linux-kernel - [PATCH v1 2/2] leds: multicolor: Read default-intensities property

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Message-Id: <03decec200aa7550f66be8454438eb3db6a2378a.1651575831.git.sven.schwermer@disruptive-technologies.com>
Date:   Tue,  3 May 2022 13:04:51 +0200
From:   Sven Schwermer <sven@...nschwermer.de>
To:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        pavel@....cz, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, dmurphy@...com,
        devicetree@...r.kernel.org
Cc:     Sven Schwermer <sven.schwermer@...ruptive-technologies.com>
Subject: [PATCH v1 2/2] leds: multicolor: Read default-intensities property

From: Sven Schwermer <sven.schwermer@...ruptive-technologies.com>

This allows to assign intensity values taken from the firmware interface
(if available) to the indivisual sub LEDs (colors) at driver probe time,
i.e. most commonly at kernel boot time. This is crucial for setting a
specific color and early in the boot process. While it would be possible
to set a static color in the bootloader, this mechanism allows setting a
pattern (e.g. blinking) at a specific color.

Signed-off-by: Sven Schwermer <sven.schwermer@...ruptive-technologies.com>
---
 drivers/leds/led-class-multicolor.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
index e317408583df..eb7f11345ec1 100644
--- a/drivers/leds/led-class-multicolor.c
+++ b/drivers/leds/led-class-multicolor.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/property.h>
 
 #include "leds.h"
 
@@ -116,6 +117,23 @@ static struct attribute *led_multicolor_attrs[] = {
 };
 ATTRIBUTE_GROUPS(led_multicolor);
 
+static void multi_load_default_intensities(struct device *parent,
+					   struct led_classdev_mc *mcled_cdev,
+					   struct fwnode_handle *fwnode)
+{
+	u32 intensities[LED_COLOR_ID_MAX];
+	int ret;
+	int i;
+
+	ret = fwnode_property_read_u32_array(fwnode, "default-intensities",
+					     intensities, mcled_cdev->num_colors);
+	if (ret < 0 && ret != -ENODATA)
+		dev_warn(parent, "failed to read default-intensities property: %d", ret);
+
+	for (i = 0; i < ret; i++)
+		mcled_cdev->subled_info[i].intensity = intensities[i];
+}
+
 int led_classdev_multicolor_register_ext(struct device *parent,
 				     struct led_classdev_mc *mcled_cdev,
 				     struct led_init_data *init_data)
@@ -134,6 +152,9 @@ int led_classdev_multicolor_register_ext(struct device *parent,
 	led_cdev = &mcled_cdev->led_cdev;
 	mcled_cdev->led_cdev.groups = led_multicolor_groups;
 
+	if (init_data && init_data->fwnode)
+		multi_load_default_intensities(parent, mcled_cdev, init_data->fwnode);
+
 	return led_classdev_register_ext(parent, led_cdev, init_data);
 }
 EXPORT_SYMBOL_GPL(led_classdev_multicolor_register_ext);
-- 
2.36.0