drivers/i2c/i2c-stub.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3     i2c-stub.c - I2C/SMBus chip emulator
   4
   5     Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
   6     Copyright (C) 2007-2014 Jean Delvare <jdelvare@suse.de>
   7
   8 */
   9
  10 #define pr_fmt(fmt) "i2c-stub: " fmt
  11
  12 #include <linux/errno.h>
  13 #include <linux/i2c.h>
  14 #include <linux/init.h>
  15 #include <linux/kernel.h>
  16 #include <linux/list.h>
  17 #include <linux/module.h>
  18 #include <linux/slab.h>
  19
  20 #define MAX_CHIPS 10
  21
  22 /*
  23  * Support for I2C_FUNC_SMBUS_BLOCK_DATA is disabled by default and must
  24  * be enabled explicitly by setting the I2C_FUNC_SMBUS_BLOCK_DATA bits
  25  * in the 'functionality' module parameter.
  26  */
  27 #define STUB_FUNC_DEFAULT \
  28                 (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 #define STUB_FUNC_ALL \
  33                 (STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA)
  34
  35 static unsigned short chip_addr[MAX_CHIPS];
  36 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
  37 MODULE_PARM_DESC(chip_addr,
  38                  "Chip addresses (up to 10, between 0x03 and 0x77)");
  39
  40 static unsigned long functionality = STUB_FUNC_DEFAULT;
  41 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  42 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  43
  44 /* Some chips have banked register ranges */
  45
  46 static u8 bank_reg[MAX_CHIPS];
  47 module_param_array(bank_reg, byte, NULL, S_IRUGO);
  48 MODULE_PARM_DESC(bank_reg, "Bank register");
  49
  50 static u8 bank_mask[MAX_CHIPS];
  51 module_param_array(bank_mask, byte, NULL, S_IRUGO);
  52 MODULE_PARM_DESC(bank_mask, "Bank value mask");
  53
  54 static u8 bank_start[MAX_CHIPS];
  55 module_param_array(bank_start, byte, NULL, S_IRUGO);
  56 MODULE_PARM_DESC(bank_start, "First banked register");
  57
  58 static u8 bank_end[MAX_CHIPS];
  59 module_param_array(bank_end, byte, NULL, S_IRUGO);
  60 MODULE_PARM_DESC(bank_end, "Last banked register");
  61
  62 struct smbus_block_data {
  63         struct list_head node;
  64         u8 command;
  65         u8 len;
  66         u8 block[I2C_SMBUS_BLOCK_MAX];
  67 };
  68
  69 struct stub_chip {
  70         u8 pointer;
  71         u16 words[256];         /* Byte operations use the LSB as per SMBus
  72                                    specification */
  73         struct list_head smbus_blocks;
  74
  75         /* For chips with banks, extra registers are allocated dynamically */
  76         u8 bank_reg;
  77         u8 bank_shift;
  78         u8 bank_mask;
  79         u8 bank_sel;            /* Currently selected bank */
  80         u8 bank_start;
  81         u8 bank_end;
  82         u16 bank_size;
  83         u16 *bank_words;        /* Room for bank_mask * bank_size registers */
  84 };
  85
  86 static struct stub_chip *stub_chips;
  87 static int stub_chips_nr;
  88
  89 static struct smbus_block_data *stub_find_block(struct device *dev,
  90                                                 struct stub_chip *chip,
  91                                                 u8 command, bool create)
  92 {
  93         struct smbus_block_data *b, *rb = NULL;
  94
  95         list_for_each_entry(b, &chip->smbus_blocks, node) {
  96                 if (b->command == command) {
  97                         rb = b;
  98                         break;
  99                 }
 100         }
 101         if (rb == NULL && create) {
 102                 rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL);
 103                 if (rb == NULL)
 104                         return rb;
 105                 rb->command = command;
 106                 list_add(&rb->node, &chip->smbus_blocks);
 107         }
 108         return rb;
 109 }
 110
 111 static u16 *stub_get_wordp(struct stub_chip *chip, u8 offset)
 112 {
 113         if (chip->bank_sel &&
 114             offset >= chip->bank_start && offset <= chip->bank_end)
 115                 return chip->bank_words +
 116                        (chip->bank_sel - 1) * chip->bank_size +
 117                        offset - chip->bank_start;
 118         else
 119                 return chip->words + offset;
 120 }
 121
 122 /* Return negative errno on error. */
 123 static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
 124         char read_write, u8 command, int size, union i2c_smbus_data *data)
 125 {
 126         s32 ret;
 127         int i, len;
 128         struct stub_chip *chip = NULL;
 129         struct smbus_block_data *b;
 130         u16 *wordp;
 131
 132         /* Search for the right chip */
 133         for (i = 0; i < stub_chips_nr; i++) {
 134                 if (addr == chip_addr[i]) {
 135                         chip = stub_chips + i;
 136                         break;
 137                 }
 138         }
 139         if (!chip)
 140                 return -ENODEV;
 141
 142         switch (size) {
 143
 144         case I2C_SMBUS_QUICK:
 145                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
 146                 ret = 0;
 147                 break;
 148
 149         case I2C_SMBUS_BYTE:
 150                 if (read_write == I2C_SMBUS_WRITE) {
 151                         chip->pointer = command;
 152                         dev_dbg(&adap->dev,
 153                                 "smbus byte - addr 0x%02x, wrote 0x%02x.\n",
