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 DEBUG 1
  11 #define pr_fmt(fmt) "i2c-stub: " fmt
  12
  13 #include <linux/errno.h>
  14 #include <linux/i2c.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/list.h>
  18 #include <linux/module.h>
  19 #include <linux/slab.h>
  20
  21 #define MAX_CHIPS 10
  22
  23 /*
  24  * Support for I2C_FUNC_SMBUS_BLOCK_DATA is disabled by default and must
  25  * be enabled explicitly by setting the I2C_FUNC_SMBUS_BLOCK_DATA bits
  26  * in the 'functionality' module parameter.
  27  */
  28 #define STUB_FUNC_DEFAULT \
  29                 (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
  30                  I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
  31                  I2C_FUNC_SMBUS_I2C_BLOCK)
  32
  33 #define STUB_FUNC_ALL \
  34                 (STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA)
  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_DEFAULT;
  42 module_param(functionality, ulong, S_IRUGO | S_IWUSR);
  43 MODULE_PARM_DESC(functionality, "Override functionality bitfield");
  44
  45 /* Some chips have banked register ranges */
  46
  47 static u8 bank_reg[MAX_CHIPS];
  48 module_param_array(bank_reg, byte, NULL, S_IRUGO);
  49 MODULE_PARM_DESC(bank_reg, "Bank register");
  50
  51 static u8 bank_mask[MAX_CHIPS];
  52 module_param_array(bank_mask, byte, NULL, S_IRUGO);
  53 MODULE_PARM_DESC(bank_mask, "Bank value mask");
  54
  55 static u8 bank_start[MAX_CHIPS];
  56 module_param_array(bank_start, byte, NULL, S_IRUGO);
  57 MODULE_PARM_DESC(bank_start, "First banked register");
  58
  59 static u8 bank_end[MAX_CHIPS];
  60 module_param_array(bank_end, byte, NULL, S_IRUGO);
  61 MODULE_PARM_DESC(bank_end, "Last banked register");
  62
  63 struct smbus_block_data {
  64         struct list_head node;
  65         u8 command;
  66         u8 len;
  67         u8 block[I2C_SMBUS_BLOCK_MAX];
  68 };
  69
  70 struct stub_chip {
  71         u8 pointer;
  72         u16 words[256];         /* Byte operations use the LSB as per SMBus
  73                                    specification */
  74         struct list_head smbus_blocks;
  75
  76         /* For chips with banks, extra registers are allocated dynamically */
  77         u8 bank_reg;
  78         u8 bank_shift;
  79         u8 bank_mask;
  80         u8 bank_sel;            /* Currently selected bank */
  81         u8 bank_start;
  82         u8 bank_end;
  83         u16 bank_size;
  84         u16 *bank_words;        /* Room for bank_mask * bank_size registers */
  85 };
  86
  87 static struct stub_chip *stub_chips;
  88 static int stub_chips_nr;
  89
  90 static struct smbus_block_data *stub_find_block(struct device *dev,
  91                                                 struct stub_chip *chip,
  92                                                 u8 command, bool create)
  93 {
  94         struct smbus_block_data *b, *rb = NULL;
  95
  96         list_for_each_entry(b, &chip->smbus_blocks, node) {
  97                 if (b->command == command) {
  98                         rb = b;
  99                         break;
 100                 }
 101         }
 102         if (rb == NULL && create) {
 103                 rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL);
 104                 if (rb == NULL)
 105                         return rb;
 106                 rb->command = command;
 107                 list_add(&rb->node, &chip->smbus_blocks);
 108         }
 109         return rb;
 110 }
 111
 112 static u16 *stub_get_wordp(struct stub_chip *chip, u8 offset)
 113 {
 114         if (chip->bank_sel &&
 115             offset >= chip->bank_start && offset <= chip->bank_end)
 116                 return chip->bank_words +
 117                        (chip->bank_sel - 1) * chip->bank_size +
 118                        offset - chip->bank_start;
 119         else
 120                 return chip->words + offset;
 121 }
 122
 123 /* Return negative errno on error. */
 124 static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
 125         char read_write, u8 command, int size, union i2c_smbus_data *data)
 126 {
 127         s32 ret;
 128         int i, len;
 129         struct stub_chip *chip = NULL;
 130         struct smbus_block_data *b;
 131         u16 *wordp;
 132
 133         /* Search for the right chip */
 134         for (i = 0; i < stub_chips_nr; i++) {
 135                 if (addr == chip_addr[i]) {
 136                         chip = stub_chips + i;
 137                         break;
 138                 }
 139         }
 140         if (!chip)
 141                 return -ENODEV;
 142
 143         switch (size) {
 144
 145         case I2C_SMBUS_QUICK:
 146                 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
 147                 ret = 0;
 148                 break;
 149
 150         case I2C_SMBUS_BYTE:
 151                 if (read_write == I2C_SMBUS_WRITE) {
 152                         chip->pointer = command;
 153                         dev_dbg(&adap->dev,
 154                                 "smbus byte - addr 0x%02x, wrote 0x%02x.\n",
 155                                 addr, command);
 156                 } else {
 157                         wordp = stub_get_wordp(chip, chip->pointer++);
 158                         data->byte = *wordp & 0xff;
