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
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;
84	status = sprintf(buf, "%+d\n", val); /* millidegrees Celsius */
85out:
86	up(&p_lm70->sem);
87	return status;
88}
89
90static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
91
92/*----------------------------------------------------------------------*/
93
94static 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
121out_dev_create_file_failed:
122	hwmon_device_unregister(p_lm70->cdev);
123out_dev_reg_failed:
124	dev_set_drvdata(&spi->dev, NULL);
125	kfree(p_lm70);
126	return status;
127}
128
129static 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
141static 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
150static int __init init_lm70(void)
151{
152	return spi_register_driver(&lm70_driver);
153}
154
155static void __exit cleanup_lm70(void)
156{
157	spi_unregister_driver(&lm70_driver);
158}
159
160module_init(init_lm70);
161module_exit(cleanup_lm70);
162
163MODULE_AUTHOR("Kaiwan N Billimoria");
164MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
165MODULE_LICENSE("GPL");
166