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     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 #include <linux/list.h>
  31
  32 #define MAX_CHIPS 10
  33
  34 /*
  35  * Support for I2C_FUNC_SMBUS_BLOCK_DATA is disabled by default and must
  36  * be enabled explicitly by setting the I2C_FUNC_SMBUS_BLOCK_DATA bits
  37  * in the 'functionality' module parameter.
  38  */
  39 #define STUB_FUNC_DEFAULT \
  40                 (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
  41                  I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
  42                  I2C_FUNC_SMBUS_I2C_BLOCK)
  43
  44 #define STUB_FUNC_ALL \
  45                 (STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA)
  46
  47 static unsigned short chip_addr[MAX_CHIPS];
  48 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  49 MODULE_PARM_DESC(chip_addr,
  50                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  51
  52 static unsigned long functionality = STUB_FUNC_DEFAULT;
  53 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  54 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  55
  56 /* Some chips have banked register ranges */
  57
  58 static u8 bank_reg[MAX_CHIPS];
  59 module_param_array(bank_reg, byte, NULL, S_IRUGO);
  60 MODULE_PARM_DESC(bank_reg, "Bank register");
  61
  62 static u8 bank_mask[MAX_CHIPS];
  63 module_param_array(bank_mask, byte, NULL, S_IRUGO);
  64 MODULE_PARM_DESC(bank_mask, "Bank value mask");
  65
  66 static u8 bank_start[MAX_CHIPS];
  67 module_param_array(bank_start, byte, NULL, S_IRUGO);
  68 MODULE_PARM_DESC(bank_start, "First banked register");
  69
  70 static u8 bank_end[MAX_CHIPS];
  71 module_param_array(bank_end, byte, NULL, S_IRUGO);
  72 MODULE_PARM_DESC(bank_end, "Last banked register");
  73
  74 struct smbus_block_data {
  75         struct list_head node;
  76         u8 command;
  77         u8 len;
  78         u8 block[I2C_SMBUS_BLOCK_MAX];
  79 };
  80
  81 struct stub_chip {
  82         u8 pointer;
  83         u16 words[256];         /* Byte operations use the LSB as per SMBus
  84                                    specification */
  85         struct list_head smbus_blocks;
  86
  87         /* For chips with banks, extra registers are allocated dynamically */
  88         u8 bank_reg;
  89         u8 bank_shift;
  90         u8 bank_mask;
  91         u8 bank_sel;            /* Currently selected bank */
  92         u8 bank_start;
  93         u8 bank_end;
  94         u16 bank_size;
  95         u16 *bank_words;        /* Room for bank_mask * bank_size registers */
  96 };
  97
  98 static struct stub_chip *stub_chips;
  99 static int stub_chips_nr;
 100
 101 static struct smbus_block_data *stub_find_block(struct device *dev,
 102                                                 struct stub_chip *chip,
 103                                                 u8 command, bool create)
 104 {
 105         struct smbus_block_data *b, *rb = NULL;
 106
 107         list_for_each_entry(b, &chip->smbus_blocks, node) {
 108                 if (b->command == command) {
 109                         rb = b;
 110                         break;
 111                 }
 112         }
 113         if (rb == NULL && create) {
 114                 rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL);
 115                 if (rb == NULL)
 116                         return rb;
 117                 rb->command = command;
 118                 list_add(&rb->node, &chip->smbus_blocks);
 119         }
 120         return rb;
 121 }
 122
 123 static u16 *stub_get_wordp(struct stub_chip *chip, u8 offset)
 124 {
 125         if (chip->bank_sel &&
 126             offset >= chip->bank_start && offset <= chip->bank_end)
 127                 return chip->bank_words +
 128                        (chip->bank_sel - 1) * chip->bank_size +
 129                        offset - chip->bank_start;
 130         else
 131                 return chip->words + offset;
 132 }
 133
 134 /* Return negative errno on error. */
 135 static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
 136         char read_write, u8 command, int size, union i2c_smbus_data *data)
 137 {
 138         s32 ret;
 139         int i, len;
 140         struct stub_chip *chip = NULL;
 141         struct smbus_block_data *b;
 142         u16 *wordp;
 143
 144         /* Search for the right chip */
 145         for (i = 0; i < stub_chips_nr; i++) {
 146                 if (addr == chip_addr[i]) {
 147                         chip = stub_chips + i;
 148                         break;
 149                 }
 150         }
 151         if (!chip)
 152                 return -ENODEV;
 153
 154         switch (size) {
 155
 156         case I2C_SMBUS_QUICK:
 157                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
 158                 ret = 0;
 159                 break;
 160
 161         case I2C_SMBUS_BYTE:
 162                 if (read_write == I2C_SMBUS_WRITE) {
 163                         chip->pointer = command;
 164                         dev_dbg(&adap->dev,
 165                                 "smbus byte - addr 0x%02x, wrote 0x%02x.\n",
 166                                 addr, command);
 167                 } else {
 168                         wordp = stub_get_wordp(chip, chip->pointer++);
