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

   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
  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
  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
  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");