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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH 09/16] Enable message delivery via IRQs
Date: Sat, 12 Jun 2010 13:21:02 +0100
References: <cover.1275811861.git.jan.kiszka@web.de>
	<c875bf0470b4f0279e93d77c55d01bc50a12f1fc.1275811861.git.jan.kiszka@web.de>
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To: qemu-devel@nongnu.org
Cc: blue Swirl <blauwirbel@gmail.com>, Jan Kiszka <jan.kiszka@siemens.com>, Jan Kiszka <jan.kiszka@web.de>, Gleb Natapov <gleb@redhat.com>, Juan Quintela <quintela@redhat.com>

> This patch allows to optionally attach a message to an IRQ event. The
> message can contain a payload reference and a callback that the IRQ
> handler may invoke to report the delivery result. The former can be used
> to model message signaling interrupts, the latter to cleanly implement
> IRQ de-coalescing logics.

I don't like this. qemu_irq is a level triggered interface. Redundant calls to 
qemu_set_irq should (in principle) be a no-op.  If you want message passing 
then IMO you should be using something else.

Paul