linux-kernel - Re: [PATCH 3/8] Add a mfd IPUv3 driver

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Message-ID: <alpine.LFD.2.00.1103011507220.2701@localhost6.localdomain6>
Date:	Tue, 1 Mar 2011 15:09:52 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arnd Bergmann <arnd@...db.de>
cc:	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org,
	Paul Mundt <lethal@...ux-sh.org>, linux-kernel@...r.kernel.org,
	linux-fbdev@...r.kernel.org, Samuel Ortiz <sameo@...ux.intel.com>,
	Alan Cox <alan@...ux.intel.com>
Subject: Re: [PATCH 3/8] Add a mfd IPUv3 driver

On Tue, 1 Mar 2011, Arnd Bergmann wrote:

> On Tuesday 01 March 2011, Sascha Hauer wrote:
> > > Taking one step back from this, have you considered making this
> > > a regular interrupt controller? That would make the client drivers
> > > more standard -- you could define the interrupt numbers as resources
> > > of a platform device or in the device tree, for instance.
> > > The cost might be more complex code, e.g. when a device requires
> > > many interrupts, but I think it will be at least as efficient
> > > at run-time, and less surprising for readers and authors of
> > > client drivers.
> > 
> > I thought about this, but hesitated to increase NR_IRQS by 463. Do you
> > think we should do this instead?
> 
> I think there is a plan to virtualize the interrupt numbers on ARM,
> and in that case NR_IRQS becomes rather meaningless. I don't know
> exactly how far that effort has come.

Also sparse irqs allows us now to allocate beyond NR_IRQS. With sparse
irqs NR_IRQS is pretty meaningless and just gives us an indicator how
large the irq space might become, but we allow up to 8k dynamically
allocated irqs beyond NR_IRQS, so this should be sufficient for your
problem.

Thanks,

	tglx
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