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22c78d1c WS |
1 | /* |
2 | * Linux I2C core SMBus and SMBus emulation code | |
3 | * | |
4 | * This file contains the SMBus functions which are always included in the I2C | |
5 | * core because they can be emulated via I2C. SMBus specific extensions | |
6 | * (e.g. smbalert) are handled in a seperate i2c-smbus module. | |
7 | * | |
8 | * All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl> | |
9 | * SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and | |
10 | * Jean Delvare <jdelvare@suse.de> | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or modify it | |
13 | * under the terms of the GNU General Public License as published by the Free | |
14 | * Software Foundation; either version 2 of the License, or (at your option) | |
15 | * any later version. | |
16 | */ | |
17 | #include <linux/device.h> | |
18 | #include <linux/err.h> | |
19 | #include <linux/i2c.h> | |
20 | ||
21 | #define CREATE_TRACE_POINTS | |
22 | #include <trace/events/smbus.h> | |
23 | ||
24 | ||
25 | /* The SMBus parts */ | |
26 | ||
27 | #define POLY (0x1070U << 3) | |
28 | static u8 crc8(u16 data) | |
29 | { | |
30 | int i; | |
31 | ||
32 | for (i = 0; i < 8; i++) { | |
33 | if (data & 0x8000) | |
34 | data = data ^ POLY; | |
35 | data = data << 1; | |
36 | } | |
37 | return (u8)(data >> 8); | |
38 | } | |
39 | ||
40 | /* Incremental CRC8 over count bytes in the array pointed to by p */ | |
41 | static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count) | |
42 | { | |
43 | int i; | |
44 | ||
45 | for (i = 0; i < count; i++) | |
46 | crc = crc8((crc ^ p[i]) << 8); | |
47 | return crc; | |
48 | } | |
49 | ||
50 | /* Assume a 7-bit address, which is reasonable for SMBus */ | |
51 | static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg) | |
52 | { | |
53 | /* The address will be sent first */ | |
54 | u8 addr = i2c_8bit_addr_from_msg(msg); | |
55 | pec = i2c_smbus_pec(pec, &addr, 1); | |
56 | ||
57 | /* The data buffer follows */ | |
58 | return i2c_smbus_pec(pec, msg->buf, msg->len); | |
59 | } | |
60 | ||
61 | /* Used for write only transactions */ | |
62 | static inline void i2c_smbus_add_pec(struct i2c_msg *msg) | |
63 | { | |
64 | msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg); | |
65 | msg->len++; | |
66 | } | |
67 | ||
68 | /* Return <0 on CRC error | |
69 | If there was a write before this read (most cases) we need to take the | |
70 | partial CRC from the write part into account. | |
71 | Note that this function does modify the message (we need to decrease the | |
72 | message length to hide the CRC byte from the caller). */ | |
73 | static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg) | |
74 | { | |
75 | u8 rpec = msg->buf[--msg->len]; | |
76 | cpec = i2c_smbus_msg_pec(cpec, msg); | |
77 | ||
78 | if (rpec != cpec) { | |
79 | pr_debug("Bad PEC 0x%02x vs. 0x%02x\n", | |
80 | rpec, cpec); | |
81 | return -EBADMSG; | |
82 | } | |
83 | return 0; | |
84 | } | |
85 | ||
86 | /** | |
87 | * i2c_smbus_read_byte - SMBus "receive byte" protocol | |
88 | * @client: Handle to slave device | |
89 | * | |
90 | * This executes the SMBus "receive byte" protocol, returning negative errno | |
91 | * else the byte received from the device. | |
92 | */ | |
93 | s32 i2c_smbus_read_byte(const struct i2c_client *client) | |
94 | { | |
95 | union i2c_smbus_data data; | |
96 | int status; | |
97 | ||
98 | status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
99 | I2C_SMBUS_READ, 0, | |
100 | I2C_SMBUS_BYTE, &data); | |
101 | return (status < 0) ? status : data.byte; | |
102 | } | |
103 | EXPORT_SYMBOL(i2c_smbus_read_byte); | |
