linux-kernel - Re: [PATCH] irq: Start the transition of irq

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Message-ID: <4BA66A7A.3070207@kernel.org>
Date:	Sun, 21 Mar 2010 11:50:34 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Julia Lawall <julia@...u.dk>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org
Subject: Re: [PATCH] irq: Start the transition of irq_chip methods taking
 a desc

On 03/21/2010 07:43 AM, Thomas Gleixner wrote:
> Eric,
> 
> On Sun, 21 Mar 2010, Eric W. Biederman wrote:
>>
>> With SPARSE_IRQ irq_to_desc becomes an unnecessary lookup operation on
>> the fast path of dispatching irqs to their handlers.  We can avoid
>> this cost by passing an irq_desc pointer instead of using an integer
>> irq token to the irq_chip methods.
>>
>> A single patch to convert all of the architectures is an unreviewable
>> 2000+ line patch.  A gradual transition scenario with two sets of
>> irq_chip methods in irq_chip is an unmanageable mess in kernel/irq.
>>
>> So instead I define some macros so the generic irq code in kernel/irq/
>> can compile either way based on a boolean Kconfig variable
>> CONFIG_CHIP_PARAM_DESC.  This allows us to convert one architecture at
>> a time, reducing the follow on patches to manageable proportions.  It
>> is a little bit ugly but it is much better than the alternatives, and
>> as soon as we finish the transition we can kill the macros.
>>
>> I introduce the macros CHIP_ARG, CHIP_VAR, and CHIP_PARAM where
>> appropriate.  I change a few declarations of irq as int to unsigned
>> int.  I normalize the variables names in the functions that call
>> chip methods to ensure that I have the variables irq and desc present
>> allowing CHIP_ARG to work properly.  Most importantly none of the irq
>> logic changes with this patch.
> 
> I like that approach very much. Is the output binary equivivalent?
> 
great.

will update x86 part and related core according to this, and give it a try.

YH
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