netdev - Re: [GIT PULL] virtio: fixes, features

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Date:   Wed, 12 Oct 2022 10:22:08 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, alvaro.karsz@...id-run.com,
        angus.chen@...uarmicro.com, gavinl@...dia.com, jasowang@...hat.com,
        lingshan.zhu@...el.com, wangdeming@...pur.com,
        xiujianfeng@...wei.com, linuxppc-dev@...ts.ozlabs.org,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [GIT PULL] virtio: fixes, features

On Wed, Oct 12, 2022 at 8:51 AM Michael S. Tsirkin <mst@...hat.com> 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