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Subject: Re: [PATCH V3 1/3] gpio: Add virtio-gpio driver
To:     Arnd Bergmann <arnd@kernel.org>,
        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?Q?Alex_Benn=c3=a9e?= <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
References: <cover.1623326176.git.viresh.kumar@linaro.org>
 <10442926ae8a65f716bfc23f32339a6b35e51d5a.1623326176.git.viresh.kumar@linaro.org>
 <CAK8P3a11YhcEOjauWc872BQv+SO-E5+gnz7Lk6UK42iVw7Oyfg@mail.gmail.com>
From:   "Enrico Weigelt, metux IT consult" <lkml@metux.net>
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Date:   Thu, 10 Jun 2021 18:00:21 +0200
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On 10.06.21 15:22, Arnd Bergmann wrote:

> 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?

Connecting between self-probing bus'es and DT is generally tricky. IMHO
we don't have any generic mechanism for that.

I've made a few attempts, but nothing practically useful, which would be
accepted by the corresponding maintainers, yet. We'd either need some
very special logic in DT probing or pseudo-bus'es for the mapping.
(DT wants to do those connections via phandle's, which in turn need the
referenced nodes to be present in the DT).

>  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.

Have you ever successfully bound a virtio device via DT ?


--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287