linux-kernel - Re: [PATCH 4/4] dts: iot2050: Support IOT2050-SM variant

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Message-ID: <ef5a6cf0-4350-483d-a1e9-ce8b0ef71280@siemens.com>
Date: Tue, 19 Dec 2023 10:54:35 +0100
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Tero Kristo <kristo@...nel.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Bao Cheng Su <baocheng.su@...mens.com>,
 Chao Zeng <chao.zeng@...mens.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, Li Hua Qian <huaqian.li@...mens.com>
Subject: Re: [PATCH 4/4] dts: iot2050: Support IOT2050-SM variant

On 19.12.23 10:50, Krzysztof Kozlowski wrote:
> On 19/12/2023 10:03, Jan Kiszka wrote:
>> On 19.12.23 09:48, Krzysztof Kozlowski wrote:
>>> On 19/12/2023 09:22, Jan Kiszka wrote:
>>>>>
>>>>>> +			gpios = <&wkup_gpio0 53 GPIO_ACTIVE_HIGH>;
>>>>>
>>>>> Ditto
>>>>>
>>>>
>>>> This is adjusting the existing LED nodes in k3-am65-iot2050-common.dtsi,
>>>> not introducing new ones. We can add the color properties in a separate
>>>
>>>
>>> Then why aren't you overriding by phandle/label?
>>>
>>
>> We could do that as well if we added labels first (they don't exist so 
>> far). Not seeing any difference, though.
> 
> Confusion? Your code suggests new node, thus you got review like you got.
> 
>>
>>>> patch, but the node names are now part of the kernel ABI. Changing them
>>>> would break existing userland.
>>>
>>> You mean label. Why node names became the ABI? Which interface exposes them?
>>
>> root@...2050-debian:~# ls -l /sys/class/leds/
>> total 0
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 mmc0:: -> ../../devices/platform/bus@...000/4fa0000.mmc/leds/mmc0::
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 mmc1:: -> ../../devices/platform/bus@...000/4f80000.mmc/leds/mmc1::
>> lrwxrwxrwx 1 root root 0 Dec 14 21:12 status-led-green -> ../../devices/platform/leds/leds/status-led-green
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 status-led-red -> ../../devices/platform/leds/leds/status-led-red
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 user-led1-green -> ../../devices/platform/leds/leds/user-led1-green
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 user-led1-red -> ../../devices/platform/leds/leds/user-led1-red
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 user-led2-green -> ../../devices/platform/leds/leds/user-led2-green
>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 user-led2-red -> ../../devices/platform/leds/leds/user-led2-red
> 
> I replied too fast previous and did not include answer here:
> 
> You have label for that... Somehow all these nodes are half-baked,
> without all the expected properties and now you call node name as ABI.
> The node name is not the ABI.

Well, existing userspace uses those names, and adding the properties
would break that interface. Now, does Linux do that?

Jan

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