i2c: break out smbus support into separate file

Break out the exported SMBus functions and the emulation layer into a
separate file. This also involved splitting up the tracing header into
an I2C and an SMBus part.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 594 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
new file mode 100644
index 000000000000..10f00a82ec9d
--- /dev/null
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -0,0 +1,594 @@
+/*
+ * Linux I2C core SMBus and SMBus emulation code
+ *
+ * This file contains the SMBus functions which are always included in the I2C
+ * core because they can be emulated via I2C. SMBus specific extensions
+ * (e.g. smbalert) are handled in a seperate i2c-smbus module.
+ *
+ * All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
+ * SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
+ * Jean Delvare <jdelvare@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/smbus.h>
+
+
+/* The SMBus parts */
+
+#define POLY    (0x1070U << 3)
+static u8 crc8(u16 data)
+{
+	int i;
+
+	for (i = 0; i < 8; i++) {
+		if (data & 0x8000)
+			data = data ^ POLY;
+		data = data << 1;
+	}
+	return (u8)(data >> 8);
+}
+
+/* Incremental CRC8 over count bytes in the array pointed to by p */
+static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
+{
+	int i;
+
+	for (i = 0; i < count; i++)
+		crc = crc8((crc ^ p[i]) << 8);
+	return crc;
+}
+
+/* Assume a 7-bit address, which is reasonable for SMBus */
+static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
+{
+	/* The address will be sent first */
+	u8 addr = i2c_8bit_addr_from_msg(msg);
+	pec = i2c_smbus_pec(pec, &addr, 1);
+
+	/* The data buffer follows */
+	return i2c_smbus_pec(pec, msg->buf, msg->len);
+}
+
+/* Used for write only transactions */
+static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
+{
+	msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
+	msg->len++;
+}
+
+/* Return <0 on CRC error
+   If there was a write before this read (most cases) we need to take the
+   partial CRC from the write part into account.
+   Note that this function does modify the message (we need to decrease the
+   message length to hide the CRC byte from the caller). */
+static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
+{
+	u8 rpec = msg->buf[--msg->len];
+	cpec = i2c_smbus_msg_pec(cpec, msg);
+
+	if (rpec != cpec) {
+		pr_debug("Bad PEC 0x%02x vs. 0x%02x\n",
+			rpec, cpec);
+		return -EBADMSG;
+	}
+	return 0;
+}
+
+/**
+ * i2c_smbus_read_byte - SMBus "receive byte" protocol
+ * @client: Handle to slave device
+ *
+ * This executes the SMBus "receive byte" protocol, returning negative errno
+ * else the byte received from the device.
+ */
+s32 i2c_smbus_read_byte(const struct i2c_client *client)
+{
+	union i2c_smbus_data data;
+	int status;
+
+	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+				I2C_SMBUS_READ, 0,
+				I2C_SMBUS_BYTE, &data);
+	return (status < 0) ? status : data.byte;
+}
+EXPORT_SYMBOL(i2c_smbus_read_byte);
+
+/**
+ * i2c_smbus_write_byte - SMBus "send byte" protocol
+ * @client: Handle to slave device
+ * @value: Byte to be sent
+ *
+ * This executes the SMBus "send byte" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
+{
+	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+	                      I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
+}
+EXPORT_SYMBOL(i2c_smbus_write_byte);
+
+/**
+ * i2c_smbus_read_byte_data - SMBus "read byte" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ *
+ * This executes the SMBus "read byte" protocol, returning negative errno
+ * else a data byte received from the device.
+ */
+s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command)
+{
+	union i2c_smbus_data data;
+	int status;
+
+	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+				I2C_SMBUS_READ, command,
+				I2C_SMBUS_BYTE_DATA, &data);
+	return (status < 0) ? status : data.byte;
+}
+EXPORT_SYMBOL(i2c_smbus_read_byte_data);
+
+/**
+ * i2c_smbus_write_byte_data - SMBus "write byte" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @value: Byte being written
+ *
+ * This executes the SMBus "write byte" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command,
+			      u8 value)
+{
+	union i2c_smbus_data data;
+	data.byte = value;
+	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+			      I2C_SMBUS_WRITE, command,
+			      I2C_SMBUS_BYTE_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_byte_data);
+
+/**
+ * i2c_smbus_read_word_data - SMBus "read word" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ *
+ * This executes the SMBus "read word" protocol, returning negative errno
+ * else a 16-bit unsigned "word" received from the device.
