linux-kernel - Re: [PATCH V3 1/3] gpio: Add virtio-gpio driver

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Message-ID: <20210614102119.qifm5sj7fpg54iqo@vireshk-i7>
Date:   Mon, 14 Jun 2021 15:51:19 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        Viresh Kumar <vireshk@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Bill Mills <bill.mills@...aro.org>,
        Alex Bennée <alex.bennee@...aro.org>,
        Stratos Mailing List <stratos-dev@...lists.linaro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Stefano Garzarella --cc virtualization @ lists . linux-foundation . org" 
        <sgarzare@...hat.com>, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH V3 1/3] gpio: Add virtio-gpio driver

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?
> 
> 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.

To be honest, I haven't tried this yet and I was expecting it to be
already taken care of. I was relying on the DTB automatically
generated by Qemu to get the driver probed and didn't have a look at
it as well.

I now understand that it won't be that straight forward. The same must
be true for adding an i2c device to an i2c bus over virtio (The way I
tested that earlier was by using the sysfs file to add a device to a
bus).

This may be something lacking generally for virtio-pci thing, not
sure though.

-- 
viresh