372 lines
10 KiB
C
372 lines
10 KiB
C
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#include <common.h>
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#include <errno.h>
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#include <i2c/i2c.h>
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/* The SMBus parts */
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#define POLY (0x1070U << 3)
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static u8 crc8(u16 data)
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{
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int i;
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for (i = 0; i < 8; i++) {
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if (data & 0x8000)
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data = data ^ POLY;
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data = data << 1;
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}
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return (u8)(data >> 8);
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}
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/* Incremental CRC8 over count bytes in the array pointed to by p */
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static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
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{
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int i;
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for (i = 0; i < count; i++)
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crc = crc8((crc ^ p[i]) << 8);
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return crc;
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}
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/* Assume a 7-bit address, which is reasonable for SMBus */
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static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
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{
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/* The address will be sent first */
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u8 addr = (msg->addr << 1) | !!(msg->flags & I2C_M_RD);
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pec = i2c_smbus_pec(pec, &addr, 1);
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/* The data buffer follows */
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return i2c_smbus_pec(pec, msg->buf, msg->len);
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}
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/* Used for write only transactions */
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static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
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{
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msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
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msg->len++;
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}
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/* Return <0 on CRC error
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If there was a write before this read (most cases) we need to take the
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partial CRC from the write part into account.
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Note that this function does modify the message (we need to decrease the
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message length to hide the CRC byte from the caller). */
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static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
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{
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u8 rpec = msg->buf[--msg->len];
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cpec = i2c_smbus_msg_pec(cpec, msg);
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if (rpec != cpec) {
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pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
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rpec, cpec);
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return -EBADMSG;
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}
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return 0;
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}
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/**
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* i2c_smbus_read_byte - SMBus "receive byte" protocol
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* @client: Handle to slave device
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*
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* This executes the SMBus "receive byte" protocol, returning negative errno
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* else the byte received from the device.
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*/
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s32 i2c_smbus_read_byte(const struct i2c_client *client)
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{
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union i2c_smbus_data data;
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int status;
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status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_READ, 0,
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I2C_SMBUS_BYTE, &data);
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return (status < 0) ? status : data.byte;
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}
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EXPORT_SYMBOL(i2c_smbus_read_byte);
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/**
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* i2c_smbus_write_byte - SMBus "send byte" protocol
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* @client: Handle to slave device
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* @value: Byte to be sent
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*
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* This executes the SMBus "send byte" protocol, returning negative errno
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* else zero on success.
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*/
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s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
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{
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return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
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}
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EXPORT_SYMBOL(i2c_smbus_write_byte);
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/**
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* i2c_smbus_read_byte_data - SMBus "read byte" protocol
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* @client: Handle to slave device
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* @command: Byte interpreted by slave
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*
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* This executes the SMBus "read byte" protocol, returning negative errno
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* else a data byte received from the device.
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*/
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s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command)
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{
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union i2c_smbus_data data;
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int status;
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status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_READ, command,
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I2C_SMBUS_BYTE_DATA, &data);
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return (status < 0) ? status : data.byte;
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}
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EXPORT_SYMBOL(i2c_smbus_read_byte_data);
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/**
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* i2c_smbus_write_byte_data - SMBus "write byte" protocol
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* @client: Handle to slave device
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* @command: Byte interpreted by slave
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* @value: Byte being written
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*
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* This executes the SMBus "write byte" protocol, returning negative errno
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* else zero on success.
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*/
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s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command,
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u8 value)
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{
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union i2c_smbus_data data;
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data.byte = value;
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return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_WRITE, command,
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I2C_SMBUS_BYTE_DATA, &data);
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}
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EXPORT_SYMBOL(i2c_smbus_write_byte_data);
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/**
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* i2c_smbus_read_word_data - SMBus "read word" protocol
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* @client: Handle to slave device
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* @command: Byte interpreted by slave
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*
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* This executes the SMBus "read word" protocol, returning negative errno
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* else a 16-bit unsigned "word" received from the device.
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*/
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s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command)
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{
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union i2c_smbus_data data;
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int status;
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status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_READ, command,
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I2C_SMBUS_WORD_DATA, &data);
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return (status < 0) ? status : data.word;
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}
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EXPORT_SYMBOL(i2c_smbus_read_word_data);
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/**
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* i2c_smbus_write_word_data - SMBus "write word" protocol
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* @client: Handle to slave device
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* @command: Byte interpreted by slave
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* @value: 16-bit "word" being written
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*
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* This executes the SMBus "write word" protocol, returning negative errno
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* else zero on success.
