Re: [PATCH 4/5] Centralise NO_IRQ definition

From: David Woodhouse
Date: Tue Nov 22 2005 - 14:03:41 EST

On Tue, 2005-11-22 at 18:37 +0000, David Howells wrote:
> (3) Having to translate a cookie for a specific IRQ means that the IRQ
> handling code will be slower and more complex, or is going to avoid the
> issue and be naughty and not deal with irq == NO_IRQ properly:
> The x86 PIC reports it as IRQ 0 having happened. In which case, by your
> argument, you _have_ to translate it: you're not allowed to pass NO_IRQ to
> setup_irq(), and you're not allowed to pass it to the interrupt handler -
> in this case timer_interrupt(). Doing otherwise is wrong, insane, etc...

This is true. If we're suddenly going to start pretending that IRQ 0
isn't a valid interrupt merely on the basis that "x86 doesn't use it"Â,
then we can't really go making an exception to allow us to use IRQ 0 on

 ...despite the fact that even that isn't true on legacy-free machines.

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