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) 2007-2014 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
  19 #define pr_fmt(fmt) "i2c-stub: " fmt
  20
  21 #include <linux/errno.h>
  22 #include <linux/i2c.h>
  23 #include <linux/init.h>
  24 #include <linux/kernel.h>
  25 #include <linux/list.h>
  26 #include <linux/module.h>
  27 #include <linux/slab.h>
  28
  29 #define MAX_CHIPS 10
  30
  31 /*
  32  * Support for I2C_FUNC_SMBUS_BLOCK_DATA is disabled by default and must
  33  * be enabled explicitly by setting the I2C_FUNC_SMBUS_BLOCK_DATA bits
  34  * in the 'functionality' module parameter.
  35  */
  36 #define STUB_FUNC_DEFAULT \
  37                 (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
  38                  I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
  39                  I2C_FUNC_SMBUS_I2C_BLOCK)
  40
  41 #define STUB_FUNC_ALL \
  42                 (STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA)
  43
  44 static unsigned short chip_addr[MAX_CHIPS];
  45 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  46 MODULE_PARM_DESC(chip_addr,
  47                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  48
  49 static unsigned long functionality = STUB_FUNC_DEFAULT;
  50 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  51 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  52
  53 /* Some chips have banked register ranges */
  54
  55 static u8 bank_reg[MAX_CHIPS];
  56 module_param_array(bank_reg, byte, NULL, S_IRUGO);
  57 MODULE_PARM_DESC(bank_reg, "Bank register");
  58
  59 static u8 bank_mask[MAX_CHIPS];
  60 module_param_array(bank_mask, byte, NULL, S_IRUGO);
  61 MODULE_PARM_DESC(bank_mask, "Bank value mask");
  62
  63 static u8 bank_start[MAX_CHIPS];
  64 module_param_array(bank_start, byte, NULL, S_IRUGO);
  65 MODULE_PARM_DESC(bank_start, "First banked register");
  66
  67 static u8 bank_end[MAX_CHIPS];
  68 module_param_array(bank_end, byte, NULL, S_IRUGO);
  69 MODULE_PARM_DESC(bank_end, "Last banked register");
  70
  71 struct smbus_block_data {
  72         struct list_head node;
  73         u8 command;
  74         u8 len;
  75         u8 block[I2C_SMBUS_BLOCK_MAX];
  76 };
  77
  78 struct stub_chip {
  79         u8 pointer;
  80         u16 words[256];         /* Byte operations use the LSB as per SMBus
  81                                    specification */
  82         struct list_head smbus_blocks;
  83
  84         /* For chips with banks, extra registers are allocated dynamically */
  85         u8 bank_reg;
  86         u8 bank_shift;
  87         u8 bank_mask;
  88         u8 bank_sel;            /* Currently selected bank */
  89         u8 bank_start;
  90         u8 bank_end;
  91         u16 bank_size;
  92         u16 *bank_words;        /* Room for bank_mask * bank_size registers */
  93 };
  94
  95 static struct stub_chip *stub_chips;
  96 static int stub_chips_nr;
  97
  98 static struct smbus_block_data *stub_find_block(struct device *dev,
  99                                                 struct stub_chip *chip,
 100                                                 u8 command, bool create)
 101 {
 102         struct smbus_block_data *b, *rb = NULL;
 103
 104         list_for_each_entry(b, &chip->smbus_blocks, node) {
 105                 if (b->command == command) {
 106                         rb = b;
 107                         break;
 108                 }
 109         }
 110         if (rb == NULL && create) {
 111                 rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL);
 112                 if (rb == NULL)
 113                         return rb;
 114                 rb->command = command;
 115                 list_add(&rb->node, &chip->smbus_blocks);
 116         }
 117         return rb;
 118 }
 119
 120 static u16 *stub_get_wordp(struct stub_chip *chip, u8 offset)
 121 {
 122         if (chip->bank_sel &&
 123             offset >= chip->bank_start && offset <= chip->bank_end)
 124                 return chip->bank_words +
 125                        (chip->bank_sel - 1) * chip->bank_size +
 126                        offset - chip->bank_start;
 127         else
 128                 return chip->words + offset;
 129 }
 130
 131 /* Return negative errno on error. */
 132 static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
 133         char read_write, u8 command, int size, union i2c_smbus_data *data)
 134 {
 135         s32 ret;
 136         int i, len;
 137         struct stub_chip *chip = NULL;
 138         struct smbus_block_data *b;
 139         u16 *wordp;
 140
 141         /* Search for the right chip */
 142         for (i = 0; i < stub_chips_nr; i++) {
 143                 if (addr == chip_addr[i]) {
 144                         chip = stub_chips + i;
 145                         break;
 146                 }
 147         }
 148         if (!chip)
 149                 return -ENODEV;
 150
 151         switch (size) {
 152
 153         case I2C_SMBUS_QUICK:
 154                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
 155                 ret = 0;
 156                 break;
 157
 158         case I2C_SMBUS_BYTE:
 159                 if (read_write == I2C_SMBUS_WRITE) {
 160                         chip->pointer = command;
 161                         dev_dbg(&adap->dev,
 162                                 "smbus byte - addr 0x%02x, wrote 0x%02x.\n",
