leds: led-class: Add generic [devm_]led_get()

Add a generic [devm_]led_get() method which can be used on both devicetree
and non devicetree platforms to get a LED classdev associated with
a specific function on a specific device, e.g. the privacy LED associated
with a specific camera sensor.

Note unlike of_led_get() this takes a string describing the function
rather then an index. This is done because e.g. camera sensors might
have a privacy LED, or a flash LED, or both and using an index
approach leaves it unclear what the function of index 0 is if there is
only 1 LED.

This uses a lookup-table mechanism for non devicetree platforms.
This allows the platform code to map specific LED class_dev-s to a specific
device,function combinations this way.

For devicetree platforms getting the LED by function-name could be made
to work using the standard devicetree pattern of adding a -names string
array to map names to the indexes.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230120114524.408368-5-hdegoede@redhat.com

1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/leds.h b/include/linux/leds.h
index ba4861ec73d3..31cb74b90ffc 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -39,6 +39,21 @@ enum led_default_state {
 	LEDS_DEFSTATE_KEEP	= 2,
 };
 
+/**
+ * struct led_lookup_data - represents a single LED lookup entry
+ *
+ * @list: internal list of all LED lookup entries
+ * @provider: name of led_classdev providing the LED
+ * @dev_id: name of the device associated with this LED
+ * @con_id: name of the LED from the device's point of view
+ */
+struct led_lookup_data {
+	struct list_head list;
+	const char *provider;
+	const char *dev_id;
+	const char *con_id;
+};
+
 struct led_init_data {
 	/* device fwnode handle */
 	struct fwnode_handle *fwnode;
@@ -211,6 +226,12 @@ void devm_led_classdev_unregister(struct device *parent,
 void led_classdev_suspend(struct led_classdev *led_cdev);
 void led_classdev_resume(struct led_classdev *led_cdev);
 
+void led_add_lookup(struct led_lookup_data *led_lookup);
+void led_remove_lookup(struct led_lookup_data *led_lookup);
+
+struct led_classdev *__must_check led_get(struct device *dev, char *con_id);
+struct led_classdev *__must_check devm_led_get(struct device *dev, char *con_id);
+
 extern struct led_classdev *of_led_get(struct device_node *np, int index);
 extern void led_put(struct led_classdev *led_cdev);
 struct led_classdev *__must_check devm_of_led_get(struct device *dev,