Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754806Ab0BTSY7 (ORCPT ); Sat, 20 Feb 2010 13:24:59 -0500 Received: from inca-roads.misterjones.org ([213.251.177.50]:48027 "EHLO inca-roads.misterjones.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752402Ab0BTSY5 (ORCPT ); Sat, 20 Feb 2010 13:24:57 -0500 Date: Sat, 20 Feb 2010 18:24:53 +0000 From: Marc Zyngier To: lkml Cc: Thomas Gleixner , Ingo Molnar , "Joachim Eastwood" Subject: [RFC][PATCH] genirq: Introduce IRQF_ALLOW_NESTED flag for request_irq() Message-ID: <20100220182453.132993be@taxman.wild-wind.fr.eu.org> Organization: Metropolis -- Nowhere X-Mailer: Claws Mail 3.7.5 (GTK+ 2.18.3; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 77.203.141.186 X-SA-Exim-Rcpt-To: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@elte.hu, Joachim.Eastwood@jotron.com X-SA-Exim-Mail-From: maz@misterjones.org X-SA-Exim-Scanned: No (on inca-roads.misterjones.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3610 Lines: 97 Now that we enjoy threaded interrupts, we're starting to see irq_chip implementations (wm831x, pca953x) that make use of threaded interrupts for the controller, and nested interrupts for the client interrupt. It all works very well, with one drawback: Drivers requesting an IRQ must now know whether the handler will run in a thread context of not, and call request_threaded_irq() or request_irq() accordingly. The problem is that the requesting driver sometimes doesn't know about the nature of the interrupt, specially when the interrupt controller is a discrete chip (typically a GPIO expander connected over I2C) that can be connected to a wide variety of otherwise perfectly supported hardware. The following patch introduces the IRQF_ALLOW_NESTED flag, that acts as a "contract" between the driver and the genirq framework. By using this flag as part of the request_irq() call, the driver informs the genirq framework that the handler will happily run either in hardirq or nested context, without any ill effect. The benefit of this is a single API for drivers. It still requires the driver to be audited, and the flag added to the request_irq() call. Of course, this goes against Linus choice of having separate APIs for both cases. The only alternative I can imagine for this is to use request_threaded_irq() with the same function provided for both the handler and the threaded handler. Ugly... This patch has been tested on ARM and Blackfin platforms. Signed-off-by: Marc Zyngier Tested-by: Joachim Eastwood --- include/linux/interrupt.h | 3 +++ kernel/irq/manage.c | 12 +++++++++--- 2 files changed, 12 insertions(+), 3 deletions(-) diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 75f3f00..d166e24 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -52,6 +52,8 @@ * IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished. * Used by threaded interrupts which need to keep the * irq line disabled until the threaded handler has been run. + * IRQF_ALLOW_NESTED - Handler can be either run as hardirq or nested + * interrupt. */ #define IRQF_DISABLED 0x00000020 #define IRQF_SAMPLE_RANDOM 0x00000040 @@ -62,6 +64,7 @@ #define IRQF_NOBALANCING 0x00000800 #define IRQF_IRQPOLL 0x00001000 #define IRQF_ONESHOT 0x00002000 +#define IRQF_ALLOW_NESTED 0x00004000 /* * Bits used by threaded handlers: diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index eb6078c..3635276 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -641,12 +641,18 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) /* * Check whether the interrupt nests into another interrupt - * thread. + * thread. Nested interrupt must provide a thread function + * unless it raises the IRQF_ALLOW_NESTED flag. */ nested = desc->status & IRQ_NESTED_THREAD; if (nested) { - if (!new->thread_fn) - return -EINVAL; + if (!new->thread_fn) { + if (new->flags & IRQF_ALLOW_NESTED) + new->thread_fn = new->handler; + else + return -EINVAL; + } + /* * Replace the primary handler which was provided from * the driver for non nested interrupt handling by the -- 1.7.0 -- I'm the slime oozin' out from your TV set... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/