 169                         data->byte = *wordp & 0xff;
 170                         dev_dbg(&adap->dev,
 171                                 "smbus byte - addr 0x%02x, read  0x%02x.\n",
 172                                 addr, data->byte);
 173                 }
 174
 175                 ret = 0;
 176                 break;
 177
 178         case I2C_SMBUS_BYTE_DATA:
 179                 wordp = stub_get_wordp(chip, command);
 180                 if (read_write == I2C_SMBUS_WRITE) {
 181                         *wordp &= 0xff00;
 182                         *wordp |= data->byte;
 183                         dev_dbg(&adap->dev,
 184                                 "smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
 185                                 addr, data->byte, command);
 186
 187                         /* Set the bank as needed */
 188                         if (chip->bank_words && command == chip->bank_reg) {
 189                                 chip->bank_sel =
 190                                         (data->byte >> chip->bank_shift)
 191                                         & chip->bank_mask;
 192                                 dev_dbg(&adap->dev,
 193                                         "switching to bank %u.\n",
 194                                         chip->bank_sel);
 195                         }
 196                 } else {
 197                         data->byte = *wordp & 0xff;
 198                         dev_dbg(&adap->dev,
 199                                 "smbus byte data - addr 0x%02x, read  0x%02x at 0x%02x.\n",
 200                                 addr, data->byte, command);
 201                 }
 202                 chip->pointer = command + 1;
 203
 204                 ret = 0;
 205                 break;
 206
 207         case I2C_SMBUS_WORD_DATA:
 208                 wordp = stub_get_wordp(chip, command);
 209                 if (read_write == I2C_SMBUS_WRITE) {
 210                         *wordp = data->word;
 211                         dev_dbg(&adap->dev,
 212                                 "smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
 213                                 addr, data->word, command);
 214                 } else {
 215                         data->word = *wordp;
 216                         dev_dbg(&adap->dev,
 217                                 "smbus word data - addr 0x%02x, read  0x%04x at 0x%02x.\n",
 218                                 addr, data->word, command);
 219                 }
 220
 221                 ret = 0;
 222                 break;
 223
 224         case I2C_SMBUS_I2C_BLOCK_DATA:
 225                 /*
 226                  * We ignore banks here, because banked chips don't use I2C
 227                  * block transfers
 228                  */
 229                 if (data->block[0] > 256 - command)     /* Avoid overrun */
 230                         data->block[0] = 256 - command;
 231                 len = data->block[0];
 232                 if (read_write == I2C_SMBUS_WRITE) {
 233                         for (i = 0; i < len; i++) {
 234                                 chip->words[command + i] &= 0xff00;
 235                                 chip->words[command + i] |= data->block[1 + i];
 236                         }
 237                         dev_dbg(&adap->dev,
 238                                 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 239                                 addr, len, command);
 240                 } else {
 241                         for (i = 0; i < len; i++) {
 242                                 data->block[1 + i] =
 243                                         chip->words[command + i] & 0xff;
 244                         }
 245                         dev_dbg(&adap->dev,
 246                                 "i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 247                                 addr, len, command);
 248                 }
 249
 250                 ret = 0;
 251                 break;
 252
 253         case I2C_SMBUS_BLOCK_DATA:
 254                 /*
 255                  * We ignore banks here, because chips typically don't use both
 256                  * banks and SMBus block transfers
 257                  */
 258                 b = stub_find_block(&adap->dev, chip, command, false);
 259                 if (read_write == I2C_SMBUS_WRITE) {
 260                         len = data->block[0];
 261                         if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
 262                                 ret = -EINVAL;
 263                                 break;
 264                         }
 265                         if (b == NULL) {
 266                                 b = stub_find_block(&adap->dev, chip, command,
 267                                                     true);
 268                                 if (b == NULL) {
 269                                         ret = -ENOMEM;
 270                                         break;
 271                                 }
 272                         }
 273                         /* Largest write sets read block length */
 274                         if (len > b->len)
 275                                 b->len = len;
 276                         for (i = 0; i < len; i++)
 277                                 b->block[i] = data->block[i + 1];
