On Mon, 28 Jan 2008 02:20:00 -0800 Andrew Morton <[EMAIL PROTECTED]> wrote:
> On Mon, 28 Jan 2008 10:59:09 +0100 Haavard Skinnemoen <[EMAIL PROTECTED]> > wrote: > > > > ho-hum. The generic uart buffer-handling code does ringbuffers the wrong > > > way. Maybe it has to handle non-power-of-two buffer sizes. > > > > Hmm...I don't understand. What does it do wrong? > > An faq ;) If the buffer size is a power-of-two it's better to allow the > head and tail indices wrap through 0xffffffff and only mask them when > subscripting. It ends up faster (usually) and you can use all of the > elements of the buffer (rather than all-1) and you get nice things like: > > is_empty = (head == tail) > is_full = (tail - head == size) > nr_items_in_ring = (tail - head) Ok, that makes sense. Thanks for explaining. Not sure if want to start improving things right now, although I'm pretty sure the circ stuff can't handle non-power-of-two buffer size currently so it should be possible. > > > All those uart_circ_*() macros reference their arg more than once and ... > > > you know the deal. > > > > Yeah. Would you like a patch that inline-ifies <linux/circ.h>? > > uh, if you're feeling especially keen. We have bigger problems than this. Well, if you put it like that; no, not really. I'll post a fix for the other things you pointed out shortly. Haavard -- 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/
