linux-kernel - Re: [RFC 2/5] i3c: Add core I3C infrastructure

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Message-ID: <20170731214211.GA11776@tetsubishi>
Date:   Mon, 31 Jul 2017 23:42:11 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-i2c@...r.kernel.org,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Przemyslaw Sroka <psroka@...ence.com>,
        Arkadiusz Golec <agolec@...ence.com>,
        Alan Douglas <adouglas@...ence.com>,
        Bartosz Folta <bfolta@...ence.com>,
        Damian Kos <dkos@...ence.com>,
        Alicja Jurasik-Urbaniak <alicja@...ence.com>,
        Jan Kotas <jank@...ence.com>,
        Cyprian Wronka <cwronka@...ence.com>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Nishanth Menon <nm@...com>, Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 2/5] i3c: Add core I3C infrastructure


> Actually, that's the first option I considered, but I3C and I2C are
> really different. I'm not talking about the physical layer here, but
> the way the bus has to be handled by the software layer. Actually, I
> thing the I3C bus is philosophically closer to auto-discoverable busses
> like USB than I2C or SPI.

Acked-by: Wolfram Sang <wsa@...-dreams.de>

> Of course, I can move all the code in drivers/i2c/, but that won't
> change the fact that I3C and I2C busses are completely different
> with little to share between them.

That wouldn't make sense.

> To me, the I2C backward compatibility is just a nice feature that was
> added to help people smoothly transition from mixed I3C busses with
> both I2C and I3C devices connected to it (I2C devices being here
> when no (affordable) equivalent exist in the I3C world) to pure I3C
> busses with only I3C devices connected to it.

Yeah, and it is still to be seen how good this really works. Devices
which do clock stretching are out of the question. Probably everything
which needs an interrupt as well?

> This being said, I'd be happy if you prove me wrong and propose a
> solution that allows us to extend the I2C framework to support I3C
> without to much pain ;-).

From all I know, I don't see that coming.


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