linux-kernel - Re: [PATCH] mmc_spi: use EILSEQ for possible transmission errors

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Date:	Tue, 19 May 2009 21:49:07 -0700
From:	David Brownell <david-b@...bell.net>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Wolfgang Mües <wolfgang.mues@...rswald.de>,
	Pierre Ossman <drzeus@...eus.cx>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Frysinger <vapier.adi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc_spi: use EILSEQ for possible transmission errors

On Tuesday 19 May 2009, Matt Fleming wrote:
> Hmm, always returning -EILSEQ is devious. What happens if we sent an
> illegal command? The value of "value" is passed up to the callers via
> cmd->error and so may eventually get printed in the pr_debug() call in
> mmc_request_done(), line 86.

True, but a pr_debug from mmc_spi could help that.  A patch doing
that would need to be less aggressive about ripping out the current
fault-parsing logic, but it could continue reporting -EILSEQ to
cope with the possible response mangling.


> Whereas before the error would display EINVAL for an illegal command
> now it'll display EILSEQ, which makes no sense. Seeing EILSEQ in my
> log when really the error is EINVAL is gonna really confuse me.
> 
> IMHO always assuming that command errors are caused by transmission
> problems is not the right solution.

Do you have a better solution to propose though?  If Wolfgang
is actually observing transmission errors there, I'm not sure
a better one is to be had.

Though I wonder what this would do for anyone trying SDIO over
the mmc_spi driver.

- Dave

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