linux-kernel - Re: [PATCH 1/2] PRUSS UIO driver support

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Message-Id: <201102181731.05644.arnd@arndb.de>
Date:	Fri, 18 Feb 2011 17:31:05 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Pratheesh Gangadhar <pratheesh@...com>,
	davinci-linux-open-source@...ux.davincidsp.com, gregkh@...e.de,
	amit.chatterjee@...com, "Hans J. Koch" <hjk@...sjkoch.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] PRUSS UIO driver support

On Friday 18 February 2011, Thomas Gleixner wrote:
> On Fri, 18 Feb 2011, Arnd Bergmann wrote:
> > On Friday 18 February 2011, Pratheesh Gangadhar wrote:
> > > Signed-off-by: Pratheesh Gangadhar <pratheesh@...com>
> > > +static irqreturn_t pruss_handler(int irq, struct uio_info *dev_info)
> > > +{
> > > +   return IRQ_HANDLED;
> > > +}
> > 
> > An empty interrupt handler is rather pointless. I guess you really
> > notify user space when the interrupt handler gets called, as this
> > is the main point of a UIO driver as far as I understand it.
> 
> The UIO core code does this for you when the driver handler returns
> IRQ_HANDLED

Ah, right.

> but the empty handler raises a different questions:
> 
> Is the interrupt edge triggerd or how do you avoid an irq storm here?
> Usually UIO drivers are requested to mask the interrupt in the device
> itself.

If it's edge triggered, it should not advertise IRQF_SHARED, right?

	Arnd
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