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