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Date:   Fri, 22 Sep 2023 22:58:26 +0200
From:   Stephan Gerhold <stephan@gerhold.net>
To:     Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc:     Bjorn Andersson <andersson@kernel.org>,
        Andy Gross <agross@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] arm64: dts: qcom: apq8016-sbc-d3-camera: Convert to
 DT overlay
Message-ID: <ZQ3_8njijHqat5eV@gerhold.net>
References: <20230922-apq8016-sbc-camera-dtso-v1-0-ce9451895ca1@gerhold.net>
 <c835c404-33f3-4f5b-8a8a-819d4019e74b@linaro.org>
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On Fri, Sep 22, 2023 at 09:47:07PM +0100, Bryan O'Donoghue wrote:
> On 22/09/2023 16:11, Stephan Gerhold wrote:
> > Follow the example of the recently added apq8016-sbc-usb-host.dtso and
> > convert apq8016-sbc-d3-camera-mezzanine.dts to a DT overlay that can be
> > applied on top of the apq8016-sbc.dtb. This makes it more clear that
> > this is not a special type of DB410c but just an addon board that can
> > be added on top.
> > 
> > I also prepended a patch that cleans up the node names a bit.
> > 
> > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> > ---
> > Stephan Gerhold (2):
> >        arm64: dts: qcom: apq8016-sbc-d3-camera: Use more generic node names
> >        arm64: dts: qcom: apq8016-sbc-d3-camera: Convert to DT overlay
> > 
> >   arch/arm64/boot/dts/qcom/Makefile                    |  5 +++--
> >   ...nine.dts => apq8016-sbc-d3-camera-mezzanine.dtso} | 20 ++++++++++++++------
> >   2 files changed, 17 insertions(+), 8 deletions(-)
> > ---
> > base-commit: 7236e86ce5c8198b01c30933c2334d07d877cf48
> > change-id: 20230922-apq8016-sbc-camera-dtso-f247bea40f99
> > 
> > Best regards,
> 
> db410c doesn't ship with a bootloader that is capable of applying a dtbo
> though, so this conversion mandates an updated or chainloaded bootloader or
> out-of-tree kernel patch to support.
> 
> __adding__ is fine but, converting implies imposes a new requirement on the
> bootchain.
> 
> Perhaps a middle road solution is to
> 
> - Add, not convert a standalone dtbo or
> - Add a dtbo that includes the mezzanine dts but amends it
> 
> Option 2 for preference but, I'm not sure the dts syntax can be meaningfully
> made to do that.
> 

With these patches the apq8016-sbc-d3-camera-mezzanine.dtb is still
magically built, by running fdtoverlay on apq8016-sbc.dtb and applying
the dtbo. It's applied during the build process so you don't need a
bootloader that supports DTBOs.

There is literally *no change* for you in terms of usage. :-)

Thanks,
Stephan