104 | ||
105 | /** | |
106 | * i2c_smbus_write_byte - SMBus "send byte" protocol | |
107 | * @client: Handle to slave device | |
108 | * @value: Byte to be sent | |
109 | * | |
110 | * This executes the SMBus "send byte" protocol, returning negative errno | |
111 | * else zero on success. | |
112 | */ | |
113 | s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value) | |
114 | { | |
115 | return i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
116 | I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL); | |
117 | } | |
118 | EXPORT_SYMBOL(i2c_smbus_write_byte); | |
119 | ||
120 | /** | |
121 | * i2c_smbus_read_byte_data - SMBus "read byte" protocol | |
122 | * @client: Handle to slave device | |
123 | * @command: Byte interpreted by slave | |
124 | * | |
125 | * This executes the SMBus "read byte" protocol, returning negative errno | |
126 | * else a data byte received from the device. | |
127 | */ | |
128 | s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command) | |
129 | { | |
130 | union i2c_smbus_data data; | |
131 | int status; | |
132 | ||
133 | status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
134 | I2C_SMBUS_READ, command, | |
135 | I2C_SMBUS_BYTE_DATA, &data); | |
136 | return (status < 0) ? status : data.byte; | |
137 | } | |
138 | EXPORT_SYMBOL(i2c_smbus_read_byte_data); | |
139 | ||
140 | /** | |
141 | * i2c_smbus_write_byte_data - SMBus "write byte" protocol | |
142 | * @client: Handle to slave device | |
143 | * @command: Byte interpreted by slave | |
144 | * @value: Byte being written | |
145 | * | |
146 | * This executes the SMBus "write byte" protocol, returning negative errno | |
147 | * else zero on success. | |
148 | */ | |
149 | s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command, | |
150 | u8 value) | |
151 | { | |
152 | union i2c_smbus_data data; | |
153 | data.byte = value; | |
154 | return i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
155 | I2C_SMBUS_WRITE, command, | |
156 | I2C_SMBUS_BYTE_DATA, &data); | |
157 | } | |
158 | EXPORT_SYMBOL(i2c_smbus_write_byte_data); | |
159 | ||
160 | /** | |
161 | * i2c_smbus_read_word_data - SMBus "read word" protocol | |
162 | * @client: Handle to slave device | |
163 | * @command: Byte interpreted by slave | |
164 | * | |
165 | * This executes the SMBus "read word" protocol, returning negative errno | |
166 | * else a 16-bit unsigned "word" received from the device. | |
167 | */ | |
168 | s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command) | |
169 | { | |
170 | union i2c_smbus_data data; | |
171 | int status; | |
172 | ||
173 | status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
174 | I2C_SMBUS_READ, command, | |
175 | I2C_SMBUS_WORD_DATA, &data); | |
176 | return (status < 0) ? status : data.word; | |
177 | } | |
178 | EXPORT_SYMBOL(i2c_smbus_read_word_data); | |
179 | ||
180 | /** | |
181 | * i2c_smbus_write_word_data - SMBus "write word" protocol | |
182 | * @client: Handle to slave device | |
183 | * @command: Byte interpreted by slave | |
184 | * @value: 16-bit "word" being written | |
185 | * | |
186 | * This executes the SMBus "write word" protocol, returning negative errno | |
187 | * else zero on success. | |
188 | */ | |
189 | s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command, | |
190 | u16 value) | |
191 | { | |
192 | union i2c_smbus_data data; | |
193 | data.word = value; | |
194 | return i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
195 | I2C_SMBUS_WRITE, command, | |
196 | I2C_SMBUS_WORD_DATA, &data); | |
197 | } | |
198 | EXPORT_SYMBOL(i2c_smbus_write_word_data); | |
199 | ||
200 | /** | |