 159                         dev_dbg(&adap->dev,
 160                                 "smbus byte - addr 0x%02x, read  0x%02x.\n",
 161                                 addr, data->byte);
 162                 }
 163
 164                 ret = 0;
 165                 break;
 166
 167         case I2C_SMBUS_BYTE_DATA:
 168                 wordp = stub_get_wordp(chip, command);
 169                 if (read_write == I2C_SMBUS_WRITE) {
 170                         *wordp &= 0xff00;
 171                         *wordp |= data->byte;
 172                         dev_dbg(&adap->dev,
 173                                 "smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
 174                                 addr, data->byte, command);
 175
 176                         /* Set the bank as needed */
 177                         if (chip->bank_words && command == chip->bank_reg) {
 178                                 chip->bank_sel =
 179                                         (data->byte >> chip->bank_shift)
 180                                         & chip->bank_mask;
 181                                 dev_dbg(&adap->dev,
 182                                         "switching to bank %u.\n",
 183                                         chip->bank_sel);
 184                         }
 185                 } else {
 186                         data->byte = *wordp & 0xff;
 187                         dev_dbg(&adap->dev,
 188                                 "smbus byte data - addr 0x%02x, read  0x%02x at 0x%02x.\n",
 189                                 addr, data->byte, command);
 190                 }
 191                 chip->pointer = command + 1;
 192
 193                 ret = 0;
 194                 break;
 195
 196         case I2C_SMBUS_WORD_DATA:
 197                 wordp = stub_get_wordp(chip, command);
 198                 if (read_write == I2C_SMBUS_WRITE) {
 199                         *wordp = data->word;
 200                         dev_dbg(&adap->dev,
 201                                 "smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
 202                                 addr, data->word, command);
 203                 } else {
 204                         data->word = *wordp;
 205                         dev_dbg(&adap->dev,
 206                                 "smbus word data - addr 0x%02x, read  0x%04x at 0x%02x.\n",
 207                                 addr, data->word, command);
 208                 }
 209
 210                 ret = 0;
 211                 break;
 212
 213         case I2C_SMBUS_I2C_BLOCK_DATA:
 214                 /*
 215                  * We ignore banks here, because banked chips don't use I2C
 216                  * block transfers
 217                  */
 218                 if (data->block[0] > 256 - command)     /* Avoid overrun */
 219                         data->block[0] = 256 - command;
 220                 len = data->block[0];
 221                 if (read_write == I2C_SMBUS_WRITE) {
 222                         for (i = 0; i < len; i++) {
 223                                 chip->words[command + i] &= 0xff00;
 224                                 chip->words[command + i] |= data->block[1 + i];
 225                         }
 226                         dev_dbg(&adap->dev,
 227                                 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 228                                 addr, len, command);
 229                 } else {
 230                         for (i = 0; i < len; i++) {
 231                                 data->block[1 + i] =
 232                                         chip->words[command + i] & 0xff;
 233                         }
 234                         dev_dbg(&adap->dev,
 235                                 "i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 236                                 addr, len, command);
 237                 }
 238
 239                 ret = 0;
 240                 break;
 241
 242         case I2C_SMBUS_BLOCK_DATA:
 243                 /*
 244                  * We ignore banks here, because chips typically don't use both
 245                  * banks and SMBus block transfers
 246                  */
 247                 b = stub_find_block(&adap->dev, chip, command, false);
 248                 if (read_write == I2C_SMBUS_WRITE) {
 249                         len = data->block[0];
 250                         if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
 251                                 ret = -EINVAL;
 252                                 break;
 253                         }
 254                         if (b == NULL) {
 255                                 b = stub_find_block(&adap->dev, chip, command,
 256                                                     true);
 257                                 if (b == NULL) {
 258                                         ret = -ENOMEM;
 259                                         break;
 260                                 }
 261                         }
 262                         /* Largest write sets read block length */
 263                         if (len > b->len)
 264                                 b->len = len;
 265                         for (i = 0; i < len; i++)
 266                                 b->block[i] = data->block[i + 1];
