linux-kernel - Re: [PATCH v3 10/15] leds: leds-gpio: Add ACPI probing support

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Date:	Wed, 01 Oct 2014 20:22:36 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Darren Hart <dvhart@...ux.intel.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-acpi@...r.kernel.org, devicetree@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Aaron Lu <aaron.lu@...el.com>
Subject: Re: [PATCH v3 10/15] leds: leds-gpio: Add ACPI probing support

On Wednesday 01 October 2014 11:11:46 Darren Hart wrote:
> >
> >No, I think in absence of drv->acpi_match_table ACPI core should just go
> >and
> >use drv->of_match_table to do the matching and be done with it.
> 
> But then you will match drivers that have of-only support that don't know
> anything about ACPI and haven't been updated to use the new API. Worse,
> some of those drivers will assume of node structs and such and potentially
> panic. Unless I'm sorry mistaken here....
> 

I don't think that is a huge danger: most drivers tend to check for
the presence of dev->of_node before calling any of the DT interfaces,
you'd only ever enter the probe function if the compatible string matches
(i.e. an old kernel with a new ACPI table), and most users of ACPI
systems will disable CONFIG_OF at compile time, so the accessors looking
at the of_node are not there.

In theory it's possible that something goes wrong here, but it's not
very likely to ever cause problems.

	Arnd
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