Robert P. J. Day wrote: > > seriously, though, there is the potential of breaking something with > this change since you can see how there is some inconsistency in how > it's done *now* just for powerpc which, in some places, defines its > own versions of this: > > ./arch/ppc/mm/pgtable.c: > #define is_power_of_2(x) ((x) != 0 && (((x) & ((x) - 1)) == 0)) > ./arch/ppc/syslib/ppc85xx_rio.c: > #define is_power_of_2(x) (((x) & ((x) - 1)) == 0) > ./arch/powerpc/mm/pgtable_32.c: > #define is_power_of_2(x) ((x) != 0 && (((x) & ((x) - 1)) == 0)) > > note how the first and third macros *won't* consider zero a power of > two, while the second one *will*. hence the need for a single > standard for all of this, just to play it safe. >
I suspect the reason the test for zero was omitted is because the author didn't want the extra cost (the test for zero needs an extra branch on a lot of architectures.) -hpa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/