linux-kernel - Re: [PATCH v3 0/2] GPIO-based hotplug i2c bus

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Message-ID: <20230730174934.vobmyhubi7jsqzjv@intel.intel>
Date:   Sun, 30 Jul 2023 19:49:34 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     Svyatoslav Ryhel <clamor95@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] GPIO-based hotplug i2c bus

Hi Svyatoslav,

On Sat, Jul 29, 2023 at 07:08:55PM +0300, Svyatoslav Ryhel wrote:
> ASUS Transformers require this driver for proper work with their dock.
> Dock is controlled by EC and its presence is detected by a GPIO.
> 
> The Transformers have a connector that's used for USB, charging or
> for attaching a keyboard (called a dock; it also has a battery and
> a touchpad). This connector probably (I don't have the means to verify
> that) has an I2C bus lines and a "detect" line (pulled low on the dock
> side) among the pins. I guess there is either no additional chip or
> a transparent bridge/buffer chip, but nothing that could be controlled
> by software. For DT this setup could be modelled like an I2C gate or
> a 2-port mux with enable joining two I2C buses (one "closer" to the
> CPU as a parent).
> 
> In this case it's hard to tell the difference if this is real or virtual
> hardware.

How did you test this device?

> This patchset is a predecessor of a possible larger patchset which
> should bring support for a asus-ec, an i2c mfd device programmed by
> Asus for their Transformers tablet line. Similar approach is used in
> Microsoft Surface RT for attachable Type Cover.

Would be nice to have a driver using this support in the series,
otherwise it looks like thrown there without any use. Do you have
any use of it already? Even in your private repository just to
take a look.

Thanks,
Andi