Re: [PATCH 2/2] uio: add an of_genirq driver

On Mon, Jun 15, 2009 at 12:12:07AM +0100, Alan Cox wrote:

quoted

quoted

+	if (!uioinfo->irq)
+		uioinfo->irq = UIO_IRQ_NONE;

Please don't do this. It's inconsistent if all other UIO drivers require
people to use UIO_IRQ_NONE and you also allow zero. UIO_IRQ_NONE was
introduced because 0 may be a legal interrupt number on some platforms.

Zero is not a valid IRQ number in the kernel (except in arch specific
depths). IRQ numbers are also *unsigned* so -1 isn't a safe definition.

The above uioinfo->irq is a signed long.

Zero means no IRQ. If any old UIO code is assuming otherwise it wants
fixing.

It doesn't. It won't complain about IRQ 0 and will pass it on to
request_irq, which will probably fail if it is as you say.

I did it that way because I saw IRQ 0 in /proc/interrupts on every PC...

It is the job of the platform to map a physical IRQ 0 to some other
representation if it exists outside of arch specific code.

Funny.

This was
decided some years ago and a large part of the kernel simply doesn't
support any notion of a real IRQ 0.

Can you tell me the reason for that decision or point me to some ml archive?

Thanks,
Hans

Alan