From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David H. Lynch Jr." Subject: Re: is_real_interrupt in 8250.c Date: Thu, 30 Nov 2006 04:32:00 -0500 Message-ID: <456EA510.3010805@dlasys.net> References: <200611291744.kATHixEN006240@oogie-boogie.ics.uci.edu> <20061129181148.GA31874@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from 24.152.213.223.res-cmts.eph.ptd.net ([24.152.213.223]:5353 "EHLO mx.dlasys.net") by vger.kernel.org with ESMTP id S933168AbWK3Jg4 (ORCPT ); Thu, 30 Nov 2006 04:36:56 -0500 Received: from l-dhlii.dlasys.net ([206.223.20.247]:2030) by mx.dlasys.net with esmtpa (Exim 4.62 #1 (Debian)) id 1Gpj6e-000131-L8 by authid with plain_server for ; Thu, 30 Nov 2006 05:25:28 -0500 In-Reply-To: <20061129181148.GA31874@thunk.org> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org Theodore Tso wrote: > On Wed, Nov 29, 2006 at 09:44:59AM -0800, Dan Nicolaescu wrote: > >> Hi, >> >> In 8250.c is_real_interrupt is defined like this: >> >> /* >> * We default to IRQ0 for the "no irq" hack. Some >> * machine types want others as well - they're free >> * to redefine this in their header file. >> */ >> #define is_real_interrupt(irq) ((irq) != 0) >> >> on my platform the UART IRQ is 0, so is_real_interrupt returns >> false. >> >> In order to allow machines to override is_real_interrupt, and for the >> code to match the comment shouldn't this patch be applied? >> > > No, IRQ 0 for linux is always "no IRQ". We should probably add this > to the LKML FAQ, since it keeps coming up. Per Linus, if there are > any architectures that has a valid IRQ #0, then the > architecture-specific kernel code should remap IRQ numbers. See: > > http://comments.gmane.org/gmane.linux.kernel/468449 > > - Ted > My reading of the messages you linked to is that is_real_interrupt should eb defined as #define is_real_interrupt(irq) ((irq) != NO_IRQ) where NO_IRQ may be defined differently for platforms where IRQ #0 is valid, not that IRQ 0 is always "no IRQ" I have not done any low level x86 linux work, but even on an x86 IRQ 0 is valid. > - > To unsubscribe from this list: send the line "unsubscribe linux-serial" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- Dave Lynch DLA Systems Software Development: Embedded Linux 717.627.3770 dhlii@dlasys.net http://www.dlasys.net fax: 1.253.369.9244 Cell: 1.717.587.7774 Over 25 years' experience in platforms, languages, and technologies too numerous to list. "Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction." Albert Einstein