1 /* 2 * lm70.c 3 * 4 * The LM70 is a temperature sensor chip from National Semiconductor (NS). 5 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com> 6 * 7 * The LM70 communicates with a host processor via an SPI/Microwire Bus 8 * interface. The complete datasheet is available at National's website 9 * here: 10 * http://www.national.com/pf/LM/LM70.html 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License as published by 14 * the Free Software Foundation; either version 2 of the License, or 15 * (at your option) any later version. 16 * 17 * This program is distributed in the hope that it will be useful, 18 * but WITHOUT ANY WARRANTY; without even the implied warranty of 19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20 * GNU General Public License for more details. 21 * 22 * You should have received a copy of the GNU General Public License 23 * along with this program; if not, write to the Free Software 24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 25 */ 26 27 #include <linux/init.h> 28 #include <linux/module.h> 29 #include <linux/kernel.h> 30 #include <linux/device.h> 31 #include <linux/err.h> 32 #include <linux/sysfs.h> 33 #include <linux/hwmon.h> 34 #include <linux/mutex.h> 35 #include <linux/spi/spi.h> 36 37 38 #define DRVNAME "lm70" 39 40 struct lm70 { 41 struct device *hwmon_dev; 42 struct mutex lock; 43 }; 44 45 /* sysfs hook function */ 46 static ssize_t lm70_sense_temp(struct device *dev, 47 struct device_attribute *attr, char *buf) 48 { 49 struct spi_device *spi = to_spi_device(dev); 50 int status, val; 51 u8 rxbuf[2]; 52 s16 raw=0; 53 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev); 54 55 if (mutex_lock_interruptible(&p_lm70->lock)) 56 return -ERESTARTSYS; 57 58 /* 59 * spi_read() requires a DMA-safe buffer; so we use 60 * spi_write_then_read(), transmitting 0 bytes. 61 */ 62 status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2); 63 if (status < 0) { 64 printk(KERN_WARNING 65 "spi_write_then_read failed with status %d\n", status); 66 goto out; 67 } 68 dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]); 69 70 raw = (rxbuf[1] << 8) + rxbuf[0]; 71 dev_dbg(dev, "raw=0x%x\n", raw); 72 73 /* 74 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's 75 * complement value. Only the MSB 11 bits (1 sign + 10 temperature 76 * bits) are meaningful; the LSB 5 bits are to be discarded. 77 * See the datasheet. 78 * 79 * Further, each bit represents 0.25 degrees Celsius; so, multiply 80 * by 0.25. Also multiply by 1000 to represent in millidegrees 81 * Celsius. 82 * So it's equivalent to multiplying by 0.25 * 1000 = 250. 83 */ 84 val = ((int)raw/32) * 250; 85 status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */ 86 out: 87 mutex_unlock(&p_lm70->lock); 88 return status; 89 } 90 91 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL); 92 93 static ssize_t lm70_show_name(struct device *dev, struct device_attribute 94 *devattr, char *buf) 95 { 96 return sprintf(buf, "lm70\n"); 97 } 98 99 static DEVICE_ATTR(name, S_IRUGO, lm70_show_name, NULL); 100 101 /*----------------------------------------------------------------------*/ 102 103 static int __devinit lm70_probe(struct spi_device *spi) 104 { 105 struct lm70 *p_lm70; 106 int status; 107 108 /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */ 109 if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE)) 110 return -EINVAL; 111 112 p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL); 113 if (!p_lm70) 114 return -ENOMEM; 115 116 mutex_init(&p_lm70->lock); 117 118 /* sysfs hook */ 119 p_lm70->hwmon_dev = hwmon_device_register(&spi->dev); 120 if (IS_ERR(p_lm70->hwmon_dev)) { 121 dev_dbg(&spi->dev, "hwmon_device_register failed.\n"); 122 status = PTR_ERR(p_lm70->hwmon_dev); 123 goto out_dev_reg_failed; 124 } 125 dev_set_drvdata(&spi->dev, p_lm70); 126 127 if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input)) 128 || (status = device_create_file(&spi->dev, &dev_attr_name))) { 129 dev_dbg(&spi->dev, "device_create_file failure.\n"); 130 goto out_dev_create_file_failed; 131 } 132 133 return 0; 134 135 out_dev_create_file_failed: 136 device_remove_file(&spi->dev, &dev_attr_temp1_input); 137 hwmon_device_unregister(p_lm70->hwmon_dev); 138 out_dev_reg_failed: 139 dev_set_drvdata(&spi->dev, NULL); 140 kfree(p_lm70); 141 return status; 142 } 143 144 static int __devexit lm70_remove(struct spi_device *spi) 145 { 146 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev); 147 148 device_remove_file(&spi->dev, &dev_attr_temp1_input); 149 device_remove_file(&spi->dev, &dev_attr_name); 150 hwmon_device_unregister(p_lm70->hwmon_dev); 151 dev_set_drvdata(&spi->dev, NULL); 152 kfree(p_lm70); 153 154 return 0; 155 } 156 157 static struct spi_driver lm70_driver = { 158 .driver = { 159 .name = "lm70", 160 .owner = THIS_MODULE, 161 }, 162 .probe = lm70_probe, 163 .remove = __devexit_p(lm70_remove), 164 }; 165 166 static int __init init_lm70(void) 167 { 168 return spi_register_driver(&lm70_driver); 169 } 170 171 static void __exit cleanup_lm70(void) 172 { 173 spi_unregister_driver(&lm70_driver); 174 } 175 176 module_init(init_lm70); 177 module_exit(cleanup_lm70); 178 179 MODULE_AUTHOR("Kaiwan N Billimoria"); 180 MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver"); 181 MODULE_LICENSE("GPL"); 182