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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH 1/3] Change qemu_set_irq() to return status
	information.
Date: Sun, 29 Jun 2008 15:53:55 +0100
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To: qemu-devel@nongnu.org
Cc: Gleb Natapov <gleb@qumranet.com>

> >> The return value is less then zero if interrupt is masked, zero if it
> >> is known that interrupt is lost (due to coalescing) or greater then zero
> >> if interrupt is delivered or was successfully queued for delivery by
> >> interrupt controller. Device emulation can use this info as it pleases.
> >> Included patch adds detection of interrupt coalescing into PIC and APIC
> >> code for edge triggered interrupts.
> >
> > Instead of negative/positive/zero, consider returning an enum for
> > readability.
>
> I thought about that, but I sometimes do arithmetics on those values
> (when delivering interrupt to multiple CPUs), so result can be more then
> 1 sometimes.

At minimum you need to document the meaning of these values. Especially as 
you've now given two contradictory definitions - "greater than zero" isn't 
something you can do arithmetic with. If you require -1/0/+1 then you have to 
say that.

Paul