From: Lothar Waßmann <l...@karo-electronics.de> Date: Tue, 4 Nov 2014 11:29:12 +0100
> Hi David, > > Lothar Waßmann wrote: >> David Miller wrote: >> > From: Lothar Waßmann <l...@karo-electronics.de> >> > Date: Thu, 30 Oct 2014 07:51:04 +0100 >> > >> > >> Also, I don't thnk your DIV_ROUND_UP() eliminate for the loop >> > >> in swap_buffer() is valid. The whole point is that the current >> > >> code handles buffers which have a length which is not a multiple >> > >> of 4 properly, after your change it will no longer do so. >> > >> >> > > Do you really think so? >> > >> > Yes, because you're rounding down so you'll miss the final >> > partial word (if any). >> > >> Nope. DIV_ROUND_UP() would give '1' as upper bound for lengths from 1 to >> 4, '2' for lengths from 5 to 8 and so on. >> >> The loop with increment 4 and i < len does exactly the same. >> Try it for yourself, if you don't believe it. >> >> > Do you still think, the loop without DIV_ROUND_UP() is incorrect, > or can this patch be applied? I haven't had the time to fully re-look into the details, I'm busy with many other things at the moment. But looking at DIV_ROUND_UP() macro it rounds up. It gives an upper bound of 4 for any value 1 to 4. Unlike what you claim. Because it goes "(n + (d - 1)) / d" Which for 'd' of 4 gives: 1 --> 4 2 --> 4 3 --> 4 4 --> 4 -- 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/
