linux-kernel - Re: [Stratos-dev] [PATCH V4 2/2] gpio: virtio: Add IRQ support

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Date:   Mon, 9 Aug 2021 13:19:29 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR QEMU'S CIRRUS DEVICE" 
        <virtualization@...ts.linux-foundation.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        Jason Wang <jasowang@...hat.com>,
        Stratos Mailing List <stratos-dev@...lists.linaro.org>
Subject: Re: [Stratos-dev] [PATCH V4 2/2] gpio: virtio: Add IRQ support

On Mon, Aug 9, 2021 at 12:47 PM Viresh Kumar via Stratos-dev
<stratos-dev@...lists.linaro.org> wrote:
>
> On 09-08-21, 09:55, Arnd Bergmann wrote:
> > Ah, right. There is already a flag that gets checked by the caller.
> >
> > It does feel odd to have an empty 'irq_mask' callback though, so
> > maybe there is still something missing, just not what I thought.
> >
> > It's probably the result of calling handle_level_irq(), which as you
> > said is closer to what we want, but is not exactly what we need for
> > this protocol.
>
> Okay, I have tried to take care of locking as well now and used local
> flags only to make sure I can depend on them to get the locking
> working properly. Lets see what's broken in this now :)

I don't see anything wrong with this version, but let's see what
Marc thinks. I expect that he can still poke some holes in it, or
at least find some simplifications.

I was slightly surprised at the relation between the disabled and
masked states, where 'disable' always implies 'mask' and
'enable' always implies 'unmask', but I don't actually know how
those two are actually defined in the irqchip code in Linux, so
I assume you did this correctly.

          Arnd