 154                                 addr, command);
 155                 } else {
 156                         wordp = stub_get_wordp(chip, chip->pointer++);
 157                         data->byte = *wordp & 0xff;
 158                         dev_dbg(&adap->dev,
 159                                 "smbus byte - addr 0x%02x, read  0x%02x.\n",
 160                                 addr, data->byte);
 161                 }
 162
 163                 ret = 0;
 164                 break;
 165
 166         case I2C_SMBUS_BYTE_DATA:
 167                 wordp = stub_get_wordp(chip, command);
 168                 if (read_write == I2C_SMBUS_WRITE) {
 169                         *wordp &= 0xff00;
 170                         *wordp |= data->byte;
 171                         dev_dbg(&adap->dev,
 172                                 "smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
 173                                 addr, data->byte, command);
 174
 175                         /* Set the bank as needed */
 176                         if (chip->bank_words && command == chip->bank_reg) {
 177                                 chip->bank_sel =
 178                                         (data->byte >> chip->bank_shift)
 179                                         & chip->bank_mask;
 180                                 dev_dbg(&adap->dev,
 181                                         "switching to bank %u.\n",
 182                                         chip->bank_sel);
 183                         }
 184                 } else {
 185                         data->byte = *wordp & 0xff;
 186                         dev_dbg(&adap->dev,
 187                                 "smbus byte data - addr 0x%02x, read  0x%02x at 0x%02x.\n",
 188                                 addr, data->byte, command);
 189                 }
 190                 chip->pointer = command + 1;
 191
 192                 ret = 0;
 193                 break;
 194
 195         case I2C_SMBUS_WORD_DATA:
 196                 wordp = stub_get_wordp(chip, command);
 197                 if (read_write == I2C_SMBUS_WRITE) {
 198                         *wordp = data->word;
 199                         dev_dbg(&adap->dev,
 200                                 "smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
 201                                 addr, data->word, command);
 202                 } else {
 203                         data->word = *wordp;
 204                         dev_dbg(&adap->dev,
 205                                 "smbus word data - addr 0x%02x, read  0x%04x at 0x%02x.\n",
 206                                 addr, data->word, command);
 207                 }
 208
 209                 ret = 0;
 210                 break;
 211
 212         case I2C_SMBUS_I2C_BLOCK_DATA:
 213                 /*
 214                  * We ignore banks here, because banked chips don't use I2C
 215                  * block transfers
 216                  */
 217                 if (data->block[0] > 256 - command)     /* Avoid overrun */
 218                         data->block[0] = 256 - command;
 219                 len = data->block[0];
 220                 if (read_write == I2C_SMBUS_WRITE) {
 221                         for (i = 0; i < len; i++) {
 222                                 chip->words[command + i] &= 0xff00;
 223                                 chip->words[command + i] |= data->block[1 + i];
 224                         }
 225                         dev_dbg(&adap->dev,
 226                                 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 227                                 addr, len, command);
 228                 } else {
 229                         for (i = 0; i < len; i++) {
 230                                 data->block[1 + i] =
 231                                         chip->words[command + i] & 0xff;
 232                         }
 233                         dev_dbg(&adap->dev,
 234                                 "i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 235                                 addr, len, command);
 236                 }
 237
 238                 ret = 0;
 239                 break;
 240
 241         case I2C_SMBUS_BLOCK_DATA:
 242                 /*
 243                  * We ignore banks here, because chips typically don't use both
 244                  * banks and SMBus block transfers
 245                  */
 246                 b = stub_find_block(&adap->dev, chip, command, false);
 247                 if (read_write == I2C_SMBUS_WRITE) {
 248                         len = data->block[0];
 249                         if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
 250                                 ret = -EINVAL;
 251                                 break;
 252                         }
 253                         if (b == NULL) {
 254                                 b = stub_find_block(&adap->dev, chip, command,
 255                                                     true);
 256                                 if (b == NULL) {
 257                                         ret = -ENOMEM;
 258                                         break;
 259                                 }
 260                         }
 261                         /* Largest write sets read block length */
 262                         if (len > b->len)
