linux-kernel - Re: [PATCH 1/4] arm64: dts: qcom: sc8280xp: rename i2c5 to i2c21

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Date:   Tue, 13 Dec 2022 16:42:55 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Shazad Hussain <quic_shazhuss@...cinc.com>
Cc:     Brian Masney <bmasney@...hat.com>, andersson@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, konrad.dybcio@...aro.org,
        robh+dt@...nel.org, johan+linaro@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, ahalaney@...hat.com,
        echanude@...hat.com
Subject: Re: [PATCH 1/4] arm64: dts: qcom: sc8280xp: rename i2c5 to i2c21

On Tue, Dec 13, 2022 at 04:39:54PM +0100, Johan Hovold wrote:
> On Tue, Dec 13, 2022 at 09:04:39PM +0530, Shazad Hussain wrote:
> > On 12/13/2022 8:58 PM, Johan Hovold wrote:

> > >> So qup2_i2c18 becomes qup2_i2c2. Would I use the flat naming scheme for
> > >> the alias like so?
> > >>
> > >>      aliases {
> > >>          i2c18 = &qup2_i2c2;
> > >>      }
> > > 
> > > Or perhaps the i2c controllers should use a zero-based index instead of
> > > being named after the serial engines (e.g. as we do for the console
> > > uart).
> > > 
> > > How are they named in the schematics?
> > 
> > We should use from 0 to N.
> 
> With N being 23 after the number of serial engines, or the number of
> available i2c buses on a particular board minus one?

Looks like the more recent Qualcomm platforms use aliases that reflect
the engine number (i.e. 0 to 23) for i2c and spi.

Johan