On Wed, 31 Oct 2012 07:30:33 +0100 Stefani Seibold <stef...@seibold.net> wrote:
> > Yes, and I guess the same to give them a 64-element one. > > > > > > > > If there's absolutely no prospect that the kfifo code will ever support > > > 100-byte fifos then I guess we should rework the API so that the caller > > > has to pass in log2 of the size, not the size itself. That way there > > > will be no surprises and no mistakes. > > > > > > That being said, the power-of-2 limitation isn't at all intrinsic to a > > > fifo, so we shouldn't do this. Ideally, we'd change the kfifo > > > implementation so it does what the caller asked it to do! > > > > I'm fine with removing the power-of-2 limitation. Stefani, what's your > > comment on that? > > > > You can't remove the power-of-2-limitation, since this would result in a > performance decrease (bit wise and vs. modulo operation). Probably an insignificant change in performance. It could be made much smaller by just never doing the modulus operation - instead do if (++index == max) index = 0; this does introduce one problem: it's no longer possible to distinguish the "full" and "empty" states by comparing the head and tail indices. But that is soluble. > Andrew is right, this is an API miss design. So it would be good to > rework the kfifo_init () and kfifo_alloc() to pass in log2 of the size, > not the size itself. The power-of-2 thing is just a restriction in the current implementation - it's not a good idea to cement that into the interface. Of course, it could later be uncemented if the implementation's restriction was later relaxed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/