linux-kernel - Re: [PATCH 12/14] x86_64 irq: Add constants for the reserved IRQ vectors.

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Date:	Sun, 25 Feb 2007 04:15:30 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Pavel Machek <pavel@....cz>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	Zwane Mwaikambo <zwane@...radead.org>,
	Ashok Raj <ashok.raj@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"Lu, Yinghai" <yinghai.lu@....com>,
	Natalie Protasevich <protasnb@...il.com>,
	Andi Kleen <ak@...e.de>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 12/14] x86_64 irq: Add constants for the reserved IRQ vectors.

Pavel Machek <pavel@....cz> writes:

> Hi!
>
>> For the ISA irqs we reserve 16 vectors.  This patch adds constants for
>> those vectors and modifies the code to use them.  Making the code a
>> little clearer and making it possible to move these vectors in the future.
>
>
>>  /*
>>   * Vectors 0x20-0x2f are used for ISA interrupts.
>>   */
>> +#define IRQ0_VECTOR		FIRST_EXTERNAL_VECTOR
>> +#define IRQ1_VECTOR		IRQ0_VECTOR + 1
>
> Maybe IRQ_VECTOR(1) would be similary readable, and would avoid 
>
>> +#define IRQ2_VECTOR		IRQ0_VECTOR + 2
>> +#define IRQ3_VECTOR		IRQ0_VECTOR + 3
>> +#define IRQ4_VECTOR		IRQ0_VECTOR + 4
>> +#define IRQ5_VECTOR		IRQ0_VECTOR + 5 
>> +#define IRQ6_VECTOR		IRQ0_VECTOR + 6
>> +#define IRQ7_VECTOR		IRQ0_VECTOR + 7
>> +#define IRQ8_VECTOR		IRQ0_VECTOR + 8
>> +#define IRQ9_VECTOR		IRQ0_VECTOR + 9
>> +#define IRQ10_VECTOR		IRQ0_VECTOR + 10
>> +#define IRQ11_VECTOR		IRQ0_VECTOR + 11
>> +#define IRQ12_VECTOR		IRQ0_VECTOR + 12
>> +#define IRQ13_VECTOR		IRQ0_VECTOR + 13
>> +#define IRQ14_VECTOR		IRQ0_VECTOR + 14
>> +#define IRQ15_VECTOR		IRQ0_VECTOR + 15
>
> ...these defines?

It would, and mostly I like it.  However, of the 1500+ possible irqs
exactly 16 have a reserved vector.  IRQ_VECTOR(N) does not convey
that in fact it conveys the opposite impression.

So I think the code is more maintainable with the distinct
definitions.

Eric
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