Date: Wed, 4 Jun 2008 09:05:43 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: =?ISO-8859-15?Q?Uwe_Kleine-K=F6nig?= <Uwe.Kleine-Koenig@digi.com>
cc: =?ISO-8859-15?Q?Hans-J=FCrgen_Koch?= <hjk@linutronix.de>,
       Randy Dunlap <randy.dunlap@oracle.com>, linux-kernel@vger.kernel.org,
       Greg Kroah-Hartman <gregkh@suse.de>,
       Jan Altenberg <jan.altenberg@linutronix.de>,
       Magnus Damm <magnus.damm@gmail.com>
Subject: Re: [PATCH 1/1] UIO: Add a write() function to enable/disable
 interrupts
In-Reply-To: <20080604063005.GA22952@digi.com>
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On Wed, 4 Jun 2008, Uwe Kleine-K?nig wrote:
> Hello Hans-J?rgen,
> 
> > Sometimes it is necessary to enable/disable the interrupt of a UIO device
> > from the userspace part of the driver. With this patch, the UIO kernel driver
> > can implement an "irqcontrol()" function that does this. Userspace can write
> > an s32 value to /dev/uioX (usually 0 or 1 to turn the irq off or on). The
> > UIO core will then call the driver's irqcontrol function.
> IMHO it would make sense to demand that irqcontrol() is idempotent and
> then call irqcontrol(ON) before blocking in read and poll.

We thought about that, but it is racy. Also explicit control is way
better than automagic hackery.

Thanks,
	tglx


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