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