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] == 0 || 218 data->block[0] > I2C_SMBUS_BLOCK_MAX) { 219 ret = -EINVAL; 220 break; 221 } 222 if (data->block[0] > 256 - command) /* Avoid overrun */ 223 data->block[0] = 256 - command; 224 len = data->block[0]; 225 if (read_write == I2C_SMBUS_WRITE) { 226 for (i = 0; i < len; i++) { 227 chip->words[command + i] &= 0xff00; 228 chip->words[command + i] |= data->block[1 + i]; 229 } 230 dev_dbg(&adap->dev, 231 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n", 232 addr, len, command); 233 } else { 234 for (i = 0; i < len; i++) { 235 data->block[1 + i] = 236 chip->words[command + i] & 0xff; 237 } 238 dev_dbg(&adap->dev, 239 "i2c block data - addr 0x%02x, read %d bytes at 0x%02x.\n", 240 addr, len, command); 241 } 242 243 ret = 0; 244 break; 245 246 case I2C_SMBUS_BLOCK_DATA: 247 /* 248 * We ignore banks here, because chips typically don't use both 249 * banks and SMBus block transfers 250 */ 251 b = stub_find_block(&adap->dev, chip, command, false); 252 if (read_write == I2C_SMBUS_WRITE) { 253 len = data->block[0]; 254 if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) { 255 ret = -EINVAL; 256 break; 257 } 258 if (b == NULL) { 259 b = stub_find_block(&adap->dev, chip, command, 260 true); 261 if (b == NULL) { 262 ret = -ENOMEM; 263 break; 264 } 265 } 266 /* Largest write sets read block length */ 267 if (len > b->len) 268 b->len = len; 269 for (i = 0; i < len; i++) 270 b->block[i] = data->block[i + 1]; 271 /* update for byte and word commands */ 272 chip->words[command] = (b->block[0] << 8) | b->len; 273 dev_dbg(&adap->dev, 274 "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n", 275 addr, len, command); 276 } else { 277 if (b == NULL) { 278 dev_dbg(&adap->dev, 279 "SMBus block read command without prior block write not supported\n"); 280 ret = -EOPNOTSUPP; 281 break; 282 } 283 len = b->len; 284 data->block[0] = len; 285 for (i = 0; i < len; i++) 286 data->block[i + 1] = b->block[i]; 287 dev_dbg(&adap->dev, 288 "smbus block data - addr 0x%02x, read %d bytes at 0x%02x.\n", 289 addr, len, command); 290 } 291 292 ret = 0; 293 break; 294 295 default: 296 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n"); 297 ret = -EOPNOTSUPP; 298 break; 299 } /* switch (size) */ 300 301 return ret; 302 } 303 304 static u32 stub_func(struct i2c_adapter *adapter) 305 { 306 return STUB_FUNC_ALL & functionality; 307 } 308 309 static const struct i2c_algorithm smbus_algorithm = { 310 .functionality = stub_func, 311 .smbus_xfer = stub_xfer, 312 }; 313 314 static struct i2c_adapter stub_adapter = { 315 .owner = THIS_MODULE, 316 .class = I2C_CLASS_HWMON, 317 .algo = &smbus_algorithm, 318 .name = "SMBus stub driver", 319 }; 320 321 static int __init i2c_stub_allocate_banks(int i) 322 { 323 struct stub_chip *chip = stub_chips + i; 324 325 chip->bank_reg = bank_reg[i]; 326 chip->bank_start = bank_start[i]; 327 chip->bank_end = bank_end[i]; 328 chip->bank_size = bank_end[i] - bank_start[i] + 1; 329 330 /* We assume that all bits in the mask are contiguous */ 331 chip->bank_mask = bank_mask[i]; 332 while (!(chip->bank_mask & 1)) { 333 chip->bank_shift++; 334 chip->bank_mask >>= 1; 335 } 336 337 chip->bank_words = kcalloc(chip->bank_mask * chip->bank_size, 338 sizeof(u16), 339 GFP_KERNEL); 340 if (!chip->bank_words) 341 return -ENOMEM; 342 343 pr_debug("Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n", 344 chip->bank_mask, chip->bank_size, chip->bank_start, 345 chip->bank_end); 346 347 return 0; 348 } 349 350 static void i2c_stub_free(void) 351 { 352 int i; 353 354 for (i = 0; i < stub_chips_nr; i++) 355 kfree(stub_chips[i].bank_words); 356 kfree(stub_chips); 357 } 358 359 static int __init i2c_stub_init(void) 360 { 361 int i, ret; 362 363 if (!chip_addr[0]) { 364 pr_err("Please specify a chip address\n"); 365 return -ENODEV; 366 } 367 368 for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) { 369 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) { 370 pr_err("Invalid chip address 0x%02x\n", 371 chip_addr[i]); 372 return -EINVAL; 373 } 374 375 pr_info("Virtual chip at 0x%02x\n", chip_addr[i]); 376 } 377 378 /* Allocate memory for all chips at once */ 379 stub_chips_nr = i; 380 stub_chips = kzalloc_objs(struct stub_chip, stub_chips_nr); 381 if (!stub_chips) 382 return -ENOMEM; 383 384 for (i = 0; i < stub_chips_nr; i++) { 385 INIT_LIST_HEAD(&stub_chips[i].smbus_blocks); 386 387 /* Allocate extra memory for banked register ranges */ 388 if (bank_mask[i]) { 389 ret = i2c_stub_allocate_banks(i); 390 if (ret) 391 goto fail_free; 392 } 393 } 394 395 ret = i2c_add_adapter(&stub_adapter); 396 if (ret) 397 goto fail_free; 398 399 return 0; 400 401 fail_free: 402 i2c_stub_free(); 403 return ret; 404 } 405 406 static void __exit i2c_stub_exit(void) 407 { 408 i2c_del_adapter(&stub_adapter); 409 i2c_stub_free(); 410 } 411 412 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>"); 413 MODULE_DESCRIPTION("I2C stub driver"); 414 MODULE_LICENSE("GPL"); 415 416 module_init(i2c_stub_init); 417 module_exit(i2c_stub_exit); 418