From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Biju Das <biju.das.jz@bp.renesas.com>, Rob Herring <robh+dt@kernel.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
Magnus Damm <magnus.damm@gmail.com>,
"linux-renesas-soc@vger.kernel.org"
<linux-renesas-soc@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Chris Paterson <Chris.Paterson2@renesas.com>,
Biju Das <biju.das@bp.renesas.com>,
Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: Re: [PATCH v4 1/5] dt-bindings: arm: renesas: Document Renesas RZ/G2UL SMARC EVK
Date: Sat, 2 Apr 2022 22:03:45 +0200 [thread overview]
Message-ID: <e3ebc5d0-d2bc-b5a8-1b19-5e0c2f3d7c41@linaro.org> (raw)
In-Reply-To: <OS0PR01MB5922C1100BCF87341534FC6E86E39@OS0PR01MB5922.jpnprd01.prod.outlook.com>
On 02/04/2022 21:54, Biju Das wrote:
>>
>> I understand that carrier board is the same, so the SoM differs.
>
> For R9A07G043 case, even SoM is same, only SOC differs.
I assumed that you cannot have same SoMs with different SoCs...
>
>> In your
>> model to figure out what type of hardware is it, your choice is to compare
>> two compatibles:
>> renesas,smarc-evk + renesas,r9a07g043u11
>>
>> If user-space compares only last compatible, it get's only SMARC, so it
>> does not know on what hardware it runs.
>
> But Here user-space can easily identify the H/W with existing scheme. See the logs from user-space.
>
> / # for i in machine family soc_id revision; do echo -n "$i: "; cat /sys/devices/soc0/$i;done
> machine: Renesas SMARC EVK based on r9a07g043u11
> family: RZ/G2UL
> soc_id: r9a07g043
> revision: 0
User-space is one example. We don't limit to this. Anyway, the
compatible is the main way to check it. Machine is just test, not
compatible, not part of ABI. soc_id and revision could help, but these
are separate ABIs. They can be not compiled-in and then you have only
compatible.
Regardless whether there is another way for user-space to figure out
hardware, it does not change the fact that such usage of compatibles
does not look correct with Devicetree spec.
"...They
allow a device to express its compatibility with a family of similar
devices, potentially allowing a single
device driver to match against several devices."
The "renesas,smarc-evk" compatible is not the most specific one, because
different configurations have it.
Again - you intend to use a pair or even a triple of compatibles to
uniquely identify type of hardware. I don't think it is correct - the
final, most specific compatible, uniquely identifies the hardware. All
other compatibles are just for fallback.
Best regards,
Krzysztof
next prev parent reply other threads:[~2022-04-02 20:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-02 7:32 [PATCH v4 1/5] dt-bindings: arm: renesas: Document Renesas RZ/G2UL SMARC EVK Biju Das
2022-04-02 16:36 ` Krzysztof Kozlowski
2022-04-02 19:05 ` Biju Das
2022-04-02 19:20 ` Krzysztof Kozlowski
2022-04-02 19:54 ` Biju Das
2022-04-02 20:03 ` Krzysztof Kozlowski [this message]
2022-04-02 20:48 ` Biju Das
2022-04-03 7:52 ` Krzysztof Kozlowski
2022-04-04 12:29 ` Geert Uytterhoeven
2022-04-04 13:00 ` Krzysztof Kozlowski
2022-04-05 11:47 ` Biju Das
2022-04-05 12:05 ` Krzysztof Kozlowski
2022-04-06 16:29 ` Rob Herring
2022-04-12 10:28 ` Geert Uytterhoeven
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