+ */
+s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command)
+{
+	union i2c_smbus_data data;
+	int status;
+
+	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+				I2C_SMBUS_READ, command,
+				I2C_SMBUS_WORD_DATA, &data);
+	return (status < 0) ? status : data.word;
+}
+EXPORT_SYMBOL(i2c_smbus_read_word_data);
+
+/**
+ * i2c_smbus_write_word_data - SMBus "write word" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @value: 16-bit "word" being written
+ *
+ * This executes the SMBus "write word" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command,
+			      u16 value)
+{
+	union i2c_smbus_data data;
+	data.word = value;
+	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+			      I2C_SMBUS_WRITE, command,
+			      I2C_SMBUS_WORD_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_word_data);
+
+/**
+ * i2c_smbus_read_block_data - SMBus "block read" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @values: Byte array into which data will be read; big enough to hold
+ *	the data returned by the slave.  SMBus allows at most 32 bytes.
+ *
+ * This executes the SMBus "block read" protocol, returning negative errno
+ * else the number of data bytes in the slave's response.
+ *
+ * Note that using this function requires that the client's adapter support
+ * the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality.  Not all adapter drivers
+ * support this; its emulation through I2C messaging relies on a specific
+ * mechanism (I2C_M_RECV_LEN) which may not be implemented.
+ */
+s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command,
+			      u8 *values)
+{
+	union i2c_smbus_data data;
+	int status;
+
+	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+				I2C_SMBUS_READ, command,
+				I2C_SMBUS_BLOCK_DATA, &data);
+	if (status)
+		return status;
+
+	memcpy(values, &data.block[1], data.block[0]);
+	return data.block[0];
+}
+EXPORT_SYMBOL(i2c_smbus_read_block_data);
+
+/**
+ * i2c_smbus_write_block_data - SMBus "block write" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @length: Size of data block; SMBus allows at most 32 bytes
+ * @values: Byte array which will be written.
+ *
+ * This executes the SMBus "block write" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command,
+			       u8 length, const u8 *values)
+{
+	union i2c_smbus_data data;
+
+	if (length > I2C_SMBUS_BLOCK_MAX)
+		length = I2C_SMBUS_BLOCK_MAX;
+	data.block[0] = length;
+	memcpy(&data.block[1], values, length);
+	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+			      I2C_SMBUS_WRITE, command,
+			      I2C_SMBUS_BLOCK_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_block_data);
+
+/* Returns the number of read bytes */
+s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
+				  u8 length, u8 *values)
+{
+	union i2c_smbus_data data;
+	int status;
+
+	if (length > I2C_SMBUS_BLOCK_MAX)
+		length = I2C_SMBUS_BLOCK_MAX;
+	data.block[0] = length;
+	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+				I2C_SMBUS_READ, command,
+				I2C_SMBUS_I2C_BLOCK_DATA, &data);
+	if (status < 0)
+		return status;
+
+	memcpy(values, &data.block[1], data.block[0]);
+	return data.block[0];
+}
+EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);
+
+s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
+				   u8 length, const u8 *values)
+{
+	union i2c_smbus_data data;
+
+	if (length > I2C_SMBUS_BLOCK_MAX)
+		length = I2C_SMBUS_BLOCK_MAX;
+	data.block[0] = length;
+	memcpy(data.block + 1, values, length);
+	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+			      I2C_SMBUS_WRITE, command,
+			      I2C_SMBUS_I2C_BLOCK_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);
+
+/* Simulate a SMBus command using the i2c protocol
+   No checking of parameters is done!  */
+static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
+				   unsigned short flags,
+				   char read_write, u8 command, int size,
+				   union i2c_smbus_data *data)
+{
+	/* So we need to generate a series of msgs. In the case of writing, we
+	  need to use only one message; when reading, we need two. We initialize
+	  most things with sane defaults, to keep the code below somewhat
+	  simpler. */
+	unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3];
+	unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
+	int num = read_write == I2C_SMBUS_READ ? 2 : 1;
+	int i;
+	u8 partial_pec = 0;
+	int status;
+	struct i2c_msg msg[2] = {
+		{
+			.addr = addr,
+			.flags = flags,
+			.len = 1,
+			.buf = msgbuf0,
+		}, {
+			.addr = addr,
+			.flags = flags | I2C_M_RD,
+			.len = 0,
+			.buf = msgbuf1,
+		},
+	};
+
+	msgbuf0[0] = command;
+	switch (size) {
+	case I2C_SMBUS_QUICK:
+		msg[0].len = 0;
+		/* Special case: The read/write field is used as data */
+		msg[0].flags = flags | (read_write == I2C_SMBUS_READ ?
