From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.ferre@atmel.com (Nicolas Ferre) Date: Wed, 31 Oct 2012 11:39:49 +0100 Subject: [PATCH v3 06/10] net/macb: clean up ring buffer logic In-Reply-To: <5090F67C.9020104@atmel.com> References: <75eb5df193c504e68ebff7d6a6a88d9a1cc678cb.1351591858.git.nicolas.ferre@atmel.com> <5090F67C.9020104@atmel.com> Message-ID: <5090FFF5.6020109@atmel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 10/31/2012 10:59 AM, Nicolas Ferre : > On 10/30/2012 07:22 PM, H?vard Skinnemoen : >> On Tue, Oct 30, 2012 at 4:12 AM, David Laight 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