201 | * i2c_smbus_read_block_data - SMBus "block read" protocol | |
202 | * @client: Handle to slave device | |
203 | * @command: Byte interpreted by slave | |
204 | * @values: Byte array into which data will be read; big enough to hold | |
205 | * the data returned by the slave. SMBus allows at most 32 bytes. | |
206 | * | |
207 | * This executes the SMBus "block read" protocol, returning negative errno | |
208 | * else the number of data bytes in the slave's response. | |
209 | * | |
210 | * Note that using this function requires that the client's adapter support | |
211 | * the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality. Not all adapter drivers | |
212 | * support this; its emulation through I2C messaging relies on a specific | |
213 | * mechanism (I2C_M_RECV_LEN) which may not be implemented. | |
214 | */ | |
215 | s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command, | |
216 | u8 *values) | |
217 | { | |
218 | union i2c_smbus_data data; | |
219 | int status; | |
220 | ||
221 | status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
222 | I2C_SMBUS_READ, command, | |
223 | I2C_SMBUS_BLOCK_DATA, &data); | |
224 | if (status) | |
225 | return status; | |
226 | ||
227 | memcpy(values, &data.block[1], data.block[0]); | |
228 | return data.block[0]; | |
229 | } | |
230 | EXPORT_SYMBOL(i2c_smbus_read_block_data); | |
231 | ||
232 | /** | |
233 | * i2c_smbus_write_block_data - SMBus "block write" protocol | |
234 | * @client: Handle to slave device | |
235 | * @command: Byte interpreted by slave | |
236 | * @length: Size of data block; SMBus allows at most 32 bytes | |
237 | * @values: Byte array which will be written. | |
238 | * | |
239 | * This executes the SMBus "block write" protocol, returning negative errno | |
240 | * else zero on success. | |
241 | */ | |
242 | s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command, | |
243 | u8 length, const u8 *values) | |
244 | { | |
245 | union i2c_smbus_data data; | |
246 | ||
247 | if (length > I2C_SMBUS_BLOCK_MAX) | |
248 | length = I2C_SMBUS_BLOCK_MAX; | |
249 | data.block[0] = length; | |
250 | memcpy(&data.block[1], values, length); | |
251 | return i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
252 | I2C_SMBUS_WRITE, command, | |
253 | I2C_SMBUS_BLOCK_DATA, &data); | |
254 | } | |
255 | EXPORT_SYMBOL(i2c_smbus_write_block_data); | |
256 | ||
257 | /* Returns the number of read bytes */ | |
258 | s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command, | |
259 | u8 length, u8 *values) | |
260 | { | |
261 | union i2c_smbus_data data; | |
262 | int status; | |
263 | ||
264 | if (length > I2C_SMBUS_BLOCK_MAX) | |
265 | length = I2C_SMBUS_BLOCK_MAX; | |
266 | data.block[0] = length; | |
267 | status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
268 | I2C_SMBUS_READ, command, | |
269 | I2C_SMBUS_I2C_BLOCK_DATA, &data); | |
270 | if (status < 0) | |
271 | return status; | |
272 | ||
273 | memcpy(values, &data.block[1], data.block[0]); | |
274 | return data.block[0]; | |
275 | } | |
276 | EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data); | |
277 | ||
278 | s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command, | |
279 | u8 length, const u8 *values) | |
280 | { | |
281 | union i2c_smbus_data data; | |
282 | ||
283 | if (length > I2C_SMBUS_BLOCK_MAX) | |
284 | length = I2C_SMBUS_BLOCK_MAX; | |
285 | data.block[0] = length; | |
286 | memcpy(data.block + 1, values, length); | |
287 | return i2c_smbus_xfer(client->adapter, client->addr, client->flags, | |
288 | I2C_SMBUS_WRITE, command, | |
289 | I2C_SMBUS_I2C_BLOCK_DATA, &data); | |
290 | } | |
291 | EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data); | |
