mirror of https://gitee.com/openkylin/linux.git
i2c: Kerneldoc for most I/O calls
Provide kerneldoc for most of the I2C and SMBus I/O calls. Add a comment summarizing some fault reporting issues which affect the ability to provide clean fault reports through I2C master transfer calls. (Making it hard to precisely specify their return values...) Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
David Brownell
Jean Delvare
parent
ae7193f7fa
commit
a1cdedac63
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@ -945,10 +945,39 @@ module_exit(i2c_exit);
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* ----------------------------------------------------
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*/
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/**
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* i2c_transfer - execute a single or combined I2C message
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* @adap: Handle to I2C bus
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* @msgs: One or more messages to execute before STOP is issued to
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* terminate the operation; each message begins with a START.
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* @num: Number of messages to be executed.
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*
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* Returns negative errno, else the number of messages executed.
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*
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* Note that there is no requirement that each message be sent to
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* the same slave address, although that is the most common model.
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*/
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int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
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{
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int ret;
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/* REVISIT the fault reporting model here is weak:
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*
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* - When we get an error after receiving N bytes from a slave,
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* there is no way to report "N".
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*
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* - When we get a NAK after transmitting N bytes to a slave,
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* there is no way to report "N" ... or to let the master
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* continue executing the rest of this combined message, if
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* that's the appropriate response.
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*
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* - When for example "num" is two and we successfully complete
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* the first message but get an error part way through the
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* second, it's unclear whether that should be reported as
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* one (discarding status on the second message) or errno
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* (discarding status on the first one).
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*/
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if (adap->algo->master_xfer) {
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#ifdef DEBUG
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for (ret = 0; ret < num; ret++) {
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@ -979,6 +1008,14 @@ int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
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}
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EXPORT_SYMBOL(i2c_transfer);
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/**
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* i2c_master_send - issue a single I2C message in master transmit mode
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* @client: Handle to slave device
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* @buf: Data that will be written to the slave
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* @count: How many bytes to write
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*
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* Returns negative errno, or else the number of bytes written.
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*/
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int i2c_master_send(struct i2c_client *client,const char *buf ,int count)
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{
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int ret;
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@ -998,6 +1035,14 @@ int i2c_master_send(struct i2c_client *client,const char *buf ,int count)
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}
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EXPORT_SYMBOL(i2c_master_send);
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/**
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* i2c_master_recv - issue a single I2C message in master receive mode
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* @client: Handle to slave device
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* @buf: Where to store data read from slave
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* @count: How many bytes to read
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*
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* Returns negative errno, or else the number of bytes read.
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*/
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int i2c_master_recv(struct i2c_client *client, char *buf ,int count)
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{
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struct i2c_adapter *adap=client->adapter;
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@ -1303,6 +1348,13 @@ static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
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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(struct i2c_client *client)
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{
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union i2c_smbus_data data;
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@ -1315,6 +1367,14 @@ s32 i2c_smbus_read_byte(struct i2c_client *client)
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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(struct i2c_client *client, u8 value)
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{
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return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
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@ -1322,6 +1382,14 @@ s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value)
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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(struct i2c_client *client, u8 command)
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{
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union i2c_smbus_data data;
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@ -1334,6 +1402,15 @@ s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command)
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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(struct i2c_client *client, u8 command, u8 value)
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{
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union i2c_smbus_data data;
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@ -1344,6 +1421,14 @@ s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value)
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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(struct i2c_client *client, u8 command)
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{
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union i2c_smbus_data data;
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@ -1356,6 +1441,15 @@ s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command)
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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(struct i2c_client *client, u8 command, u16 value)
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{
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union i2c_smbus_data data;
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@ -1367,15 +1461,14 @@ s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value)
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EXPORT_SYMBOL(i2c_smbus_write_word_data);
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/**
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* i2c_smbus_read_block_data - SMBus block read request
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* i2c_smbus_read_block_data - SMBus "block read" protocol
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* @client: Handle to slave device
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* @command: Command byte issued to let the slave know what data should
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* be returned
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* @command: Byte interpreted by slave
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* @values: Byte array into which data will be read; big enough to hold
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* the data returned by the slave. SMBus allows at most 32 bytes.
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*
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* Returns the number of bytes read in the slave's response, else a
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* negative number to indicate some kind of error.
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* This executes the SMBus "block read" protocol, returning negative errno
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* else the number of data bytes in the slave's response.
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*
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* Note that using this function requires that the client's adapter support
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* the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality. Not all adapter drivers
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@ -1399,6 +1492,16 @@ s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command,
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}
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EXPORT_SYMBOL(i2c_smbus_read_block_data);
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/**
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* i2c_smbus_write_block_data - SMBus "block write" protocol
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* @client: Handle to slave device
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* @command: Byte interpreted by slave
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* @length: Size of data block; SMBus allows at most 32 bytes
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* @values: Byte array which will be written.
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*
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* This executes the SMBus "block write" protocol, returning negative errno
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* else zero on success.
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*/
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s32 i2c_smbus_write_block_data(struct i2c_client *client, u8 command,
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u8 length, const u8 *values)
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{
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@ -1615,9 +1718,21 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
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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 size,
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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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@ -1627,11 +1742,11 @@ s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,
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if (adapter->algo->smbus_xfer) {
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mutex_lock(&adapter->bus_lock);
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res = adapter->algo->smbus_xfer(adapter,addr,flags,read_write,
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command,size,data);
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command, protocol, data);
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mutex_unlock(&adapter->bus_lock);
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} else
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res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,
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command,size,data);
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command, protocol, data);
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return res;
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}
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