From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:50067)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <zhihuili@linux.vnet.ibm.com>) id 1SfS7a-0003xm-NK
	for qemu-devel@nongnu.org; Fri, 15 Jun 2012 04:43:16 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <zhihuili@linux.vnet.ibm.com>) id 1SfS7W-0004c9-3n
	for qemu-devel@nongnu.org; Fri, 15 Jun 2012 04:43:10 -0400
Received: from e28smtp02.in.ibm.com ([122.248.162.2]:41733)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <zhihuili@linux.vnet.ibm.com>) id 1SfS7V-0004bI-EP
	for qemu-devel@nongnu.org; Fri, 15 Jun 2012 04:43:06 -0400
Received: from /spool/local
	by e28smtp02.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use
	Only! Violators will be prosecuted
	for <qemu-devel@nongnu.org> from <zhihuili@linux.vnet.ibm.com>;
	Fri, 15 Jun 2012 14:12:54 +0530
Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66])
	by d28relay04.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id
	q5F8gTNi62062700
	for <qemu-devel@nongnu.org>; Fri, 15 Jun 2012 14:12:30 +0530
Received: from d28av04.in.ibm.com (loopback [127.0.0.1])
	by d28av04.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id
	q5FECHrD008588
	for <qemu-devel@nongnu.org>; Sat, 16 Jun 2012 00:12:17 +1000
Message-ID: <4FDAF574.4000208@linux.vnet.ibm.com>
Date: Fri, 15 Jun 2012 16:42:28 +0800
From: Zhi Hui Li <zhihuili@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: [Qemu-devel] question about irq update
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: QEMU-devel <qemu-devel@nongnu.org>, Kevin Wolf <kwolf@redhat.com>



In the code of libqtest.c have a function :



bool qtest_get_irq(QTestState *s, int num)
{
     /* dummy operation in order to make sure irq is up to date */
     qtest_inb(s, 0);

     return s->irq_level[num];
}

but I don't know how it can make the irq up to date
and why we will read from the address of 0 ?


can anybody explain for me?
Thank you very much!