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   1 /*
   2     i2c-stub.c - I2C/SMBus chip emulator
   3
   4     Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
   5     Copyright (C) 2007 Jean Delvare <khali@linux-fr.org>
   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/slab.h>
  28 #include <linux/errno.h>
  29 #include <linux/i2c.h>
  30
  31 #define MAX_CHIPS 10
  32
  33 static unsigned short chip_addr[MAX_CHIPS];
  34 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  35 MODULE_PARM_DESC(chip_addr,
  36                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  37
  38 struct stub_chip {
  39         u8 pointer;
  40         u16 words[256];         /* Byte operations use the LSB as per SMBus
  41                                    specification */
  42 };
  43
  44 static struct stub_chip *stub_chips;
  45
  46 /* Return negative errno on error. */
  47 static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
  48         char read_write, u8 command, int size, union i2c_smbus_data * data)
  49 {
  50         s32 ret;
  51         int i;
  52         struct stub_chip *chip = NULL;
  53
  54         /* Search for the right chip */
  55         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
  56                 if (addr == chip_addr[i]) {
  57                         chip = stub_chips + i;
  58                         break;
  59                 }
  60         }
  61         if (!chip)
  62                 return -ENODEV;
  63
  64         switch (size) {
  65
  66         case I2C_SMBUS_QUICK:
  67                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
  68                 ret = 0;
  69                 break;
  70
  71         case I2C_SMBUS_BYTE:
  72                 if (read_write == I2C_SMBUS_WRITE) {
  73                         chip->pointer = command;
  74                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  75                                         "wrote 0x%02x.\n",
  76                                         addr, command);
  77                 } else {
  78                         data->byte = chip->words[chip->pointer++] & 0xff;
  79                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  80                                         "read  0x%02x.\n",
  81                                         addr, data->byte);
  82                 }
  83
  84                 ret = 0;
  85                 break;
  86
  87         case I2C_SMBUS_BYTE_DATA:
  88                 if (read_write == I2C_SMBUS_WRITE) {
  89                         chip->words[command] &= 0xff00;
  90                         chip->words[command] |= data->byte;
  91                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
  92                                         "wrote 0x%02x at 0x%02x.\n",
  93                                         addr, data->byte, command);
  94                 } else {
  95                         data->byte = chip->words[command] & 0xff;
  96                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
  97                                         "read  0x%02x at 0x%02x.\n",
  98                                         addr, data->byte, command);
  99                 }
 100                 chip->pointer = command + 1;
 101
 102                 ret = 0;
 103                 break;
 104
 105         case I2C_SMBUS_WORD_DATA:
 106                 if (read_write == I2C_SMBUS_WRITE) {
 107                         chip->words[command] = data->word;
 108                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
 109                                         "wrote 0x%04x at 0x%02x.\n",
 110                                         addr, data->word, command);
 111                 } else {
 112                         data->word = chip->words[command];
 113                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
 114                                         "read  0x%04x at 0x%02x.\n",
 115                                         addr, data->word, command);
 116                 }
 117
 118                 ret = 0;
 119                 break;
 120
 121         default:
 122                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 123                 ret = -EOPNOTSUPP;
 124                 break;
 125         } /* switch (size) */
 126
 127         return ret;
 128 }
 129
 130 static u32 stub_func(struct i2c_adapter *adapter)
 131 {
 132         return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
 133                 I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
 134 }
 135
 136 static const struct i2c_algorithm smbus_algorithm = {
 137         .functionality  = stub_func,
 138         .smbus_xfer     = stub_xfer,
 139 };
 140
 141 static struct i2c_adapter stub_adapter = {
 142         .owner          = THIS_MODULE,
 143         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 144         .algo           = &smbus_algorithm,
 145         .name           = "SMBus stub driver",
 146 };
 147
 148 static int __init i2c_stub_init(void)
 149 {
 150         int i, ret;
 151
 152         if (!chip_addr[0]) {
 153                 printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
 154                 return -ENODEV;
 155         }
 156
 157         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 158                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 159                         printk(KERN_ERR "i2c-stub: Invalid chip address "
 160                                "0x%02x\n", chip_addr[i]);
 161                         return -EINVAL;
 162                 }
 163
 164                 printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n",
 165                        chip_addr[i]);
 166         }
 167
 168         /* Allocate memory for all chips at once */
 169         stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
 170         if (!stub_chips) {
 171                 printk(KERN_ERR "i2c-stub: Out of memory\n");
 172                 return -ENOMEM;
 173         }
 174
 175         ret = i2c_add_adapter(&stub_adapter);
 176         if (ret)
 177                 kfree(stub_chips);
 178         return ret;
 179 }
 180
 181 static void __exit i2c_stub_exit(void)
 182 {
 183         i2c_del_adapter(&stub_adapter);
 184         kfree(stub_chips);
 185 }
 186
 187 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 188 MODULE_DESCRIPTION("I2C stub driver");
 189 MODULE_LICENSE("GPL");
 190
 191 module_init(i2c_stub_init);
 192 module_exit(i2c_stub_exit);
 193