292 | ||
293 | /* Simulate a SMBus command using the i2c protocol | |
294 | No checking of parameters is done! */ | |
295 | static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, | |
296 | unsigned short flags, | |
297 | char read_write, u8 command, int size, | |
298 | union i2c_smbus_data *data) | |
299 | { | |
300 | /* So we need to generate a series of msgs. In the case of writing, we | |
301 | need to use only one message; when reading, we need two. We initialize | |
302 | most things with sane defaults, to keep the code below somewhat | |
303 | simpler. */ | |
304 | unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3]; | |
305 | unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2]; | |
306 | int num = read_write == I2C_SMBUS_READ ? 2 : 1; | |
307 | int i; | |
308 | u8 partial_pec = 0; | |
309 | int status; | |
310 | struct i2c_msg msg[2] = { | |
311 | { | |
312 | .addr = addr, | |
313 | .flags = flags, | |
314 | .len = 1, | |
315 | .buf = msgbuf0, | |
316 | }, { | |
317 | .addr = addr, | |
318 | .flags = flags | I2C_M_RD, | |
319 | .len = 0, | |
320 | .buf = msgbuf1, | |
321 | }, | |
322 | }; | |
323 | ||
324 | msgbuf0[0] = command; | |
325 | switch (size) { | |
326 | case I2C_SMBUS_QUICK: | |
327 | msg[0].len = 0; | |
328 | /* Special case: The read/write field is used as data */ | |
329 | msg[0].flags = flags | (read_write == I2C_SMBUS_READ ? | |
330 | I2C_M_RD : 0); | |
331 | num = 1; | |
332 | break; | |
333 | case I2C_SMBUS_BYTE: | |
334 | if (read_write == I2C_SMBUS_READ) { | |
335 | /* Special case: only a read! */ | |
336 | msg[0].flags = I2C_M_RD | flags; | |
337 | num = 1; | |
338 | } | |
339 | break; | |
340 | case I2C_SMBUS_BYTE_DATA: | |
341 | if (read_write == I2C_SMBUS_READ) | |
342 | msg[1].len = 1; | |
343 | else { | |
344 | msg[0].len = 2; | |
345 | msgbuf0[1] = data->byte; | |
346 | } | |
347 | break; | |
348 | case I2C_SMBUS_WORD_DATA: | |
349 | if (read_write == I2C_SMBUS_READ) | |
350 | msg[1].len = 2; | |
351 | else { | |
352 | msg[0].len = 3; | |
353 | msgbuf0[1] = data->word & 0xff; | |
354 | msgbuf0[2] = data->word >> 8; | |
355 | } | |
356 | break; | |
357 | case I2C_SMBUS_PROC_CALL: | |
358 | num = 2; /* Special case */ | |
359 | read_write = I2C_SMBUS_READ; | |
360 | msg[0].len = 3; | |
361 | msg[1].len = 2; | |
362 | msgbuf0[1] = data->word & 0xff; | |
363 | msgbuf0[2] = data->word >> 8; | |
364 | break; | |
365 | case I2C_SMBUS_BLOCK_DATA: | |
366 | if (read_write == I2C_SMBUS_READ) { | |
367 | msg[1].flags |= I2C_M_RECV_LEN; | |
368 | msg[1].len = 1; /* block length will be added by | |
369 | the underlying bus driver */ | |
370 | } else { | |
371 | msg[0].len = data->block[0] + 2; | |
372 | if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) { | |
373 | dev_err(&adapter->dev, | |
374 | "Invalid block write size %d\n", | |
375 | data->block[0]); | |
376 | return -EINVAL; | |
377 | } | |
378 | for (i = 1; i < msg[0].len; i++) | |
379 | msgbuf0[i] = data->block[i-1]; | |
380 | } | |
381 | break; | |
382 | case I2C_SMBUS_BLOCK_PROC_CALL: | |
383 | num = 2; /* Another special case */ | |
384 | read_write = I2C_SMBUS_READ; | |
385 | if (data->block[0] > I2C_SMBUS_BLOCK_MAX) { | |
386 | dev_err(&adapter->dev, | |
387 | "Invalid block write size %d\n", | |
388 | data->block[0]); | |
389 | return -EINVAL; | |
390 | } | |
391 | msg[0].len = data->block[0] + 2; | |
392 | for (i = 1; i < msg[0].len; i++) | |
393 | msgbuf0[i] = data->block[i-1]; | |
394 | msg[1].flags |= I2C_M_RECV_LEN; | |
395 | msg[1].len = 1; /* block length will be added by | |
396 | the underlying bus driver */ | |
397 | break; | |
