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
23 struct leds_multicolor {
24 struct led_classdev_mc mc_cdev;
25 struct led_classdev **monochromatics;
26 };
27
leds_gmc_set(struct led_classdev * cdev,enum led_brightness brightness)28 static 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
restore_sysfs_write_access(void * data)54 static void restore_sysfs_write_access(void *data)
55 {
56 struct led_classdev *led_cdev = data;
57
58 /* Restore the write acccess 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
leds_gmc_probe(struct platform_device * pdev)64 static 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;
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 priv->monochromatics[count] = led_cdev;
95
96 max_brightness = max(max_brightness, led_cdev->max_brightness);
97
98 count++;
99 }
100
101 subled = devm_kcalloc(dev, count, sizeof(*subled), GFP_KERNEL);
102 if (!subled)
103 return -ENOMEM;
104 priv->mc_cdev.subled_info = subled;
105
106 for (i = 0; i < count; i++) {
107 struct led_classdev *led_cdev = priv->monochromatics[i];
108
109 subled[i].color_index = led_cdev->color;
110
111 /* Configure the LED intensity to its maximum */
112 subled[i].intensity = max_brightness;
113 }
114
115 /* Initialise the multicolor's LED class device */
116 cdev = &priv->mc_cdev.led_cdev;
117 cdev->flags = LED_CORE_SUSPENDRESUME;
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 init_data.fwnode = dev_fwnode(dev);
124 ret = devm_led_classdev_multicolor_register_ext(dev, &priv->mc_cdev, &init_data);
125 if (ret)
126 return dev_err_probe(dev, ret, "failed to register multicolor LED for %s.\n",
127 cdev->name);
128
129 ret = leds_gmc_set(cdev, cdev->brightness);
130 if (ret)
131 return dev_err_probe(dev, ret, "failed to set LED value for %s.", cdev->name);
132
133 for (i = 0; i < count; i++) {
134 struct led_classdev *led_cdev = priv->monochromatics[i];
135
136 /*
137 * Make the individual LED sysfs interface read-only to prevent the user
138 * to change the brightness of the individual LEDs of the group.
139 */
140 mutex_lock(&led_cdev->led_access);
141 led_sysfs_disable(led_cdev);
142 mutex_unlock(&led_cdev->led_access);
143
144 /* Restore the write access to the LED sysfs when the group is destroyed */
145 devm_add_action_or_reset(dev, restore_sysfs_write_access, led_cdev);
146 }
147
148 return 0;
149 }
150
151 static const struct of_device_id of_leds_group_multicolor_match[] = {
152 { .compatible = "leds-group-multicolor" },
153 {}
154 };
155 MODULE_DEVICE_TABLE(of, of_leds_group_multicolor_match);
156
157 static struct platform_driver leds_group_multicolor_driver = {
158 .probe = leds_gmc_probe,
159 .driver = {
160 .name = "leds_group_multicolor",
161 .of_match_table = of_leds_group_multicolor_match,
162 }
163 };
164 module_platform_driver(leds_group_multicolor_driver);
165
166 MODULE_AUTHOR("Jean-Jacques Hiblot <jjhiblot@traphandler.com>");
167 MODULE_DESCRIPTION("LEDs group multicolor driver");
168 MODULE_LICENSE("GPL");
169 MODULE_ALIAS("platform:leds-group-multicolor");
170