/* * 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; /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */ if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE)) return -EINVAL; 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");