 263                                 b->len = len;
 264                         for (i = 0; i < len; i++)
 265                                 b->block[i] = data->block[i + 1];
 266                         /* update for byte and word commands */
 267                         chip->words[command] = (b->block[0] << 8) | b->len;
 268                         dev_dbg(&adap->dev,
 269                                 "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 270                                 addr, len, command);
 271                 } else {
 272                         if (b == NULL) {
 273                                 dev_dbg(&adap->dev,
 274                                         "SMBus block read command without prior block write not supported\n");
 275                                 ret = -EOPNOTSUPP;
 276                                 break;
 277                         }
 278                         len = b->len;
 279                         data->block[0] = len;
 280                         for (i = 0; i < len; i++)
 281                                 data->block[i + 1] = b->block[i];
 282                         dev_dbg(&adap->dev,
 283                                 "smbus block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 284                                 addr, len, command);
 285                 }
 286
 287                 ret = 0;
 288                 break;
 289
 290         default:
 291                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 292                 ret = -EOPNOTSUPP;
 293                 break;
 294         } /* switch (size) */
 295
 296         return ret;
 297 }
 298
 299 static u32 stub_func(struct i2c_adapter *adapter)
 300 {
 301         return STUB_FUNC_ALL & functionality;
 302 }
 303
 304 static const struct i2c_algorithm smbus_algorithm = {
 305         .functionality  = stub_func,
 306         .smbus_xfer     = stub_xfer,
 307 };
 308
 309 static struct i2c_adapter stub_adapter = {
 310         .owner          = THIS_MODULE,
 311         .class          = I2C_CLASS_HWMON,
 312         .algo           = &smbus_algorithm,
 313         .name           = "SMBus stub driver",
 314 };
 315
 316 static int __init i2c_stub_allocate_banks(int i)
 317 {
 318         struct stub_chip *chip = stub_chips + i;
 319
 320         chip->bank_reg = bank_reg[i];
 321         chip->bank_start = bank_start[i];
 322         chip->bank_end = bank_end[i];
 323         chip->bank_size = bank_end[i] - bank_start[i] + 1;
 324
 325         /* We assume that all bits in the mask are contiguous */
 326         chip->bank_mask = bank_mask[i];
 327         while (!(chip->bank_mask & 1)) {
 328                 chip->bank_shift++;
 329                 chip->bank_mask >>= 1;
 330         }
 331
 332         chip->bank_words = kcalloc(chip->bank_mask * chip->bank_size,
 333                                    sizeof(u16),
 334                                    GFP_KERNEL);
 335         if (!chip->bank_words)
 336                 return -ENOMEM;
 337
 338         pr_debug("Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n",
 339                  chip->bank_mask, chip->bank_size, chip->bank_start,
 340                  chip->bank_end);
 341
 342         return 0;
 343 }
 344
 345 static void i2c_stub_free(void)
 346 {
 347         int i;
 348
 349         for (i = 0; i < stub_chips_nr; i++)
 350                 kfree(stub_chips[i].bank_words);
 351         kfree(stub_chips);
 352 }
 353
 354 static int __init i2c_stub_init(void)
 355 {
 356         int i, ret;
 357
 358         if (!chip_addr[0]) {
 359                 pr_err("Please specify a chip address\n");
 360                 return -ENODEV;
 361         }
 362
 363         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 364                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 365                         pr_err("Invalid chip address 0x%02x\n",
 366                                chip_addr[i]);
 367                         return -EINVAL;
 368                 }
 369
 370                 pr_info("Virtual chip at 0x%02x\n", chip_addr[i]);
 371         }
 372
 373         /* Allocate memory for all chips at once */
 374         stub_chips_nr = i;
 375         stub_chips = kcalloc(stub_chips_nr, sizeof(struct stub_chip),
 376                              GFP_KERNEL);
 377         if (!stub_chips)
 378                 return -ENOMEM;
 379
 380         for (i = 0; i < stub_chips_nr; i++) {
 381                 INIT_LIST_HEAD(&stub_chips[i].smbus_blocks);
 382
 383                 /* Allocate extra memory for banked register ranges */
 384                 if (bank_mask[i]) {
 385                         ret = i2c_stub_allocate_banks(i);
 386                         if (ret)
 387                                 goto fail_free;
 388                 }
 389         }
 390
 391         ret = i2c_add_adapter(&stub_adapter);
 392         if (ret)
 393                 goto fail_free;
 394
 395         return 0;
 396
 397  fail_free:
 398         i2c_stub_free();
 399         return ret;
 400 }
 401
 402 static void __exit i2c_stub_exit(void)
 403 {
 404         i2c_del_adapter(&stub_adapter);
 405         i2c_stub_free();
 406 }
 407
 408 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 409 MODULE_DESCRIPTION("I2C stub driver");
 410 MODULE_LICENSE("GPL");
 411
 412 module_init(i2c_stub_init);
 413 module_exit(i2c_stub_exit);