Return-Path: <linux-kernel-owner+w=401wt.eu-S1756422AbYKCVQg@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1756422AbYKCVQg (ORCPT <rfc822;w@1wt.eu>);
	Mon, 3 Nov 2008 16:16:36 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754582AbYKCVQ2
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Mon, 3 Nov 2008 16:16:28 -0500
Received: from trinity.fluff.org ([89.145.97.151]:37138 "EHLO
	trinity.fluff.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754363AbYKCVQ1 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 3 Nov 2008 16:16:27 -0500
Date: Mon, 3 Nov 2008 21:16:25 +0000
From: Ben Dooks <ben-linux@fluff.org>
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Ben Dooks <ben-linux@fluff.org>, linux-kernel@vger.kernel.org,
       drzeus-mmc@drzeus.cx, sdhci-devel@list.drzeus.cx
Subject: Re: [patch 6/7] SDHCI: Check DMA for overruns at end of transfer
Message-ID: <20081103211625.GG14806@trinity.fluff.org>
References: <20081103200944.099353331@fluff.org.uk> <20081103201010.820070757@fluff.org.uk> <20081103211200.GA10721@khazad-dum.debian.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20081103211200.GA10721@khazad-dum.debian.net>
X-Disclaimer: These are my views alone.
X-URL: http://www.fluff.org/
User-Agent: Mutt/1.5.9i
X-SA-Exim-Connect-IP: <locally generated>
X-SA-Exim-Mail-From: ben@trinity.fluff.org
X-SA-Exim-Scanned: No (on trinity.fluff.org); SAEximRunCond expanded to false
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 956
Lines: 23

On Mon, Nov 03, 2008 at 07:12:00PM -0200, Henrique de Moraes Holschuh wrote:
> Maybe I didn't understand it right, but if the DMA controller could overrun
> a buffer, don't you ALSO need to add defensive padding (i.e. increase the
> buffer) to make sure nothing important gets overrun?

This is only generated by problems elsewhere in the driver, such as
getting the timeout clock wrong. It is here just as a precaution and
as an aide to debugging, it should not trigger in normal circumstances.

There is a seperate problem where the DMA buffer is passed from the stack
which is, IIRC, a complete no-no under Linux. 

-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.

--
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/