linux-kernel - Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT)

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Date:	Wed, 14 May 2014 20:16:53 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	Rob Herring <robherring2@...il.com>
CC:	Grant Likely <grant.likely@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Jon Loeliger <jdl@....com>,
	Russell King <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization
 order based on the DT)

Am 14.05.2014 19:53, schrieb Alexander Holler:
> Am 14.05.2014 19:45, schrieb Alexander Holler:
>
>> One of the biggest problem of the deferred probe stuff is the problem
>> how to identify real problems if everything ends up with a deferred
>> probe when an error occurs? That means if you display an error whenever
>> something is deferred, the log becomes almost unreadable. If you don't
>> display an error, you never will see an error. And how do you display
>> the real error when deferred probes finally do fail? The deferred probe
>> stuff doesn't has any information about the underlying error, so it
>> can't display it.
>
> And that is a real problem. I've recently tried to identify why a driver
> failed and it was a nightmare because nothing offered any message (debug
> or not) when a probe was deferred. So I had to insert tons of printks to
> walk upwards to find the finally place where the probe failed.
> Everything afterwards just has forwarded the -EPROBE_DEFER without
> printing any message.

To add some numbers, I had to insert around 20-30 printks in around 10 
or more files to find the underlying problem. Having to do such whenever 
an error happens because everything assumes the error will disappear in 
a later try, which doesn't happen for real errors, is just a nightmare.

Regards,

Alexander Holler

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