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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Thu, 10 Jun 2021 15:22:10 +0200
Message-ID: <CAK8P3a11YhcEOjauWc872BQv+SO-E5+gnz7Lk6UK42iVw7Oyfg@mail.gmail.com>
Subject: Re: [PATCH V3 1/3] gpio: Add virtio-gpio driver
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        "Enrico Weigelt, metux IT consult" <info@metux.net>,
        Viresh Kumar <vireshk@kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Bill Mills <bill.mills@linaro.org>,
        =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>,
        Stratos Mailing List <stratos-dev@op-lists.linaro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        "Stefano Garzarella --cc virtualization @ lists . linux-foundation . org" 
        <sgarzare@redhat.com>, virtualization@lists.linux-foundation.org
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On Thu, Jun 10, 2021 at 2:18 PM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> From: "Enrico Weigelt, metux IT consult" <info@metux.net>
>
> This patch adds a new driver for Virtio based GPIO devices.
>
> This allows a guest VM running Linux to access GPIO device provided by
> the host. It supports all basic operations for now, except interrupts
> for the GPIO lines.
>
> Signed-off-by: "Enrico Weigelt, metux IT consult" <info@metux.net>
> Co-developed-by: Viresh Kumar <viresh.kumar@linaro.org>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Can you give an example of how this would be hooked up to other drivers
using those gpios. Can you give an example of how using the "gpio-keys" or
"gpio-leds" drivers in combination with virtio-gpio looks like in the DT?

Would qemu simply add the required DT properties to the device node that
corresponds to the virtio device in this case?

From what I can tell, both the mmio and pci variants of virtio can have their
dev->of_node populated, but I don't see the logic in register_virtio_device()
that looks up the of_node of the virtio_device that the of_gpio code then
tries to refer to.

        Arnd