linux-kernel - Re: Ok to call disable_irq before request

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Message-ID: <4D9A7B9D.7060604@metafoo.de>
Date:	Tue, 05 Apr 2011 04:17:01 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Timur Tabi <timur@...escale.com>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Ok to call disable_irq before request_irq?

On 04/05/2011 02:53 AM, Timur Tabi wrote:
> Is it okay to call disable_irq() before calling request_irq()?  My
> device creates lots of spurious interrupts, and so I want the
> interrupt enable only when I expect a real interrupt to occur.  It
> seems to work, but I just want to make sure it's a proper technique.
> 

It might work in your case, but in general that would certainly be really bad
practice.
If the irq was not requested before request_irq should enable the IRQ
regardless of whether irq_disable was called or not.

I have a patch which adds the IRQF_NOAUTOEN flag, which allows you to request a
IRQ without automatically enabling it. Unfortunately the current version of the
patch will fail if your irq_chip implements the irq_startup callback. I've
attached the patch.

- Lars

View attachment "irqf_noautoen.patch" of type "text/x-diff" (1682 bytes)