CONFIG_SYS_MXC_I2C3_SPEED - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE If those defines are not set, default value is 100000 for speed, and 0 for slave....