linux-kernel - Re: [PATCH V15 6/9] mfd: pm8008: Use i2c_new_dummy

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Message-ID: <YzXdhVN/Zp7DDIzB@google.com>
Date:   Thu, 29 Sep 2022 19:01:41 +0100
From:   Lee Jones <lee@...nel.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Satya Priya Kakitapalli <quic_c_skakit@...cinc.com>,
        Mark Brown <broonie@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_collinsd@...cinc.com,
        quic_subbaram@...cinc.com, quic_jprakash@...cinc.com
Subject: Re: [PATCH V15 6/9] mfd: pm8008: Use i2c_new_dummy_device() API

On Wed, 28 Sep 2022, Stephen Boyd wrote:

> Quoting Lee Jones (2022-09-28 03:20:30)
> > Wouldn't it make more sense to simply separate the instantiation of
> > the 2 I2C devices?  Similar to what you suggested [0] in v9.  That way
> > they can handle their own resources and we can avoid all of the I2C
> > dummy / shared Regmap passing faff.
> >
> > [0] https://lore.kernel.org/all/CAE-0n53G-atsuwqcgNvi3nvWyiO3P=pSj5zDUMYj0ELVYJE54Q@mail.gmail.com/
> >
> 
> You can continue reading the thread[1]. My understanding is it's one
> chip that responds on two i2c addresses, thus we don't describe that as
> two i2c device nodes in DT. Instead we describe one node and use the
> dummy API to make the second i2c device.
> 
> [1] https://lore.kernel.org/all/Yk3NkNK3e+fgj4eG@sirena.org.uk/

As Mark says, it's probably 2 separate dies that have been encased in
the same IC and are otherwise unconnected.  Not sure I understand the
comment about not requiring another 'struct device'.  It will still
require that whether it's a platform device or an I2C device, right?

-- 
Lee Jones [李琼斯]