 163                                 addr, command);
 164                 } else {
 165                         wordp = stub_get_wordp(chip, chip->pointer++);
 166                         data->byte = *wordp & 0xff;
 167                         dev_dbg(&adap->dev,
 168                                 "smbus byte - addr 0x%02x, read  0x%02x.\n",
 169                                 addr, data->byte);
 170                 }
 171
 172                 ret = 0;
 173                 break;
 174
 175         case I2C_SMBUS_BYTE_DATA:
 176                 wordp = stub_get_wordp(chip, command);
 177                 if (read_write == I2C_SMBUS_WRITE) {
 178                         *wordp &= 0xff00;
 179                         *wordp |= data->byte;
 180                         dev_dbg(&adap->dev,
 181                                 "smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
 182                                 addr, data->byte, command);
 183
 184                         /* Set the bank as needed */
 185                         if (chip->bank_words && command == chip->bank_reg) {
 186                                 chip->bank_sel =
 187                                         (data->byte >> chip->bank_shift)
 188                                         & chip->bank_mask;
 189                                 dev_dbg(&adap->dev,
 190                                         "switching to bank %u.\n",
 191                                         chip->bank_sel);
 192                         }
 193                 } else {
 194                         data->byte = *wordp & 0xff;
 195                         dev_dbg(&adap->dev,
 196                                 "smbus byte data - addr 0x%02x, read  0x%02x at 0x%02x.\n",
 197                                 addr, data->byte, command);
 198                 }
 199                 chip->pointer = command + 1;
 200
 201                 ret = 0;
 202                 break;
 203
 204         case I2C_SMBUS_WORD_DATA:
 205                 wordp = stub_get_wordp(chip, command);
 206                 if (read_write == I2C_SMBUS_WRITE) {
 207                         *wordp = data->word;
 208                         dev_dbg(&adap->dev,
 209                                 "smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
 210                                 addr, data->word, command);
 211                 } else {
 212                         data->word = *wordp;
 213                         dev_dbg(&adap->dev,
 214                                 "smbus word data - addr 0x%02x, read  0x%04x at 0x%02x.\n",
 215                                 addr, data->word, command);
 216                 }
 217
 218                 ret = 0;
 219                 break;
 220
 221         case I2C_SMBUS_I2C_BLOCK_DATA:
 222                 /*
 223                  * We ignore banks here, because banked chips don't use I2C
 224                  * block transfers
 225                  */
 226                 if (data->block[0] > 256 - command)     /* Avoid overrun */
 227                         data->block[0] = 256 - command;
 228                 len = data->block[0];
 229                 if (read_write == I2C_SMBUS_WRITE) {
 230                         for (i = 0; i < len; i++) {
 231                                 chip->words[command + i] &= 0xff00;
 232                                 chip->words[command + i] |= data->block[1 + i];
 233                         }
 234                         dev_dbg(&adap->dev,
 235                                 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 236                                 addr, len, command);
 237                 } else {
 238                         for (i = 0; i < len; i++) {
 239                                 data->block[1 + i] =
 240                                         chip->words[command + i] & 0xff;
 241                         }
 242                         dev_dbg(&adap->dev,
 243                                 "i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 244                                 addr, len, command);
 245                 }
 246
 247                 ret = 0;
 248                 break;
 249
 250         case I2C_SMBUS_BLOCK_DATA:
 251                 /*
 252                  * We ignore banks here, because chips typically don't use both
 253                  * banks and SMBus block transfers
 254                  */
 255                 b = stub_find_block(&adap->dev, chip, command, false);
 256                 if (read_write == I2C_SMBUS_WRITE) {
 257                         len = data->block[0];
 258                         if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
 259                                 ret = -EINVAL;
 260                                 break;
 261                         }
 262                         if (b == NULL) {
 263                                 b = stub_find_block(&adap->dev, chip, command,
 264                                                     true);
 265                                 if (b == NULL) {
 266                                         ret = -ENOMEM;
 267                                         break;
 268                                 }
 269                         }
 270                         /* Largest write sets read block length */
 271                         if (len > b->len)
