linux-kernel - Re: [PATCH] Platform: x86: chromeos_laptop: defer probing if no i2c busses found

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Message-ID: <CAOesGMg5F-+Sco0sA1s2ACD2ZcqG2Z1Ovq51oyo=fO19S6Njfg@mail.gmail.com>
Date:	Thu, 18 Apr 2013 15:44:20 -0700
From:	Olof Johansson <olof@...om.net>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Benson Leung <bleung@...omium.org>, dirk@...ndel.org,
	Olof Johansson <olof@...om.net>
Subject: Re: [PATCH] Platform: x86: chromeos_laptop: defer probing if no i2c
 busses found

On Thu, Apr 18, 2013 at 3:05 PM, Olof Johansson <olof@...om.net> wrote:
> On Thu, Apr 18, 2013 at 2:55 PM, Olof Johansson <olof@...om.net> wrote:
>> If chromeos_laptop is loaded before the DRM driver, the i2c busses will
>> not yet be available. Defer probe for that case and try again later.
>>
>> Trickling the error up to the module init function is unfortuantely a
>> little awkward, since the i2c bus lookup and device registration happens
>> as a dmi callback.
>
> Uh, wait, hold off on this. I'm returning -EPROBE_DEFER from the
> module init function. It's not valid outside of the driver model.

Ugh. Ok, so that worked just because any error seem to re-trigger an
attempt to load the module later on my system (three times, it seems),
and most of the reproductions I had happened to work out on the second
load.

Looks like keeping the module loaded and adding a bus notifier to wait
for the right busses to show up is the only way to do this in a
foolproof way. Revised patch tonight or tomorrow.


-Olof
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