drivers/i2c/i2c-stub.c

   1 /*
   2     i2c-stub.c - I2C/SMBus chip emulator
   3
   4     Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
   5     Copyright (C) 2007, 2012 Jean Delvare <jdelvare@suse.de>
   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
  18 #define DEBUG 1
  19
  20 #include <linux/init.h>
  21 #include <linux/module.h>
  22 #include <linux/kernel.h>
  23 #include <linux/slab.h>
  24 #include <linux/errno.h>
  25 #include <linux/i2c.h>
  26
  27 #define MAX_CHIPS 10
  28 #define STUB_FUNC (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
  29                    I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
  30                    I2C_FUNC_SMBUS_I2C_BLOCK)
  31
  32 static unsigned short chip_addr[MAX_CHIPS];
  33 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  34 MODULE_PARM_DESC(chip_addr,
  35                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  36
  37 static unsigned long functionality = STUB_FUNC;
  38 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  39 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  40
  41 struct stub_chip {
  42         u8 pointer;
  43         u16 words[256];         /* Byte operations use the LSB as per SMBus
  44                                    specification */
  45 };
  46
  47 static struct stub_chip *stub_chips;
  48
  49 /* Return negative errno on error. */
  50 static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
  51         char read_write, u8 command, int size, union i2c_smbus_data *data)
  52 {
  53         s32 ret;
  54         int i, len;
  55         struct stub_chip *chip = NULL;
  56
  57         /* Search for the right chip */
  58         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
  59                 if (addr == chip_addr[i]) {
  60                         chip = stub_chips + i;
  61                         break;
  62                 }
  63         }
  64         if (!chip)
  65                 return -ENODEV;
  66
  67         switch (size) {
  68
  69         case I2C_SMBUS_QUICK:
  70                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
  71                 ret = 0;
  72                 break;
  73
  74         case I2C_SMBUS_BYTE:
  75                 if (read_write == I2C_SMBUS_WRITE) {
  76                         chip->pointer = command;
  77                         dev_dbg(&adap->dev,
  78                                 "smbus byte - addr 0x%02x, wrote 0x%02x.\n",
  79                                 addr, command);
  80                 } else {
  81                         data->byte = chip->words[chip->pointer++] & 0xff;
  82                         dev_dbg(&adap->dev,
  83                                 "smbus byte - addr 0x%02x, read  0x%02x.\n",
  84                                 addr, data->byte);
  85                 }
  86
  87                 ret = 0;
  88                 break;
  89
  90         case I2C_SMBUS_BYTE_DATA:
  91                 if (read_write == I2C_SMBUS_WRITE) {
  92                         chip->words[command] &= 0xff00;
  93                         chip->words[command] |= data->byte;
  94                         dev_dbg(&adap->dev,
  95                                 "smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
  96                                 addr, data->byte, command);
  97                 } else {
  98                         data->byte = chip->words[command] & 0xff;
  99                         dev_dbg(&adap->dev,
 100                                 "smbus byte data - addr 0x%02x, read  0x%02x at 0x%02x.\n",
 101                                 addr, data->byte, command);
 102                 }
 103                 chip->pointer = command + 1;
 104
 105                 ret = 0;
 106                 break;
 107
 108         case I2C_SMBUS_WORD_DATA:
 109                 if (read_write == I2C_SMBUS_WRITE) {
 110                         chip->words[command] = data->word;
 111                         dev_dbg(&adap->dev,
 112                                 "smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
 113                                 addr, data->word, command);
 114                 } else {
 115                         data->word = chip->words[command];
 116                         dev_dbg(&adap->dev,
 117                                 "smbus word data - addr 0x%02x, read  0x%04x at 0x%02x.\n",
 118                                 addr, data->word, command);
 119                 }
 120
 121                 ret = 0;
 122                 break;
 123
 124         case I2C_SMBUS_I2C_BLOCK_DATA:
 125                 len = data->block[0];
 126                 if (read_write == I2C_SMBUS_WRITE) {
 127                         for (i = 0; i < len; i++) {
 128                                 chip->words[command + i] &= 0xff00;
 129                                 chip->words[command + i] |= data->block[1 + i];
 130                         }
 131                         dev_dbg(&adap->dev,
 132                                 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 133                                 addr, len, command);
 134                 } else {
 135                         for (i = 0; i < len; i++) {
 136                                 data->block[1 + i] =
 137                                         chip->words[command + i] & 0xff;
 138                         }
 139                         dev_dbg(&adap->dev,
 140                                 "i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 141                                 addr, len, command);
 142                 }
 143
 144                 ret = 0;
 145                 break;
 146
 147         default:
 148                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 149                 ret = -EOPNOTSUPP;
 150                 break;
 151         } /* switch (size) */
 152
 153         return ret;
 154 }
 155
 156 static u32 stub_func(struct i2c_adapter *adapter)
 157 {
 158         return STUB_FUNC & functionality;
 159 }
 160
 161 static const struct i2c_algorithm smbus_algorithm = {
 162         .functionality  = stub_func,
 163         .smbus_xfer     = stub_xfer,
 164 };
 165
 166 static struct i2c_adapter stub_adapter = {
 167         .owner          = THIS_MODULE,
 168         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 169         .algo           = &smbus_algorithm,
 170         .name           = "SMBus stub driver",
 171 };
 172
 173 static int __init i2c_stub_init(void)
 174 {
 175         int i, ret;
 176
 177         if (!chip_addr[0]) {
 178                 pr_err("i2c-stub: Please specify a chip address\n");
 179                 return -ENODEV;
 180         }
 181
 182         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 183                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 184                         pr_err("i2c-stub: Invalid chip address 0x%02x\n",
 185                                chip_addr[i]);
 186                         return -EINVAL;
 187                 }
 188
 189                 pr_info("i2c-stub: Virtual chip at 0x%02x\n", chip_addr[i]);
 190         }
 191
 192         /* Allocate memory for all chips at once */
 193         stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
 194         if (!stub_chips) {
 195                 pr_err("i2c-stub: Out of memory\n");
 196                 return -ENOMEM;
 197         }
 198
 199         ret = i2c_add_adapter(&stub_adapter);
 200         if (ret)
 201                 kfree(stub_chips);
 202         return ret;
 203 }
 204
 205 static void __exit i2c_stub_exit(void)
 206 {
 207         i2c_del_adapter(&stub_adapter);
 208         kfree(stub_chips);
 209 }
 210
 211 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 212 MODULE_DESCRIPTION("I2C stub driver");
 213 MODULE_LICENSE("GPL");
 214
 215 module_init(i2c_stub_init);
 216 module_exit(i2c_stub_exit);