 272                                 b->len = len;
 273                         for (i = 0; i < len; i++)
 274                                 b->block[i] = data->block[i + 1];
 275                         /* update for byte and word commands */
 276                         chip->words[command] = (b->block[0] << 8) | b->len;
 277                         dev_dbg(&adap->dev,
 278                                 "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 279                                 addr, len, command);
 280                 } else {
 281                         if (b == NULL) {
 282                                 dev_dbg(&adap->dev,
 283                                         "SMBus block read command without prior block write not supported\n");
 284                                 ret = -EOPNOTSUPP;
 285                                 break;
 286                         }
 287                         len = b->len;
 288                         data->block[0] = len;
 289                         for (i = 0; i < len; i++)
 290                                 data->block[i + 1] = b->block[i];
 291                         dev_dbg(&adap->dev,
 292                                 "smbus block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 293                                 addr, len, command);
 294                 }
 295
 296                 ret = 0;
 297                 break;
 298
 299         default:
 300                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 301                 ret = -EOPNOTSUPP;
 302                 break;
 303         } /* switch (size) */
 304
 305         return ret;
 306 }
 307
 308 static u32 stub_func(struct i2c_adapter *adapter)
 309 {
 310         return STUB_FUNC_ALL & functionality;
 311 }
 312
 313 static const struct i2c_algorithm smbus_algorithm = {
 314         .functionality  = stub_func,
 315         .smbus_xfer     = stub_xfer,
 316 };
 317
 318 static struct i2c_adapter stub_adapter = {
 319         .owner          = THIS_MODULE,
 320         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 321         .algo           = &smbus_algorithm,
 322         .name           = "SMBus stub driver",
 323 };
 324
 325 static int __init i2c_stub_allocate_banks(int i)
 326 {
 327         struct stub_chip *chip = stub_chips + i;
 328
 329         chip->bank_reg = bank_reg[i];
 330         chip->bank_start = bank_start[i];
 331         chip->bank_end = bank_end[i];
 332         chip->bank_size = bank_end[i] - bank_start[i] + 1;
 333
 334         /* We assume that all bits in the mask are contiguous */
 335         chip->bank_mask = bank_mask[i];
 336         while (!(chip->bank_mask & 1)) {
 337                 chip->bank_shift++;
 338                 chip->bank_mask >>= 1;
 339         }
 340
 341         chip->bank_words = kzalloc(chip->bank_mask * chip->bank_size *
 342                                    sizeof(u16), GFP_KERNEL);
 343         if (!chip->bank_words)
 344                 return -ENOMEM;
 345
 346         pr_debug("Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n",
 347                  chip->bank_mask, chip->bank_size, chip->bank_start,
 348                  chip->bank_end);
 349
 350         return 0;
 351 }
 352
 353 static void i2c_stub_free(void)
 354 {
 355         int i;
 356
 357         for (i = 0; i < stub_chips_nr; i++)
 358                 kfree(stub_chips[i].bank_words);
 359         kfree(stub_chips);
 360 }
 361
 362 static int __init i2c_stub_init(void)
 363 {
 364         int i, ret;
 365
 366         if (!chip_addr[0]) {
 367                 pr_err("Please specify a chip address\n");
 368                 return -ENODEV;
 369         }
 370
 371         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 372                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 373                         pr_err("Invalid chip address 0x%02x\n",
 374                                chip_addr[i]);
 375                         return -EINVAL;
 376                 }
 377
 378                 pr_info("Virtual chip at 0x%02x\n", chip_addr[i]);
 379         }
 380
 381         /* Allocate memory for all chips at once */
 382         stub_chips_nr = i;
 383         stub_chips = kcalloc(stub_chips_nr, sizeof(struct stub_chip),
 384                              GFP_KERNEL);
 385         if (!stub_chips)
 386                 return -ENOMEM;
 387
 388         for (i = 0; i < stub_chips_nr; i++) {
 389                 INIT_LIST_HEAD(&stub_chips[i].smbus_blocks);
 390
 391                 /* Allocate extra memory for banked register ranges */
 392                 if (bank_mask[i]) {
 393                         ret = i2c_stub_allocate_banks(i);
 394                         if (ret)
 395                                 goto fail_free;
 396                 }
 397         }
 398
 399         ret = i2c_add_adapter(&stub_adapter);
 400         if (ret)
 401                 goto fail_free;
 402
 403         return 0;
 404
 405  fail_free:
 406         i2c_stub_free();
 407         return ret;
 408 }
 409
 410 static void __exit i2c_stub_exit(void)
 411 {
 412         i2c_del_adapter(&stub_adapter);
 413         i2c_stub_free();
 414 }
 415
 416 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 417 MODULE_DESCRIPTION("I2C stub driver");
 418 MODULE_LICENSE("GPL");
 419
 420 module_init(i2c_stub_init);
 421 module_exit(i2c_stub_exit);