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
stub_find_block(struct device * dev,struct stub_chip * chip,u8 command,bool create)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
stub_get_wordp(struct stub_chip * chip,u8 offset)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. */
stub_xfer(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)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
stub_func(struct i2c_adapter * adapter)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
i2c_stub_allocate_banks(int i)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
i2c_stub_free(void)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
i2c_stub_init(void)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
i2c_stub_exit(void)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