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jjhiblotlag-linaro
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leds: rgb: Add a multicolor LED driver to group monochromatic LEDs
Grouping multiple monochrome LEDs into a multicolor LED device has a few benefits over handling the group in user-space: - The state of the LEDs relative to each other is consistent. In other words, if 2 threads competes to set the LED to green and red, the end-result cannot be black or yellow. - The multicolor LED as a whole can be driven through the sysfs LED interface. Signed-off-by: Jean-Jacques Hiblot <[email protected]> Reviewed-by: Lee Jones <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Lee Jones <[email protected]>
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‎drivers/leds/rgb/Kconfig

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if LEDS_CLASS_MULTICOLOR
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config LEDS_GROUP_MULTICOLOR
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tristate "LEDs group multi-color support"
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depends on OF || COMPILE_TEST
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help
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This option enables support for monochrome LEDs that are grouped
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into multicolor LEDs which is useful in the case where LEDs of
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different colors are physically grouped in a single multi-color LED
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and driven by a controller that doesn't have multi-color support.
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To compile this driver as a module, choose M here: the module
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will be called leds-group-multicolor.
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config LEDS_PWM_MULTICOLOR
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tristate "PWM driven multi-color LED Support"
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depends on PWM

‎drivers/leds/rgb/Makefile

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# SPDX-License-Identifier: GPL-2.0
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obj-$(CONFIG_LEDS_GROUP_MULTICOLOR) += leds-group-multicolor.o
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obj-$(CONFIG_LEDS_PWM_MULTICOLOR) += leds-pwm-multicolor.o
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obj-$(CONFIG_LEDS_QCOM_LPG) += leds-qcom-lpg.o
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obj-$(CONFIG_LEDS_MT6370_RGB) += leds-mt6370-rgb.o

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

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Multi-color LED built with monochromatic LED devices
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*
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* This driver groups several monochromatic LED devices in a single multicolor LED device.
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*
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* Compared to handling this grouping in user-space, the benefits are:
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* - The state of the monochromatic LED relative to each other is always consistent.
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* - The sysfs interface of the LEDs can be used for the group as a whole.
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*
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* Copyright 2023 Jean-Jacques Hiblot <[email protected]>
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*/
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#include <linux/err.h>
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#include <linux/leds.h>
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#include <linux/led-class-multicolor.h>
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#include <linux/math.h>
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#include <linux/module.h>
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#include <linux/mod_devicetable.h>
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#include <linux/platform_device.h>
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#include <linux/property.h>
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struct leds_multicolor {
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struct led_classdev_mc mc_cdev;
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struct led_classdev **monochromatics;
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};
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static int leds_gmc_set(struct led_classdev *cdev, enum led_brightness brightness)
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{
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struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
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struct leds_multicolor *priv = container_of(mc_cdev, struct leds_multicolor, mc_cdev);
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const unsigned int group_max_brightness = mc_cdev->led_cdev.max_brightness;
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int i;
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for (i = 0; i < mc_cdev->num_colors; i++) {
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struct led_classdev *mono = priv->monochromatics[i];
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const unsigned int mono_max_brightness = mono->max_brightness;
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unsigned int intensity = mc_cdev->subled_info[i].intensity;
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int mono_brightness;
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/*
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* Scale the brightness according to relative intensity of the
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* color AND the max brightness of the monochromatic LED.
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*/
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mono_brightness = DIV_ROUND_CLOSEST(brightness * intensity * mono_max_brightness,
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group_max_brightness * group_max_brightness);
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led_set_brightness(mono, mono_brightness);
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}
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return 0;
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}
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static void restore_sysfs_write_access(void *data)
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{
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struct led_classdev *led_cdev = data;
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/* Restore the write acccess to the LED */
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mutex_lock(&led_cdev->led_access);
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led_sysfs_enable(led_cdev);
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mutex_unlock(&led_cdev->led_access);
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}
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static int leds_gmc_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct led_init_data init_data = {};
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struct led_classdev *cdev;
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struct mc_subled *subled;
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struct leds_multicolor *priv;
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unsigned int max_brightness = 0;
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int i, ret, count = 0;
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priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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for (;;) {
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struct led_classdev *led_cdev;
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led_cdev = devm_of_led_get_optional(dev, count);
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if (IS_ERR(led_cdev))
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return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
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count);
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if (!led_cdev)
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break;
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priv->monochromatics = devm_krealloc_array(dev, priv->monochromatics,
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count + 1, sizeof(*priv->monochromatics),
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GFP_KERNEL);
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if (!priv->monochromatics)
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return -ENOMEM;
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priv->monochromatics[count] = led_cdev;
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max_brightness = max(max_brightness, led_cdev->max_brightness);
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count++;
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}
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subled = devm_kcalloc(dev, count, sizeof(*subled), GFP_KERNEL);
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if (!subled)
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return -ENOMEM;
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priv->mc_cdev.subled_info = subled;
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for (i = 0; i < count; i++) {
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struct led_classdev *led_cdev = priv->monochromatics[i];
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subled[i].color_index = led_cdev->color;
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/* Configure the LED intensity to its maximum */
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subled[i].intensity = max_brightness;
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}
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/* Initialise the multicolor's LED class device */
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cdev = &priv->mc_cdev.led_cdev;
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cdev->flags = LED_CORE_SUSPENDRESUME;
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cdev->brightness_set_blocking = leds_gmc_set;
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cdev->max_brightness = max_brightness;
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cdev->color = LED_COLOR_ID_MULTI;
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priv->mc_cdev.num_colors = count;
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init_data.fwnode = dev_fwnode(dev);
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ret = devm_led_classdev_multicolor_register_ext(dev, &priv->mc_cdev, &init_data);
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if (ret)
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return dev_err_probe(dev, ret, "failed to register multicolor LED for %s.\n",
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cdev->name);
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ret = leds_gmc_set(cdev, cdev->brightness);
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if (ret)
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return dev_err_probe(dev, ret, "failed to set LED value for %s.", cdev->name);
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for (i = 0; i < count; i++) {
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struct led_classdev *led_cdev = priv->monochromatics[i];
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/*
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* Make the individual LED sysfs interface read-only to prevent the user
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* to change the brightness of the individual LEDs of the group.
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*/
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mutex_lock(&led_cdev->led_access);
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led_sysfs_disable(led_cdev);
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mutex_unlock(&led_cdev->led_access);
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/* Restore the write access to the LED sysfs when the group is destroyed */
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devm_add_action_or_reset(dev, restore_sysfs_write_access, led_cdev);
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}
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return 0;
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}
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static const struct of_device_id of_leds_group_multicolor_match[] = {
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{ .compatible = "leds-group-multicolor" },
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{}
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};
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MODULE_DEVICE_TABLE(of, of_leds_group_multicolor_match);
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static struct platform_driver leds_group_multicolor_driver = {
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.probe = leds_gmc_probe,
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.driver = {
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.name = "leds_group_multicolor",
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.of_match_table = of_leds_group_multicolor_match,
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}
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};
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module_platform_driver(leds_group_multicolor_driver);
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MODULE_AUTHOR("Jean-Jacques Hiblot <[email protected]>");
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MODULE_DESCRIPTION("LEDs group multicolor driver");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:leds-group-multicolor");

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