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Date:   Thu, 1 Oct 2020 09:32:08 +0200
From:   Krzysztof Kozlowski <krzk@kernel.org>
To:     Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc:     Rob Herring <robh+dt@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Anson Huang <Anson.Huang@nxp.com>,
        Andreas Kemnade <andreas@kemnade.info>,
        Stefan Riedmueller <s.riedmueller@phytec.de>,
        Robert Jones <rjones@gateworks.com>,
        Li Yang <leoyang.li@nxp.com>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 08/12] ARM: dts: imx6dl-pico: fix board compatibles
Message-ID: <20201001073208.GA5208@kozik-lap>
References: <20200930190143.27032-1-krzk@kernel.org>
 <20200930190143.27032-9-krzk@kernel.org>
 <0a0afea6-8cbb-3e89-5a4f-89660c942ca3@pengutronix.de>
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On Thu, Oct 01, 2020 at 09:22:03AM +0200, Ahmad Fatoum wrote:
> Hello Krzysztof,
> 
> On 9/30/20 9:01 PM, Krzysztof Kozlowski wrote:
> > There are four flavors of TechNexion PICO-IMX6 boards.  They have their
> > own DTSes, even though in Dwarf, Nymph and Pi are exactly the same.
> > They also have their own bindings so adjust the compatibles to match the
> > bindings.
> > 
> > Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> > 
> > ---
> > 
> > Changes since v1:
> > 1. None
> > ---
> >  arch/arm/boot/dts/imx6dl-pico-dwarf.dts  | 2 +-
> >  arch/arm/boot/dts/imx6dl-pico-hobbit.dts | 2 +-
> >  arch/arm/boot/dts/imx6dl-pico-nymph.dts  | 2 +-
> >  arch/arm/boot/dts/imx6dl-pico-pi.dts     | 2 +-
> >  4 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/arm/boot/dts/imx6dl-pico-dwarf.dts b/arch/arm/boot/dts/imx6dl-pico-dwarf.dts
> > index 659a8e8714ea..d85b15a8c127 100644
> > --- a/arch/arm/boot/dts/imx6dl-pico-dwarf.dts
> > +++ b/arch/arm/boot/dts/imx6dl-pico-dwarf.dts
> > @@ -13,5 +13,5 @@
> >  
> >  / {
> >  	model = "TechNexion PICO-IMX6 DualLite/Solo Board and Dwarf baseboard";
> > -	compatible = "technexion,imx6dl-pico", "fsl,imx6dl";
> > +	compatible = "technexion,imx6dl-pico-dwarf", "fsl,imx6dl";
> 
> Could you change this to have all three compatibles ("technexion,imx6dl-pico-dwarf", "technexion,imx6dl-pico",
> "fsl,imx6dl") and likewise for the other files? 
> That way other firmware that reuses the Linux device tree files and match against the SoM compatible
> continues to work after update.
> 
> >  };
> > diff --git a/arch/arm/boot/dts/imx6dl-pico-hobbit.dts b/arch/arm/boot/dts/imx6dl-pico-hobbit.dts
> > index d7403c5c4337..08fedcbcc91b 100644
> > --- a/arch/arm/boot/dts/imx6dl-pico-hobbit.dts
> > +++ b/arch/arm/boot/dts/imx6dl-pico-hobbit.dts
> > @@ -13,5 +13,5 @@
> >  
> >  / {
> >  	model = "TechNexion PICO-IMX6 DualLite/Solo Board and Hobbit baseboard";
> > -	compatible = "technexion,imx6dl-pico", "fsl,imx6dl";
> > +	compatible = "technexion,imx6dl-pico-hobbit", "fsl,imx6dl";
> >  };
> > diff --git a/arch/arm/boot/dts/imx6dl-pico-nymph.dts b/arch/arm/boot/dts/imx6dl-pico-nymph.dts
> > index b282dbf953aa..32ccfc5d41ce 100644
> > --- a/arch/arm/boot/dts/imx6dl-pico-nymph.dts
> > +++ b/arch/arm/boot/dts/imx6dl-pico-nymph.dts
> > @@ -13,5 +13,5 @@
> >  
> >  / {
> >  	model = "TechNexion PICO-IMX6 DualLite/Solo Board and Nymph baseboard";
> > -	compatible = "technexion,imx6dl-pico", "fsl,imx6dl";
> > +	compatible = "technexion,imx6dl-pico-nymph", "fsl,imx6dl";
> >  };
> > diff --git a/arch/arm/boot/dts/imx6dl-pico-pi.dts b/arch/arm/boot/dts/imx6dl-pico-pi.dts
> > index b7b1c07f96f3..4590e8ad9a91 100644
> > --- a/arch/arm/boot/dts/imx6dl-pico-pi.dts
> > +++ b/arch/arm/boot/dts/imx6dl-pico-pi.dts

The bindings, added in commit 53b61224ca40 ("dt-bindings: arm: fsl: Add
TechNexion boards"), describe that these are the only valid compatibles.
"technexion,imx6dl-pico" is not valid and would require changing the
bindings, thus breaking compatibility which you want to avoid.

The bindings, not what is present in DTS, is considered ABI.

Best regards,
Krzysztof