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 | I2C_CLASS_SPD, 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); 414