 267                         /* update for byte and word commands */
 268                         chip->words[command] = (b->block[0] << 8) | b->len;
 269                         dev_dbg(&adap->dev,
 270                                 "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
 271                                 addr, len, command);
 272                 } else {
 273                         if (b == NULL) {
 274                                 dev_dbg(&adap->dev,
 275                                         "SMBus block read command without prior block write not supported\n");
 276                                 ret = -EOPNOTSUPP;
 277                                 break;
 278                         }
 279                         len = b->len;
 280                         data->block[0] = len;
 281                         for (i = 0; i < len; i++)
 282                                 data->block[i + 1] = b->block[i];
 283                         dev_dbg(&adap->dev,
 284                                 "smbus block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
 285                                 addr, len, command);
 286                 }
 287
 288                 ret = 0;
 289                 break;
 290
 291         default:
 292                 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
 293                 ret = -EOPNOTSUPP;
 294                 break;
 295         } /* switch (size) */
 296
 297         return ret;
 298 }
 299
 300 static u32 stub_func(struct i2c_adapter *adapter)
 301 {
 302         return STUB_FUNC_ALL & functionality;
 303 }
 304
 305 static const struct i2c_algorithm smbus_algorithm = {
 306         .functionality  = stub_func,
 307         .smbus_xfer     = stub_xfer,
 308 };
 309
 310 static struct i2c_adapter stub_adapter = {
 311         .owner          = THIS_MODULE,
 312         .class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
 313         .algo           = &smbus_algorithm,
 314         .name           = "SMBus stub driver",
 315 };
 316
 317 static int __init i2c_stub_allocate_banks(int i)
 318 {
 319         struct stub_chip *chip = stub_chips + i;
 320
 321         chip->bank_reg = bank_reg[i];
 322         chip->bank_start = bank_start[i];
 323         chip->bank_end = bank_end[i];
 324         chip->bank_size = bank_end[i] - bank_start[i] + 1;
 325
 326         /* We assume that all bits in the mask are contiguous */
 327         chip->bank_mask = bank_mask[i];
 328         while (!(chip->bank_mask & 1)) {
 329                 chip->bank_shift++;
 330                 chip->bank_mask >>= 1;
 331         }
 332
 333         chip->bank_words = kcalloc(chip->bank_mask * chip->bank_size,
 334                                    sizeof(u16),
 335                                    GFP_KERNEL);
 336         if (!chip->bank_words)
 337                 return -ENOMEM;
 338
 339         pr_debug("Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n",
 340                  chip->bank_mask, chip->bank_size, chip->bank_start,
 341                  chip->bank_end);
 342
 343         return 0;
 344 }
 345
 346 static void i2c_stub_free(void)
 347 {
 348         int i;
 349
 350         for (i = 0; i < stub_chips_nr; i++)
 351                 kfree(stub_chips[i].bank_words);
 352         kfree(stub_chips);
 353 }
 354
 355 static int __init i2c_stub_init(void)
 356 {
 357         int i, ret;
 358
 359         if (!chip_addr[0]) {
 360                 pr_err("Please specify a chip address\n");
 361                 return -ENODEV;
 362         }
 363
 364         for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
 365                 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
 366                         pr_err("Invalid chip address 0x%02x\n",
 367                                chip_addr[i]);
 368                         return -EINVAL;
 369                 }
 370
 371                 pr_info("Virtual chip at 0x%02x\n", chip_addr[i]);
 372         }
 373
 374         /* Allocate memory for all chips at once */
 375         stub_chips_nr = i;
 376         stub_chips = kcalloc(stub_chips_nr, sizeof(struct stub_chip),
 377                              GFP_KERNEL);
 378         if (!stub_chips)
 379                 return -ENOMEM;
 380
 381         for (i = 0; i < stub_chips_nr; i++) {
 382                 INIT_LIST_HEAD(&stub_chips[i].smbus_blocks);
 383
 384                 /* Allocate extra memory for banked register ranges */
 385                 if (bank_mask[i]) {
 386                         ret = i2c_stub_allocate_banks(i);
 387                         if (ret)
 388                                 goto fail_free;
 389                 }
 390         }
 391
 392         ret = i2c_add_adapter(&stub_adapter);
 393         if (ret)
 394                 goto fail_free;
 395
 396         return 0;
 397
 398  fail_free:
 399         i2c_stub_free();
 400         return ret;
 401 }
 402
 403 static void __exit i2c_stub_exit(void)
 404 {
 405         i2c_del_adapter(&stub_adapter);
 406         i2c_stub_free();
 407 }
 408
 409 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 410 MODULE_DESCRIPTION("I2C stub driver");
 411 MODULE_LICENSE("GPL");
 412
 413 module_init(i2c_stub_init);
 414 module_exit(i2c_stub_exit);