1/*
2 i2c-stub.c - I2C/SMBus chip emulator
3
4 Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
5 Copyright (C) 2007-2014 Jean Delvare <jdelvare@suse.de>
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16*/
17
18#define DEBUG 1
19#define pr_fmt(fmt) "i2c-stub: " fmt
20
21#include <linux/errno.h>
22#include <linux/i2c.h>
23#include <linux/init.h>
24#include <linux/kernel.h>
25#include <linux/list.h>
26#include <linux/module.h>
27#include <linux/slab.h>
28
29#define MAX_CHIPS 10
30
31/*
32 * Support for I2C_FUNC_SMBUS_BLOCK_DATA is disabled by default and must
33 * be enabled explicitly by setting the I2C_FUNC_SMBUS_BLOCK_DATA bits
34 * in the 'functionality' module parameter.
35 */
36#define STUB_FUNC_DEFAULT \
37 (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
38 I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
39 I2C_FUNC_SMBUS_I2C_BLOCK)
40
41#define STUB_FUNC_ALL \
42 (STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA)
43
44static unsigned short chip_addr[MAX_CHIPS];
45module_param_array(chip_addr, ushort, NULL, S_IRUGO);
46MODULE_PARM_DESC(chip_addr,
47 "Chip addresses (up to 10, between 0x03 and 0x77)");
48
49static unsigned long functionality = STUB_FUNC_DEFAULT;
50module_param(functionality, ulong, S_IRUGO | S_IWUSR);
51MODULE_PARM_DESC(functionality, "Override functionality bitfield");
52
53/* Some chips have banked register ranges */
54
55static u8 bank_reg[MAX_CHIPS];
56module_param_array(bank_reg, byte, NULL, S_IRUGO);
57MODULE_PARM_DESC(bank_reg, "Bank register");
58
59static u8 bank_mask[MAX_CHIPS];
60module_param_array(bank_mask, byte, NULL, S_IRUGO);
61MODULE_PARM_DESC(bank_mask, "Bank value mask");
62
63static u8 bank_start[MAX_CHIPS];
64module_param_array(bank_start, byte, NULL, S_IRUGO);
65MODULE_PARM_DESC(bank_start, "First banked register");
66
67static u8 bank_end[MAX_CHIPS];
68module_param_array(bank_end, byte, NULL, S_IRUGO);
69MODULE_PARM_DESC(bank_end, "Last banked register");
70
71struct smbus_block_data {
72 struct list_head node;
73 u8 command;
74 u8 len;
75 u8 block[I2C_SMBUS_BLOCK_MAX];
76};
77
78struct stub_chip {
79 u8 pointer;
80 u16 words[256]; /* Byte operations use the LSB as per SMBus
81 specification */
82 struct list_head smbus_blocks;
83
84 /* For chips with banks, extra registers are allocated dynamically */
85 u8 bank_reg;
86 u8 bank_shift;
87 u8 bank_mask;
88 u8 bank_sel; /* Currently selected bank */
89 u8 bank_start;
90 u8 bank_end;
91 u16 bank_size;
92 u16 *bank_words; /* Room for bank_mask * bank_size registers */
93};
94
95static struct stub_chip *stub_chips;
96static int stub_chips_nr;
97
98static struct smbus_block_data *stub_find_block(struct device *dev,
99 struct stub_chip *chip,
100 u8 command, bool create)
101{
102 struct smbus_block_data *b, *rb = NULL;
103
104 list_for_each_entry(b, &chip->smbus_blocks, node) {
105 if (b->command == command) {
106 rb = b;
107 break;
108 }
109 }
110 if (rb == NULL && create) {
111 rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL);
112 if (rb == NULL)
113 return rb;
114 rb->command = command;
115 list_add(&rb->node, &chip->smbus_blocks);
116 }
117 return rb;
118}
119
120static u16 *stub_get_wordp(struct stub_chip *chip, u8 offset)
121{
122 if (chip->bank_sel &&
123 offset >= chip->bank_start && offset <= chip->bank_end)
124 return chip->bank_words +
125 (chip->bank_sel - 1) * chip->bank_size +
126 offset - chip->bank_start;
127 else
128 return chip->words + offset;
129}
130
131/* Return negative errno on error. */
132static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
