WDDM based display driver question..

does user mode display driver must implement all functions mentioned in D3DDI_DEVICEFUNCS structure or some functions are optional as in XPDM based display driver??

one other question :
if i want to use compression for the data i sent to h/w then

does windows provide in buit support of compression or i need extra s/w library or h/w to do that ? or is there any other way…?

thanks for any help…