398 | case I2C_SMBUS_I2C_BLOCK_DATA: | |
399 | if (read_write == I2C_SMBUS_READ) { | |
400 | msg[1].len = data->block[0]; | |
401 | } else { | |
402 | msg[0].len = data->block[0] + 1; | |
403 | if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) { | |
404 | dev_err(&adapter->dev, | |
405 | "Invalid block write size %d\n", | |
406 | data->block[0]); | |
407 | return -EINVAL; | |
408 | } | |
409 | for (i = 1; i <= data->block[0]; i++) | |
410 | msgbuf0[i] = data->block[i]; | |
411 | } | |
412 | break; | |
413 | default: | |
414 | dev_err(&adapter->dev, "Unsupported transaction %d\n", size); | |
415 | return -EOPNOTSUPP; | |
416 | } | |
417 | ||
418 | i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK | |
419 | && size != I2C_SMBUS_I2C_BLOCK_DATA); | |
420 | if (i) { | |
421 | /* Compute PEC if first message is a write */ | |
422 | if (!(msg[0].flags & I2C_M_RD)) { | |
423 | if (num == 1) /* Write only */ | |
424 | i2c_smbus_add_pec(&msg[0]); | |
425 | else /* Write followed by read */ | |
426 | partial_pec = i2c_smbus_msg_pec(0, &msg[0]); | |
427 | } | |
428 | /* Ask for PEC if last message is a read */ | |
429 | if (msg[num-1].flags & I2C_M_RD) | |
430 | msg[num-1].len++; | |
431 | } | |
432 | ||
433 | status = i2c_transfer(adapter, msg, num); | |
434 | if (status < 0) | |
435 | return status; | |
436 | ||
437 | /* Check PEC if last message is a read */ | |
438 | if (i && (msg[num-1].flags & I2C_M_RD)) { | |
439 | status = i2c_smbus_check_pec(partial_pec, &msg[num-1]); | |
440 | if (status < 0) | |
441 | return status; | |
442 | } | |
443 | ||
444 | if (read_write == I2C_SMBUS_READ) | |
445 | switch (size) { | |
446 | case I2C_SMBUS_BYTE: | |
447 | data->byte = msgbuf0[0]; | |
448 | break; | |
449 | case I2C_SMBUS_BYTE_DATA: | |
450 | data->byte = msgbuf1[0]; | |
451 | break; | |
452 | case I2C_SMBUS_WORD_DATA: | |
453 | case I2C_SMBUS_PROC_CALL: | |
454 | data->word = msgbuf1[0] | (msgbuf1[1] << 8); | |
455 | break; | |
456 | case I2C_SMBUS_I2C_BLOCK_DATA: | |
457 | for (i = 0; i < data->block[0]; i++) | |
458 | data->block[i+1] = msgbuf1[i]; | |
459 | break; | |
460 | case I2C_SMBUS_BLOCK_DATA: | |
461 | case I2C_SMBUS_BLOCK_PROC_CALL: | |
462 | for (i = 0; i < msgbuf1[0] + 1; i++) | |
463 | data->block[i] = msgbuf1[i]; | |
464 | break; | |
465 | } | |
466 | return 0; | |
467 | } | |
468 | ||
469 | /** | |
470 | * i2c_smbus_xfer - execute SMBus protocol operations | |
471 | * @adapter: Handle to I2C bus | |
472 | * @addr: Address of SMBus slave on that bus | |
473 | * @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC) | |
474 | * @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE | |
475 | * @command: Byte interpreted by slave, for protocols which use such bytes | |
476 | * @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL | |
477 | * @data: Data to be read or written | |
478 | * | |
479 | * This executes an SMBus protocol operation, and returns a negative | |
480 | * errno code else zero on success. | |
481 | */ | |
482 | s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, | |
483 | char read_write, u8 command, int protocol, | |
484 | union i2c_smbus_data *data) | |
485 | { | |
486 | unsigned long orig_jiffies; | |
487 | int try; | |
488 | s32 res; | |
489 | ||
490 | /* If enabled, the following two tracepoints are conditional on | |
491 | * read_write and protocol. | |
492 | */ | |
493 | trace_smbus_write(adapter, addr, flags, read_write, | |
494 | command, protocol, data); | |
495 | trace_smbus_read(adapter, addr, flags, read_write, | |
496 | command, protocol); | |
497 | ||
498 | flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB; | |
499 | ||
