1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
/*
* lm70.c
*
* The LM70 is a temperature sensor chip from National Semiconductor (NS).
* Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
*
* The LM70 communicates with a host processor via an SPI/Microwire Bus
* interface. The complete datasheet is available at National's website
* here:
* http://www.national.com/pf/LM/LM70.html
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/sysfs.h>
#include <linux/hwmon.h>
#include <linux/spi/spi.h>
#include <asm/semaphore.h>
#define DRVNAME "lm70"
struct lm70 {
struct class_device *cdev;
struct semaphore sem;
};
/* sysfs hook function */
static ssize_t lm70_sense_temp(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct spi_device *spi = to_spi_device(dev);
int status, val;
u8 rxbuf[2];
s16 raw=0;
struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
if (down_interruptible(&p_lm70->sem))
return -ERESTARTSYS;
/*
* spi_read() requires a DMA-safe buffer; so we use
* spi_write_then_read(), transmitting 0 bytes.
*/
status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
if (status < 0) {
printk(KERN_WARNING
"spi_write_then_read failed with status %d\n", status);
goto out;
}
dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]);
raw = (rxbuf[1] << 8) + rxbuf[0];
dev_dbg(dev, "raw=0x%x\n", raw);
/*
* The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
* complement value. Only the MSB 11 bits (1 sign + 10 temperature
* bits) are meaningful; the LSB 5 bits are to be discarded.
* See the datasheet.
*
* Further, each bit represents 0.25 degrees Celsius; so, multiply
* by 0.25. Also multiply by 1000 to represent in millidegrees
* Celsius.
* So it's equivalent to multiplying by 0.25 * 1000 = 250.
*/
val = ((int)raw/32) * 250;
status = sprintf(buf, "%+d\n", val); /* millidegrees Celsius */
out:
up(&p_lm70->sem);
return status;
}
static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
/*----------------------------------------------------------------------*/
static int __devinit lm70_probe(struct spi_device *spi)
{
struct lm70 *p_lm70;
int status;
p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
if (!p_lm70)
return -ENOMEM;
init_MUTEX(&p_lm70->sem);
/* sysfs hook */
p_lm70->cdev = hwmon_device_register(&spi->dev);
if (IS_ERR(p_lm70->cdev)) {
dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
status = PTR_ERR(p_lm70->cdev);
goto out_dev_reg_failed;
}
dev_set_drvdata(&spi->dev, p_lm70);
if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))) {
dev_dbg(&spi->dev, "device_create_file failure.\n");
goto out_dev_create_file_failed;
}
return 0;
out_dev_create_file_failed:
hwmon_device_unregister(p_lm70->cdev);
out_dev_reg_failed:
dev_set_drvdata(&spi->dev, NULL);
kfree(p_lm70);
return status;
}
static int __exit lm70_remove(struct spi_device *spi)
{
struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
device_remove_file(&spi->dev, &dev_attr_temp1_input);
hwmon_device_unregister(p_lm70->cdev);
dev_set_drvdata(&spi->dev, NULL);
kfree(p_lm70);
return 0;
}
static struct spi_driver lm70_driver = {
.driver = {
.name = "lm70",
.owner = THIS_MODULE,
},
.probe = lm70_probe,
.remove = __devexit_p(lm70_remove),
};
static int __init init_lm70(void)
{
return spi_register_driver(&lm70_driver);
}
static void __exit cleanup_lm70(void)
{
spi_unregister_driver(&lm70_driver);
}
module_init(init_lm70);
module_exit(cleanup_lm70);
MODULE_AUTHOR("Kaiwan N Billimoria");
MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
MODULE_LICENSE("GPL");
|
