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/spi/spi.h> 35 #include <asm/semaphore.h> 36 37 #define DRVNAME "lm70" 38 39 struct lm70 { 40 struct class_device *cdev; 41 struct semaphore sem; 42 }; 43 44 /* sysfs hook function */ 45 static ssize_t lm70_sense_temp(struct device *dev, 46 struct device_attribute *attr, char *buf) 47 { 48 struct spi_device *spi = to_spi_device(dev); 49 int status, val; 50 u8 rxbuf[2]; 51 s16 raw=0; 52 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev); 53 54 if (down_interruptible(&p_lm70->sem)) 55 return -ERESTARTSYS; 56 57 /* 58 * spi_read() requires a DMA-safe buffer; so we use 59 * spi_write_then_read(), transmitting 0 bytes. 60 */ 61 status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2); 62 if (status < 0) { 63 printk(KERN_WARNING 64 "spi_write_then_read failed with status %d\n", status); 65 goto out; 66 } 67 dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]); 68 69 raw = (rxbuf[1] << 8) + rxbuf[0]; 70 dev_dbg(dev, "raw=0x%x\n", raw); 71 72 /* 73 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's 74 * complement value. Only the MSB 11 bits (1 sign + 10 temperature 75 * bits) are meaningful; the LSB 5 bits are to be discarded. 76 * See the datasheet. 77 * 78 * Further, each bit represents 0.25 degrees Celsius; so, multiply 79 * by 0.25. Also multiply by 1000 to represent in millidegrees 80 * Celsius. 81 * So it's equivalent to multiplying by 0.25 * 1000 = 250. 82 */ 83 val = ((int)raw/32) * 250; 84 status = sprintf(buf, "%+d\n", val); /* millidegrees Celsius */ 85 out: 86 up(&p_lm70->sem); 87 return status; 88 } 89 90 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL); 91 92 /*----------------------------------------------------------------------*/ 93 94 static int __devinit lm70_probe(struct spi_device *spi) 95 { 96 struct lm70 *p_lm70; 97 int status; 98 99 /* signaling is SPI_MODE_0 on a 3-wire link (shared SI/SO) */ 100 if ((spi->mode & (SPI_CPOL|SPI_CPHA)) || !(spi->mode & SPI_3WIRE)) 101 return -EINVAL; 102 103 p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL); 104 if (!p_lm70) 105 return -ENOMEM; 106 107 init_MUTEX(&p_lm70->sem); 108 109 /* sysfs hook */ 110 p_lm70->cdev = hwmon_device_register(&spi->dev); 111 if (IS_ERR(p_lm70->cdev)) { 112 dev_dbg(&spi->dev, "hwmon_device_register failed.\n"); 113 status = PTR_ERR(p_lm70->cdev); 114 goto out_dev_reg_failed; 115 } 116 dev_set_drvdata(&spi->dev, p_lm70); 117 118 if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))) { 119 dev_dbg(&spi->dev, "device_create_file failure.\n"); 120 goto out_dev_create_file_failed; 121 } 122 123 return 0; 124 125 out_dev_create_file_failed: 126 hwmon_device_unregister(p_lm70->cdev); 127 out_dev_reg_failed: 128 dev_set_drvdata(&spi->dev, NULL); 129 kfree(p_lm70); 130 return status; 131 } 132 133 static int __devexit lm70_remove(struct spi_device *spi) 134 { 135 struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev); 136 137 device_remove_file(&spi->dev, &dev_attr_temp1_input); 138 hwmon_device_unregister(p_lm70->cdev); 139 dev_set_drvdata(&spi->dev, NULL); 140 kfree(p_lm70); 141 142 return 0; 143 } 144 145 static struct spi_driver lm70_driver = { 146 .driver = { 147 .name = "lm70", 148 .owner = THIS_MODULE, 149 }, 150 .probe = lm70_probe, 151 .remove = __devexit_p(lm70_remove), 152 }; 153 154 static int __init init_lm70(void) 155 { 156 return spi_register_driver(&lm70_driver); 157 } 158 159 static void __exit cleanup_lm70(void) 160 { 161 spi_unregister_driver(&lm70_driver); 162 } 163 164 module_init(init_lm70); 165 module_exit(cleanup_lm70); 166 167 MODULE_AUTHOR("Kaiwan N Billimoria"); 168 MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver"); 169 MODULE_LICENSE("GPL"); 170