2 * Linux I2C core SMBus and SMBus emulation code
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.
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>
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)
17 #include <linux/device.h>
18 #include <linux/err.h>
19 #include <linux/i2c.h>
20 #include <linux/i2c-smbus.h>
21 #include <linux/slab.h>
23 #define CREATE_TRACE_POINTS
24 #include <trace/events/smbus.h>
29 #define POLY (0x1070U << 3)
30 static u8 crc8(u16 data)
34 for (i = 0; i < 8; i++) {
39 return (u8)(data >> 8);
42 /* Incremental CRC8 over count bytes in the array pointed to by p */
43 static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
47 for (i = 0; i < count; i++)
48 crc = crc8((crc ^ p[i]) << 8);
52 /* Assume a 7-bit address, which is reasonable for SMBus */
53 static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
55 /* The address will be sent first */
56 u8 addr = i2c_8bit_addr_from_msg(msg);
57 pec = i2c_smbus_pec(pec, &addr, 1);
59 /* The data buffer follows */
60 return i2c_smbus_pec(pec, msg->buf, msg->len);
63 /* Used for write only transactions */
64 static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
66 msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
70 /* Return <0 on CRC error
71 If there was a write before this read (most cases) we need to take the
72 partial CRC from the write part into account.
73 Note that this function does modify the message (we need to decrease the
74 message length to hide the CRC byte from the caller). */
75 static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
77 u8 rpec = msg->buf[--msg->len];
78 cpec = i2c_smbus_msg_pec(cpec, msg);
81 pr_debug("Bad PEC 0x%02x vs. 0x%02x\n",
89 * i2c_smbus_read_byte - SMBus "receive byte" protocol
90 * @client: Handle to slave device
92 * This executes the SMBus "receive byte" protocol, returning negative errno
93 * else the byte received from the device.
95 s32 i2c_smbus_read_byte(const struct i2c_client *client)
97 union i2c_smbus_data data;
100 status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
102 I2C_SMBUS_BYTE, &data);
103 return (status < 0) ? status : data.byte;
105 EXPORT_SYMBOL(i2c_smbus_read_byte);
108 * i2c_smbus_write_byte - SMBus "send byte" protocol
109 * @client: Handle to slave device
110 * @value: Byte to be sent
112 * This executes the SMBus "send byte" protocol, returning negative errno
113 * else zero on success.
115 s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
117 return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
118 I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
120 EXPORT_SYMBOL(i2c_smbus_write_byte);
123 * i2c_smbus_read_byte_data - SMBus "read byte" protocol
124 * @client: Handle to slave device
125 * @command: Byte interpreted by slave
127 * This executes the SMBus "read byte" protocol, returning negative errno
128 * else a data byte received from the device.
130 s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command)
132 union i2c_smbus_data data;
135 status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
136 I2C_SMBUS_READ, command,
137 I2C_SMBUS_BYTE_DATA, &data);
138 return (status < 0) ? status : data.byte;
140 EXPORT_SYMBOL(i2c_smbus_read_byte_data);
143 * i2c_smbus_write_byte_data - SMBus "write byte" protocol
144 * @client: Handle to slave device
145 * @command: Byte interpreted by slave
146 * @value: Byte being written
148 * This executes the SMBus "write byte" protocol, returning negative errno
149 * else zero on success.
151 s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command,
154 union i2c_smbus_data data;
156 return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
157 I2C_SMBUS_WRITE, command,
158 I2C_SMBUS_BYTE_DATA, &data);
160 EXPORT_SYMBOL(i2c_smbus_write_byte_data);
163 * i2c_smbus_read_word_data - SMBus "read word" protocol
164 * @client: Handle to slave device
165 * @command: Byte interpreted by slave
167 * This executes the SMBus "read word" protocol, returning negative errno
168 * else a 16-bit unsigned "word" received from the device.
170 s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command)
172 union i2c_smbus_data data;
175 status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
176 I2C_SMBUS_READ, command,
177 I2C_SMBUS_WORD_DATA, &data);
178 return (status < 0) ? status : data.word;
180 EXPORT_SYMBOL(i2c_smbus_read_word_data);
183 * i2c_smbus_write_word_data - SMBus "write word" protocol
184 * @client: Handle to slave device
185 * @command: Byte interpreted by slave
186 * @value: 16-bit "word" being written
188 * This executes the SMBus "write word" protocol, returning negative errno
189 * else zero on success.
