linux-kernel - Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

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Date:   Wed, 30 Jun 2021 10:29:40 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Jie Deng <jie.deng@...el.com>, Wolfram Sang <wsa@...nel.org>,
        Linux I2C <linux-i2c@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, conghui.chen@...el.com,
        kblaiech@...lanox.com, jarkko.nikula@...ux.intel.com,
        Sergey Semin <Sergey.Semin@...kalelectronics.ru>,
        Mike Rapoport <rppt@...nel.org>, loic.poulain@...aro.org,
        Tali Perry <tali.perry1@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        yu1.wang@...el.com, shuo.a.liu@...el.com,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

On Wed, Jun 30, 2021 at 10:09 AM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Wed, Jun 30, 2021 at 09:55:49AM +0200, Arnd Bergmann wrote:
> > On Wed, Jun 30, 2021 at 9:51 AM Jie Deng <jie.deng@...el.com> wrote:
>
> ...
>
> > On a related note, we are apparently still missing the bit in the virtio bus
> > layer that fills in the dev->of_node pointer of the virtio device. Without
> > this, it is not actually possible to automatically probe i2c devices connected
> > to a virtio-i2c bus. The same problem came up again with the virtio-gpio
> > driver that suffers from the same issue.
>
> Don't we need to take care about fwnode handle as well?

I'm fairly sure this gets set up automatically on DT based systems, based
on the dev->of_node of the virtio device, with no changes to the i2c
core core.

If you want to automatically probe i2c devices on a virtio-i2c controller
with ACPI, I have no idea if that would require changes to both
i2c-core-acpi.c as well as the virtio core, or just one of them.
So far, my assumption was that this would not be needed with ACPI.

        Arnd