> my_data = read_drom_device() > swap_to_cpu(my_data) > do_whatever(my_data) > store the data somewhere else in the device structs for > later use, maybe. > do_something_else(my_data) > > You see that now you have only _one_ place that you have to care about. > And if you have to write your data back at some point, simply do it > just before the write. The thing is that Tomas is saying that because they don't have a function to "read_from_device()" but that is rather only "shared_structure->something" it is special and completely different than regular drivers. The absolute worst thing imo is in the current radiotap code (before my patch) where it passes around a value as "u16" but then needs to convert it to __le16 before accessing bits in it because things are defined as LE. Also, let me reiterate the argument that this is not using more code/run-time-memory size: Consider u16 phyflags = le16_to_cpu(shared_struct->phy_flags); [...] if (phyflags & ...) [...] vs. [...] if (shared_struct->phy_flags & ...) [...] If you have a LE machine, then the compiler should in both cases emit the same code. If you have BE machine, you have a *single* "superfluous" byteswap, and if there are multi-bit fields you have far *fewer* byteswaps. If you instead wrote u16 phyflags = le16_to_cpup(&shared_struct->phy_flags); then most likely the byteswap would be microcoded/done by hardware during the load. The actual runtime penalty of byteswaps is insignificant since fetching the value from memory already takes forever. johannes
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