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 <jjhiblot@xxxxxxxxxxxxxxx>
---
drivers/leds/rgb/Kconfig | 13 ++
drivers/leds/rgb/Makefile | 1 +
drivers/leds/rgb/leds-group-multicolor.c | 164 +++++++++++++++++++++++
3 files changed, 178 insertions(+)
create mode 100644 drivers/leds/rgb/leds-group-multicolor.c
diff --git a/drivers/leds/rgb/Kconfig b/drivers/leds/rgb/Kconfig
index 204cf470beae..1f85df5b691d 100644
--- a/drivers/leds/rgb/Kconfig
+++ b/drivers/leds/rgb/Kconfig
@@ -2,6 +2,19 @@
if LEDS_CLASS_MULTICOLOR
+config LEDS_GROUP_MULTICOLOR
+ tristate "LEDs group multi-color support"
+ depends on OF || COMPILE_TEST
+ help
+ This option enables support for monochrome LEDs that are
+ grouped into multicolor LEDs.
+ This useful in the case where LEDs of different colors are
+ physically grouped in a single multi-color LED and driven
+ by a controller that doesn't have multi-color support.
+
+ To compile this driver as a module, choose M here: the module
+ will be called leds-group-multicolor.
+
config LEDS_PWM_MULTICOLOR
tristate "PWM driven multi-color LED Support"
depends on PWM
diff --git a/drivers/leds/rgb/Makefile b/drivers/leds/rgb/Makefile
index 0675bc0f6e18..64d0d7ad5341 100644
--- a/drivers/leds/rgb/Makefile
+++ b/drivers/leds/rgb/Makefile
@@ -1,4 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_LEDS_GROUP_MULTICOLOR) += leds-group-multicolor.o
obj-$(CONFIG_LEDS_PWM_MULTICOLOR) += leds-pwm-multicolor.o
obj-$(CONFIG_LEDS_QCOM_LPG) += leds-qcom-lpg.o
diff --git a/drivers/leds/rgb/leds-group-multicolor.c b/drivers/leds/rgb/leds-group-multicolor.c
new file mode 100644
index 000000000000..27c80c84de88
--- /dev/null
+++ b/drivers/leds/rgb/leds-group-multicolor.c
@@ -0,0 +1,164 @@
+// 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 the 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@xxxxxxxxxxxxxxx>
+ */
+
+#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 led_mcg_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_access(void *data)
+{
+ struct led_classdev *led_cdev = data;
+
+ mutex_lock(&led_cdev->led_access);
+ led_sysfs_enable(led_cdev);
+ mutex_unlock(&led_cdev->led_access);
+}
+
+static int led_mcg_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;
+
+ 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;
+
+ 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->flags = LED_CORE_SUSPENDRESUME;
+ cdev->brightness_set_blocking = led_mcg_set;
+ cdev->max_brightness = max_brightness;
+ cdev->color = LED_COLOR_ID_MULTI;
+ priv->mc_cdev.num_colors = count;
+
+ 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 = led_mcg_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 sysfs of the monochromatic LED read-only */
+ mutex_lock(&led_cdev->led_access);
+ led_sysfs_disable(led_cdev);
+ mutex_unlock(&led_cdev->led_access);
+
+ /* Restore sysfs access when the multicolor LED is released */
+ devm_add_action_or_reset(dev, restore_sysfs_access, led_cdev);
+ }
+
+ return 0;
+}
+
+static const struct of_device_id of_led_group_multicolor_match[] = {
+ { .compatible = "leds-group-multicolor" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, of_led_group_multicolor_match);
+
+static struct platform_driver led_group_multicolor_driver = {
+ .probe = led_mcg_probe,
+ .driver = {
+ .name = "leds_group_multicolor",
+ .of_match_table = of_led_group_multicolor_match,
+ }
+};
+module_platform_driver(led_group_multicolor_driver);
+
+MODULE_AUTHOR("Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("LEDs group multicolor driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:leds-group-multicolor");
--
2.25.1
