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
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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
29 #include <linux/init.h>
30 #include <linux/module.h>
31 #include <linux/kernel.h>
32 #include <linux/device.h>
33 #include <linux/err.h>
34 #include <linux/sysfs.h>
35 #include <linux/hwmon.h>
36 #include <linux/mutex.h>
37 #include <linux/mod_devicetable.h>
38 #include <linux/spi/spi.h>
39 #include <linux/slab.h>
42 #define DRVNAME "lm70"
44 #define LM70_CHIP_LM70 0 /* original NS LM70 */
45 #define LM70_CHIP_TMP121 1 /* TI TMP121/TMP123 */
46 #define LM70_CHIP_LM71 2 /* NS LM71 */
47 #define LM70_CHIP_LM74 3 /* NS LM74 */
50 struct spi_device
*spi
;
55 /* sysfs hook function */
56 static ssize_t
lm70_sense_temp(struct device
*dev
,
57 struct device_attribute
*attr
, char *buf
)
59 struct lm70
*p_lm70
= dev_get_drvdata(dev
);
60 struct spi_device
*spi
= p_lm70
->spi
;
65 if (mutex_lock_interruptible(&p_lm70
->lock
))
69 * spi_read() requires a DMA-safe buffer; so we use
70 * spi_write_then_read(), transmitting 0 bytes.
72 status
= spi_write_then_read(spi
, NULL
, 0, &rxbuf
[0], 2);
74 pr_warn("spi_write_then_read failed with status %d\n", status
);
77 raw
= (rxbuf
[0] << 8) + rxbuf
[1];
78 dev_dbg(dev
, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
79 rxbuf
[0], rxbuf
[1], raw
);
83 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
84 * complement value. Only the MSB 11 bits (1 sign + 10 temperature
85 * bits) are meaningful; the LSB 5 bits are to be discarded.
88 * Further, each bit represents 0.25 degrees Celsius; so, multiply
89 * by 0.25. Also multiply by 1000 to represent in millidegrees
91 * So it's equivalent to multiplying by 0.25 * 1000 = 250.
93 * LM74 and TMP121/TMP123:
94 * 13 bits of 2's complement data, discard LSB 3 bits,
95 * resolution 0.0625 degrees celsius.
98 * 14 bits of 2's complement data, discard LSB 2 bits,
99 * resolution 0.0312 degrees celsius.
101 switch (p_lm70
->chip
) {
103 val
= ((int)raw
/ 32) * 250;
106 case LM70_CHIP_TMP121
:
108 val
= ((int)raw
/ 8) * 625 / 10;
112 val
= ((int)raw
/ 4) * 3125 / 100;
116 status
= sprintf(buf
, "%d\n", val
); /* millidegrees Celsius */
118 mutex_unlock(&p_lm70
->lock
);
122 static DEVICE_ATTR(temp1_input
, S_IRUGO
, lm70_sense_temp
, NULL
);
124 static struct attribute
*lm70_attrs
[] = {
125 &dev_attr_temp1_input
.attr
,
129 ATTRIBUTE_GROUPS(lm70
);
131 /*----------------------------------------------------------------------*/
133 static int lm70_probe(struct spi_device
*spi
)
135 int chip
= spi_get_device_id(spi
)->driver_data
;
136 struct device
*hwmon_dev
;
139 /* signaling is SPI_MODE_0 */
140 if (spi
->mode
& (SPI_CPOL
| SPI_CPHA
))
143 /* NOTE: we assume 8-bit words, and convert to 16 bits manually */
145 p_lm70
= devm_kzalloc(&spi
->dev
, sizeof(*p_lm70
), GFP_KERNEL
);
149 mutex_init(&p_lm70
->lock
);
153 hwmon_dev
= devm_hwmon_device_register_with_groups(&spi
->dev
,
155 p_lm70
, lm70_groups
);
156 return PTR_ERR_OR_ZERO(hwmon_dev
);
159 static const struct spi_device_id lm70_ids
[] = {
160 { "lm70", LM70_CHIP_LM70
},
161 { "tmp121", LM70_CHIP_TMP121
},
162 { "lm71", LM70_CHIP_LM71
},
163 { "lm74", LM70_CHIP_LM74
},
166 MODULE_DEVICE_TABLE(spi
, lm70_ids
);
168 static struct spi_driver lm70_driver
= {
171 .owner
= THIS_MODULE
,
173 .id_table
= lm70_ids
,
177 module_spi_driver(lm70_driver
);
179 MODULE_AUTHOR("Kaiwan N Billimoria");
180 MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
181 MODULE_LICENSE("GPL");
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