1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Multi-color LED built with monochromatic LED devices
  4 *
  5 * This driver groups several monochromatic LED devices in a single multicolor LED device.
  6 *
  7 * Compared to handling this grouping in user-space, the benefits are:
  8 * - The state of the monochromatic LED relative to each other is always consistent.
  9 * - The sysfs interface of the LEDs can be used for the group as a whole.
 10 *
 11 * Copyright 2023 Jean-Jacques Hiblot <jjhiblot@traphandler.com>
 12 */
 13
 14#include <linux/err.h>
 15#include <linux/leds.h>
 16#include <linux/led-class-multicolor.h>
 17#include <linux/math.h>
 18#include <linux/module.h>
 19#include <linux/mod_devicetable.h>
 20#include <linux/platform_device.h>
 21#include <linux/property.h>
 22
 23struct leds_multicolor {
 24	struct led_classdev_mc mc_cdev;
 25	struct led_classdev **monochromatics;
 26};
 27
 28static int leds_gmc_set(struct led_classdev *cdev, enum led_brightness brightness)
 29{
 30	struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
 31	struct leds_multicolor *priv = container_of(mc_cdev, struct leds_multicolor, mc_cdev);
 32	const unsigned int group_max_brightness = mc_cdev->led_cdev.max_brightness;
 33	int i;
 34
 35	for (i = 0; i < mc_cdev->num_colors; i++) {
 36		struct led_classdev *mono = priv->monochromatics[i];
 37		const unsigned int mono_max_brightness = mono->max_brightness;
 38		unsigned int intensity = mc_cdev->subled_info[i].intensity;
 39		int mono_brightness;
 40
 41		/*
 42		 * Scale the brightness according to relative intensity of the
 43		 * color AND the max brightness of the monochromatic LED.
 44		 */
 45		mono_brightness = DIV_ROUND_CLOSEST(brightness * intensity * mono_max_brightness,
 46						    group_max_brightness * group_max_brightness);
 47
 48		led_set_brightness(mono, mono_brightness);
 49	}
 50
 51	return 0;
 52}
 53
 54static void restore_sysfs_write_access(void *data)
 55{
 56	struct led_classdev *led_cdev = data;
 57
 58	/* Restore the write access to the LED */
 59	mutex_lock(&led_cdev->led_access);
 60	led_sysfs_enable(led_cdev);
 61	mutex_unlock(&led_cdev->led_access);
 62}
 63
 64static int leds_gmc_probe(struct platform_device *pdev)
 65{
 66	struct device *dev = &pdev->dev;
 67	struct led_init_data init_data = {};
 68	struct led_classdev *cdev;
 69	struct mc_subled *subled;
 70	struct leds_multicolor *priv;
 71	unsigned int max_brightness = 0;
 72	int i, ret, count = 0, common_flags = 0;
 73
 74	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 75	if (!priv)
 76		return -ENOMEM;
 77
 78	for (;;) {
 79		struct led_classdev *led_cdev;
 80
 81		led_cdev = devm_of_led_get_optional(dev, count);
 82		if (IS_ERR(led_cdev))
 83			return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
 84					     count);
 85		if (!led_cdev)
 86			break;
 87
 88		priv->monochromatics = devm_krealloc_array(dev, priv->monochromatics,
 89					count + 1, sizeof(*priv->monochromatics),
 90					GFP_KERNEL);
 91		if (!priv->monochromatics)
 92			return -ENOMEM;
 93
 94		common_flags |= led_cdev->flags;
 95		priv->monochromatics[count] = led_cdev;
 96
 97		max_brightness = max(max_brightness, led_cdev->max_brightness);
 98
 99		count++;
100	}
101
102	subled = devm_kcalloc(dev, count, sizeof(*subled), GFP_KERNEL);
103	if (!subled)
104		return -ENOMEM;
105	priv->mc_cdev.subled_info = subled;
106
107	for (i = 0; i < count; i++) {
108		struct led_classdev *led_cdev = priv->monochromatics[i];
109
110		subled[i].color_index = led_cdev->color;
111
112		/* Configure the LED intensity to its maximum */
113		subled[i].intensity = max_brightness;
114	}
115
116	/* Initialise the multicolor's LED class device */
117	cdev = &priv->mc_cdev.led_cdev;
118	cdev->brightness_set_blocking = leds_gmc_set;
119	cdev->max_brightness = max_brightness;
120	cdev->color = LED_COLOR_ID_MULTI;
121	priv->mc_cdev.num_colors = count;
122
123	/* we only need suspend/resume if a sub-led requests it */
124	if (common_flags & LED_CORE_SUSPENDRESUME)
125		cdev->flags = LED_CORE_SUSPENDRESUME;
126
127	init_data.fwnode = dev_fwnode(dev);
128	ret = devm_led_classdev_multicolor_register_ext(dev, &priv->mc_cdev, &init_data);
129	if (ret)
130		return dev_err_probe(dev, ret, "failed to register multicolor LED for %s.\n",
131				     cdev->name);
132
133	ret = leds_gmc_set(cdev, cdev->brightness);
134	if (ret)
135		return dev_err_probe(dev, ret, "failed to set LED value for %s.", cdev->name);
136
137	for (i = 0; i < count; i++) {
138		struct led_classdev *led_cdev = priv->monochromatics[i];
139
140		/*
141		 * Make the individual LED sysfs interface read-only to prevent the user
142		 * to change the brightness of the individual LEDs of the group.
143		 */
144		mutex_lock(&led_cdev->led_access);
145		led_sysfs_disable(led_cdev);
146		mutex_unlock(&led_cdev->led_access);
147
148		/* Restore the write access to the LED sysfs when the group is destroyed */
149		devm_add_action_or_reset(dev, restore_sysfs_write_access, led_cdev);
150	}
151
152	return 0;
153}
154
155static const struct of_device_id of_leds_group_multicolor_match[] = {
156	{ .compatible = "leds-group-multicolor" },
157	{}
158};
159MODULE_DEVICE_TABLE(of, of_leds_group_multicolor_match);
160
161static struct platform_driver leds_group_multicolor_driver = {
162	.probe		= leds_gmc_probe,
163	.driver		= {
164		.name	= "leds_group_multicolor",
165		.of_match_table = of_leds_group_multicolor_match,
166	}
167};
168module_platform_driver(leds_group_multicolor_driver);
169
170MODULE_AUTHOR("Jean-Jacques Hiblot <jjhiblot@traphandler.com>");
171MODULE_DESCRIPTION("LEDs group multicolor driver");
172MODULE_LICENSE("GPL");
173MODULE_ALIAS("platform:leds-group-multicolor");