Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934178Ab2J3SWz (ORCPT ); Tue, 30 Oct 2012 14:22:55 -0400 Received: from mail-ob0-f174.google.com ([209.85.214.174]:59367 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759674Ab2J3SWw (ORCPT ); Tue, 30 Oct 2012 14:22:52 -0400 MIME-Version: 1.0 X-Originating-IP: [2620:0:1000:2602:baac:6fff:fe8c:a1a5] In-Reply-To: References: <75eb5df193c504e68ebff7d6a6a88d9a1cc678cb.1351591858.git.nicolas.ferre@atmel.com> Date: Tue, 30 Oct 2012 11:22:51 -0700 Message-ID: Subject: Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic From: =?ISO-8859-1?Q?H=E5vard_Skinnemoen?= To: David Laight Cc: Nicolas Ferre , netdev@vger.kernel.org, davem@davemloft.net, bhutchings@solarflare.com, linux-arm-kernel@lists.infradead.org, plagnioj@jcrosoft.com, patrice.vilchez@atmel.com, linux-kernel@vger.kernel.org, manabian@gmail.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 927 Lines: 23 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. Havard -- 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/