linux-kernel - Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

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Date:   Tue, 8 Oct 2019 15:30:22 +0200
From:   Jean-Jacques Hiblot <jjhiblot@...com>
To:     Rob Herring <robh+dt@...nel.org>
CC:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>,
        Sebastian Reichel <sre@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Dan Murphy <dmurphy@...com>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>
Subject: Re: [PATCH v9 4/5] dt-bindings: backlight: Add led-backlight binding

Rob,

On 08/10/2019 14:51, Jean-Jacques Hiblot wrote:
> Hi Rob,
>
> On 07/10/2019 18:15, Rob Herring wrote:
>> Please send DT bindings to DT list or it's never in my queue. IOW,
>> send patches to the lists that get_maintainers.pl tells you to.
>>
>> On Mon, Oct 7, 2019 at 7:45 AM Jean-Jacques Hiblot <jjhiblot@...com> 
>> wrote:
>>> Add DT binding for led-backlight.
>>>
>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...com>
>>> Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>
>>> Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>
>>> ---
>>>   .../bindings/leds/backlight/led-backlight.txt | 28 
>>> +++++++++++++++++++
>>>   1 file changed, 28 insertions(+)
>>>   create mode 100644 
>>> Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>> Please make this a DT schema.
>
> OK.
>
> BTW I used "make dt_binding_check" but had to fix a couple of YAMLs 
> file to get it to work. Do you have a kernel tree with already all the 
> YAML files in good shape ? Or do you want me to post the changes to 
> devicetree@...r.kernel.org ?
>
>
>>
>>> diff --git 
>>> a/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt 
>>> b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>>> new file mode 100644
>>> index 000000000000..4c7dfbe7f67a
>>> --- /dev/null
>>> +++ 
>>> b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>>> @@ -0,0 +1,28 @@
>>> +led-backlight bindings
>>> +
>>> +This binding is used to describe a basic backlight device made of 
>>> LEDs.
>>> +It can also be used to describe a backlight device controlled by 
>>> the output of
>>> +a LED driver.
>>> +
>>> +Required properties:
>>> +  - compatible: "led-backlight"
>>> +  - leds: a list of LEDs
>> 'leds' is already used as a node name and mixing is not ideal.
>>
>> We already have 'flash-leds' in use and with the same definition, so
>> lets continue that and use 'backlight-leds'.
> OK

I am taking that back. I have added of_get_led() and devm_of_get_led() 
to the LED core to make it easier to get a LED from the DT. I modeled 
the interface like it is done for PWM, PHYs or clocks. The property 
containing list/array of phandle  is always named the same. To get one 
particular PWM/PHY/clock, a identifier (name or integer) must be provided.

So unless there is a strong incentive to do otherwise I's rather keep 
this name here.


JJ


>>> +
>>> +Optional properties:
>>> +  - brightness-levels: Array of distinct brightness levels. The 
>>> levels must be
>>> +                       in the range accepted by the underlying LED 
>>> devices.
>>> +                       This is used to translate a backlight 
>>> brightness level
>>> +                       into a LED brightness level. If it is not 
>>> provided, the
>>> +                       identity mapping is used.
>>> +
>>> +  - default-brightness-level: The default brightness level.
>> You can just assume these 2 get a common schema at some point. So just
>> need to define any additional constraints if possible.
>
> Maybe we should keep them until such a common schema is written ?
>
> JJ
>
>>
>> Rob