linux-kernel - Re: [PATCH 1/3] dt-bindings: leds: add LED_FUNCTION

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Message-ID: <368e9817-0000-4f69-9f09-568827466121@linaro.org>
Date: Wed, 3 Apr 2024 10:36:09 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Hans de Goede <hdegoede@...hat.com>, Gergo Koteles <soyer@....hu>,
 Ike Panhc <ike.pan@...onical.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-leds@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: leds: add LED_FUNCTION_FNLOCK

On 03/04/2024 10:31, Hans de Goede wrote:
> Hi Krzysztof,
> 
> On 4/2/24 3:55 PM, Krzysztof Kozlowski wrote:
>> On 02/04/2024 15:21, Gergo Koteles wrote:
>>> Newer laptops have FnLock LED.
>>>
>>> Add a define for this very common function.
>>>
>>> Signed-off-by: Gergo Koteles <soyer@....hu>
>>> ---
>>>  include/dt-bindings/leds/common.h | 1 +
>>
>> Do we really need to define all these possible LED functions? Please
>> link to DTS user for this.
> 
> It is useful to have well established names for common
> LED functions instead of having each driver come up
> with its own name with slightly different spelling
> for various fixed function LEDs.
> 
> This is even documented in:
> 
> Documentation/leds/leds-class.rst :
> 
> """
> LED Device Naming
> =================
> 
> Is currently of the form:
> 
>         "devicename:color:function"
> 
> ...
> 
> 
> - function:
>         one of LED_FUNCTION_* definitions from the header
>         include/dt-bindings/leds/common.h.
> """
> 
> Note this even specifies these definitions should go into
> include/dt-bindings/leds/common.h .
> 
> In this case there is no dts user (yet) only an in kernel
> driver which wants to use a LED_FUNCTION_* define to
> establish how to identify FN-lock LEDs going forward.

Ack, reasonable.

> 
> Since a lot of LED_FUNCTION_* defines happen to be used
> in dts files these happen to live under include/dt-bindings/
> but the dts files are not the only consumer of these defines (1).

Yes, but if there was no DTS consumer at all, then it is not a binding,
so it should not go to include/dt-bindings.

> 
> IMHO having a hard this must be used in a dts file rule
> is not helpful for these kinda files with defines shared
> between dts and non dts cases.
> 
> If we were to follow this logic then any addition to
> 
> include/uapi/linux/input-event-codes.h
> 
> must have a dts user before being approved too ? Since
> that file is included from include/dt-bindings/input/input.h ?

Wait, that's UAPI :) and we just share the constants. That's kind of
special case, but I get what you mean.

> 
> TL;DR: not only is this patch fine, this is actually
> the correct place to add such a define according to
> the docs in Documentation/leds/leds-class.rst :
> 
> Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>


Best regards,
Krzysztof