drivers/i2c/busses/i2c-stub.c

   1 /*
   2     i2c-stub.c - Part of lm_sensors, Linux kernel modules for hardware
   3               monitoring
   4
   5     Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
   6
   7     This program is free software; you can redistribute it and/or modify
   8     it under the terms of the GNU General Public License as published by
   9     the Free Software Foundation; either version 2 of the License, or
  10     (at your option) any later version.
  11
  12     This program is distributed in the hope that it will be useful,
  13     but WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15     GNU General Public License for more details.
  16
  17     You should have received a copy of the GNU General Public License
  18     along with this program; if not, write to the Free Software
  19     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #define DEBUG 1
  23
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26 #include <linux/kernel.h>
  27 #include <linux/errno.h>
  28 #include <linux/i2c.h>
  29
  30 static unsigned short chip_addr;
  31 module_param(chip_addr, ushort, S_IRUGO);
  32 MODULE_PARM_DESC(chip_addr, "Chip address (between 0x03 and 0x77)\n");
  33
  34 static u8  stub_pointer;
  35 static u8  stub_bytes[256];
  36 static u16 stub_words[256];
  37
  38 /* Return -1 on error. */
  39 static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
  40         char read_write, u8 command, int size, union i2c_smbus_data * data)
  41 {
  42         s32 ret;
  43
  44         if (addr != chip_addr)
  45                 return -ENODEV;
  46
  47         switch (size) {
  48
  49         case I2C_SMBUS_QUICK:
  50                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
  51                 ret = 0;
  52                 break;
  53
  54         case I2C_SMBUS_BYTE:
  55                 if (read_write == I2C_SMBUS_WRITE) {
  56                         stub_pointer = command;
  57                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  58                                         "wrote 0x%02x.\n",
  59                                         addr, command);
  60                 } else {
  61                         data->byte = stub_bytes[stub_pointer++];
  62                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  63                                         "read  0x%02x.\n",
  64                                         addr, data->byte);
  65                 }
  66
  67                 ret = 0;
  68                 break;
  69
  70         case I2C_SMBUS_BYTE_DATA:
  71                 if (read_write == I2C_SMBUS_WRITE) {
  72                         stub_bytes[command] = data->byte;
  73                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
  74                                         "wrote 0x%02x at 0x%02x.\n",
  75                                         addr, data->byte, command);
  76                 } else {
  77                         data->byte = stub_bytes[command];
  78                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
  79                                         "read  0x%02x at 0x%02x.\n",
  80                                         addr, data->byte, command);
  81                 }
  82                 stub_pointer = command + 1;
  83
  84                 ret = 0;
  85                 break;
  86
  87         case I2C_SMBUS_WORD_DATA:
  88                 if (read_write == I2C_SMBUS_WRITE) {
  89                         stub_words[command] = data->word;
  90                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
  91                                         "wrote 0x%04x at 0x%02x.\n",
  92                                         addr, data->word, command);
  93                 } else {
  94                         data->word = stub_words[command];
  95                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
  96                                         "read  0x%04x at 0x%02x.\n",
  97                                         addr, data->word, command);
  98                 }
  99
 100                 ret = 0;
 101                 break;
 102
 103         default:
 104                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 105                 ret = -1;
 106                 break;
 107         } /* switch (size) */
 108
 109         return ret;
 110 }
 111
 112 static u32 stub_func(struct i2c_adapter *adapter)
 113 {
 114         return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
 115                 I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
 116 }
 117
 118 static const struct i2c_algorithm smbus_algorithm = {
 119         .functionality  = stub_func,
 120         .smbus_xfer     = stub_xfer,
 121 };
 122
 123 static struct i2c_adapter stub_adapter = {
 124         .owner          = THIS_MODULE,
 125         .class          = I2C_CLASS_HWMON,
 126         .algo           = &smbus_algorithm,
 127         .name           = "SMBus stub driver",
 128 };
 129
 130 static int __init i2c_stub_init(void)
 131 {
 132         if (!chip_addr) {
 133                 printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
 134                 return -ENODEV;
 135         }
 136         if (chip_addr < 0x03 || chip_addr > 0x77) {
 137                 printk(KERN_ERR "i2c-stub: Invalid chip address 0x%02x\n",
 138                        chip_addr);
 139                 return -EINVAL;
 140         }
 141
 142         printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n", chip_addr);
 143         return i2c_add_adapter(&stub_adapter);
 144 }
 145
 146 static void __exit i2c_stub_exit(void)
 147 {
 148         i2c_del_adapter(&stub_adapter);
 149 }
 150
 151 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 152 MODULE_DESCRIPTION("I2C stub driver");
 153 MODULE_LICENSE("GPL");
 154
 155 module_init(i2c_stub_init);
 156 module_exit(i2c_stub_exit);
 157