linux-kernel - Re: [PATCH 2/2] uio: add an of

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Date:	Mon, 15 Jun 2009 01:46:43 +0200
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	Wolfgang Grandegger <wg@...ndegger.com>,
	devicetree-discuss@...abs.org, Magnus Damm <magnus.damm@...il.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Greg KH <gregkh@...e.de>
Subject: Re: [PATCH 2/2] uio: add an of_genirq driver

> driver. A user _has_ to setup irq, if there is none, he still has to set
> irq=UIO_IRQ_NONE. For that matter, 'not specified' and 'not found' is both
> the same bad thing.

Hmm, what should I do?

A typical interrupts-property in a device-tree is specified as:

	interrupts = <&irq_controller_node irq_number irq_sense>;

Something like UIO_IRQ_NONE does not fit into this scheme, even more as it is
Linux-specific and device trees need to be OS independant.

I'm pretty sure the correct way to state that you don't need an interrupt in
the device-tree is to simply not specify the above interrupt property.

Well, yes, that means you can't distinguish between 'forgotten' and
'intentionally left out'. I wonder if it is really that bad? If something does
not work (= one is missing interrupts), the first place to look at is the
device tree. If one does not see an interrupt-property, voila, problem solved.

(Note that with my latest suggestion, a _wrong_ interrupt is handled the same
way as with platform_data. request_irq() should equally fail if the
return-value from irq_of_parse_and_map() is simply forwarded.)

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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