133 char read_write, u8 command, int size, union i2c_smbus_data *data)
134{
135 s32 ret;
136 int i, len;
137 struct stub_chip *chip = NULL;
138 struct smbus_block_data *b;
139 u16 *wordp;
140
141 /* Search for the right chip */
142 for (i = 0; i < stub_chips_nr; i++) {
143 if (addr == chip_addr[i]) {
144 chip = stub_chips + i;
145 break;
146 }
147 }
148 if (!chip)
149 return -ENODEV;
150
151 switch (size) {
152
153 case I2C_SMBUS_QUICK:
154 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
155 ret = 0;
156 break;
157
158 case I2C_SMBUS_BYTE:
159 if (read_write == I2C_SMBUS_WRITE) {
160 chip->pointer = command;
161 dev_dbg(&adap->dev,
162 "smbus byte - addr 0x%02x, wrote 0x%02x.\n",
163 addr, command);
164 } else {
165 wordp = stub_get_wordp(chip, chip->pointer++);
166 data->byte = *wordp & 0xff;
167 dev_dbg(&adap->dev,
168 "smbus byte - addr 0x%02x, read 0x%02x.\n",
169 addr, data->byte);
170 }
171
172 ret = 0;
173 break;
174
175 case I2C_SMBUS_BYTE_DATA:
176 wordp = stub_get_wordp(chip, command);
177 if (read_write == I2C_SMBUS_WRITE) {
178 *wordp &= 0xff00;
179 *wordp |= data->byte;
180 dev_dbg(&adap->dev,
181 "smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
182 addr, data->byte, command);
183
184 /* Set the bank as needed */
185 if (chip->bank_words && command == chip->bank_reg) {
186 chip->bank_sel =
187 (data->byte >> chip->bank_shift)
188 & chip->bank_mask;
189 dev_dbg(&adap->dev,
190 "switching to bank %u.\n",
191 chip->bank_sel);
192 }
193 } else {
194 data->byte = *wordp & 0xff;
195 dev_dbg(&adap->dev,
196 "smbus byte data - addr 0x%02x, read 0x%02x at 0x%02x.\n",
197 addr, data->byte, command);
198 }
199 chip->pointer = command + 1;
200
201 ret = 0;
202 break;
203
204 case I2C_SMBUS_WORD_DATA:
205 wordp = stub_get_wordp(chip, command);
206 if (read_write == I2C_SMBUS_WRITE) {
207 *wordp = data->word;
208 dev_dbg(&adap->dev,
209 "smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
210 addr, data->word, command);
211 } else {
212 data->word = *wordp;
213 dev_dbg(&adap->dev,
214 "smbus word data - addr 0x%02x, read 0x%04x at 0x%02x.\n",
215 addr, data->word, command);
216 }
217
218 ret = 0;
219 break;
220
221 case I2C_SMBUS_I2C_BLOCK_DATA:
222 /*
223 * We ignore banks here, because banked chips don't use I2C
224 * block transfers
225 */
226 if (data->block[0] > 256 - command) /* Avoid overrun */
227 data->block[0] = 256 - command;
228 len = data->block[0];
229 if (read_write == I2C_SMBUS_WRITE) {
230 for (i = 0; i < len; i++) {
231 chip->words[command + i] &= 0xff00;
232 chip->words[command + i] |= data->block[1 + i];
233 }
234 dev_dbg(&adap->dev,
235 "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
236 addr, len, command);
237 } else {
238 for (i = 0; i < len; i++) {
239 data->block[1 + i] =
240 chip->words[command + i] & 0xff;
241 }
242 dev_dbg(&adap->dev,
243 "i2c block data - addr 0x%02x, read %d bytes at 0x%02x.\n",
244 addr, len, command);
245 }
246
247 ret = 0;
248 break;
249
250 case I2C_SMBUS_BLOCK_DATA:
251 /*
252 * We ignore banks here, because chips typically don't use both
253 * banks and SMBus block transfers
254 */
255 b = stub_find_block(&adap->dev, chip, command, false);
256 if (read_write == I2C_SMBUS_WRITE) {
257 len = data->block[0];
258 if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
259 ret = -EINVAL;
260 break;
261 }
262 if (b == NULL) {
263 b = stub_find_block(&adap->dev, chip, command,
264 true);
265 if (b == NULL) {
266 ret = -ENOMEM;
267 break;
268 }
269 }
270 /* Largest write sets read block length */
271 if (len > b->len)
272 b->len = len;
273 for (i = 0; i < len; i++)
