Re: [PATCH v5 05/11] [RFC] leds: led-class: Add devicetree support to led_get()

[Aleksandrs Vinarskis <alex.vinarskis@gmail.com>]

On 1/20/23 12:45, Hans de Goede wrote:
> 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.
>
> Note the new led-names property for LED consumers is not added
> to the devicetree documentation because there seems to be no
> documentation for the leds property itself to extend it with this.
> It seems that how LED consumers should be described is not documented
> at all ATM.
>
> This patch is marked as RFC because of both the missing devicetree
> documentation and because there are no devicetree users of
> the generic [devm_]led_get() function for now.
>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>


Hi,

It appears this patch was marked as RFC due some missing dt-bindings and 
not having direct DT consumers at the time, and was eventually left out. 
With recent inflow of arm64-power laptops (Snapdragon X1E/X1P) which 
mostly use MIPI cameras, this feature becomes more desired. I have 
rebased this patch onto 6.17-rc2, and can confirm its (still) working as 
expected (with respective DT changes) on Dell XPS 9345.

What would be the best approach to revive this patch? For Hans to respin 
this? Alternatively I could respin it myself keeping the original 
authorship.
Regarding missing dt-binding documentation, would 
`Documentation/devicetree/bindings/leds/common.yaml` be the good place 
for it? Afaiu it was mentioned that no  appropriate LED bindings exists 
in this series (3yo), but this binding is ~6yo, so perhaps its not a 
right place after all.

Thank you in advance,
Alex

> ---
>   drivers/leds/led-class.c | 37 ++++++++++++++++++++++++++++---------
>   1 file changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 0c4b8d8d2b4f..2f3af6e30208 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -234,19 +234,18 @@ static struct led_classdev *led_module_get(struct device *led_dev)
>   	return led_cdev;
>   }
>   
> -/**
> - * 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)
> +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);
> @@ -256,6 +255,19 @@ 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);
>   
>   /**
> @@ -329,9 +341,16 @@ 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)) &&