diff options
Diffstat (limited to 'drivers/hwmon/lm70.c')
| -rw-r--r-- | drivers/hwmon/lm70.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/drivers/hwmon/lm70.c b/drivers/hwmon/lm70.c new file mode 100644 index 0000000..6ba8473 --- /dev/null +++ b/drivers/hwmon/lm70.c @@ -0,0 +1,165 @@ +/* + * 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"); |