linux-kernel - Re: [PATCH] driver-core: platform: Resolve DT interrupt references late

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Message-ID: <4589157.TquA4Q59fC@wuerfel>
Date:	Wed, 08 Jan 2014 14:41:19 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Tony Lindgren <tony@...mide.com>, devicetree@...r.kernel.org,
	Paul Walmsley <paul@...an.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...aro.org>,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH] driver-core: platform: Resolve DT interrupt references late

On Wednesday 08 January 2014 13:51:17 Thierry Reding wrote:
> When devices are probed from the device tree, any interrupts that they
> reference are resolved at device creation time. This causes problems if
> the interrupt provider hasn't been registered yet at that time, which
> results in the interrupt being set to 0.

Thanks for looking at this problem, it has bothered a lot of people
for a long time. I'm sorry I wasn't there for the discussion in November,
but when it came up before, I suggested a different solution that
apparently didn't get implemented.

> Note that this patch is the easy way out to fix a large part of the
> problems for now. A more proper solution for the long term would be to
> transition drivers to an API that always resolves resources of any kind
> (not only interrupts) at probe time.
> 
> For some background and discussion on possible solutions, see:
> 
> 	https://lkml.org/lkml/2013/11/22/520

I hope I read this thread correctly, sorry if I missed an important
part. My idea was to add the code not in platform_get_irq() but add
the resource in platform_drv_probe(), and just bail out with
-EPROBE_DEFER there if necessary.

We could then skip adding the resources at device creation time.
Is this something you already plan to do later, or is there a reason
it wouldn't work?

In the meantime, I don't see anything with your patch, but it also
wouldn't hurt to do it now if it solves all the problems.

	Arnd
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