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Date: Wed, 14 Feb 2024 18:26:06 +0530
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Subject: Re: [PATCH 0/2] Add board-id support for multiple DT selection
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From: Amrit Anand <quic_amrianan@quicinc.com>
To: Rob Herring <robh@kernel.org>
CC: <krzysztof.kozlowski+dt@linaro.org>, <conor+dt@kernel.org>,
        <agross@kernel.org>, <andersson@kernel.org>,
        <konrad.dybcio@linaro.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <kernel@quicinc.com>
References: <1705749649-4708-1-git-send-email-quic_amrianan@quicinc.com>
 <20240124145631.GA873781-robh@kernel.org>
 <b929f0cd-89b6-c48d-d466-db6bbed621b5@quicinc.com>
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On 2/2/2024 10:30 AM, Amrit Anand wrote:
<snip>
>> There's a similar issue for EFI boot with how to select an OS installed
>> DTB[1]. You might not care now, but users may later on (like we have
>> already with QCom devices with fixed bootloaders). If you do this
>> board-id route, then no doubt that compatible values won't be specific
>> enough or have suitable fallbacks to be used. Then EFI boot can't use
>> compatible either and needs to use this QCom specific logic. It may be a
>> common property name, but all the types you defined are QCom specific
>> and the matching logic is pretty much undocumented. I'm not saying we
>> have to use compatible. There wasn't even agreement to use it for EFI
>> boot case. This does need to work for multiple vendors and multiple boot
>> scenarios.
>>
> Agree, given so many hardware identifiers Qcom uses to find the DT 
> based on a best and exact match algorithm, it may not work as is for 
> other vendors/users outside the scope of Qcom.
> Since we have none to very limited visibility into complete set of DT 
> selection identifiers being used by other users or into their 
> selection algorithms since it is mostly undocumented,
> designing a perfectly generic solution (one-size-fits-all) could be 
> far-fetched. The number of board files in Qcom DT selection software 
> package often reaches over 100 DT files due to multiple SoCs and
> board types being supported out of a single software package and these 
> multiple hardware identifiers helps to pick the closest best match DT 
> within a very large pool of DTs.
> Not to affect other users/vendors who would be using their own set of 
> identifiers and an entirely different algorithm for DT selection, 
> would it make more sense to define these Qcom specific
> identifiers within Qcom specific bindings (qcom.yaml), along with 
> detailed documentation on our DT selection algorithm?


I have written a patch for defining Qcom specific identifiers within 
Qcom specific bindings (qcom.yaml) along with documentation on DT 
selection algorithm, would it be okay to send for review?

>
> Thanks,
> Amrit
>
>>
>> Rob
>>
>> [1] https://lore.kernel.org/u-boot/20231114232012.GD6601@bill-the-cat/#r