ad7291 baremetal example issue


I reviewed AD7291 example in:

AD7291 - Microcontroller No-OS Driver [Analog Devices Wiki] 

and there is something I misunderstand:

AD7291_GetVoltageConversionResults() checks the channel mask, but I don't see anywhere in example where that channel mask is being set,

By default, the command register is 0 according to datasheet, so how can it function if the channel mask is not being set by driver ?

Thank you,