linux-kernel - Re: [PATCH] ARM: supplementing IO accessors with 64 bit capability

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Message-ID: <CANLsYkzPWnqLzhNpiKqM2jd8J4uZe4G7BL3fystXgHaE4_KkOQ@mail.gmail.com>
Date:	Wed, 22 Oct 2014 19:55:55 +0200
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	ezequiel.garcia@...e-electrons.com,
	Liviu Dudau <Liviu.Dudau@....com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: supplementing IO accessors with 64 bit capability

On 22 October 2014 19:19, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Wed, Oct 22, 2014 at 06:22:09PM +0200, Mathieu Poirier wrote:
>> I had this conversation with a colleague who reviewed the work.  If
>> the architecture is < 5 the __raw_ versions aren't included and the
>> compiler won't complain until someone tries to use the macros.  We
>> achieve the same result - the macros aren't accessible when the
>> architecture doesn't support it - while saving an #if condition in the
>> file.
>>
>> I'm not strongly opinionated on this - I can enclose the macros in an
>> #if statement.
>
> What you're missing is that some driver may test for their presence by
> doing:
>
> #ifndef readq_relaxed
> ... do something else
>
> which would now break as a detection method, as the macro is always
> defined no matter whether it's present or not.

Good point - thanks for showing me the light.

>
> --
> FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
> according to speedtest.net.
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