Kok, Auke wrote:
Maybe this is not most important for ixgbe, where we only have 8 or so
flags, but the new e1000 driver that I posted this weekend currently has
63 (you wanted flags ;)) of them. Do you want me to use 63 integers or
just 2 ?
Don't be silly. We are talking about single-bit feature flags
implemented using machine ints (a la tg3 with 32 flags per int), versus
bitfields.
Bitfields are to be avoided for many reasons:
* more difficult, in general, for a compiler to generate optimal code
* in particular, known to generate worse code on various architectures
* often causes endian problems
* often enhances programmer confusion, when trying to review structs and
determine optimal layout and alignment
* programmers have proven they will screw up bitfields in e.g. cases
with 1-bit and signedness.
I can probably think up more reasons to avoid bitfields if given another
5 minutes :)
Jeff
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