191 s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command,
194 union i2c_smbus_data data;
196 return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
197 I2C_SMBUS_WRITE, command,
198 I2C_SMBUS_WORD_DATA, &data);
200 EXPORT_SYMBOL(i2c_smbus_write_word_data);
203 * i2c_smbus_read_block_data - SMBus "block read" protocol
204 * @client: Handle to slave device
205 * @command: Byte interpreted by slave
206 * @values: Byte array into which data will be read; big enough to hold
207 * the data returned by the slave. SMBus allows at most 32 bytes.
209 * This executes the SMBus "block read" protocol, returning negative errno
210 * else the number of data bytes in the slave's response.
212 * Note that using this function requires that the client's adapter support
213 * the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality. Not all adapter drivers
214 * support this; its emulation through I2C messaging relies on a specific
215 * mechanism (I2C_M_RECV_LEN) which may not be implemented.
217 s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command,
220 union i2c_smbus_data data;
223 status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
224 I2C_SMBUS_READ, command,
225 I2C_SMBUS_BLOCK_DATA, &data);
229 memcpy(values, &data.block[1], data.block[0]);
230 return data.block[0];
232 EXPORT_SYMBOL(i2c_smbus_read_block_data);
235 * i2c_smbus_write_block_data - SMBus "block write" protocol
236 * @client: Handle to slave device
237 * @command: Byte interpreted by slave
238 * @length: Size of data block; SMBus allows at most 32 bytes
239 * @values: Byte array which will be written.
241 * This executes the SMBus "block write" protocol, returning negative errno
242 * else zero on success.
244 s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command,
245 u8 length, const u8 *values)
247 union i2c_smbus_data data;
249 if (length > I2C_SMBUS_BLOCK_MAX)
250 length = I2C_SMBUS_BLOCK_MAX;
251 data.block[0] = length;
252 memcpy(&data.block[1], values, length);
253 return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
254 I2C_SMBUS_WRITE, command,
255 I2C_SMBUS_BLOCK_DATA, &data);
257 EXPORT_SYMBOL(i2c_smbus_write_block_data);
259 /* Returns the number of read bytes */
260 s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
261 u8 length, u8 *values)
263 union i2c_smbus_data data;
266 if (length > I2C_SMBUS_BLOCK_MAX)
267 length = I2C_SMBUS_BLOCK_MAX;
268 data.block[0] = length;
269 status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
270 I2C_SMBUS_READ, command,
271 I2C_SMBUS_I2C_BLOCK_DATA, &data);
275 memcpy(values, &data.block[1], data.block[0]);
276 return data.block[0];
278 EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);
280 s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
281 u8 length, const u8 *values)
283 union i2c_smbus_data data;
285 if (length > I2C_SMBUS_BLOCK_MAX)
286 length = I2C_SMBUS_BLOCK_MAX;
287 data.block[0] = length;
288 memcpy(data.block + 1, values, length);
289 return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
290 I2C_SMBUS_WRITE, command,
291 I2C_SMBUS_I2C_BLOCK_DATA, &data);
293 EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);
295 static void i2c_smbus_try_get_dmabuf(struct i2c_msg *msg, u8 init_val)
297 bool is_read = msg->flags & I2C_M_RD;
298 unsigned char *dma_buf;
300 dma_buf = kzalloc(I2C_SMBUS_BLOCK_MAX + (is_read ? 2 : 3), GFP_KERNEL);
305 msg->flags |= I2C_M_DMA_SAFE;
308 msg->buf[0] = init_val;
312 * Simulate a SMBus command using the I2C protocol.
313 * No checking of parameters is done!
315 static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
316 unsigned short flags,
317 char read_write, u8 command, int size,
318 union i2c_smbus_data *data)
321 * So we need to generate a series of msgs. In the case of writing, we
322 * need to use only one message; when reading, we need two. We
323 * initialize most things with sane defaults, to keep the code below
326 unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3];
327 unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
328 int num = read_write == I2C_SMBUS_READ ? 2 : 1;
332 struct i2c_msg msg[2] = {
340 .flags = flags | I2C_M_RD,
346 msgbuf0[0] = command;
348 case I2C_SMBUS_QUICK:
350 /* Special case: The read/write field is used as data */
351 msg[0].flags = flags | (read_write == I2C_SMBUS_READ ?
