From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=40607 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1OCTSe-0002WY-0y
	for qemu-devel@nongnu.org; Thu, 13 May 2010 04:08:04 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <paolo.bonzini@gmail.com>) id 1OCSyY-0003Qs-Lk
	for qemu-devel@nongnu.org; Thu, 13 May 2010 03:37:01 -0400
Received: from mail-wy0-f173.google.com ([74.125.82.173]:41705)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <paolo.bonzini@gmail.com>) id 1OCSyS-0003PW-Tj
	for qemu-devel@nongnu.org; Thu, 13 May 2010 03:36:53 -0400
Received: by wyf19 with SMTP id 19so677339wyf.4
	for <qemu-devel@nongnu.org>; Thu, 13 May 2010 00:36:50 -0700 (PDT)
Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
Message-ID: <4BEBAC0F.8010900@redhat.com>
Date: Thu, 13 May 2010 09:36:47 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <4BE32178.2090103@msgid.tls.msk.ru> <4BE7B8C1.9060807@redhat.com>
	<4BE7C0A5.3090909@redhat.com>
	<alpine.DEB.2.00.1005121316240.11380@kaball-desktop>
	<4BEAA0CC.4090906@redhat.com>
	<alpine.DEB.2.00.1005121349070.11380@kaball-desktop>
	<4BEABABC.6080305@redhat.com>
	<alpine.DEB.2.00.1005121537370.11380@kaball-desktop>
In-Reply-To: <alpine.DEB.2.00.1005121537370.11380@kaball-desktop>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: [Qemu-devel] Re: Another SIGFPE in display code, now in cirrus
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/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: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Brian Kress <kressb@moose.net>, Michael Tokarev <mjt@tls.msk.ru>, Avi Kivity <avi@redhat.com>, KVM list <kvm@vger.kernel.org>, qemu-devel <qemu-devel@nongnu.org>

On 05/12/2010 05:57 PM, Stefano Stabellini wrote:
> I guess even a src blt pitch of 0 could be useful there, however in
> practice I think the only rop function that was written with this case in
> mind has:
>
> dstpitch -= bltwidth;
> srcpitch -= bltwidth;
>
> if (dstpitch<  0 || srcpitch<  0) {
>      /* is 0 valid? srcpitch == 0 could be useful */
>      return;
> }

Note that here srcpitch == 0 is actually srcpitch == bltwidth, which 
_is_ obviously useful.

The "real" srcpitch == 0 case would result in srcpitch == -bltwidth, and 
it is actually quite useful if you want to stretch a Nx1 bitmap to NxN.

Paolo