From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262952AbUB0Slo (ORCPT ); Fri, 27 Feb 2004 13:41:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262939AbUB0SlK (ORCPT ); Fri, 27 Feb 2004 13:41:10 -0500 Received: from chaos.analogic.com ([204.178.40.224]:22658 "EHLO chaos.analogic.com") by vger.kernel.org with ESMTP id S262952AbUB0Sjo (ORCPT ); Fri, 27 Feb 2004 13:39:44 -0500 Date: Fri, 27 Feb 2004 13:42:12 -0500 (EST) From: "Richard B. Johnson" X-X-Sender: root@chaos Reply-To: root@chaos.analogic.com To: Chris Friesen cc: "Grover, Andrew" , Helge Hafting , linux-kernel@vger.kernel.org Subject: Re: Why no interrupt priorities? In-Reply-To: <403F894C.1050808@nortelnetworks.com> Message-ID: References: <403F894C.1050808@nortelnetworks.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Feb 2004, Chris Friesen wrote: > Grover, Andrew wrote: > > > If a device later in the handler chain is also interrupting, then the > > interrupt will immediately trigger again. The irq line will remain > > asserted until nobody is asserting it. > > I thought I saw examples of edge-triggered shared interrupts earlier in > the thread. Doesn't that give the reason for this behaviour? > > Chris > > -- > Chris Friesen | MailStop: 043/33/F10 > Nortel Networks | work: (613) 765-0557 > 3500 Carling Avenue | fax: (613) 765-2986 > Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com In the early IBM/AT, there was a port to which a user of a shared "edge" interrupt could write. If the interrupt line was still asserted, this would generate another edge. This meant that any ISR needed to know about other users of the same interrupt. This is probably why it didn't catch on. Cheers, Dick Johnson Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips). Note 96.31% of all statistics are fiction.