linux-kernel - Re: [PATCH 2/2] leds: led-class: Add devicetree support to led

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Message-ID: <8aa9dfc5-5e77-48af-b2f4-f1964d20d6d1@kernel.org>
Date: Tue, 2 Sep 2025 14:25:37 +0200
From: Hans de Goede <hansg@...nel.org>
To: Aleksandrs Vinarskis <alex@...arskis.com>, Lee Jones <lee@...nel.org>,
 Pavel Machek <pavel@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc: linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Andy Shevchenko <andy.shevchenko@...il.com>,
 Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 2/2] leds: led-class: Add devicetree support to led_get()

Hi Aleksandrs,

Thank you for working on this.

On 2-Sep-25 1:10 PM, Aleksandrs Vinarskis wrote:
> From: Hans de Goede <hansg@...nel.org>
> 
> Turn of_led_get() into a more generic __of_led_get() helper function,
> which can lookup LEDs in devicetree by either name or index.
> 
> And use this new helper to add devicetree support to the generic
> (non devicetree specific) [devm_]led_get() function.
> 
> This uses the standard devicetree pattern of adding a -names string array
> to map names to the indexes for an array of resources.
> 
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
> Reviewed-by: Lee Jones <lee@...nel.org>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>

Please update this to:

Reviewed-by: Hans de Goede <hansg@...nel.org>

to match the update of the author which you already did.

Also note that checkpatch should complain about the mismatch,
please ensure to run checkpatch before posting v2.

> Tested-by: Aleksandrs Vinarskis <alex@...arskis.com>
> ---
>  drivers/leds/led-class.c | 38 +++++++++++++++++++++++++++++---------
>  1 file changed, 29 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 15633fbf3c166aa4f521774d245f6399a642bced..6f2ef4fa556b44ed3bf69dff556ae16fd2b7652b 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -248,19 +248,18 @@ static const struct class leds_class = {
>  	.pm = &leds_class_dev_pm_ops,
>  };
>  
> -/**
> - * of_led_get() - request a LED device via the LED framework
> - * @np: device node to get the LED device from
> - * @index: the index of the LED
> - *
> - * Returns the LED device parsed from the phandle specified in the "leds"
> - * property of a device tree node or a negative error-code on failure.
> - */
> -static struct led_classdev *of_led_get(struct device_node *np, int index)
> +static struct led_classdev *__of_led_get(struct device_node *np, int index,
> +					 const char *name)
>  {
>  	struct device *led_dev;
>  	struct device_node *led_node;
>  
> +	/*
> +	 * For named LEDs, first look up the name in the "led-names" property.
> +	 * If it cannot be found, then of_parse_phandle() will propagate the error.
> +	 */
> +	if (name)
> +		index = of_property_match_string(np, "led-names", name);
>  	led_node = of_parse_phandle(np, "leds", index);
>  	if (!led_node)
>  		return ERR_PTR(-ENOENT);
> @@ -271,6 +270,20 @@ static struct led_classdev *of_led_get(struct device_node *np, int index)
>  	return led_module_get(led_dev);
>  }
>  
> +/**
> + * of_led_get() - request a LED device via the LED framework
> + * @np: device node to get the LED device from
> + * @index: the index of the LED
> + *
> + * Returns the LED device parsed from the phandle specified in the "leds"
> + * property of a device tree node or a negative error-code on failure.
> + */
> +struct led_classdev *of_led_get(struct device_node *np, int index)
> +{
> +	return __of_led_get(np, index, NULL);
> +}
> +EXPORT_SYMBOL_GPL(of_led_get);

I probably did this myself, but since of_led_get() is private now
(I guess it was not private before?) and since we are moving away from
"of" specific functions to using generic dev_xxxx functions in the kernel
in general, I think this just should be a static helper.

Or probably even better: just add the name argument to of_led_get()
before without renaming it, update the existing callers to pass
an extra NULL arg and completely drop this wrapper.

Also notice that adding the EXPORT_SYMBOL_GPL() while there was
none before should go hand in hand with adding a prototype to
a relevant .h file. However please just keep this private and
drop the wrapper.

Regards,

Hans




> +
>  /**
>   * led_put() - release a LED device
>   * @led_cdev: LED device
> @@ -342,9 +355,16 @@ EXPORT_SYMBOL_GPL(devm_of_led_get);
>  struct led_classdev *led_get(struct device *dev, char *con_id)
>  {
>  	struct led_lookup_data *lookup;
> +	struct led_classdev *led_cdev;
>  	const char *provider = NULL;
>  	struct device *led_dev;
>  
> +	if (dev->of_node) {
> +		led_cdev = __of_led_get(dev->of_node, -1, con_id);
> +		if (!IS_ERR(led_cdev) || PTR_ERR(led_cdev) != -ENOENT)
> +			return led_cdev;
> +	}
> +
>  	mutex_lock(&leds_lookup_lock);
>  	list_for_each_entry(lookup, &leds_lookup_list, list) {
>  		if (!strcmp(lookup->dev_id, dev_name(dev)) &&
>