356 if (read_write == I2C_SMBUS_READ) {
357 /* Special case: only a read! */
358 msg[0].flags = I2C_M_RD | flags;
362 case I2C_SMBUS_BYTE_DATA:
363 if (read_write == I2C_SMBUS_READ)
367 msgbuf0[1] = data->byte;
370 case I2C_SMBUS_WORD_DATA:
371 if (read_write == I2C_SMBUS_READ)
375 msgbuf0[1] = data->word & 0xff;
376 msgbuf0[2] = data->word >> 8;
379 case I2C_SMBUS_PROC_CALL:
380 num = 2; /* Special case */
381 read_write = I2C_SMBUS_READ;
384 msgbuf0[1] = data->word & 0xff;
385 msgbuf0[2] = data->word >> 8;
387 case I2C_SMBUS_BLOCK_DATA:
388 if (read_write == I2C_SMBUS_READ) {
389 msg[1].flags |= I2C_M_RECV_LEN;
390 msg[1].len = 1; /* block length will be added by
391 the underlying bus driver */
392 i2c_smbus_try_get_dmabuf(&msg[1], 0);
394 msg[0].len = data->block[0] + 2;
395 if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
396 dev_err(&adapter->dev,
397 "Invalid block write size %d\n",
402 i2c_smbus_try_get_dmabuf(&msg[0], command);
403 for (i = 1; i < msg[0].len; i++)
404 msg[0].buf[i] = data->block[i - 1];
407 case I2C_SMBUS_BLOCK_PROC_CALL:
408 num = 2; /* Another special case */
409 read_write = I2C_SMBUS_READ;
410 if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
411 dev_err(&adapter->dev,
412 "Invalid block write size %d\n",
417 msg[0].len = data->block[0] + 2;
418 i2c_smbus_try_get_dmabuf(&msg[0], command);
419 for (i = 1; i < msg[0].len; i++)
420 msg[0].buf[i] = data->block[i - 1];
422 msg[1].flags |= I2C_M_RECV_LEN;
423 msg[1].len = 1; /* block length will be added by
424 the underlying bus driver */
425 i2c_smbus_try_get_dmabuf(&msg[1], 0);
427 case I2C_SMBUS_I2C_BLOCK_DATA:
428 if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
429 dev_err(&adapter->dev, "Invalid block %s size %d\n",
430 read_write == I2C_SMBUS_READ ? "read" : "write",
435 if (read_write == I2C_SMBUS_READ) {
436 msg[1].len = data->block[0];
437 i2c_smbus_try_get_dmabuf(&msg[1], 0);
439 msg[0].len = data->block[0] + 1;
441 i2c_smbus_try_get_dmabuf(&msg[0], command);
442 for (i = 1; i <= data->block[0]; i++)
443 msg[0].buf[i] = data->block[i];
447 dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
451 i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
452 && size != I2C_SMBUS_I2C_BLOCK_DATA);
454 /* Compute PEC if first message is a write */
455 if (!(msg[0].flags & I2C_M_RD)) {
456 if (num == 1) /* Write only */
457 i2c_smbus_add_pec(&msg[0]);
458 else /* Write followed by read */
459 partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
461 /* Ask for PEC if last message is a read */
462 if (msg[num-1].flags & I2C_M_RD)
466 status = i2c_transfer(adapter, msg, num);
475 /* Check PEC if last message is a read */
476 if (i && (msg[num-1].flags & I2C_M_RD)) {
477 status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
482 if (read_write == I2C_SMBUS_READ)
485 data->byte = msgbuf0[0];
487 case I2C_SMBUS_BYTE_DATA:
488 data->byte = msgbuf1[0];
490 case I2C_SMBUS_WORD_DATA:
491 case I2C_SMBUS_PROC_CALL:
492 data->word = msgbuf1[0] | (msgbuf1[1] << 8);
494 case I2C_SMBUS_I2C_BLOCK_DATA:
495 for (i = 0; i < data->block[0]; i++)
496 data->block[i + 1] = msg[1].buf[i];
498 case I2C_SMBUS_BLOCK_DATA:
499 case I2C_SMBUS_BLOCK_PROC_CALL:
500 for (i = 0; i < msg[1].buf[0] + 1; i++)
501 data->block[i] = msg[1].buf[i];
506 if (msg[0].flags & I2C_M_DMA_SAFE)
508 if (msg[1].flags & I2C_M_DMA_SAFE)
515 * i2c_smbus_xfer - execute SMBus protocol operations
516 * @adapter: Handle to I2C bus
517 * @addr: Address of SMBus slave on that bus
518 * @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC)
519 * @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE
520 * @command: Byte interpreted by slave, for protocols which use such bytes
521 * @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL
522 * @data: Data to be read or written
524 * This executes an SMBus protocol operation, and returns a negative
525 * errno code else zero on success.
