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![Kaiwan N Billimoria](/assets/img/avatar_default.png)
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. Signed-off-by: Kaiwan N Billimoria <kaiwan@designergraphix.com> Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
165 lines
4.3 KiB
C
165 lines
4.3 KiB
C
/*
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* lm70.c
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*
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* The LM70 is a temperature sensor chip from National Semiconductor (NS).
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* Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
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*
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* The LM70 communicates with a host processor via an SPI/Microwire Bus
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* interface. The complete datasheet is available at National's website
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* here:
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* http://www.national.com/pf/LM/LM70.html
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/sysfs.h>
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#include <linux/hwmon.h>
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#include <linux/spi/spi.h>
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#include <asm/semaphore.h>
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#define DRVNAME "lm70"
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struct lm70 {
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struct class_device *cdev;
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struct semaphore sem;
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};
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/* sysfs hook function */
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static ssize_t lm70_sense_temp(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct spi_device *spi = to_spi_device(dev);
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int status, val;
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u8 rxbuf[2];
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s16 raw=0;
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struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
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if (down_interruptible(&p_lm70->sem))
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return -ERESTARTSYS;
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/*
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* spi_read() requires a DMA-safe buffer; so we use
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* spi_write_then_read(), transmitting 0 bytes.
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*/
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status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
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if (status < 0) {
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printk(KERN_WARNING
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"spi_write_then_read failed with status %d\n", status);
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goto out;
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}
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dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]);
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raw = (rxbuf[1] << 8) + rxbuf[0];
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dev_dbg(dev, "raw=0x%x\n", raw);
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/*
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* The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
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* complement value. Only the MSB 11 bits (1 sign + 10 temperature
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* bits) are meaningful; the LSB 5 bits are to be discarded.
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* See the datasheet.
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*
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* Further, each bit represents 0.25 degrees Celsius; so, multiply
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* by 0.25. Also multiply by 1000 to represent in millidegrees
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* Celsius.
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* So it's equivalent to multiplying by 0.25 * 1000 = 250.
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*/
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val = ((int)raw/32) * 250;
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status = sprintf(buf, "%+d\n", val); /* millidegrees Celsius */
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out:
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up(&p_lm70->sem);
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return status;
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}
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static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
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/*----------------------------------------------------------------------*/
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static int __devinit lm70_probe(struct spi_device *spi)
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{
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struct lm70 *p_lm70;
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int status;
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p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
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if (!p_lm70)
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return -ENOMEM;
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init_MUTEX(&p_lm70->sem);
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/* sysfs hook */
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p_lm70->cdev = hwmon_device_register(&spi->dev);
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if (IS_ERR(p_lm70->cdev)) {
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dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
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status = PTR_ERR(p_lm70->cdev);
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goto out_dev_reg_failed;
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}
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dev_set_drvdata(&spi->dev, p_lm70);
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if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))) {
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dev_dbg(&spi->dev, "device_create_file failure.\n");
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goto out_dev_create_file_failed;
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}
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return 0;
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out_dev_create_file_failed:
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hwmon_device_unregister(p_lm70->cdev);
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out_dev_reg_failed:
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dev_set_drvdata(&spi->dev, NULL);
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kfree(p_lm70);
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return status;
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}
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static int __exit lm70_remove(struct spi_device *spi)
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{
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struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
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device_remove_file(&spi->dev, &dev_attr_temp1_input);
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hwmon_device_unregister(p_lm70->cdev);
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dev_set_drvdata(&spi->dev, NULL);
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kfree(p_lm70);
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return 0;
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}
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static struct spi_driver lm70_driver = {
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.driver = {
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.name = "lm70",
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.owner = THIS_MODULE,
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},
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.probe = lm70_probe,
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.remove = __devexit_p(lm70_remove),
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};
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static int __init init_lm70(void)
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{
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return spi_register_driver(&lm70_driver);
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}
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static void __exit cleanup_lm70(void)
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{
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spi_unregister_driver(&lm70_driver);
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}
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module_init(init_lm70);
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module_exit(cleanup_lm70);
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MODULE_AUTHOR("Kaiwan N Billimoria");
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MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
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MODULE_LICENSE("GPL");
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