULE_DEVICE_TABLE(spi, lm70_ids);

static struct spi_driver lm70_driver = {
        .driver = {
                .name   = "lm70",
                .of_match_table = of_match_ptr(lm70_of_ids),
        },
        .id_table = lm70_ids,
        .probe  = lm70_probe,
};

module_spi_driver(lm70_driver);

MODULE_AUTHOR("Kaiwan N Billimoria");
MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
MODULE_LICENSE("GPL");