kernel/drivers/w1/slaves/w1_ds2423.c

   1 /*
   2  *      w1_ds2423.c
   3  *
   4  * Copyright (c) 2010 Mika Laitio <lamikr@pilppa.org>
   5  *
   6  * This driver will read and write the value of 4 counters to w1_slave file in
   7  * sys filesystem.
   8  * Inspired by the w1_therm and w1_ds2431 drivers.
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the therms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  23  */
  24
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/device.h>
  29 #include <linux/types.h>
  30 #include <linux/delay.h>
  31 #include <linux/crc16.h>
  32
  33 #include "../w1.h"
  34 #include "../w1_int.h"
  35 #include "../w1_family.h"
  36
  37 #define CRC16_VALID     0xb001
  38 #define CRC16_INIT      0
  39
  40 #define COUNTER_COUNT 4
  41 #define READ_BYTE_COUNT 42
  42
  43 static ssize_t w1_slave_show(struct device *device,
  44                              struct device_attribute *attr, char *out_buf)
  45 {
  46         struct w1_slave *sl = dev_to_w1_slave(device);
  47         struct w1_master *dev = sl->master;
  48         u8 rbuf[COUNTER_COUNT * READ_BYTE_COUNT];
  49         u8 wrbuf[3];
  50         int rom_addr;
  51         int read_byte_count;
  52         int result;
  53         ssize_t c;
  54         int ii;
  55         int p;
  56         int crc;
  57
  58         c               = PAGE_SIZE;
  59         rom_addr        = (12 << 5) + 31;
  60         wrbuf[0]        = 0xA5;
  61         wrbuf[1]        = rom_addr & 0xFF;
  62         wrbuf[2]        = rom_addr >> 8;
  63         mutex_lock(&dev->bus_mutex);
  64         if (!w1_reset_select_slave(sl)) {
  65                 w1_write_block(dev, wrbuf, 3);
  66                 read_byte_count = 0;
  67                 for (p = 0; p < 4; p++) {
  68                         /*
  69                          * 1 byte for first bytes in ram page read
  70                          * 4 bytes for counter
  71                          * 4 bytes for zero bits
  72                          * 2 bytes for crc
  73                          * 31 remaining bytes from the ram page
  74                          */
  75                         read_byte_count += w1_read_block(dev,
  76                                 rbuf + (p * READ_BYTE_COUNT), READ_BYTE_COUNT);
  77                         for (ii = 0; ii < READ_BYTE_COUNT; ++ii)
  78                                 c -= snprintf(out_buf + PAGE_SIZE - c,
  79                                         c, "%02x ",
  80                                         rbuf[(p * READ_BYTE_COUNT) + ii]);
  81                         if (read_byte_count != (p + 1) * READ_BYTE_COUNT) {
  82                                 dev_warn(device,
  83                                         "w1_counter_read() returned %u bytes "
  84                                         "instead of %d bytes wanted.\n",
  85                                         read_byte_count,
  86                                         READ_BYTE_COUNT);
  87                                 c -= snprintf(out_buf + PAGE_SIZE - c,
  88                                         c, "crc=NO\n");
  89                         } else {
  90                                 if (p == 0) {
  91                                         crc = crc16(CRC16_INIT, wrbuf, 3);
  92                                         crc = crc16(crc, rbuf, 11);
  93                                 } else {
  94                                         /*
  95                                          * DS2423 calculates crc from all bytes
  96                                          * read after the previous crc bytes.
  97                                          */
  98                                         crc = crc16(CRC16_INIT,
  99                                                 (rbuf + 11) +
 100                                                 ((p - 1) * READ_BYTE_COUNT),
 101                                                 READ_BYTE_COUNT);
 102                                 }
 103                                 if (crc == CRC16_VALID) {
 104                                         result = 0;
 105                                         for (ii = 4; ii > 0; ii--) {
 106                                                 result <<= 8;
 107                                                 result |= rbuf[(p *
 108                                                         READ_BYTE_COUNT) + ii];
 109                                         }
 110                                         c -= snprintf(out_buf + PAGE_SIZE - c,
 111                                                 c, "crc=YES c=%d\n", result);
 112                                 } else {
 113                                         c -= snprintf(out_buf + PAGE_SIZE - c,
 114                                                 c, "crc=NO\n");
 115                                 }
 116                         }
 117                 }
 118         } else {
 119                 c -= snprintf(out_buf + PAGE_SIZE - c, c, "Connection error");
 120         }
 121         mutex_unlock(&dev->bus_mutex);
 122         return PAGE_SIZE - c;
 123 }
 124
 125 static DEVICE_ATTR_RO(w1_slave);
 126
 127 static struct attribute *w1_f1d_attrs[] = {
 128         &dev_attr_w1_slave.attr,
 129         NULL,
 130 };
 131 ATTRIBUTE_GROUPS(w1_f1d);
 132
 133 static struct w1_family_ops w1_f1d_fops = {
 134         .groups         = w1_f1d_groups,
 135 };
 136
 137 static struct w1_family w1_family_1d = {
 138         .fid = W1_COUNTER_DS2423,
 139         .fops = &w1_f1d_fops,
 140 };
 141
 142 static int __init w1_f1d_init(void)
 143 {
 144         return w1_register_family(&w1_family_1d);
 145 }
 146
 147 static void __exit w1_f1d_exit(void)
 148 {
 149         w1_unregister_family(&w1_family_1d);
 150 }
 151
 152 module_init(w1_f1d_init);
 153 module_exit(w1_f1d_exit);
 154
 155 MODULE_LICENSE("GPL");
 156 MODULE_AUTHOR("Mika Laitio <lamikr@pilppa.org>");
 157 MODULE_DESCRIPTION("w1 family 1d driver for DS2423, 4 counters and 4kb ram");
 158 MODULE_ALIAS("w1-family-" __stringify(W1_COUNTER_DS2423));