+					I2C_M_RD : 0);
+		num = 1;
+		break;
+	case I2C_SMBUS_BYTE:
+		if (read_write == I2C_SMBUS_READ) {
+			/* Special case: only a read! */
+			msg[0].flags = I2C_M_RD | flags;
+			num = 1;
+		}
+		break;
+	case I2C_SMBUS_BYTE_DATA:
+		if (read_write == I2C_SMBUS_READ)
+			msg[1].len = 1;
+		else {
+			msg[0].len = 2;
+			msgbuf0[1] = data->byte;
+		}
+		break;
+	case I2C_SMBUS_WORD_DATA:
+		if (read_write == I2C_SMBUS_READ)
+			msg[1].len = 2;
+		else {
+			msg[0].len = 3;
+			msgbuf0[1] = data->word & 0xff;
+			msgbuf0[2] = data->word >> 8;
+		}
+		break;
+	case I2C_SMBUS_PROC_CALL:
+		num = 2; /* Special case */
+		read_write = I2C_SMBUS_READ;
+		msg[0].len = 3;
+		msg[1].len = 2;
+		msgbuf0[1] = data->word & 0xff;
+		msgbuf0[2] = data->word >> 8;
+		break;
+	case I2C_SMBUS_BLOCK_DATA:
+		if (read_write == I2C_SMBUS_READ) {
+			msg[1].flags |= I2C_M_RECV_LEN;
+			msg[1].len = 1; /* block length will be added by
+					   the underlying bus driver */
+		} else {
+			msg[0].len = data->block[0] + 2;
+			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
+				dev_err(&adapter->dev,
+					"Invalid block write size %d\n",
+					data->block[0]);
+				return -EINVAL;
+			}
+			for (i = 1; i < msg[0].len; i++)
+				msgbuf0[i] = data->block[i-1];
+		}
+		break;
+	case I2C_SMBUS_BLOCK_PROC_CALL:
+		num = 2; /* Another special case */
+		read_write = I2C_SMBUS_READ;
+		if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
+			dev_err(&adapter->dev,
+				"Invalid block write size %d\n",
+				data->block[0]);
+			return -EINVAL;
+		}
+		msg[0].len = data->block[0] + 2;
+		for (i = 1; i < msg[0].len; i++)
+			msgbuf0[i] = data->block[i-1];
+		msg[1].flags |= I2C_M_RECV_LEN;
+		msg[1].len = 1; /* block length will be added by
+				   the underlying bus driver */
+		break;
+	case I2C_SMBUS_I2C_BLOCK_DATA:
+		if (read_write == I2C_SMBUS_READ) {
+			msg[1].len = data->block[0];
+		} else {
+			msg[0].len = data->block[0] + 1;
+			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
+				dev_err(&adapter->dev,
+					"Invalid block write size %d\n",
+					data->block[0]);
+				return -EINVAL;
+			}
+			for (i = 1; i <= data->block[0]; i++)
+				msgbuf0[i] = data->block[i];
+		}
+		break;
+	default:
+		dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
+		return -EOPNOTSUPP;
+	}
+
+	i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
+				      && size != I2C_SMBUS_I2C_BLOCK_DATA);
+	if (i) {
+		/* Compute PEC if first message is a write */
+		if (!(msg[0].flags & I2C_M_RD)) {
+			if (num == 1) /* Write only */
+				i2c_smbus_add_pec(&msg[0]);
+			else /* Write followed by read */
+				partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
+		}
+		/* Ask for PEC if last message is a read */
+		if (msg[num-1].flags & I2C_M_RD)
+			msg[num-1].len++;
+	}
+
+	status = i2c_transfer(adapter, msg, num);
+	if (status < 0)
+		return status;
+
+	/* Check PEC if last message is a read */
+	if (i && (msg[num-1].flags & I2C_M_RD)) {
+		status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
+		if (status < 0)
+			return status;
+	}
+
+	if (read_write == I2C_SMBUS_READ)
+		switch (size) {
+		case I2C_SMBUS_BYTE:
+			data->byte = msgbuf0[0];
+			break;
+		case I2C_SMBUS_BYTE_DATA:
+			data->byte = msgbuf1[0];
+			break;
+		case I2C_SMBUS_WORD_DATA:
+		case I2C_SMBUS_PROC_CALL:
+			data->word = msgbuf1[0] | (msgbuf1[1] << 8);
+			break;
+		case I2C_SMBUS_I2C_BLOCK_DATA:
+			for (i = 0; i < data->block[0]; i++)
+				data->block[i+1] = msgbuf1[i];
+			break;
+		case I2C_SMBUS_BLOCK_DATA:
+		case I2C_SMBUS_BLOCK_PROC_CALL:
+			for (i = 0; i < msgbuf1[0] + 1; i++)
+				data->block[i] = msgbuf1[i];
+			break;
+		}
+	return 0;
+}
+
+/**
+ * i2c_smbus_xfer - execute SMBus protocol operations
+ * @adapter: Handle to I2C bus
+ * @addr: Address of SMBus slave on that bus
+ * @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC)
+ * @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE
+ * @command: Byte interpreted by slave, for protocols which use such bytes
+ * @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL
+ * @data: Data to be read or written
+ *
+ * This executes an SMBus protocol operation, and returns a negative
+ * errno code else zero on success.
