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drivers: led: Provide a fallback implementation of blink API
The LED blink API i squite useful but this is not supported by all the LED controller. This provides a software implementation of blink that use a delayable work to blink a LED. This could be enabled using Kconfig, as well the maximum number of LED that could blink at the same time using blink fallback. This does not requires any changes to driver to be used. Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
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‎drivers/led/CMakeLists.txt

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@@ -28,3 +28,5 @@ zephyr_library_sources_ifdef(CONFIG_TLC59108 tlc59108.c)
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zephyr_library_sources_ifdef(CONFIG_LED_SHELL led_shell.c)
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zephyr_library_sources_ifdef(CONFIG_USERSPACE led_handlers.c)
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zephyr_library_sources_ifdef(CONFIG_LED_BLINK_FALLBACK blink_fallback.c)

‎drivers/led/Kconfig

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@@ -26,6 +26,23 @@ config LED_SHELL
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help
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Enable LED shell for testing.
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config LED_BLINK_FALLBACK
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bool "LED Blink fallback"
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help
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Provides a software implementation of LED blink API.
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This could be used when the LED controller doesn't support blinking.
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if LED_BLINK_FALLBACK
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config LED_BLINK_FALLBACK_COUNT
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int "Maximum of LED using blink fallback"
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default 3
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help
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This set the maximum number of LED that could blink
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in the same time using blink fallback.
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endif # LED_BLINK_FALLBACK
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# zephyr-keep-sorted-start
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source "drivers/led/Kconfig.axp192"
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source "drivers/led/Kconfig.dac"

‎drivers/led/blink_fallback.c

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,130 @@
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/*
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* Copyright (c) 2025 BayLibre SAS
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/drivers/led.h>
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#include <zephyr/device.h>
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#include <zephyr/kernel.h>
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struct led_blink_fallback_data {
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const struct device *dev;
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uint32_t led;
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struct k_work_delayable work;
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uint32_t delay_on;
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uint32_t delay_off;
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};
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static void led_blink_fallback_off(struct k_work *work);
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static K_MUTEX_DEFINE(led_blink_fallback_mutex);
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static struct led_blink_fallback_data blink_fallback_data[CONFIG_LED_BLINK_FALLBACK_COUNT];
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static void led_blink_fallback_on(struct k_work *work)
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{
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struct k_work_delayable *dwork = k_work_delayable_from_work(work);
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struct led_blink_fallback_data *data =
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CONTAINER_OF(dwork, struct led_blink_fallback_data, work);
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const struct led_driver_api *api = (const struct led_driver_api *)data->dev->api;
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if (api->on) {
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api->on(data->dev, data->led);
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} else {
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api->set_brightness(data->dev, data->led, LED_BRIGTHNESS_MAX);
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}
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k_work_init_delayable(&data->work, led_blink_fallback_off);
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k_work_schedule(&data->work, K_MSEC(data->delay_on));
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}
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static void led_blink_fallback_off(struct k_work *work)
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{
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struct k_work_delayable *dwork = k_work_delayable_from_work(work);
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struct led_blink_fallback_data *data =
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CONTAINER_OF(dwork, struct led_blink_fallback_data, work);
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const struct led_driver_api *api = (const struct led_driver_api *)data->dev->api;
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if (api->off) {
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api->off(data->dev, data->led);
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} else {
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api->set_brightness(data->dev, data->led, 0);
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}
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k_work_init_delayable(&data->work, led_blink_fallback_on);
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k_work_schedule(&data->work, K_MSEC(data->delay_off));
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}
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static struct led_blink_fallback_data *led_fallback_get_data(const struct device *dev, uint32_t led)
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{
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/*
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* Find the first unused blink_fallback_data or
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* if the led is already bliking, return the currently used blink_fallback_data.
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*/
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for (int i = 0; i < CONFIG_LED_BLINK_FALLBACK_COUNT; i++) {
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struct led_blink_fallback_data *data = &blink_fallback_data[i];
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if (data->dev == dev && data->led == led) {
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return data;
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}
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if (data->dev == NULL) {
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return data;
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}
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}
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return NULL;
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}
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int led_blink_fallback(const struct device *dev, uint32_t led, uint32_t delay_on,
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uint32_t delay_off)
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{
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const struct led_driver_api *api = (const struct led_driver_api *)dev->api;
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struct led_blink_fallback_data *data;
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int ret = 0;
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/* Make sure the expected API are supported before we use them */
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if (!api->set_brightness && (!api->on || !api->off)) {
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return -ENOSYS;
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}
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k_mutex_lock(&led_blink_fallback_mutex, K_FOREVER);
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data = led_fallback_get_data(dev, led);
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if (!data) {
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ret = -ENOMEM;
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goto out;
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}
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/* Stop blinking, more likely when we use led_on or led_off */
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if (delay_on == 0 && delay_off == 0) {
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struct k_work_sync sync;
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if (!data->dev) {
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ret = -ENODEV;
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goto out;
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}
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k_work_cancel_delayable_sync(&data->work, &sync);
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data->dev = NULL;
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goto out;
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}
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/* Only update the timings if the LED is already blinking */
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if (data->dev) {
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data->delay_on = delay_on;
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data->delay_off = delay_off;
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goto out;
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}
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data->dev = dev;
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data->led = led;
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data->delay_on = delay_on;
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data->delay_off = delay_off;
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k_work_init_delayable(&data->work, led_blink_fallback_on);
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k_work_schedule(&data->work, K_NO_WAIT);
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out:
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k_mutex_unlock(&led_blink_fallback_mutex);
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return ret;
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}

‎include/zephyr/drivers/led.h

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Original file line numberDiff line numberDiff line change
@@ -128,6 +128,11 @@ __subsystem struct led_driver_api {
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led_api_write_channels write_channels;
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};
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#ifdef CONFIG_LED_BLINK_FALLBACK
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int led_blink_fallback(const struct device *dev, uint32_t led, uint32_t delay_on,
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uint32_t delay_off);
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#endif
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/**
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* @brief Blink an LED
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*
@@ -150,7 +155,11 @@ static inline int z_impl_led_blink(const struct device *dev, uint32_t led,
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(const struct led_driver_api *)dev->api;
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if (api->blink == NULL) {
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#ifdef CONFIG_LED_BLINK_FALLBACK
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return led_blink_fallback(dev, led, delay_on, delay_off);
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#else
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return -ENOSYS;
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#endif
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}
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return api->blink(dev, led, delay_on, delay_off);
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}
@@ -331,6 +340,13 @@ static inline int z_impl_led_on(const struct device *dev, uint32_t led)
331340
const struct led_driver_api *api =
332341
(const struct led_driver_api *)dev->api;
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#ifdef CONFIG_LED_BLINK_FALLBACK
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/* Stop blinking */
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if (api->blink == NULL) {
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led_blink_fallback(dev, led, 0, 0);
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}
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#endif
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if (api->set_brightness == NULL && api->on == NULL) {
335351
return -ENOSYS;
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}
@@ -361,6 +377,13 @@ static inline int z_impl_led_off(const struct device *dev, uint32_t led)
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const struct led_driver_api *api =
362378
(const struct led_driver_api *)dev->api;
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#ifdef CONFIG_LED_BLINK_FALLBACK
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/* Stop blinking */
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if (api->blink == NULL) {
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led_blink_fallback(dev, led, 0, 0);
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}
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#endif
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364387
if (api->set_brightness == NULL && api->off == NULL) {
365388
return -ENOSYS;
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}

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