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*/
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s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command,
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u16 value)
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{
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union i2c_smbus_data data;
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data.word = value;
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return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_WRITE, command,
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I2C_SMBUS_WORD_DATA, &data);
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}
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EXPORT_SYMBOL(i2c_smbus_write_word_data);
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/* Returns the number of read bytes */
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s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
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u8 length, u8 *values)
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{
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union i2c_smbus_data data;
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int status;
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if (length > I2C_SMBUS_BLOCK_MAX)
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length = I2C_SMBUS_BLOCK_MAX;
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data.block[0] = length;
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status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_READ, command,
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I2C_SMBUS_I2C_BLOCK_DATA, &data);
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if (status < 0)
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return status;
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memcpy(values, &data.block[1], data.block[0]);
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return data.block[0];
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}
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EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);
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s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
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u8 length, const u8 *values)
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{
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union i2c_smbus_data data;
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if (length > I2C_SMBUS_BLOCK_MAX)
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length = I2C_SMBUS_BLOCK_MAX;
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data.block[0] = length;
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memcpy(data.block + 1, values, length);
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return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
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I2C_SMBUS_WRITE, command,
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I2C_SMBUS_I2C_BLOCK_DATA, &data);
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}
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EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);
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/* Simulate a SMBus command using the i2c protocol
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No checking of parameters is done! */
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static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
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unsigned short flags,
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char read_write, u8 command, int size,
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union i2c_smbus_data *data)
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{
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/* So we need to generate a series of msgs. In the case of writing, we
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need to use only one message; when reading, we need two. We initialize
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most things with sane defaults, to keep the code below somewhat
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simpler. */
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unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3];
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unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
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int num = read_write == I2C_SMBUS_READ ? 2 : 1;
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int i;
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u8 partial_pec = 0;
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int status;
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struct i2c_msg msg[2] = {
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{
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.addr = addr,
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.flags = flags,
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.len = 1,
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.buf = msgbuf0,
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}, {
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.addr = addr,
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.flags = flags | I2C_M_RD,
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.len = 0,
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.buf = msgbuf1,
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},
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};
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msgbuf0[0] = command;
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switch (size) {
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case I2C_SMBUS_QUICK:
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msg[0].len = 0;
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/* Special case: The read/write field is used as data */
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msg[0].flags = flags | (read_write == I2C_SMBUS_READ ?
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I2C_M_RD : 0);
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num = 1;
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break;
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case I2C_SMBUS_BYTE:
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if (read_write == I2C_SMBUS_READ) {
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/* Special case: only a read! */
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msg[0].flags = I2C_M_RD | flags;
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num = 1;
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}
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break;
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case I2C_SMBUS_BYTE_DATA:
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if (read_write == I2C_SMBUS_READ)
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msg[1].len = 1;
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else {
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msg[0].len = 2;
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msgbuf0[1] = data->byte;
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}
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break;
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case I2C_SMBUS_WORD_DATA:
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if (read_write == I2C_SMBUS_READ)
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msg[1].len = 2;
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else {
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msg[0].len = 3;
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msgbuf0[1] = data->word & 0xff;
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msgbuf0[2] = data->word >> 8;
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}
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break;
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case I2C_SMBUS_I2C_BLOCK_DATA:
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if (read_write == I2C_SMBUS_READ) {
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msg[1].len = data->block[0];
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} else {
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msg[0].len = data->block[0] + 1;
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if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
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dev_err(&adapter->dev,
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"Invalid block write size %d\n",
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data->block[0]);
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return -EINVAL;
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}
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for (i = 1; i <= data->block[0]; i++)
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msgbuf0[i] = data->block[i];
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}
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break;
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default:
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dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
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return -EOPNOTSUPP;
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}
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i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
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&& size != I2C_SMBUS_I2C_BLOCK_DATA);
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if (i) {
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/* Compute PEC if first message is a write */
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if (!(msg[0].flags & I2C_M_RD)) {
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if (num == 1) /* Write only */
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i2c_smbus_add_pec(&msg[0]);
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else /* Write followed by read */
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partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
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}
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/* Ask for PEC if last message is a read */
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if (msg[num-1].flags & I2C_M_RD)
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msg[num-1].len++;
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}
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status = i2c_transfer(adapter, msg, num);
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if (status < 0)
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return status;
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/* Check PEC if last message is a read */
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if (i && (msg[num-1].flags & I2C_M_RD)) {
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status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
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if (status < 0)
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return status;
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}
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if (read_write == I2C_SMBUS_READ)
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switch (size) {
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case I2C_SMBUS_BYTE:
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data->byte = msgbuf0[0];
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break;
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case I2C_SMBUS_BYTE_DATA:
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data->byte = msgbuf1[0];
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break;
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case I2C_SMBUS_WORD_DATA:
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data->word = msgbuf1[0] | (msgbuf1[1] << 8);
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break;
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case I2C_SMBUS_I2C_BLOCK_DATA:
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for (i = 0; i < data->block[0]; i++)
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data->block[i+1] = msgbuf1[i];
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break;
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}
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return 0;
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}
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/**
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* i2c_smbus_xfer - execute SMBus protocol operations
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* @adapter: Handle to I2C bus
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* @addr: Address of SMBus slave on that bus
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* @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC)
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* @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE
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* @command: Byte interpreted by slave, for protocols which use such bytes
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* @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL
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* @data: Data to be read or written
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*
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* This executes an SMBus protocol operation, and returns a negative
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* errno code else zero on success.
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*/
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s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
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char read_write, u8 command, int protocol,
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union i2c_smbus_data *data)
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{
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s32 res;
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flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
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res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
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command, protocol, data);
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return res;
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}
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EXPORT_SYMBOL(i2c_smbus_xfer);
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