linux-kernel - Re: [patch 6/7] SDHCI: Check DMA for overruns at end of transfer

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Message-ID: <20081103211625.GG14806@trinity.fluff.org>
Date:	Mon, 3 Nov 2008 21:16:25 +0000
From:	Ben Dooks <ben-linux@...ff.org>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Ben Dooks <ben-linux@...ff.org>, linux-kernel@...r.kernel.org,
	drzeus-mmc@...eus.cx, sdhci-devel@...t.drzeus.cx
Subject: Re: [patch 6/7] SDHCI: Check DMA for overruns at end of transfer

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.

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