davinci: explain CLOCK_TICK_RATE of 27MHz in include/mach/timex.h
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / hwmon / lm70.c
blobab8a5d3c769048a1a15635c09648740bad64e9ef
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/mod_devicetable.h>
36 #include <linux/spi/spi.h>
39 #define DRVNAME "lm70"
41 #define LM70_CHIP_LM70 0 /* original NS LM70 */
42 #define LM70_CHIP_TMP121 1 /* TI TMP121/TMP123 */
44 struct lm70 {
45 struct device *hwmon_dev;
46 struct mutex lock;
47 unsigned int chip;
50 /* sysfs hook function */
51 static ssize_t lm70_sense_temp(struct device *dev,
52 struct device_attribute *attr, char *buf)
54 struct spi_device *spi = to_spi_device(dev);
55 int status, val = 0;
56 u8 rxbuf[2];
57 s16 raw=0;
58 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
60 if (mutex_lock_interruptible(&p_lm70->lock))
61 return -ERESTARTSYS;
64 * spi_read() requires a DMA-safe buffer; so we use
65 * spi_write_then_read(), transmitting 0 bytes.
67 status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
68 if (status < 0) {
69 printk(KERN_WARNING
70 "spi_write_then_read failed with status %d\n", status);
71 goto out;
73 raw = (rxbuf[0] << 8) + rxbuf[1];
74 dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
75 rxbuf[0], rxbuf[1], raw);
78 * LM70:
79 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
80 * complement value. Only the MSB 11 bits (1 sign + 10 temperature
81 * bits) are meaningful; the LSB 5 bits are to be discarded.
82 * See the datasheet.
84 * Further, each bit represents 0.25 degrees Celsius; so, multiply
85 * by 0.25. Also multiply by 1000 to represent in millidegrees
86 * Celsius.
87 * So it's equivalent to multiplying by 0.25 * 1000 = 250.
89 * TMP121/TMP123:
90 * 13 bits of 2's complement data, discard LSB 3 bits,
91 * resolution 0.0625 degrees celsius.
93 switch (p_lm70->chip) {
94 case LM70_CHIP_LM70:
95 val = ((int)raw / 32) * 250;
96 break;
98 case LM70_CHIP_TMP121:
99 val = ((int)raw / 8) * 625 / 10;
100 break;
103 status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
104 out:
105 mutex_unlock(&p_lm70->lock);
106 return status;
109 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
111 static ssize_t lm70_show_name(struct device *dev, struct device_attribute
112 *devattr, char *buf)
114 struct lm70 *p_lm70 = dev_get_drvdata(dev);
115 int ret;
117 switch (p_lm70->chip) {
118 case LM70_CHIP_LM70:
119 ret = sprintf(buf, "lm70\n");
120 break;
121 case LM70_CHIP_TMP121:
122 ret = sprintf(buf, "tmp121\n");
123 break;
124 default:
125 ret = -EINVAL;
127 return ret;
130 static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);
132 /*----------------------------------------------------------------------*/
134 static int __devinit lm70_probe(struct spi_device *spi)
136 int chip = spi_get_device_id(spi)->driver_data;
137 struct lm70 *p_lm70;
138 int status;
140 /* signaling is SPI_MODE_0 for both LM70 and TMP121 */
141 if (spi->mode & (SPI_CPOL | SPI_CPHA))
142 return -EINVAL;
144 /* 3-wire link (shared SI/SO) for LM70 */
145 if (chip == LM70_CHIP_LM70 && !(spi->mode & SPI_3WIRE))
146 return -EINVAL;
148 /* NOTE: we assume 8-bit words, and convert to 16 bits manually */
150 p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
151 if (!p_lm70)
152 return -ENOMEM;
154 mutex_init(&p_lm70->lock);
155 p_lm70->chip = chip;
157 /* sysfs hook */
158 p_lm70->hwmon_dev = hwmon_device_register(&spi->dev);
159 if (IS_ERR(p_lm70->hwmon_dev)) {
160 dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
161 status = PTR_ERR(p_lm70->hwmon_dev);
162 goto out_dev_reg_failed;
164 dev_set_drvdata(&spi->dev, p_lm70);
166 if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))
167 || (status = device_create_file(&spi->dev, &dev_attr_name))) {
168 dev_dbg(&spi->dev, "device_create_file failure.\n");
169 goto out_dev_create_file_failed;
172 return 0;
174 out_dev_create_file_failed:
175 device_remove_file(&spi->dev, &dev_attr_temp1_input);
176 hwmon_device_unregister(p_lm70->hwmon_dev);
177 out_dev_reg_failed:
178 dev_set_drvdata(&spi->dev, NULL);
179 kfree(p_lm70);
180 return status;
183 static int __devexit lm70_remove(struct spi_device *spi)
185 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
187 device_remove_file(&spi->dev, &dev_attr_temp1_input);
188 device_remove_file(&spi->dev, &dev_attr_name);
189 hwmon_device_unregister(p_lm70->hwmon_dev);
190 dev_set_drvdata(&spi->dev, NULL);
191 kfree(p_lm70);
193 return 0;
197 static const struct spi_device_id lm70_ids[] = {
198 { "lm70", LM70_CHIP_LM70 },
199 { "tmp121", LM70_CHIP_TMP121 },
200 { },
202 MODULE_DEVICE_TABLE(spi, lm70_ids);
204 static struct spi_driver lm70_driver = {
205 .driver = {
206 .name = "lm70",
207 .owner = THIS_MODULE,
209 .id_table = lm70_ids,
210 .probe = lm70_probe,
211 .remove = __devexit_p(lm70_remove),
214 static int __init init_lm70(void)
216 return spi_register_driver(&lm70_driver);
219 static void __exit cleanup_lm70(void)
221 spi_unregister_driver(&lm70_driver);
224 module_init(init_lm70);
225 module_exit(cleanup_lm70);
227 MODULE_AUTHOR("Kaiwan N Billimoria");
228 MODULE_DESCRIPTION("NS LM70 / TI TMP121/TMP123 Linux driver");
229 MODULE_LICENSE("GPL");