spi - real protocols

Hello, As I understand word length in spi, defines the cs active time. It therefore seems that linux driver suits when dealing with simple spi protocols which keeps word size constant. How can we deal with spi protocols which use different spi size as part of protocol. for example cs need to be active for sending spi word - 9 bits, and then reading spi - 8 bit word (only after write+read spi changes values back to non active), How can we implement that ? Do we need to set bits_per_word size for the sending and then another bits_per_word for the receiving ? Regards, Ran