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

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>
---
 drivers/leds/led-class.c | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

On Fri, 20 Jan 2023, 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>
> ---
>  drivers/leds/led-class.c | 37 ++++++++++++++++++++++++++++---------
>  1 file changed, 28 insertions(+), 9 deletions(-)

Reviewed-by: Lee Jones <lee@kernel.org>

> 
> 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)) &&
> -- 
> 2.39.0
>