+ */
+s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
+		   char read_write, u8 command, int protocol,
+		   union i2c_smbus_data *data)
+{
+	unsigned long orig_jiffies;
+	int try;
+	s32 res;
+
+	/* If enabled, the following two tracepoints are conditional on
+	 * read_write and protocol.
+	 */
+	trace_smbus_write(adapter, addr, flags, read_write,
+			  command, protocol, data);
+	trace_smbus_read(adapter, addr, flags, read_write,
+			 command, protocol);
+
+	flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
+
+	if (adapter->algo->smbus_xfer) {
+		i2c_lock_bus(adapter, I2C_LOCK_SEGMENT);
+
+		/* Retry automatically on arbitration loss */
+		orig_jiffies = jiffies;
+		for (res = 0, try = 0; try <= adapter->retries; try++) {
+			res = adapter->algo->smbus_xfer(adapter, addr, flags,
+							read_write, command,
+							protocol, data);
+			if (res != -EAGAIN)
+				break;
+			if (time_after(jiffies,
+				       orig_jiffies + adapter->timeout))
+				break;
+		}
+		i2c_unlock_bus(adapter, I2C_LOCK_SEGMENT);
+
+		if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
+			goto trace;
+		/*
+		 * Fall back to i2c_smbus_xfer_emulated if the adapter doesn't
+		 * implement native support for the SMBus operation.
+		 */
+	}
+
+	res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
+				      command, protocol, data);
+
+trace:
+	/* If enabled, the reply tracepoint is conditional on read_write. */
+	trace_smbus_reply(adapter, addr, flags, read_write,
+			  command, protocol, data);
+	trace_smbus_result(adapter, addr, flags, read_write,
+			   command, protocol, res);
+
+	return res;
+}
+EXPORT_SYMBOL(i2c_smbus_xfer);
+
+/**
+ * i2c_smbus_read_i2c_block_data_or_emulated - read block or emulate
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @length: Size of data block; SMBus allows at most I2C_SMBUS_BLOCK_MAX bytes
+ * @values: Byte array into which data will be read; big enough to hold
+ *	the data returned by the slave.  SMBus allows at most
+ *	I2C_SMBUS_BLOCK_MAX bytes.
+ *
+ * This executes the SMBus "block read" protocol if supported by the adapter.
+ * If block read is not supported, it emulates it using either word or byte
+ * read protocols depending on availability.
+ *
+ * The addresses of the I2C slave device that are accessed with this function
+ * must be mapped to a linear region, so that a block read will have the same
+ * effect as a byte read. Before using this function you must double-check
+ * if the I2C slave does support exchanging a block transfer with a byte
+ * transfer.
+ */
+s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
+					      u8 command, u8 length, u8 *values)
+{
+	u8 i = 0;
+	int status;
+
+	if (length > I2C_SMBUS_BLOCK_MAX)
+		length = I2C_SMBUS_BLOCK_MAX;
+
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
+		return i2c_smbus_read_i2c_block_data(client, command, length, values);
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA))
+		return -EOPNOTSUPP;
+
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+		while ((i + 2) <= length) {
+			status = i2c_smbus_read_word_data(client, command + i);
+			if (status < 0)
+				return status;
+			values[i] = status & 0xff;
+			values[i + 1] = status >> 8;
+			i += 2;
+		}
+	}
+
+	while (i < length) {
+		status = i2c_smbus_read_byte_data(client, command + i);
+		if (status < 0)
+			return status;
+		values[i] = status;
+		i++;
+	}
+
+	return i;
+}
+EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data_or_emulated);