x86: fix bootup crash in native_read_tsc()
[wrt350n-kernel.git] / drivers / hwmon / lm70.c
blobd435f003292dfd290a2d89fda730fa597c45eef2
1 /*
2 * lm70.c
4 * The LM70 is a temperature sensor chip from National Semiconductor (NS).
5 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
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
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.
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.
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.
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>
38 #define DRVNAME "lm70"
40 struct lm70 {
41 struct device *hwmon_dev;
42 struct mutex lock;
45 /* sysfs hook function */
46 static ssize_t lm70_sense_temp(struct device *dev,
47 struct device_attribute *attr, char *buf)
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);
55 if (mutex_lock_interruptible(&p_lm70->lock))
56 return -ERESTARTSYS;
59 * spi_read() requires a DMA-safe buffer; so we use
60 * spi_write_then_read(), transmitting 0 bytes.
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;
68 dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]);
70 raw = (rxbuf[1] << 8) + rxbuf[0];
71 dev_dbg(dev, "raw=0x%x\n", raw);
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.
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.
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;
91 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
93 static ssize_t lm70_show_name(struct device *dev, struct device_attribute
94 *devattr, char *buf)
96 return sprintf(buf, "lm70\n");
99 static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);
101 /*----------------------------------------------------------------------*/
103 static int __devinit lm70_probe(struct spi_device *spi)
105 struct lm70 *p_lm70;
106 int status;
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;
112 p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
113 if (!p_lm70)
114 return -ENOMEM;
116 mutex_init(&p_lm70->lock);
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;
125 dev_set_drvdata(&spi->dev, p_lm70);
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;
133 return 0;
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;
144 static int __devexit lm70_remove(struct spi_device *spi)
146 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
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);
154 return 0;
157 static struct spi_driver lm70_driver = {
158 .driver = {
159 .name = "lm70",
160 .owner = THIS_MODULE,
162 .probe = lm70_probe,
163 .remove = __devexit_p(lm70_remove),
166 static int __init init_lm70(void)
168 return spi_register_driver(&lm70_driver);
171 static void __exit cleanup_lm70(void)
173 spi_unregister_driver(&lm70_driver);
176 module_init(init_lm70);
177 module_exit(cleanup_lm70);
179 MODULE_AUTHOR("Kaiwan N Billimoria");
180 MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
181 MODULE_LICENSE("GPL");