Man page 9 : i2c_transfer

i2c_transfer - execute a single or combined I2C message

int i2c_transfer(struct i2c_adapter *  adap , struct i2c_msg *  msgs , int  num );

adap
    Handle to I2C bus

msgs
    One or more messages to execute before STOP is issued to terminate the operation; each message begins with a START.

num
    Number of messages to be executed.

Returns negative errno, else the number of messages executed.

Note that there is no requirement that each message be sent to the same slave address, although that is the most common model.