From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S934732AbcATQ0r (ORCPT <rfc822;w@1wt.eu>);
	Wed, 20 Jan 2016 11:26:47 -0500
Received: from unicorn.mansr.com ([81.2.72.234]:49887 "EHLO unicorn.mansr.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S934015AbcATQ0o convert rfc822-to-8bit (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 20 Jan 2016 11:26:44 -0500
From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= <mans@mansr.com>
To: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>, Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Sebastian Frias <sf84@laposte.net>, Arnd Bergmann <arnd@arndb.de>
Subject: Re: [RFC PATCH v3] irqchip: Add support for Tango interrupt controller
References: <569CE0F2.1060507@sigmadesigns.com>
	<569D0B80.1010908@sigmadesigns.com>
	<569D165E.4060004@sigmadesigns.com> <569FAFF5.4090909@arm.com>
	<yw1xr3hcqlix.fsf@unicorn.mansr.com>
	<569FB4AE.8000506@sigmadesigns.com>
Date: Wed, 20 Jan 2016 16:26:43 +0000
In-Reply-To: <569FB4AE.8000506@sigmadesigns.com> (Marc Gonzalez's message of
	"Wed, 20 Jan 2016 17:24:14 +0100")
Message-ID: <yw1xio2oqksc.fsf@unicorn.mansr.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Marc Gonzalez <marc_gonzalez@sigmadesigns.com> writes:

> On 20/01/2016 17:10, Måns Rullgård wrote:
>
>> Marc Zyngier wrote:
>> 
>>>> +	if (of_property_read_u32(node, "reg", &ctl))
>>>> +		panic("%s: failed to get reg base", node->name);
>>>> +
>>>> +	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
>>>> +	chip->ctl = ctl;
>>>> +	chip->base = base;
>> 
>> As I said before, this assumes the outer DT node uses a ranges
>> property.  Normally reg properties work the same whether they specify an
>> offset within an outer "ranges" or have a full address directly.  It
>> would be easy enough to make this work with either, so I don't see any
>> reason not to.
>
> IIRC, I was told very early in the review process that the ranges prop
> was mandatory. Lemme look for it... It was Arnd:
>
> http://thread.gmane.org/gmane.linux.ports.arm.kernel/444131/focus=444207
>
>> You are missing a ranges property that describes what address
>> space these addresses are in.
>>
>> 'ranges;' would be wrong here, as the interrupt controller is
>> not a bus. If you have no ranges property, the bus is interpreted
>> as having its own address space with no relation to the parent bus
>> (e.g. an I2C bus uses addresses that are not memory mapped).
>> 
>> Just list the addresses that are actually decoded by child
>> devices here.
>
> Did I misunderstand?

It's still possible to create such a device tree, and that will fail in
very hard to debug ways.  Better to be a bit robust.

-- 
Måns Rullgård