Re: [PATCH V15 6/9] mfd: pm8008: Use i2c_new_dummy_device() API

From: Lee Jones <lee@kernel.org>
To: Stephen Boyd <swboyd@chromium.org>
Cc: Lee Jones <lee.jones@linaro.org>,
	Satya Priya Kakitapalli <quic_c_skakit@quicinc.com>,
	Mark Brown <broonie@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, quic_collinsd@quicinc.com,
	quic_subbaram@quicinc.com, quic_jprakash@quicinc.com
Subject: Re: [PATCH V15 6/9] mfd: pm8008: Use i2c_new_dummy_device() API
Date: Thu, 29 Sep 2022 19:01:41 +0100	[thread overview]
Message-ID: <YzXdhVN/Zp7DDIzB@google.com> (raw)
In-Reply-To: <CAE-0n50cX5ky3By976RTecKkpeMoAjoBA4tYuWSZ150JfS9wiQ@mail.gmail.com>

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]