drivers/leds/rgb/leds-group-multicolor.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Multi-color LED built with monochromatic LED devices
 *
 * This driver groups several monochromatic LED devices in a single multicolor LED device.
 *
 * Compared to handling this grouping in user-space, the benefits are:
 * - The state of the monochromatic LED relative to each other is always consistent.
 * - The sysfs interface of the LEDs can be used for the group as a whole.
 *
 * Copyright 2023 Jean-Jacques Hiblot <jjhiblot@traphandler.com>
 */

#include <linux/err.h>
#include <linux/leds.h>
#include <linux/led-class-multicolor.h>
#include <linux/math.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/property.h>

struct leds_multicolor {
	struct led_classdev_mc mc_cdev;
	struct led_classdev **monochromatics;
};

static int leds_gmc_set(struct led_classdev *cdev, enum led_brightness brightness)
{
	struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
	struct leds_multicolor *priv = container_of(mc_cdev, struct leds_multicolor, mc_cdev);
	const unsigned int group_max_brightness = mc_cdev->led_cdev.max_brightness;
	int i;

	for (i = 0; i < mc_cdev->num_colors; i++) {
		struct led_classdev *mono = priv->monochromatics[i];
		const unsigned int mono_max_brightness = mono->max_brightness;
		unsigned int intensity = mc_cdev->subled_info[i].intensity;
		int mono_brightness;

		/*
		 * Scale the brightness according to relative intensity of the
		 * color AND the max brightness of the monochromatic LED.
		 */
		mono_brightness = DIV_ROUND_CLOSEST(brightness * intensity * mono_max_brightness,
						    group_max_brightness * group_max_brightness);

		led_set_brightness(mono, mono_brightness);
	}

	return 0;
}

static void restore_sysfs_write_access(void *data)
{
	struct led_classdev *led_cdev = data;

	/* Restore the write acccess to the LED */
	mutex_lock(&led_cdev->led_access);
	led_sysfs_enable(led_cdev);
	mutex_unlock(&led_cdev->led_access);
}

static int leds_gmc_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct led_init_data init_data = {};
	struct led_classdev *cdev;
	struct mc_subled *subled;
	struct leds_multicolor *priv;
	unsigned int max_brightness = 0;
	int i, ret, count = 0, common_flags = 0;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	for (;;) {
		struct led_classdev *led_cdev;

		led_cdev = devm_of_led_get_optional(dev, count);
		if (IS_ERR(led_cdev))
			return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
					     count);
		if (!led_cdev)
			break;

		priv->monochromatics = devm_krealloc_array(dev, priv->monochromatics,
					count + 1, sizeof(*priv->monochromatics),
					GFP_KERNEL);
		if (!priv->monochromatics)
			return -ENOMEM;

		common_flags |= led_cdev->flags;
		priv->monochromatics[count] = led_cdev;

		max_brightness = max(max_brightness, led_cdev->max_brightness);

		count++;
	}

	subled = devm_kcalloc(dev, count, sizeof(*subled), GFP_KERNEL);
	if (!subled)
		return -ENOMEM;
	priv->mc_cdev.subled_info = subled;

	for (i = 0; i < count; i++) {
		struct led_classdev *led_cdev = priv->monochromatics[i];

		subled[i].color_index = led_cdev->color;

		/* Configure the LED intensity to its maximum */
		subled[i].intensity = max_brightness;
	}

	/* Initialise the multicolor's LED class device */
	cdev = &priv->mc_cdev.led_cdev;
	cdev->brightness_set_blocking = leds_gmc_set;
	cdev->max_brightness = max_brightness;
	cdev->color = LED_COLOR_ID_MULTI;
	priv->mc_cdev.num_colors = count;

	/* we only need suspend/resume if a sub-led requests it */
	if (common_flags & LED_CORE_SUSPENDRESUME)
		cdev->flags = LED_CORE_SUSPENDRESUME;

	init_data.fwnode = dev_fwnode(dev);
	ret = devm_led_classdev_multicolor_register_ext(dev, &priv->mc_cdev, &init_data);
	if (ret)
		return dev_err_probe(dev, ret, "failed to register multicolor LED for %s.\n",
				     cdev->name);

	ret = leds_gmc_set(cdev, cdev->brightness);
	if (ret)
		return dev_err_probe(dev, ret, "failed to set LED value for %s.", cdev->name);

	for (i = 0; i < count; i++) {
		struct led_classdev *led_cdev = priv->monochromatics[i];

		/*
		 * Make the individual LED sysfs interface read-only to prevent the user
		 * to change the brightness of the individual LEDs of the group.
		 */
		mutex_lock(&led_cdev->led_access);
		led_sysfs_disable(led_cdev);
		mutex_unlock(&led_cdev->led_access);

		/* Restore the write access to the LED sysfs when the group is destroyed */
		devm_add_action_or_reset(dev, restore_sysfs_write_access, led_cdev);
	}

	return 0;
}

static const struct of_device_id of_leds_group_multicolor_match[] = {
	{ .compatible = "leds-group-multicolor" },
	{}
};
MODULE_DEVICE_TABLE(of, of_leds_group_multicolor_match);

static struct platform_driver leds_group_multicolor_driver = {
	.probe		= leds_gmc_probe,
	.driver		= {
		.name	= "leds_group_multicolor",
		.of_match_table = of_leds_group_multicolor_match,
	}
};
module_platform_driver(leds_group_multicolor_driver);

MODULE_AUTHOR("Jean-Jacques Hiblot <jjhiblot@traphandler.com>");
MODULE_DESCRIPTION("LEDs group multicolor driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:leds-group-multicolor");