From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753383AbYH0AHg (ORCPT ); Tue, 26 Aug 2008 20:07:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751931AbYH0AH2 (ORCPT ); Tue, 26 Aug 2008 20:07:28 -0400 Received: from gate.crashing.org ([63.228.1.57]:47589 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887AbYH0AH1 (ORCPT ); Tue, 26 Aug 2008 20:07:27 -0400 Subject: Re: [PATCH] genirq: irq_chip->startup() usage in setup_irq and set_irq_chained handler From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Pawel MOLL Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Thomas Gleixner In-Reply-To: <1219745676.16078.219.camel@bri1004.bri.st.com> References: <1219313656.31630.89.camel@bri1004.bri.st.com> <1219416584.31630.639.camel@bri1004.bri.st.com> <20080823160859.GE27974@elte.hu> <1219531395.21386.200.camel@pasglop> <1219745676.16078.219.camel@bri1004.bri.st.com> Content-Type: text/plain Date: Wed, 27 Aug 2008 10:06:59 +1000 Message-Id: <1219795619.13162.166.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-08-26 at 11:14 +0100, Pawel MOLL wrote: > Let me briefly explain my situation. I have a main interrupt controller > which provides startup() and unmask/mask() functions. The first one is > rather expensive (as the controller itself is... hmmm... > complicated ;-), the second - very cheap. And that is how I understand > the different "levels" of interrupt access - startup() should be called > once, somewhere during request_irq(), (un)masking may be used > frequently. Oh, I don't disagree. It's probably a good idea. I'm just worried of the potential impact on existing code written around the current behaviour. We have 23 calls to set_irq_chained_handler in arch/powerpc, and I need to audit them all. Luckily, we mostly don't have startup() callbacks. (... some time later ...) It looks good. Of course, we'll have to test at one point, but at this stage, I think powerpc is happy with the change. Interestingly enough, I can see a case where we would have a problem -without- your change :-) Not with the current code, but in conjunction with another change that's planned for .28. So Acked-by: Benjamin Herrenschmidt Cheers, Ben.