drivers/hwmon/lm70.c

   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 #define LM70_CHIP_LM71          2       /* NS LM71 */
  47 #define LM70_CHIP_LM74          3       /* NS LM74 */
  48
  49 struct lm70 {
  50         struct spi_device *spi;
  51         struct mutex lock;
  52         unsigned int chip;
  53 };
  54
  55 /* sysfs hook function */
  56 static ssize_t lm70_sense_temp(struct device *dev,
  57                 struct device_attribute *attr, char *buf)
  58 {
  59         struct lm70 *p_lm70 = dev_get_drvdata(dev);
  60         struct spi_device *spi = p_lm70->spi;
  61         int status, val = 0;
  62         u8 rxbuf[2];
  63         s16 raw = 0;
  64
  65         if (mutex_lock_interruptible(&p_lm70->lock))
  66                 return -ERESTARTSYS;
  67
  68         /*
  69          * spi_read() requires a DMA-safe buffer; so we use
  70          * spi_write_then_read(), transmitting 0 bytes.
  71          */
  72         status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
  73         if (status < 0) {
  74                 pr_warn("spi_write_then_read failed with status %d\n", status);
  75                 goto out;
  76         }
  77         raw = (rxbuf[0] << 8) + rxbuf[1];
  78         dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
  79                 rxbuf[0], rxbuf[1], raw);
  80
  81         /*
  82          * LM70:
  83          * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
  84          * complement value. Only the MSB 11 bits (1 sign + 10 temperature
  85          * bits) are meaningful; the LSB 5 bits are to be discarded.
  86          * See the datasheet.
  87          *
  88          * Further, each bit represents 0.25 degrees Celsius; so, multiply
  89          * by 0.25. Also multiply by 1000 to represent in millidegrees
  90          * Celsius.
  91          * So it's equivalent to multiplying by 0.25 * 1000 = 250.
  92          *
  93          * LM74 and TMP121/TMP123:
  94          * 13 bits of 2's complement data, discard LSB 3 bits,
  95          * resolution 0.0625 degrees celsius.
  96          *
  97          * LM71:
  98          * 14 bits of 2's complement data, discard LSB 2 bits,
  99          * resolution 0.0312 degrees celsius.
 100          */
 101         switch (p_lm70->chip) {
 102         case LM70_CHIP_LM70:
 103                 val = ((int)raw / 32) * 250;
 104                 break;
 105
 106         case LM70_CHIP_TMP121:
 107         case LM70_CHIP_LM74:
 108                 val = ((int)raw / 8) * 625 / 10;
 109                 break;
 110
 111         case LM70_CHIP_LM71:
 112                 val = ((int)raw / 4) * 3125 / 100;
 113                 break;
 114         }
 115
 116         status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
 117 out:
 118         mutex_unlock(&p_lm70->lock);
 119         return status;
 120 }
 121
 122 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
 123
 124 static struct attribute *lm70_attrs[] = {
 125         &dev_attr_temp1_input.attr,
 126         NULL
 127 };
 128
 129 ATTRIBUTE_GROUPS(lm70);
 130
 131 /*----------------------------------------------------------------------*/
 132
 133 static int lm70_probe(struct spi_device *spi)
 134 {
 135         int chip = spi_get_device_id(spi)->driver_data;
 136         struct device *hwmon_dev;
 137         struct lm70 *p_lm70;
 138
 139         /* signaling is SPI_MODE_0 */
 140         if (spi->mode & (SPI_CPOL | SPI_CPHA))
 141                 return -EINVAL;
 142
 143         /* NOTE:  we assume 8-bit words, and convert to 16 bits manually */
 144
 145         p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL);
 146         if (!p_lm70)
 147                 return -ENOMEM;
 148
 149         mutex_init(&p_lm70->lock);
 150         p_lm70->chip = chip;
 151         p_lm70->spi = spi;
 152
 153         hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev,
 154                                                            spi->modalias,
 155                                                            p_lm70, lm70_groups);
 156         return PTR_ERR_OR_ZERO(hwmon_dev);
 157 }
 158
 159 static const struct spi_device_id lm70_ids[] = {
 160         { "lm70",   LM70_CHIP_LM70 },
 161         { "tmp121", LM70_CHIP_TMP121 },
 162         { "lm71",   LM70_CHIP_LM71 },
 163         { "lm74",   LM70_CHIP_LM74 },
 164         { },
 165 };
 166 MODULE_DEVICE_TABLE(spi, lm70_ids);
 167
 168 static struct spi_driver lm70_driver = {
 169         .driver = {
 170                 .name   = "lm70",
 171                 .owner  = THIS_MODULE,
 172         },
 173         .id_table = lm70_ids,
 174         .probe  = lm70_probe,
 175 };
 176
 177 module_spi_driver(lm70_driver);
 178
 179 MODULE_AUTHOR("Kaiwan N Billimoria");
 180 MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
 181 MODULE_LICENSE("GPL");