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