On Wed, Oct 12, 2022 at 8:51 AM Michael S. Tsirkin [off-list ref] wrote:

Are you sure?

MichaelE is right.

This is just bogus historical garbage:

arch/arm/include/asm/irq.h:#ifndef NO_IRQ
arch/arm/include/asm/irq.h:#define NO_IRQ       ((unsigned int)(-1))

that I've tried to get rid of for years, but for some reason it just won't die.

NO_IRQ should be zero. Or rather, it shouldn't exist at all. It's a bogus thing.

You can see just how bogus it is from grepping for it - the users are
all completely and utterly confused, and all are entirely historical
brokenness.

The correct way to check for "no irq" doesn't use NO_IRQ at all, it just does

        if (dev->irq) ...

which is why you will only find a few instances of NO_IRQ in the tree
in the first place.

The NO_IRQ thing is mainly actually defined by a few drivers that just
never got converted to the proper world order, and even then you can
see the confusion (ie some drivers use "-1", others use "0", and yet
others use "((unsigned int)(-1)".

                   Linus