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Date:   Tue, 5 Oct 2021 08:52:59 +0200
From:   Geert Uytterhoeven <>
To:     Viresh Kumar <>
Cc:     Linus Walleij <>,
        Bartosz Golaszewski <>,
        Enrico@....of.borg, Weigelt@....of.borg,
        metux IT consult <>,
        Andy Shevchenko <>,
        Arnd Bergmann <>,
        "open list:GPIO SUBSYSTEM" <>,
        Linux-Renesas <>,
        Linux Kernel Mailing List <>,,
Subject: Re: [PATCH] gpio: aggregator: Add interrupt support

Hi Viresh,

On Tue, Oct 5, 2021 at 7:50 AM Viresh Kumar <> wrote:
> On 04-10-21, 14:44, Geert Uytterhoeven wrote:
> > Currently the GPIO Aggregator does not support interrupts.  This means
> > that kernel drivers going from a GPIO to an IRQ using gpiod_to_irq(),
> > and userspace applications using line events do not work.
> >
> > Add interrupt support by providing a gpio_chip.to_irq() callback, which
> > just calls into the parent GPIO controller.
> >
> > Note that this does not implement full interrupt controller (irq_chip)
> > support, so using e.g. gpio-keys with "interrupts" instead of "gpios"
> > still does not work.
> Thanks for looking into this. I am not sure of the difference it makes
> with and without full irq-chip, but lemme explain the use case that we
> are concerned about with virtio.
> Eventually the interrupt should be visible to userspace, with
> something like libgpiod. Which can then send the information over
> virtio to the guest.

Exactly, that was what I had in mind, too.

> Will the interrupts be visible in userspace with your patch ?

Yes they are.
Before, gpiomon (test app from libgpiod) didn't work, now it does.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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