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

[Jan Kiszka <jan.kiszka@siemens.com>]

On 19.12.23 10:58, Krzysztof Kozlowski wrote:
> On 19/12/2023 10:54, Jan Kiszka wrote:
>>>>> You mean label. Why node names became the ABI? Which interface exposes them?
>>>>
>>>> root@iot2050-debian:~# ls -l /sys/class/leds/
>>>> total 0
>>>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 mmc0:: -> ../../devices/platform/bus@100000/4fa0000.mmc/leds/mmc0::
>>>> lrwxrwxrwx 1 root root 0 Dec 19 08:55 mmc1:: -> ../../devices/platform/bus@100000/4f80000.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?
> 
> I don't think you understood the concept. There is no change for
> userspace. Same interface, same names. No ABI break.

I do understand the impact very well:
open("/sys/class/leds/user-led1-red") has to work for all the variants,
consistently and backward-compatible for userspace.

> 
> Anyway, changing them is not part of this patchset since these are not
> new nodes.

Fine, then we can leave the LED topic aside for now.

I will look into the other comments.

Jan

-- 
Siemens AG, Technology
Linux Expert Center