Re: [PATCH] gpio: aggregator: Add interrupt support

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Enrico@rox.of.borg, Weigelt@rox.of.borg,
	metux IT consult <lkml@metux.net>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Arnd Bergmann <arnd@kernel.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	virtualization@lists.linux-foundation.org,
	stratos-dev@op-lists.linaro.org
Subject: Re: [PATCH] gpio: aggregator: Add interrupt support
Date: Tue, 5 Oct 2021 08:52:59 +0200	[thread overview]
Message-ID: <CAMuHMdVk6gDcHtYSM=Y8BAK=GVJuLqxTHk7zS4-MJPi0H0T=jQ@mail.gmail.com> (raw)
In-Reply-To: <20211005055050.ggimidaqis5tfxav@vireshk-i7>

Hi Viresh,

On Tue, Oct 5, 2021 at 7:50 AM Viresh Kumar <viresh.kumar@linaro.org> 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.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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