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