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Date: Thu, 3 Jun 2010 09:34:56 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] Re: [RFT][PATCH 07/15] qemu_irq: Add IRQ handlers
	with delivery feedback
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Blue Swirl <blauwirbel@gmail.com>, qemu-devel@nongnu.org, Juan Quintela <quintela@redhat.com>

On Thu, Jun 03, 2010 at 08:23:46AM +0200, Jan Kiszka wrote:
> Blue Swirl wrote:
> > But how about if we introduced instead a message based IRQ? Then the
> > message could specify the originator device, maybe ACK/coalesce/NACK
> > callbacks and a bigger payload than just 1 bit of level. I think that
> > could achieve the same coalescing effect as what the bidirectional
> > IRQ. The payload could be useful for other purposes, for example
> > Sparc64 IRQ messages contain three 64 bit words.
> 
> If there are more users than just IRQ de-coalescing, this indeed sounds
> superior. We could pass objects like this one around:
> 
> struct qemu_irq_msg {
> 	void (*delivery_cb)(int result);
> 	void *payload;
> };
> 
> They would be valid within the scope of the IRQ handlers. Whoever
> terminates or actually delivers the IRQ would invoke the callback. And
> platforms like sparc64 could evaluate the additional payload pointer in
> their irqchips or wherever they need it. IRQ routers on platforms that
> make use of these messages would have to replicate them when forwarding
> an event.
> 
> OK?
> 
Let me see if I understand you correctly. qemu_set_irq() will get
additional parameter qemu_irq_msg and if irq was not coalesced
delivery_cb is called, so there is a guaranty that if delivery_cb is
called it is done before qemu_set_irq() returns. Correct?

--
			Gleb.