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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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* 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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* http://www.national.com/pf/LM/LM70.html
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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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* 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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* 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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#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/mutex.h>
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#include <linux/mod_devicetable.h>
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#include <linux/spi/spi.h>
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#include <linux/slab.h>
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#define DRVNAME "lm70"
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#define LM70_CHIP_LM70 0 /* original NS LM70 */
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#define LM70_CHIP_TMP121 1 /* TI TMP121/TMP123 */
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struct device *hwmon_dev;
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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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struct spi_device *spi = to_spi_device(dev);
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struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
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if (mutex_lock_interruptible(&p_lm70->lock))
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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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status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
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"spi_write_then_read failed with status %d\n", status);
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raw = (rxbuf[0] << 8) + rxbuf[1];
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dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
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rxbuf[0], rxbuf[1], raw);
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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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* 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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* So it's equivalent to multiplying by 0.25 * 1000 = 250.
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* 13 bits of 2's complement data, discard LSB 3 bits,
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* resolution 0.0625 degrees celsius.
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switch (p_lm70->chip) {
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val = ((int)raw / 32) * 250;
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case LM70_CHIP_TMP121:
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val = ((int)raw / 8) * 625 / 10;
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status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
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mutex_unlock(&p_lm70->lock);
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static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
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static ssize_t lm70_show_name(struct device *dev, struct device_attribute
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struct lm70 *p_lm70 = dev_get_drvdata(dev);
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switch (p_lm70->chip) {
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ret = sprintf(buf, "lm70\n");
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case LM70_CHIP_TMP121:
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ret = sprintf(buf, "tmp121\n");
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static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL);
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/*----------------------------------------------------------------------*/
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static int __devinit lm70_probe(struct spi_device *spi)
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int chip = spi_get_device_id(spi)->driver_data;
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/* signaling is SPI_MODE_0 for both LM70 and TMP121 */
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if (spi->mode & (SPI_CPOL | SPI_CPHA))
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/* 3-wire link (shared SI/SO) for LM70 */
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if (chip == LM70_CHIP_LM70 && !(spi->mode & SPI_3WIRE))
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/* NOTE: we assume 8-bit words, and convert to 16 bits manually */
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p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
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mutex_init(&p_lm70->lock);
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p_lm70->hwmon_dev = hwmon_device_register(&spi->dev);
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if (IS_ERR(p_lm70->hwmon_dev)) {
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dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
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status = PTR_ERR(p_lm70->hwmon_dev);
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goto out_dev_reg_failed;
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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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|| (status = device_create_file(&spi->dev, &dev_attr_name))) {
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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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out_dev_create_file_failed:
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device_remove_file(&spi->dev, &dev_attr_temp1_input);
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hwmon_device_unregister(p_lm70->hwmon_dev);
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dev_set_drvdata(&spi->dev, NULL);
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static int __devexit lm70_remove(struct spi_device *spi)
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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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device_remove_file(&spi->dev, &dev_attr_name);
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hwmon_device_unregister(p_lm70->hwmon_dev);
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dev_set_drvdata(&spi->dev, NULL);
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static const struct spi_device_id lm70_ids[] = {
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{ "lm70", LM70_CHIP_LM70 },
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{ "tmp121", LM70_CHIP_TMP121 },
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MODULE_DEVICE_TABLE(spi, lm70_ids);
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static struct spi_driver lm70_driver = {
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.owner = THIS_MODULE,
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.id_table = lm70_ids,
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.remove = __devexit_p(lm70_remove),
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static int __init init_lm70(void)
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return spi_register_driver(&lm70_driver);
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static void __exit cleanup_lm70(void)
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spi_unregister_driver(&lm70_driver);
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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("NS LM70 / TI TMP121/TMP123 Linux driver");
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MODULE_LICENSE("GPL");