linux-kernel - Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support debug_dma_mapping

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Date:	Tue, 30 Oct 2012 13:58:46 -0600
From:	Shuah Khan <shuah.khan@...com>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	ralf@...ux-mips.org, kyungmin.park@...sung.com, arnd@...db.de,
	andrzej.p@...sung.com, m.szyprowski@...sung.com,
	linux-mips@...ux-mips.org, LKML <linux-kernel@...r.kernel.org>,
	shuahkhan@...il.com
Subject: Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support
 debug_dma_mapping_error

On Fri, 2012-10-26 at 15:31 -0700, David Daney wrote:
> On 10/26/2012 02:51 PM, Shuah Khan wrote:
> 
> >>>> On 10/26/2012 09:01 AM, Shuah Khan wrote:
> >>>>> Add support for debug_dma_mapping_error() call to avoid warning from
> >>>>> debug_dma_unmap() interface when it checks for mapping error checked
> >>>>> status. Without this patch, device driver failed to check map error
> >>>>> warning is generated.
> 
> I'm confused.
> 
> Your claim that a 'warning is generated' seems to be in conflict with...
> 
> 
> [...]
> > Got it. Thanks. I would volunteer to look at fixing all the problems,
> > but unfortunately I don't have a MIPS box handy
> 
> This statement that you don't have hardware that exhibits the problem.
> 
> How was the patch tested?  How do you even know there is a problem?

I enhanced the existing dma debug interfaces to add an interface to
debug missing dma_mapping_error() checks. That went into linux-next.
With this patch, when dma_map_page() and dma_map_single() are debugged
with a call to debug_dma_map_page() and the corresponding
dma_mapping_error() interface doesn't call debug_dma_mapping_error()
interface, a warning will be generated. I have been sending changes to
arch specific dma_mapping_error() routines to add this debug interface.
That is why I marked this patch RFT requesting testing.

Thanks,
-- Shuah


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