527 s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
528 char read_write, u8 command, int protocol,
529 union i2c_smbus_data *data)
531 unsigned long orig_jiffies;
535 /* If enabled, the following two tracepoints are conditional on
536 * read_write and protocol.
538 trace_smbus_write(adapter, addr, flags, read_write,
539 command, protocol, data);
540 trace_smbus_read(adapter, addr, flags, read_write,
543 flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
545 if (adapter->algo->smbus_xfer) {
546 i2c_lock_bus(adapter, I2C_LOCK_SEGMENT);
548 /* Retry automatically on arbitration loss */
549 orig_jiffies = jiffies;
550 for (res = 0, try = 0; try <= adapter->retries; try++) {
551 res = adapter->algo->smbus_xfer(adapter, addr, flags,
556 if (time_after(jiffies,
557 orig_jiffies + adapter->timeout))
560 i2c_unlock_bus(adapter, I2C_LOCK_SEGMENT);
562 if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
565 * Fall back to i2c_smbus_xfer_emulated if the adapter doesn't
566 * implement native support for the SMBus operation.
570 res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
571 command, protocol, data);
574 /* If enabled, the reply tracepoint is conditional on read_write. */
575 trace_smbus_reply(adapter, addr, flags, read_write,
576 command, protocol, data);
577 trace_smbus_result(adapter, addr, flags, read_write,
578 command, protocol, res);
582 EXPORT_SYMBOL(i2c_smbus_xfer);
585 * i2c_smbus_read_i2c_block_data_or_emulated - read block or emulate
586 * @client: Handle to slave device
587 * @command: Byte interpreted by slave
588 * @length: Size of data block; SMBus allows at most I2C_SMBUS_BLOCK_MAX bytes
589 * @values: Byte array into which data will be read; big enough to hold
590 * the data returned by the slave. SMBus allows at most
591 * I2C_SMBUS_BLOCK_MAX bytes.
593 * This executes the SMBus "block read" protocol if supported by the adapter.
594 * If block read is not supported, it emulates it using either word or byte
595 * read protocols depending on availability.
597 * The addresses of the I2C slave device that are accessed with this function
598 * must be mapped to a linear region, so that a block read will have the same
599 * effect as a byte read. Before using this function you must double-check
600 * if the I2C slave does support exchanging a block transfer with a byte
603 s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
604 u8 command, u8 length, u8 *values)
609 if (length > I2C_SMBUS_BLOCK_MAX)
610 length = I2C_SMBUS_BLOCK_MAX;
612 if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
613 return i2c_smbus_read_i2c_block_data(client, command, length, values);
615 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA))
618 if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)) {
619 while ((i + 2) <= length) {
620 status = i2c_smbus_read_word_data(client, command + i);
623 values[i] = status & 0xff;
624 values[i + 1] = status >> 8;
630 status = i2c_smbus_read_byte_data(client, command + i);
639 EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data_or_emulated);
642 * i2c_setup_smbus_alert - Setup SMBus alert support
643 * @adapter: the target adapter
644 * @setup: setup data for the SMBus alert handler
647 * Setup handling of the SMBus alert protocol on a given I2C bus segment.
649 * Handling can be done either through our IRQ handler, or by the
650 * adapter (from its handler, periodic polling, or whatever).
652 * NOTE that if we manage the IRQ, we *MUST* know if it's level or
653 * edge triggered in order to hand it to the workqueue correctly.
654 * If triggering the alert seems to wedge the system, you probably
655 * should have said it's level triggered.
657 * This returns the ara client, which should be saved for later use with
658 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
659 * to indicate an error.
661 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
662 struct i2c_smbus_alert_setup *setup)
664 struct i2c_board_info ara_board_info = {
665 I2C_BOARD_INFO("smbus_alert", 0x0c),
666 .platform_data = setup,
669 return i2c_new_device(adapter, &ara_board_info);
671 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
673 #if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_OF)
674 int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter)
676 struct i2c_client *client;
679 irq = of_property_match_string(adapter->dev.of_node, "interrupt-names",
681 if (irq == -EINVAL || irq == -ENODATA)
686 client = i2c_setup_smbus_alert(adapter, NULL);
692 EXPORT_SYMBOL_GPL(of_i2c_setup_smbus_alert);