Re: [PATCH 2/6] led-uclass: honour ->label field populated by driver's own .bind

[Marek Vasut <marex@denx.de>]

On 10/23/23 10:51, Rasmus Villemoes wrote:
> On 19/10/2023 15.54, Marek Vasut wrote:
>> On 10/19/23 11:58, Rasmus Villemoes wrote:
>>> If the driver's own .bind method has populated uc_plat->label, don't
>>> override that. This is necessary for an upcoming driver for ti,lp5562,
>>> where the DT binding unfortunately says to use "chan-name" and not
>>> "label".
>>>
>>> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
>>> ---
>>>    drivers/led/led-uclass.c | 4 +++-
>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/led/led-uclass.c b/drivers/led/led-uclass.c
>>> index 5a5d07b9a7..0232fa84de 100644
>>> --- a/drivers/led/led-uclass.c
>>> +++ b/drivers/led/led-uclass.c
>>> @@ -71,7 +71,9 @@ static int led_post_bind(struct udevice *dev)
>>>        struct led_uc_plat *uc_plat = dev_get_uclass_plat(dev);
>>>        const char *default_state;
>>>    -    uc_plat->label = dev_read_string(dev, "label");
>>> +    if (!uc_plat->label)
>>> +        uc_plat->label = dev_read_string(dev, "label");
>>> +
>>
>> One thing I have to wonder about is, why does this controller have label
>> property in the top-level node , what is that used for ?
>>
>> (see Linux Documentation/devicetree/bindings/leds/leds-lp55xx.yaml)
>>
>> Reviewed-by: Marek Vasut <marex@denx.de>
> 
> Reading the linux driver, it seems that the top-level label, if any, is
> used as part of the naming for individual channels if they don't have
> individual chan-name properties:
> 
> 
>          if (pdata->led_config[chan].name) {
>                  led->cdev.name = pdata->led_config[chan].name;
>          } else {
>                  snprintf(name, sizeof(name), "%s:channel%d",
>                          pdata->label ? : chip->cl->name, chan);
>                  led->cdev.name = name;
>          }
> 
> but I think the rationale in d1188adb2dabc is a bit weak, since the only
> example also does have individual chan-name properties.
> 
> [Complete aside: At first I thought it was related to the multi-color
> LED work that has been ongoing for many many years (I think there was an
> LWN article at some point), where this could be exposed as a single
> multi-color LED, as opposed to the "traditional" three/four individual
> LEDs. In the former case, there would only be one sysfs entry, but with
> attributes exposing the multicolor functionality. I must admit I don't
> know the status of that work, when something reaches v31,
> http://archive.lwn.net:8080/linux-kernel/20200722071055.GA8984@amd/t/ ,
> it's hard to know if it ever lands, or if pieces of it has landed.]

+CC Pavel