In many cases its not needed. Devices tend to be structured to avoid having
to force pci writes - that by definition is a CPU stall and loses you marks
in the benchmarketing and the pretty zdnet graphs.
There other thing it can also hide is pci write merging bugs (which some
devices have). For example at least one ethernet chip fails if you do
writew(mac_addr, ioport+foo);
writew(mac_addr+2, ioport+foo+2);
writew(mac_addr+4, ioport+foo+4);
because the writes get merged and a chip bug causes a bus hang on the 32bit
write of the mac address. In that case its not the posting being masked but
the merging.
Alan
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