Hello!
Upon looking for a function/macro for computing the logarithm to the
base 2 I found multiple implementations in the kernel source
(2.6.10-rc3), but none fitting my requirements:
* generic (will compute logarithm instead of a table lookup)
* portable (unlike e.g. ceil_log2 only in asm-alpha)
It kind of looks like everyone is reinventing the wheel with several
implementations under differing names are within the kernel. Sometimes
they are hardcoded (results already put in as constant), sometimes a
lookup table is used, and several slightly different algorithms with bit
shift are used.
Is this desirable? While it may be some reduction for special cases
using a table (like in the log2_2048 function I found - it computes only
a certain of log2 and multiplies this with 2048), wouldn't a more
generic implementation like ceil_log2 and floor_log2 not be desirable
for all platforms?
Or have I simply overlooked the right function?
Thanks and with kind regards,
Oliver Korpilla
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