274 b->block[i] = data->block[i + 1];
275 /* update for byte and word commands */
276 chip->words[command] = (b->block[0] << 8) | b->len;
277 dev_dbg(&adap->dev,
278 "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
279 addr, len, command);
280 } else {
281 if (b == NULL) {
282 dev_dbg(&adap->dev,
283 "SMBus block read command without prior block write not supported\n");
284 ret = -EOPNOTSUPP;
285 break;
286 }
287 len = b->len;
288 data->block[0] = len;
289 for (i = 0; i < len; i++)
290 data->block[i + 1] = b->block[i];
291 dev_dbg(&adap->dev,
292 "smbus block data - addr 0x%02x, read %d bytes at 0x%02x.\n",
293 addr, len, command);
294 }
295
296 ret = 0;
297 break;
298
299 default:
300 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
301 ret = -EOPNOTSUPP;
302 break;
303 } /* switch (size) */
304
305 return ret;
306}
307
308static u32 stub_func(struct i2c_adapter *adapter)
309{
310 return STUB_FUNC_ALL & functionality;
311}
312
313static const struct i2c_algorithm smbus_algorithm = {
314 .functionality = stub_func,
315 .smbus_xfer = stub_xfer,
316};
317
318static struct i2c_adapter stub_adapter = {
319 .owner = THIS_MODULE,
320 .class = I2C_CLASS_HWMON | I2C_CLASS_SPD,
321 .algo = &smbus_algorithm,
322 .name = "SMBus stub driver",
323};
324
325static int __init i2c_stub_allocate_banks(int i)
326{
327 struct stub_chip *chip = stub_chips + i;
328
329 chip->bank_reg = bank_reg[i];
330 chip->bank_start = bank_start[i];
331 chip->bank_end = bank_end[i];
332 chip->bank_size = bank_end[i] - bank_start[i] + 1;
333
334 /* We assume that all bits in the mask are contiguous */
335 chip->bank_mask = bank_mask[i];
336 while (!(chip->bank_mask & 1)) {
337 chip->bank_shift++;
338 chip->bank_mask >>= 1;
339 }
340
341 chip->bank_words = kcalloc(chip->bank_mask * chip->bank_size,
342 sizeof(u16),
343 GFP_KERNEL);
344 if (!chip->bank_words)
345 return -ENOMEM;
346
347 pr_debug("Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n",
348 chip->bank_mask, chip->bank_size, chip->bank_start,
349 chip->bank_end);
350
351 return 0;
352}
353
354static void i2c_stub_free(void)
355{
356 int i;
357
358 for (i = 0; i < stub_chips_nr; i++)
359 kfree(stub_chips[i].bank_words);
360 kfree(stub_chips);
361}
362
363static int __init i2c_stub_init(void)
364{
365 int i, ret;
366
367 if (!chip_addr[0]) {
368 pr_err("Please specify a chip address\n");
369 return -ENODEV;
370 }
371
372 for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
373 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
374 pr_err("Invalid chip address 0x%02x\n",
375 chip_addr[i]);
376 return -EINVAL;
377 }
378
379 pr_info("Virtual chip at 0x%02x\n", chip_addr[i]);
380 }
381
382 /* Allocate memory for all chips at once */
383 stub_chips_nr = i;
384 stub_chips = kcalloc(stub_chips_nr, sizeof(struct stub_chip),
385 GFP_KERNEL);
386 if (!stub_chips)
387 return -ENOMEM;
388
389 for (i = 0; i < stub_chips_nr; i++) {
390 INIT_LIST_HEAD(&stub_chips[i].smbus_blocks);
391
392 /* Allocate extra memory for banked register ranges */
393 if (bank_mask[i]) {
394 ret = i2c_stub_allocate_banks(i);
395 if (ret)
396 goto fail_free;
397 }
398 }
399
400 ret = i2c_add_adapter(&stub_adapter);
401 if (ret)
402 goto fail_free;
403
404 return 0;
405
406 fail_free:
407 i2c_stub_free();
408 return ret;
409}
410
411static void __exit i2c_stub_exit(void)
412{
413 i2c_del_adapter(&stub_adapter);
414 i2c_stub_free();
415}
416
417MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
418MODULE_DESCRIPTION("I2C stub driver");
419MODULE_LICENSE("GPL");
420
421module_init(i2c_stub_init);
422module_exit(i2c_stub_exit);
423