linux/drivers/hwmon/lm70.c
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   1/*
   2 * lm70.c
   3 *
   4 * The LM70 is a temperature sensor chip from National Semiconductor (NS).
   5 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
   6 *
   7 * The LM70 communicates with a host processor via an SPI/Microwire Bus
   8 * interface. The complete datasheet is available at National's website
   9 * here:
  10 * http://www.national.com/pf/LM/LM70.html
  11 *
  12 * This program is free software; you can redistribute it and/or modify
  13 * it under the terms of the GNU General Public License as published by
  14 * the Free Software Foundation; either version 2 of the License, or
  15 * (at your option) any later version.
  16 *
  17 * This program is distributed in the hope that it will be useful,
  18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 * GNU General Public License for more details.
  21 *
  22 * You should have received a copy of the GNU General Public License
  23 * along with this program; if not, write to the Free Software
  24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  25 */
  26
  27#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  28
  29#include <linux/init.h>
  30#include <linux/module.h>
  31#include <linux/kernel.h>
  32#include <linux/device.h>
  33#include <linux/err.h>
  34#include <linux/sysfs.h>
  35#include <linux/hwmon.h>
  36#include <linux/mutex.h>
  37#include <linux/mod_devicetable.h>
  38#include <linux/spi/spi.h>
  39#include <linux/slab.h>
  40
  41
  42#define DRVNAME         "lm70"
  43
  44#define LM70_CHIP_LM70          0       /* original NS LM70 */
  45#define LM70_CHIP_TMP121        1       /* TI TMP121/TMP123 */
  46
  47struct lm70 {
  48        struct device *hwmon_dev;
  49        struct mutex lock;
  50        unsigned int chip;
  51};
  52
  53/* sysfs hook function */
  54static ssize_t lm70_sense_temp(struct device *dev,
  55                struct device_attribute *attr, char *buf)
  56{
  57        struct spi_device *spi = to_spi_device(dev);
  58        int status, val = 0;
  59        u8 rxbuf[2];
  60        s16 raw = 0;
  61        struct lm70 *p_lm70 = spi_get_drvdata(spi);
  62
  63        if (mutex_lock_interruptible(&p_lm70->lock))
  64                return -ERESTARTSYS;
  65
  66        /*
  67         * spi_read() requires a DMA-safe buffer; so we use
  68         * spi_write_then_read(), transmitting 0 bytes.
  69         */
  70        status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
  71        if (status < 0) {
  72                pr_warn("spi_write_then_read failed with status %d\n", status);
  73                goto out;
  74        }
  75        raw = (rxbuf[0] << 8) + rxbuf[1];
  76        dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
  77                rxbuf[0], rxbuf[1], raw);
  78
  79        /*
  80         * LM70:
  81         * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
  82         * complement value. Only the MSB 11 bits (1 sign + 10 temperature
  83         * bits) are meaningful; the LSB 5 bits are to be discarded.
  84         * See the datasheet.
  85         *
  86         * Further, each bit represents 0.25 degrees Celsius; so, multiply
  87         * by 0.25. Also multiply by 1000 to represent in millidegrees
  88         * Celsius.
  89         * So it's equivalent to multiplying by 0.25 * 1000 = 250.
  90         *
  91         * TMP121/TMP123:
  92         * 13 bits of 2's complement data, discard LSB 3 bits,
  93         * resolution 0.0625 degrees celsius.
