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Date:   Wed, 12 Oct 2022 18:08:27 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        xiujianfeng@huawei.com, kvm@vger.kernel.org,
        alvaro.karsz@solid-run.com, Jason Wang <jasowang@redhat.com>,
        angus.chen@jaguarmicro.com, wangdeming@inspur.com,
        linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Netdev <netdev@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>, lingshan.zhu@intel.com,
        linuxppc-dev@lists.ozlabs.org, gavinl@nvidia.com
Subject: Re: [GIT PULL] virtio: fixes, features
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On Wed, Oct 12, 2022 at 11:06:54PM +0200, Arnd Bergmann wrote:
> On Wed, Oct 12, 2022, at 7:22 PM, Linus Torvalds wrote:
> >
> > 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)".
> 
> The last time I looked at removing it for arch/arm/, one problem was
> that there were a number of platforms using IRQ 0 as a valid number.
> We have converted most of them in the meantime, leaving now only
> mach-rpc and mach-footbridge. For the other platforms, we just
> renumbered all interrupts to add one, but footbridge apparently
> relies on hardcoded ISA interrupts in device drivers. For rpc,
> it looks like IRQ 0 (printer) already wouldn't work, and it
> looks like there was never a driver referencing it either.


Do these two boxes even have pci?

> I see that openrisc and parisc also still define NO_IRQ to -1, but at
> least openrisc already relies on 0 being the invalid IRQ (from
> CONFIG_IRQ_DOMAIN), probably parisc as well.
> 
>      Arnd