On Tue, 6 Dec 2011, Dave Martin wrote:

On Mon, Dec 05, 2011 at 02:49:01PM -0500, Nicolas Pitre wrote:

quoted

No need to convert everything.

First move is to make irq=0 meaning no IRQ.  That means making things 
like:

	if (irq < 0)
	if (irq >= 0)

into

	if (irq <= 0)
	if (irq > 0)

And replace NO_IRQ with 0.

That change shouldn't break anything, except those drivers which are 1) 
being passed an actual IRQ #0 and 2) testing for no IRQ.  I suspect that 
those conditions aren't very common together.

To clarify, you're suggesting that the meanings of all other IRQ values
would not change initially?

Initially, or even ever.

(i.e., we remap HW irq 0, if there is one,
to some other random number but have a 1:1 mapping for everything else).

Exact.

That could make sense as an approach.

You might notice that a true IRQ #0 passed to generic drivers is not 
really frequent.


Nicolas