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

[Rasmus Villemoes <rasmus.villemoes@prevas.dk>]

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.]

Rasmus