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); 415