/*
* 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 __devexit 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");