 278                         /* update for byte and word commands */
 279                         chip->words[command] = (b->block[0] << 8) | b->len;
 280                         dev_dbg(&adap->dev,
 281                                 "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 282                                 addr, len, command);
 283                 } else {
 284                         if (b == NULL) {
 285                                 dev_dbg(&adap->dev,
 286                                         "SMBus block read command without prior block write not supported\n");
 287                                 ret = -EOPNOTSUPP;
 288                                 break;
 289                         }
 290                         len = b->len;
 291                         data->block[0] = len;
 292                         for (i = 0; i < len; i++)
 293                                 data->block[i + 1] = b->block[i];
 294                         dev_dbg(&adap->dev,
 295                                 "smbus block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 296                                 addr, len, command);
 297                 }
 298
 299                 ret = 0;
 300                 break;
 301
 302         default:
 303                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 304                 ret = -EOPNOTSUPP;
 305                 break;
 306         } /* switch (size) */
 307
 308         return ret;
 309 }
 310
 311 static u32 stub_func(struct i2c_adapter *adapter)
 312 {
 313         return STUB_FUNC_ALL & functionality;
 314 }
 315
 316 static const struct i2c_algorithm smbus_algorithm = {
 317         .functionality  = stub_func,
 318         .smbus_xfer     = stub_xfer,
 319 };
 320
 321 static struct i2c_adapter stub_adapter = {
 322         .owner          = THIS_MODULE,
 323         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 324         .algo           = &smbus_algorithm,
 325         .name           = "SMBus stub driver",
 326 };
 327
 328 static int __init i2c_stub_allocate_banks(int i)
 329 {
 330         struct stub_chip *chip = stub_chips + i;
 331
 332         chip->bank_reg = bank_reg[i];
 333         chip->bank_start = bank_start[i];
 334         chip->bank_end = bank_end[i];
 335         chip->bank_size = bank_end[i] - bank_start[i] + 1;
 336
 337         /* We assume that all bits in the mask are contiguous */
 338         chip->bank_mask = bank_mask[i];
 339         while (!(chip->bank_mask & 1)) {
 340                 chip->bank_shift++;
 341                 chip->bank_mask >>= 1;
 342         }
 343
 344         chip->bank_words = kzalloc(chip->bank_mask * chip->bank_size *
 345                                    sizeof(u16), GFP_KERNEL);
 346         if (!chip->bank_words)
 347                 return -ENOMEM;
 348
 349         pr_debug("i2c-stub: Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n",
 350                  chip->bank_mask, chip->bank_size, chip->bank_start,
 351                  chip->bank_end);
 352
 353         return 0;
 354 }
 355
 356 static void i2c_stub_free(void)
 357 {
 358         int i;
 359
 360         for (i = 0; i < stub_chips_nr; i++)
 361                 kfree(stub_chips[i].bank_words);
 362         kfree(stub_chips);
 363 }
 364
 365 static int __init i2c_stub_init(void)
 366 {
 367         int i, ret;
 368
 369         if (!chip_addr[0]) {
 370                 pr_err("i2c-stub: Please specify a chip address\n");
 371                 return -ENODEV;
 372         }
 373
 374         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 375                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 376                         pr_err("i2c-stub: Invalid chip address 0x%02x\n",
 377                                chip_addr[i]);
 378                         return -EINVAL;
 379                 }
 380
 381                 pr_info("i2c-stub: Virtual chip at 0x%02x\n", chip_addr[i]);
 382         }
 383
 384         /* Allocate memory for all chips at once */
 385         stub_chips_nr = i;
 386         stub_chips = kcalloc(stub_chips_nr, sizeof(struct stub_chip),
 387                              GFP_KERNEL);
 388         if (!stub_chips) {
 389                 pr_err("i2c-stub: Out of memory\n");
 390                 return -ENOMEM;
 391         }
 392         for (i = 0; i < stub_chips_nr; i++) {
 393                 INIT_LIST_HEAD(&stub_chips[i].smbus_blocks);
 394
 395                 /* Allocate extra memory for banked register ranges */
 396                 if (bank_mask[i]) {
 397                         ret = i2c_stub_allocate_banks(i);
 398                         if (ret)
 399                                 goto fail_free;
 400                 }
 401         }
 402
 403         ret = i2c_add_adapter(&stub_adapter);
 404         if (ret)
 405                 goto fail_free;
 406
 407         return 0;
 408
 409  fail_free:
 410         i2c_stub_free();
 411         return ret;
 412 }
 413
 414 static void __exit i2c_stub_exit(void)
 415 {
 416         i2c_del_adapter(&stub_adapter);
 417         i2c_stub_free();
 418 }
 419
 420 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 421 MODULE_DESCRIPTION("I2C stub driver");
 422 MODULE_LICENSE("GPL");
 423
 424 module_init(i2c_stub_init);
 425 module_exit(i2c_stub_exit);