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Date: Tue, 16 Jun 2009 22:23:39 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] Register uhci_reset() callback.
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: Paul Brook <paul@codesourcery.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>

On Tue, Jun 16, 2009 at 10:10:59PM +0300, Blue Swirl wrote:
> >  That's why real hardware has a nice long reset pulse, during which
> >  every input change is ignored until the reset pulse is removed.
> 
> qemu_irq does not have state. It's different from real HW IRQ, so QEMU
> devices don't need to do anything. I also had this confused earlier.
> 
Yes, qemu_irq does not have state, but nonetheless the sate exists. It is
maintained inside piix3 (this is just implementation detail that may
or may not go away). But who, if not device itself, should know better
what IRQ level should be in any given time? You can literally call
qemu_irq() after each line of device emulation code and it will be OK,
slow may be, but correct. The more you call qemu_irq() the more closely
you emulate real HW level interrupt.

--
			Gleb.