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 #include <linux/init.h>
  28 #include <linux/module.h>
  29 #include <linux/kernel.h>
  30 #include <linux/device.h>
  31 #include <linux/err.h>
  32 #include <linux/sysfs.h>
  33 #include <linux/hwmon.h>
  34 #include <linux/mutex.h>
  35 #include <linux/spi/spi.h>
  36
  37
  38 #define DRVNAME         "lm70"
  39
  40 struct lm70 {
  41         struct device *hwmon_dev;
  42         struct mutex lock;
  43 };
  44
  45 /* sysfs hook function */
  46 static ssize_t lm70_sense_temp(struct device *dev,
  47                 struct device_attribute *attr, char *buf)
  48 {
  49         struct spi_device *spi = to_spi_device(dev);
  50         int status, val;
  51         u8 rxbuf[2];
  52         s16 raw=0;
  53         struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
  54
  55         if (mutex_lock_interruptible(&p_lm70->lock))
  56                 return -ERESTARTSYS;
  57
  58         /*
  59          * spi_read() requires a DMA-safe buffer; so we use
  60          * spi_write_then_read(), transmitting 0 bytes.
  61          */
  62         status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
  63         if (status < 0) {
  64                 printk(KERN_WARNING
  65                 "spi_write_then_read failed with status %d\n", status);
  66                 goto out;
  67         }
  68         dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]);
  69
  70         raw = (rxbuf[1] << 8) + rxbuf[0];
  71         dev_dbg(dev, "raw=0x%x\n", raw);
  72
  73         /*
  74          * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
  75          * complement value. Only the MSB 11 bits (1 sign + 10 temperature
  76          * bits) are meaningful; the LSB 5 bits are to be discarded.
  77          * See the datasheet.
  78          *
  79          * Further, each bit represents 0.25 degrees Celsius; so, multiply
  80          * by 0.25. Also multiply by 1000 to represent in millidegrees
  81          * Celsius.
  82          * So it's equivalent to multiplying by 0.25 * 1000 = 250.
  83          */
  84         val = ((int)raw/32) * 250;
  85         status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
  86 out:
  87         mutex_unlock(&p_lm70->lock);
  88         return status;
  89 }
  90
  91 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
  92
  93 static ssize_t lm70_show_name(struct device *dev, struct device_attribute
  94                               *devattr, char *buf)
  95 {
  96         return sprintf(buf, "lm70\n");
  97 }
  98
  99 static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);
 100
 101 /*----------------------------------------------------------------------*/
 102
 103 static int __devinit lm70_probe(struct spi_device *spi)
 104 {
 105         struct lm70 *p_lm70;
 106         int status;
 107
 108         /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */
 109         if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE))
 110                 return -EINVAL;
 111
 112         p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
 113         if (!p_lm70)
 114                 return -ENOMEM;
 115
 116         mutex_init(&p_lm70->lock);
 117
 118         /* sysfs hook */
 119         p_lm70->hwmon_dev = hwmon_device_register(&spi->dev);
 120         if (IS_ERR(p_lm70->hwmon_dev)) {
 121                 dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
 122                 status = PTR_ERR(p_lm70->hwmon_dev);
 123                 goto out_dev_reg_failed;
 124         }
 125         dev_set_drvdata(&spi->dev, p_lm70);
 126
 127         if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))
 128          || (status = device_create_file(&spi->dev, &dev_attr_name))) {
 129                 dev_dbg(&spi->dev, "device_create_file failure.\n");
 130                 goto out_dev_create_file_failed;
 131         }
 132
 133         return 0;
 134
 135 out_dev_create_file_failed:
 136         device_remove_file(&spi->dev, &dev_attr_temp1_input);
 137         hwmon_device_unregister(p_lm70->hwmon_dev);
 138 out_dev_reg_failed:
 139         dev_set_drvdata(&spi->dev, NULL);
 140         kfree(p_lm70);
 141         return status;
 142 }
 143
 144 static int __devexit lm70_remove(struct spi_device *spi)
 145 {
 146         struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
 147
 148         device_remove_file(&spi->dev, &dev_attr_temp1_input);
 149         device_remove_file(&spi->dev, &dev_attr_name);
 150         hwmon_device_unregister(p_lm70->hwmon_dev);
 151         dev_set_drvdata(&spi->dev, NULL);
 152         kfree(p_lm70);
 153
 154         return 0;
 155 }
 156
 157 static struct spi_driver lm70_driver = {
 158         .driver = {
 159                 .name   = "lm70",
 160                 .owner  = THIS_MODULE,
 161         },
 162         .probe  = lm70_probe,
 163         .remove = __devexit_p(lm70_remove),
 164 };
 165
 166 static int __init init_lm70(void)
 167 {
 168         return spi_register_driver(&lm70_driver);
 169 }
 170
 171 static void __exit cleanup_lm70(void)
 172 {
 173         spi_unregister_driver(&lm70_driver);
 174 }
 175
 176 module_init(init_lm70);
 177 module_exit(cleanup_lm70);
 178
 179 MODULE_AUTHOR("Kaiwan N Billimoria");
 180 MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
 181 MODULE_LICENSE("GPL");