  94         */
  95        switch (p_lm70->chip) {
  96        case LM70_CHIP_LM70:
  97                val = ((int)raw / 32) * 250;
  98                break;
  99
 100        case LM70_CHIP_TMP121:
 101                val = ((int)raw / 8) * 625 / 10;
 102                break;
 103        }
 104
 105        status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
 106out:
 107        mutex_unlock(&p_lm70->lock);
 108        return status;
 109}
 110
 111static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
 112
 113static ssize_t lm70_show_name(struct device *dev, struct device_attribute
 114                              *devattr, char *buf)
 115{
 116        struct lm70 *p_lm70 = dev_get_drvdata(dev);
 117        int ret;
 118
 119        switch (p_lm70->chip) {
 120        case LM70_CHIP_LM70:
 121                ret = sprintf(buf, "lm70\n");
 122                break;
 123        case LM70_CHIP_TMP121:
 124                ret = sprintf(buf, "tmp121\n");
 125                break;
 126        default:
 127                ret = -EINVAL;
 128        }
 129        return ret;
 130}
 131
 132static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);
 133
 134/*----------------------------------------------------------------------*/
 135
 136static int __devinit lm70_probe(struct spi_device *spi)
 137{
 138        int chip = spi_get_device_id(spi)->driver_data;
 139        struct lm70 *p_lm70;
 140        int status;
 141
 142        /* signaling is SPI_MODE_0 for both LM70 and TMP121 */
 143        if (spi->mode & (SPI_CPOL | SPI_CPHA))
 144                return -EINVAL;
 145
 146        /* 3-wire link (shared SI/SO) for LM70 */
 147        if (chip == LM70_CHIP_LM70 && !(spi->mode & SPI_3WIRE))
 148                return -EINVAL;
 149
 150        /* NOTE:  we assume 8-bit words, and convert to 16 bits manually */
 151
 152        p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
 153        if (!p_lm70)
 154                return -ENOMEM;
 155
 156        mutex_init(&p_lm70->lock);
 157        p_lm70->chip = chip;
 158
 159        spi_set_drvdata(spi, p_lm70);
 160
 161        status = device_create_file(&spi->dev, &dev_attr_temp1_input);
 162        if (status)
 163                goto out_dev_create_temp_file_failed;
 164        status = device_create_file(&spi->dev, &dev_attr_name);
 165        if (status)
 166                goto out_dev_create_file_failed;
 167
 168        /* sysfs hook */
 169        p_lm70->hwmon_dev = hwmon_device_register(&spi->dev);
 170        if (IS_ERR(p_lm70->hwmon_dev)) {
 171                dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
 172                status = PTR_ERR(p_lm70->hwmon_dev);
 173                goto out_dev_reg_failed;
 174        }
 175
 176        return 0;
 177
 178out_dev_reg_failed:
 179        device_remove_file(&spi->dev, &dev_attr_name);
 180out_dev_create_file_failed:
 181        device_remove_file(&spi->dev, &dev_attr_temp1_input);
 182out_dev_create_temp_file_failed:
 183        spi_set_drvdata(spi, NULL);
 184        kfree(p_lm70);
 185        return status;
 186}
 187
 188static int __devexit lm70_remove(struct spi_device *spi)
 189{
 190        struct lm70 *p_lm70 = spi_get_drvdata(spi);
 191
 192        hwmon_device_unregister(p_lm70->hwmon_dev);
 193        device_remove_file(&spi->dev, &dev_attr_temp1_input);
 194        device_remove_file(&spi->dev, &dev_attr_name);
 195        spi_set_drvdata(spi, NULL);
 196        kfree(p_lm70);
 197
 198        return 0;
 199}
 200
 201
 202static const struct spi_device_id lm70_ids[] = {
 203        { "lm70",   LM70_CHIP_LM70 },
 204        { "tmp121", LM70_CHIP_TMP121 },
 205        { },
 206};
 207MODULE_DEVICE_TABLE(spi, lm70_ids);
 208
 209static struct spi_driver lm70_driver = {
 210        .driver = {
 211                .name   = "lm70",
 212                .owner  = THIS_MODULE,
 213        },
 214        .id_table = lm70_ids,
 215        .probe  = lm70_probe,
 216        .remove = __devexit_p(lm70_remove),
 217};
 218
 219module_spi_driver(lm70_driver);
 220
 221MODULE_AUTHOR("Kaiwan N Billimoria");
 222MODULE_DESCRIPTION("NS LM70 / TI TMP121/TMP123 Linux driver");
 223MODULE_LICENSE("GPL");
 224
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