500 | if (adapter->algo->smbus_xfer) { | |
501 | i2c_lock_bus(adapter, I2C_LOCK_SEGMENT); | |
502 | ||
503 | /* Retry automatically on arbitration loss */ | |
504 | orig_jiffies = jiffies; | |
505 | for (res = 0, try = 0; try <= adapter->retries; try++) { | |
506 | res = adapter->algo->smbus_xfer(adapter, addr, flags, | |
507 | read_write, command, | |
508 | protocol, data); | |
509 | if (res != -EAGAIN) | |
510 | break; | |
511 | if (time_after(jiffies, | |
512 | orig_jiffies + adapter->timeout)) | |
513 | break; | |
514 | } | |
515 | i2c_unlock_bus(adapter, I2C_LOCK_SEGMENT); | |
516 | ||
517 | if (res != -EOPNOTSUPP || !adapter->algo->master_xfer) | |
518 | goto trace; | |
519 | /* | |
520 | * Fall back to i2c_smbus_xfer_emulated if the adapter doesn't | |
521 | * implement native support for the SMBus operation. | |
522 | */ | |
523 | } | |
524 | ||
525 | res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write, | |
526 | command, protocol, data); | |
527 | ||
528 | trace: | |
529 | /* If enabled, the reply tracepoint is conditional on read_write. */ | |
530 | trace_smbus_reply(adapter, addr, flags, read_write, | |
531 | command, protocol, data); | |
532 | trace_smbus_result(adapter, addr, flags, read_write, | |
533 | command, protocol, res); | |
534 | ||
535 | return res; | |
536 | } | |
537 | EXPORT_SYMBOL(i2c_smbus_xfer); | |
538 | ||
539 | /** | |
540 | * i2c_smbus_read_i2c_block_data_or_emulated - read block or emulate | |
541 | * @client: Handle to slave device | |
542 | * @command: Byte interpreted by slave | |
543 | * @length: Size of data block; SMBus allows at most I2C_SMBUS_BLOCK_MAX bytes | |
544 | * @values: Byte array into which data will be read; big enough to hold | |
545 | * the data returned by the slave. SMBus allows at most | |
546 | * I2C_SMBUS_BLOCK_MAX bytes. | |
547 | * | |
548 | * This executes the SMBus "block read" protocol if supported by the adapter. | |
549 | * If block read is not supported, it emulates it using either word or byte | |
550 | * read protocols depending on availability. | |
551 | * | |
552 | * The addresses of the I2C slave device that are accessed with this function | |
553 | * must be mapped to a linear region, so that a block read will have the same | |
554 | * effect as a byte read. Before using this function you must double-check | |
555 | * if the I2C slave does support exchanging a block transfer with a byte | |
556 | * transfer. | |
557 | */ | |
558 | s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client, | |
559 | u8 command, u8 length, u8 *values) | |
560 | { | |
561 | u8 i = 0; | |
562 | int status; | |
563 | ||
564 | if (length > I2C_SMBUS_BLOCK_MAX) | |
565 | length = I2C_SMBUS_BLOCK_MAX; | |
566 | ||
567 | if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) | |
568 | return i2c_smbus_read_i2c_block_data(client, command, length, values); | |
569 | ||
570 | if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) | |
571 | return -EOPNOTSUPP; | |
572 | ||
573 | if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)) { | |
574 | while ((i + 2) <= length) { | |
575 | status = i2c_smbus_read_word_data(client, command + i); | |
576 | if (status < 0) | |
577 | return status; | |
578 | values[i] = status & 0xff; | |
579 | values[i + 1] = status >> 8; | |
580 | i += 2; | |
581 | } | |
582 | } | |
583 | ||
584 | while (i < length) { | |
585 | status = i2c_smbus_read_byte_data(client, command + i); | |
586 | if (status < 0) | |
587 | return status; | |
588 | values[i] = status; | |
589 | i++; | |
590 | } | |
591 | ||
592 | return i; | |
593 | } | |
594 | EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data_or_emulated); |