drivers/i2c/busses/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 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 #define STUB_FUNC (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
  33                    I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
  34                    I2C_FUNC_SMBUS_I2C_BLOCK)
  35
  36 static unsigned short chip_addr[MAX_CHIPS];
  37 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  38 MODULE_PARM_DESC(chip_addr,
  39                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  40
  41 static unsigned long functionality = STUB_FUNC;
  42 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  43 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  44
  45 struct stub_chip {
  46         u8 pointer;
  47         u16 words[256];         /* Byte operations use the LSB as per SMBus
  48                                    specification */
  49 };
  50
  51 static struct stub_chip *stub_chips;
  52
  53 /* Return negative errno on error. */
  54 static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
  55         char read_write, u8 command, int size, union i2c_smbus_data * data)
  56 {
  57         s32 ret;
  58         int i, len;
  59         struct stub_chip *chip = NULL;
  60
  61         /* Search for the right chip */
  62         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
  63                 if (addr == chip_addr[i]) {
  64                         chip = stub_chips + i;
  65                         break;
  66                 }
  67         }
  68         if (!chip)
  69                 return -ENODEV;
  70
  71         switch (size) {
  72
  73         case I2C_SMBUS_QUICK:
  74                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
  75                 ret = 0;
  76                 break;
  77
  78         case I2C_SMBUS_BYTE:
  79                 if (read_write == I2C_SMBUS_WRITE) {
  80                         chip->pointer = command;
  81                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  82                                         "wrote 0x%02x.\n",
  83                                         addr, command);
  84                 } else {
  85                         data->byte = chip->words[chip->pointer++] & 0xff;
  86                         dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
  87                                         "read  0x%02x.\n",
  88                                         addr, data->byte);
  89                 }
  90
  91                 ret = 0;
  92                 break;
  93
  94         case I2C_SMBUS_BYTE_DATA:
  95                 if (read_write == I2C_SMBUS_WRITE) {
  96                         chip->words[command] &= 0xff00;
  97                         chip->words[command] |= data->byte;
  98                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
  99                                         "wrote 0x%02x at 0x%02x.\n",
 100                                         addr, data->byte, command);
 101                 } else {
 102                         data->byte = chip->words[command] & 0xff;
 103                         dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
 104                                         "read  0x%02x at 0x%02x.\n",
 105                                         addr, data->byte, command);
 106                 }
 107                 chip->pointer = command + 1;
 108
 109                 ret = 0;
 110                 break;
 111
 112         case I2C_SMBUS_WORD_DATA:
 113                 if (read_write == I2C_SMBUS_WRITE) {
 114                         chip->words[command] = data->word;
 115                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
 116                                         "wrote 0x%04x at 0x%02x.\n",
 117                                         addr, data->word, command);
 118                 } else {
 119                         data->word = chip->words[command];
 120                         dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
 121                                         "read  0x%04x at 0x%02x.\n",
 122                                         addr, data->word, command);
 123                 }
 124
 125                 ret = 0;
 126                 break;
 127
 128         case I2C_SMBUS_I2C_BLOCK_DATA:
 129                 len = data->block[0];
 130                 if (read_write == I2C_SMBUS_WRITE) {
 131                         for (i = 0; i < len; i++) {
 132                                 chip->words[command + i] &= 0xff00;
 133                                 chip->words[command + i] |= data->block[1 + i];
 134                         }
 135                         dev_dbg(&adap->dev, "i2c block data - addr 0x%02x, "
 136                                         "wrote %d bytes at 0x%02x.\n",
 137                                         addr, len, command);
 138                 } else {
 139                         for (i = 0; i < len; i++) {
 140                                 data->block[1 + i] =
 141                                         chip->words[command + i] & 0xff;
 142                         }
 143                         dev_dbg(&adap->dev, "i2c block data - addr 0x%02x, "
 144                                         "read  %d bytes at 0x%02x.\n",
 145                                         addr, len, command);
 146                 }
 147
 148                 ret = 0;
 149                 break;
 150
 151         default:
 152                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 153                 ret = -EOPNOTSUPP;
 154                 break;
 155         } /* switch (size) */
 156
 157         return ret;
 158 }
 159
 160 static u32 stub_func(struct i2c_adapter *adapter)
 161 {
 162         return STUB_FUNC & functionality;
 163 }
 164
 165 static const struct i2c_algorithm smbus_algorithm = {
 166         .functionality  = stub_func,
 167         .smbus_xfer     = stub_xfer,
 168 };
 169
 170 static struct i2c_adapter stub_adapter = {
 171         .owner          = THIS_MODULE,
 172         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 173         .algo           = &smbus_algorithm,
 174         .name           = "SMBus stub driver",
 175 };
 176
 177 static int __init i2c_stub_init(void)
 178 {
 179         int i, ret;
 180
 181         if (!chip_addr[0]) {
 182                 printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
 183                 return -ENODEV;
 184         }
 185
 186         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 187                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 188                         printk(KERN_ERR "i2c-stub: Invalid chip address "
 189                                "0x%02x\n", chip_addr[i]);
 190                         return -EINVAL;
 191                 }
 192
 193                 printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n",
 194                        chip_addr[i]);
 195         }
 196
 197         /* Allocate memory for all chips at once */
 198         stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
 199         if (!stub_chips) {
 200                 printk(KERN_ERR "i2c-stub: Out of memory\n");
 201                 return -ENOMEM;
 202         }
 203
 204         ret = i2c_add_adapter(&stub_adapter);
 205         if (ret)
 206                 kfree(stub_chips);
 207         return ret;
 208 }
 209
 210 static void __exit i2c_stub_exit(void)
 211 {
 212         i2c_del_adapter(&stub_adapter);
 213         kfree(stub_chips);
 214 }
 215
 216 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 217 MODULE_DESCRIPTION("I2C stub driver");
 218 MODULE_LICENSE("GPL");
 219
 220 module_init(i2c_stub_init);
 221 module_exit(i2c_stub_exit);
 222