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Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +02001/*
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
39struct lm70 {
40 struct class_device *cdev;
41 struct semaphore sem;
42};
43
44/* sysfs hook function */
45static 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;
Jean Delvare67f921d2007-08-17 17:31:35 +020084 status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +020085out:
86 up(&p_lm70->sem);
87 return status;
88}
89
90static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
91
Jean Delvare67f921d2007-08-17 17:31:35 +020092static ssize_t lm70_show_name(struct device *dev, struct device_attribute
93 *devattr, char *buf)
94{
95 return sprintf(buf, "lm70\n");
96}
97
98static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);
99
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +0200100/*----------------------------------------------------------------------*/
101
102static int __devinit lm70_probe(struct spi_device *spi)
103{
104 struct lm70 *p_lm70;
105 int status;
106
David Brownellc06e6772007-07-17 04:04:03 -0700107 /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */
108 if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE))
109 return -EINVAL;
110
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +0200111 p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
112 if (!p_lm70)
113 return -ENOMEM;
114
115 init_MUTEX(&p_lm70->sem);
116
117 /* sysfs hook */
118 p_lm70->cdev = hwmon_device_register(&spi->dev);
119 if (IS_ERR(p_lm70->cdev)) {
120 dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
121 status = PTR_ERR(p_lm70->cdev);
122 goto out_dev_reg_failed;
123 }
124 dev_set_drvdata(&spi->dev, p_lm70);
125
Jean Delvare67f921d2007-08-17 17:31:35 +0200126 if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))
127 || (status = device_create_file(&spi->dev, &dev_attr_name))) {
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +0200128 dev_dbg(&spi->dev, "device_create_file failure.\n");
129 goto out_dev_create_file_failed;
130 }
131
132 return 0;
133
134out_dev_create_file_failed:
Jean Delvare67f921d2007-08-17 17:31:35 +0200135 device_remove_file(&spi->dev, &dev_attr_temp1_input);
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +0200136 hwmon_device_unregister(p_lm70->cdev);
137out_dev_reg_failed:
138 dev_set_drvdata(&spi->dev, NULL);
139 kfree(p_lm70);
140 return status;
141}
142
Ralf Baechle41be7222007-02-14 21:15:04 +0100143static int __devexit lm70_remove(struct spi_device *spi)
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +0200144{
145 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
146
147 device_remove_file(&spi->dev, &dev_attr_temp1_input);
Jean Delvare67f921d2007-08-17 17:31:35 +0200148 device_remove_file(&spi->dev, &dev_attr_name);
Kaiwan N Billimoriae1a8e912006-06-12 22:00:05 +0200149 hwmon_device_unregister(p_lm70->cdev);
150 dev_set_drvdata(&spi->dev, NULL);
151 kfree(p_lm70);
152
153 return 0;
154}
155
156static struct spi_driver lm70_driver = {
157 .driver = {
158 .name = "lm70",
159 .owner = THIS_MODULE,
160 },
161 .probe = lm70_probe,
162 .remove = __devexit_p(lm70_remove),
163};
164
165static int __init init_lm70(void)
166{
167 return spi_register_driver(&lm70_driver);
168}
169
170static void __exit cleanup_lm70(void)
171{
172 spi_unregister_driver(&lm70_driver);
173}
174
175module_init(init_lm70);
176module_exit(cleanup_lm70);
177
178MODULE_AUTHOR("Kaiwan N Billimoria");
179MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
180MODULE_LICENSE("GPL");