linux-kernel - Re: [PATCH 0/5] Add support for Xiaomi Poco F1 EBBG variant

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Date:   Thu, 4 Aug 2022 18:21:05 +0200
From:   Pavel Machek <pavel@....cz>
To:     Konrad Dybcio <konrad.dybcio@...ainline.org>
Cc:     Joel Selvaraj <jo@...amily.in>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org
Subject: Re: [PATCH 0/5] Add support for Xiaomi Poco F1 EBBG variant

Hi!

> > - Tianma variant with NOVATEK NT36672A panel + touchscreen manufactured
> >   by Tianma
> > - EBBG variant with Focaltech FT8719 panel + touchscreen manufactured
> >   by EBBG
> > 
> > The current sdm845-xiaomi-beryllium.dts represents tianma panel variant.
> > 
> > To add support for the EBBG variant, let's split this into 3 files,
> > - sdm845-xiaomi-beryllium-common.dtsi which contains all the common nodes
> > - sdm845-xiaomi-beryllium-tianma.dts for the tianma variant
> > - sdm845-xiaomi-beryllium-ebbg.dts for the ebbg variant
> > 
> > Note:
> > -----
> > Both the panels are already upstreamed and the split is based on them.
> > There were patches earlier for both the touchscreens, but they are not
> > accepted upstream yet. Once they are accepted, we will add them to
> > respective variants.
> Hi,
> 
> I believe this is not the correct approach. This may work short-term, but
> you will have to prepare 2 separate images for the device and mistaking them
> may cause irreversible hw damage at worst, or lots of user complaining at best.
> Instead, I think it's about time we should look into implementing dynamic panel
> detection.

It is certainly better than current state. Now user will need to decide what
panel he has.

> Qualcomm devices do this by parsing the command line [1], as LK/XBL
> gives you a nice-ish string to work with that you can simply match
> against a label. Other vendors may use custom mechanisms, such as
> a resistor / GPIO to determine which panel (or generally hw config),
> but implementing this mechanism would make upstreaming of lots of other
> devices easier..

I believe ideal solution would be bootloader passing the correct dtb to the
kernel...

Best regards,								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html