From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nicolas Ferre <nicolas.ferre@atmel.com>
Subject: Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
Date: Wed, 31 Oct 2012 10:59:24 +0100
Message-ID: <5090F67C.9020104@atmel.com>
References: <cover.1351591858.git.nicolas.ferre@atmel.com> <75eb5df193c504e68ebff7d6a6a88d9a1cc678cb.1351591858.git.nicolas.ferre@atmel.com> <AE90C24D6B3A694183C094C60CF0A2F6026B707D@saturn3.aculab.com> <CACiLriQnQcoXFqrqNt3nkY47nR8FnXbqWjtPRp250gueHSMDmQ@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: <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>
To: =?ISO-8859-1?Q?H=E5vard_Skinnemoen?= <havard@skinnemoen.net>,
	David Laight <David.Laight@aculab.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <CACiLriQnQcoXFqrqNt3nkY47nR8FnXbqWjtPRp250gueHSMDmQ@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

On 10/30/2012 07:22 PM, H=E5vard Skinnemoen :
> On Tue, Oct 30, 2012 at 4:12 AM, David Laight <David.Laight@aculab.co=
m> 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 a=
ccessor
>>> functions to do the subscripting properly to minimize the chances o=
f 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'
>=20
> Why is that? head and tail can never be more than TX_RING_SIZE apart,
> so it shouldn't make any difference.

Absolutely.

Best regards,
--=20
Nicolas Ferre