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
35static unsigned short chip_addr[MAX_CHIPS];
36module_param_array(chip_addr, ushort, NULL, S_IRUGO);
37MODULE_PARM_DESC(chip_addr,
38		 "Chip addresses (up to 10, between 0x03 and 0x77)");
39
40static unsigned long functionality = STUB_FUNC_DEFAULT;
41module_param(functionality, ulong, S_IRUGO | S_IWUSR);
42MODULE_PARM_DESC(functionality, "Override functionality bitfield");
43
44/* Some chips have banked register ranges */
45
46static u8 bank_reg[MAX_CHIPS];
47module_param_array(bank_reg, byte, NULL, S_IRUGO);
48MODULE_PARM_DESC(bank_reg, "Bank register");
49
50static u8 bank_mask[MAX_CHIPS];
51module_param_array(bank_mask, byte, NULL, S_IRUGO);
52MODULE_PARM_DESC(bank_mask, "Bank value mask");
53
54static u8 bank_start[MAX_CHIPS];
55module_param_array(bank_start, byte, NULL, S_IRUGO);
56MODULE_PARM_DESC(bank_start, "First banked register");
57
58static u8 bank_end[MAX_CHIPS];
59module_param_array(bank_end, byte, NULL, S_IRUGO);
60MODULE_PARM_DESC(bank_end, "Last banked register");
61
62struct smbus_block_data {
63	struct list_head node;
64	u8 command;
65	u8 len;
66	u8 block[I2C_SMBUS_BLOCK_MAX];
67};
68
69struct 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
86static struct stub_chip *stub_chips;
87static int stub_chips_nr;
88
89static 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
111static 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. */
123static 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
299static u32 stub_func(struct i2c_adapter *adapter)
300{
301	return STUB_FUNC_ALL & functionality;
302}
303
304static const struct i2c_algorithm smbus_algorithm = {
305	.functionality	= stub_func,
306	.smbus_xfer	= stub_xfer,
307};
308
309static struct i2c_adapter stub_adapter = {
310	.owner		= THIS_MODULE,
311	.class		= I2C_CLASS_HWMON,
312	.algo		= &smbus_algorithm,
313	.name		= "SMBus stub driver",
314};
315
316static 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
345static 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
354static 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
402static void __exit i2c_stub_exit(void)
403{
404	i2c_del_adapter(&stub_adapter);
405	i2c_stub_free();
406}
407
408MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
409MODULE_DESCRIPTION("I2C stub driver");
410MODULE_LICENSE("GPL");
411
412module_init(i2c_stub_init);
413module_exit(i2c_stub_exit);
414