linux-kernel - Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver

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Date:   Thu, 18 Mar 2021 15:52:41 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Jie Deng <jie.deng@...el.com>,
        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>,
        Wolfram Sang <wsa@...nel.org>,
        Jason Wang <jasowang@...hat.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.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,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver

On Thu, Mar 18, 2021 at 3:42 PM Enrico Weigelt, metux IT consult
<lkml@...ux.net> wrote:
>
> On 16.03.21 08:44, Viresh Kumar wrote:
>
> > FWIW, this limits this driver to support a single device ever. We
> > can't bind multiple devices to this driver now. Yeah, perhaps we will
> > never be required to do so, but who knows.
>
> Actually, I believe multiple devices really should be possible.
>
> The major benefit of virtio-i2c is either bridging certan real bus'es
> into a confined workload, or creating virtual hw testbeds w/o having to
> write a complete emulation (in this case, for dozens of different i2c
> controllers) - and having multiple i2c interfaces in one machine isn't
> exactly rare.

Allowing multiple virtio-i2c controllers in one system, and multiple i2c
devices attached to each controller is clearly something that has to work.

I don't actually see a limitation though. Viresh, what is the problem
you see for having multiple controllers?

         Arnd