linux-kernel - Re: [PATCH v6 00/10] Add the I3C subsystem

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Date:   Fri, 20 Jul 2018 12:39:37 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Wolfram Sang <wsa@...-dreams.de>,
        linux-i2c@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <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>,
        Cyprian Wronka <cwronka@...ence.com>,
        Suresh Punnoose <sureshp@...ence.com>,
        Rafal Ciepiela <rafalc@...ence.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.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>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Vitor Soares <Vitor.Soares@...opsys.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Xiang Lin <Xiang.Lin@...aptics.com>,
        linux-gpio@...r.kernel.org, Sekhar Nori <nsekhar@...com>,
        Przemyslaw Gaj <pgaj@...ence.com>
Subject: Re: [PATCH v6 00/10] Add the I3C subsystem

On 2018-07-20 12:05, Boris Brezillon wrote:
> On Fri, 20 Jul 2018 11:57:56 +0200 Peter Rosin <peda@...ntia.se> wrote:
>> Maybe a bit-bang I3C master isn't feasible for some fundamental
>> reason?
> 
> No, it's clearly not. The way an I3C master is supposed to switch from
> open-drain to push-pull during a transaction or the concept of IBIs
> are the first things that come to mind, but I guess you have plenty of
> other reasons preventing you from implementing a i3c-bit-bang master.

Why can't a bit-banger switch from open-drain to push-pull? That's just
a matter of disconnecting some pull-ups, no? And maybe you know that no
device on your bus uses IBIs? Maybe none of reasons for why bit-banging
isn't feasible are applicable?

I.e. maybe there can be a I3C bit-banger that perhaps isn't generic and
isn't full-featured, but does work just fine in some specific setup?

Cheers,
Peter