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From: Arnd Bergmann <arnd@arndb.de>
Date: Mon, 31 Jul 2017 22:16:42 +0200
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Subject: Re: [RFC 2/5] i3c: Add core I3C infrastructure
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Wolfram Sang <wsa@the-dreams.de>, linux-i2c@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org,
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On Mon, Jul 31, 2017 at 6:24 PM, Boris Brezillon
<boris.brezillon@free-electrons.com> wrote:
> Add core infrastructure to support I3C in Linux and document it.

> - I2C backward compatibility has been designed to be transparent to I2C
>   drivers and the I2C subsystem. The I3C master just registers an I2C
>   adapter which creates a new I2C bus. I'd say that, from a
>   representation PoV it's not ideal because what should appear as a
>   single I3C bus exposing I3C and I2C devices here appears as 2
>   different busses connected to each other through the parenting (the
>   I3C master is the parent of the I2C and I3C busses).
>   On the other hand, I don't see a better solution if we want something
>   that is not invasive.

Can you describe the reasons for making i3c a separate subsystem then,
rather than extending the i2c subsystem to handle both i2c devices as
before and also i3c devices and hosts?

        Arnd