linux-kernel - Re: [PATCH v2] dma-debug: New interfaces to debug dma mapping errors

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Date:	Thu, 27 Sep 2012 08:13:10 -0600
From:	Shuah Khan <shuah.khan@...com>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	konrad.wilk@...cle.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, rob@...dley.net, akpm@...ux-foundation.org,
	bhelgaas@...gle.com, stern@...land.harvard.edu,
	LKML <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
	devel@...uxdriverproject.org, x86@...nel.org, shuahkhan@...il.com
Subject: Re: [PATCH v2] dma-debug: New interfaces to debug dma mapping errors

Hi Joerg,

On Thu, 2012-09-27 at 12:20 +0200, Joerg Roedel wrote:
> Hi Shuah,
> 
> the patch looks better then the older versions. It comes closer to a
> merge, but I see one issue here:
> 
> On Tue, Sep 25, 2012 at 07:05:17PM -0600, Shuah Khan wrote:
> > debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr):
> > 	Sets dma map error checked status for the dma map entry if one is
> > 	found. Decrements the system wide dma_map_errors_not_checked counter
> > 	that is incremented by debug_dma_map_page() when it checks for
> > 	mapping error before adding it to the dma debug entry table.
> 
> It is problematic that the DMA debug code can no longer call
> dma_mapping_error because of this. How about adding a special version of
> that function which does no checking and use it in the DMA debug code
> instead?

Yes. Konrad expressed the same concern and I understand the reasons.
Defining a special version of dma_mapping_error() will eliminate the
problem that prevents this routine being used from dma-debug api. Will
do that. Working on a v3 patch to fix this problem as well as the other
review comments from Konrad. Hoping I can have it ready in by the end of
this week(end)

Thanks,
-- Shuah

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