[PATCH] lm70: New hardware monitoring driver

Kernel driver lm70

==================

Supported chip:

  * National Semiconductor LM70

    Datasheet: http://www.national.com/pf/LM/LM70.html

Author:

        Kaiwan N Billimoria <kaiwan@designergraphix.com>

Description

-----------

This driver implements support for the National Semiconductor LM70

temperature sensor.

The LM70 temperature sensor chip supports a single temperature sensor.

It communicates with a host processor (or microcontroller) via an

SPI/Microwire Bus interface.

Communication with the LM70 is simple: when the temperature is to be sensed,

the driver accesses the LM70 using SPI communication: 16 SCLK cycles

comprise the MOSI/MISO loop. At the end of the transfer, the 11-bit 2's

complement digital temperature (sent via the SIO line), is available in the

driver for interpretation. This driver makes use of the kernel's in-core

SPI support.

Thanks to

---------

Jean Delvare <khali@linux-fr.org> for mentoring the hwmon-side driver

development.

	  This driver can also be built as a module.  If so, the module

	  will be called lm63.

config SENSORS_LM70

	tristate "National Semiconductor LM70"

	depends on HWMON && SPI_MASTER && EXPERIMENTAL

	help

	  If you say yes here you get support for the National Semiconductor

	  LM70 digital temperature sensor chip.

	  This driver can also be built as a module.  If so, the module

	  will be called lm70.

config SENSORS_LM75

	tristate "National Semiconductor LM75 and compatibles"

	depends on HWMON && I2C

obj-$(CONFIG_SENSORS_HDAPS)	+= hdaps.o

obj-$(CONFIG_SENSORS_IT87)	+= it87.o

obj-$(CONFIG_SENSORS_LM63)	+= lm63.o

obj-$(CONFIG_SENSORS_LM70)	+= lm70.o

obj-$(CONFIG_SENSORS_LM75)	+= lm75.o

obj-$(CONFIG_SENSORS_LM77)	+= lm77.o

obj-$(CONFIG_SENSORS_LM78)	+= lm78.o

/*

 * 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");