Please refer below code for possible values of I2CRegAddr to pass to I2cInitEx for the Tegra platform.
case 0x7000c000: i2c_channel = 1; break; // I2C1
case 0x7000c400: i2c_channel = 2; break; // I2C2
case 0x7000c500: i2c_channel = 3; break; // I2C3
case 0x7000c700: i2c_channel = 4; break; // I2C4 (T30 only)
case 0x7000d000: i2c_channel = 5; break; // I2C5 (T30 only) = DVC
e.g.: I2CInitEx(0x7000C500) // I2C_3
We have new Toradex CE libraries, there these things are handled internally inside the library and you just need to pass I2c channel to the I2c_Init function, please refer Toradex_CE_Libraries.chm documentation and libDemos for demo applications.
Please feel free to contact us if you have any other questions.