From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751340AbWFTWaG (ORCPT ); Tue, 20 Jun 2006 18:30:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751370AbWFTW33 (ORCPT ); Tue, 20 Jun 2006 18:29:29 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:39133 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1751340AbWFTW3H (ORCPT ); Tue, 20 Jun 2006 18:29:07 -0400 From: "Eric W. Biederman" To: Andrew Morton Cc: , , , , Ingo Molnar , Thomas Gleixner , Andi Kleen , "Natalie Protasevich" , "Len Brown" , "Kimball Murray" , Brice Goglin , Greg Lindahl , Dave Olson , Jeff Garzik , Greg KH , Grant Grundler , "bibo,mao" , Rajesh Shah , Mark Maule , Jesper Juhl , Shaohua Li , Matthew Wilcox , "Michael S. Tsirkin" , Ashok Raj , Randy Dunlap , Roland Dreier , Tony Luck , "Eric W. Biederman" Subject: [PATCH 25/25] irq: Document what an IRQ is. Reply-To: "Eric W. Biederman" Date: Tue, 20 Jun 2006 16:28:38 -0600 Message-Id: <11508425271395-git-send-email-ebiederm@xmission.com> X-Mailer: git-send-email 1.4.0.gc07e In-Reply-To: <1150842527127-git-send-email-ebiederm@xmission.com> References: <11508425183073-git-send-email-ebiederm@xmission.com> <11508425191381-git-send-email-ebiederm@xmission.com> <11508425192220-git-send-email-ebiederm@xmission.com> <11508425191063-git-send-email-ebiederm@xmission.com> <1150842520235-git-send-email-ebiederm@xmission.com> <11508425201406-git-send-email-ebiederm@xmission.com> <1150842520775-git-send-email-ebiederm@xmission.com> <11508425213394-git-send-email-ebiederm@xmission.com> <115084252131-git-send-email-ebiederm@xmission.com> <11508425213795-git-send-email-ebiederm@xmission.com> <11508425222427-git-send-email-ebiederm@xmission.com> <11508425221394-git-send-email-ebiederm@xmission.com> <11508425223015-git-send-email-ebiederm@xmission.com> <1150842523493-git-send-email-ebiederm@xmission.com> <11508425231168-git-send-email-ebiederm@xmission.com> <1150842524863-git-send-email-ebiederm@xmission.com> <1150842524755-git-send-email-ebiederm@xmission.com> <115084252460-git-send-! email-ebiederm@xmission.com> <11508425251099-git-send-email-ebiederm@xmission.com> <11508425253581-git-send-email-ebiederm@xmission.com> <11508425254020-git-send-email-ebiederm@xmission.com> <11508425262259-git-send-email-ebiederm@xmission.com> <11508425263761-git-send-email-ebiederm@xmission.com> <1150842527127-git-send-email-ebiederm@xmission.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Eric W. Biederman Signed-off-by: Eric W. Biederman --- Documentation/IRQ.txt | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-) diff --git a/Documentation/IRQ.txt b/Documentation/IRQ.txt new file mode 100644 index 0000000..237235d --- /dev/null +++ b/Documentation/IRQ.txt @@ -0,0 +1,22 @@ +What is an IRQ? + +An IRQ is an interrupt request from a device. +Currently they can come in over a pin, or over a packet. +Several devices may be connected to the same pin thus +sharing an IRQ. + +An IRQ number is a kernel identifier used to talk about a hardware +interrupt source. Typically this is an index into the global irq_desc +array, but except for what linux/interrupt.h implements the details +are architecture specific. + +An IRQ number is an enumeration of the possible interrupt sources on a +machine. Typically what is enumerated is the number of input pins on +all of the interrupt controller in the system. In the case of ISA +what is enumerated are the 16 input pins on the two i8259 interrupt +controllers. + +Architectures can assign additional meaning to the IRQ numbers, and +are encouraged to in the case where there is any manual configuration +of the hardware involved. The ISA IRQs are a classic example of +assigning this kind of additional meaning. -- 1.4.0.gc07e