Messages in this thread | | | Date | Wed, 31 Oct 2012 11:39:49 +0100 | From | Nicolas Ferre <> | Subject | Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic |
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On 10/31/2012 10:59 AM, Nicolas Ferre : > On 10/30/2012 07:22 PM, Håvard Skinnemoen : >> On Tue, Oct 30, 2012 at 4:12 AM, David Laight <David.Laight@aculab.com> wrote: >>>> Instead of masking head and tail every time we increment them, just let them >>>> wrap through UINT_MAX and mask them when subscripting. Add simple accessor >>>> functions to do the subscripting properly to minimize the chances of messing >>>> this up. >>> ... >>>> +static unsigned int macb_tx_ring_avail(struct macb *bp) >>>> +{ >>>> + return TX_RING_SIZE - (bp->tx_head - bp->tx_tail); >>>> +} >>> >>> That one doesn't look quite right to me. >>> Surely it should be masking with 'TX_RING_SIZE - 1' >> >> Why is that? head and tail can never be more than TX_RING_SIZE apart, >> so it shouldn't make any difference. > > Absolutely.
Well not so absolute, after having thinking twice ;-)
We should move to:
static unsigned int macb_tx_ring_avail(struct macb *bp) { return (TX_RING_SIZE - (bp->tx_head - bp->tx_tail) & (TX_RING_SIZE - 1)); }
Thanks David!
(sorry for the noise) Bye, -- Nicolas Ferre -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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