modules: lvgl: Add zephyr OSAL implementation

This patch adds the OSAL implementation of dynamic thread creation, mutex
and thread syncronization primitive (semaphore) enabling the use of the
parallel rendering architecture provided with LVGL 9.0. To use it, set
`CONFIG_LV_Z_USE_OSAL` and your preferred dynamic thread stack allocation
method (pool or heap).

Signed-off-by: Fabian Blatz <fabianblatz@gmail.com>

modules/lvgl/CMakeLists.txt

@@ -329,6 +329,8 @@ zephyr_library_sources_ifdef(CONFIG_LV_Z_BUTTON_INPUT input/lvgl_button_input.c)
 zephyr_library_sources_ifdef(CONFIG_LV_Z_ENCODER_INPUT input/lvgl_encoder_input.c)
 zephyr_library_sources_ifdef(CONFIG_LV_Z_KEYPAD_INPUT input/lvgl_keypad_input.c)
 
+zephyr_library_sources_ifdef(CONFIG_LV_Z_USE_OSAL lvgl_zephyr_osal.c)
+
 zephyr_library_link_libraries(LVGL)
 target_link_libraries(LVGL INTERFACE zephyr_interface)
 

modules/lvgl/Kconfig

@@ -155,6 +155,13 @@ config LV_DRAW_DMA2D_HAL_INCLUDE
 	  Must be defined to include path of CMSIS header of target processor
 	  e.g. "stm32f769xx.h" or "stm32f429xx.h"
 
+config LV_Z_USE_OSAL
+	bool "Use OSAL enabling parallel rendering"
+	depends on DYNAMIC_THREAD
+	help
+	  Use the Zephyr LVGL OSAL to enable parallel rendering
+	  pipelines.
+
 rsource "Kconfig.memory"
 rsource "Kconfig.input"
 rsource "Kconfig.shell"

modules/lvgl/include/lv_conf.h

@@ -39,6 +39,11 @@
 #define LV_COLOR_16_SWAP 1
 #endif /* CONFIG_LV_COLOR_16_SWAP */
 
+#ifdef CONFIG_LV_Z_USE_OSAL
+#define LV_USE_OS            LV_OS_CUSTOM
+#define LV_OS_CUSTOM_INCLUDE "lvgl_zephyr_osal.h"
+#endif /* CONFIG_LV_Z_USE_OSAL */
+
 /*
  * Needed because of a workaround for a GCC bug,
  * see https://github.com/lvgl/lvgl/issues/3078

modules/lvgl/include/lvgl_zephyr_osal.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2024 Fabian Blatz <fabianblatz@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_MODULES_LVGL_ZEPHYR_OSAL_H_
+#define ZEPHYR_MODULES_LVGL_ZEPHYR_OSAL_H_
+
+#include <zephyr/kernel.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct {
+	k_tid_t tid;
+	k_thread_stack_t *stack;
+	struct k_thread thread;
+} lv_thread_t;
+
+typedef struct k_mutex lv_mutex_t;
+
+typedef struct k_sem lv_thread_sync_t;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_MODULES_LVGL_ZEPHYR_OSAL_H_ */

modules/lvgl/lvgl_zephyr_osal.c

@@ -0,0 +1,151 @@
+/*
+ * Copyright (c) 2024 Fabian Blatz <fabianblatz@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "lvgl_zephyr_osal.h"
+#include <lvgl.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(lvgl, CONFIG_LV_Z_LOG_LEVEL);
+
+typedef void (*lv_thread_entry)(void *);
+static void thread_entry(void *thread, void *cb, void *user_data);
+
+lv_result_t lv_thread_init(lv_thread_t *thread, lv_thread_prio_t prio, void (*callback)(void *),
+			   size_t stack_size, void *user_data)
+{
+	int thread_priority;
+
+	thread->stack = k_thread_stack_alloc(stack_size, 0);
+	if (thread->stack == NULL) {
+		return LV_RESULT_INVALID;
+	}
+
+	thread_priority = (CONFIG_NUM_PREEMPT_PRIORITIES - 1) -
+			  ((prio * (CONFIG_NUM_PREEMPT_PRIORITIES - 1)) / LV_THREAD_PRIO_HIGHEST);
+
+	thread->tid = k_thread_create(&thread->thread, thread->stack, stack_size, thread_entry,
+				      thread, callback, user_data, thread_priority, 0, K_NO_WAIT);
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_thread_delete(lv_thread_t *thread)
+{
+	int ret;
+
+	k_thread_abort(thread->tid);
+	ret = k_thread_stack_free(thread->stack);
+	if (ret < 0) {
+		LOG_ERR("Failled to delete thread: %d", ret);
+		return LV_RESULT_INVALID;
+	}
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_mutex_init(lv_mutex_t *mutex)
+{
+	k_mutex_init(mutex);
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_mutex_lock(lv_mutex_t *mutex)
+{
+	int ret;
+
+	ret = k_mutex_lock(mutex, K_FOREVER);
+	if (ret != 0) {
+		LOG_ERR("Failed to lock mutex: %d", ret);
+		return LV_RESULT_INVALID;
+	}
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_mutex_lock_isr(lv_mutex_t *mutex)
+{
+	int ret;
+
+	ret = k_mutex_lock(mutex, K_NO_WAIT);
+	if (ret != 0) {
+		LOG_ERR("Failed to lock mutex: %d", ret);
+		return LV_RESULT_INVALID;
+	}
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_mutex_unlock(lv_mutex_t *mutex)
+{
+	int ret;
+
+	ret = k_mutex_unlock(mutex);
+	if (ret != 0) {
+		LOG_ERR("Failed to unlock mutex: %d", ret);
+		return LV_RESULT_INVALID;
+	}
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_mutex_delete(lv_mutex_t *mutex)
+{
+	ARG_UNUSED(mutex);
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_thread_sync_init(lv_thread_sync_t *sync)
+{
+	int ret;
+
+	ret = k_sem_init(sync, 0, 1);
+	if (ret != 0) {
+		LOG_ERR("Failed to init thread sync: %d", ret);
+		return LV_RESULT_INVALID;
+	}
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_thread_sync_wait(lv_thread_sync_t *sync)
+{
+	int ret;
+
+	ret = k_sem_take(sync, K_FOREVER);
+	if (ret < 0) {
+		LOG_ERR("Error waiting on thread sync: %d", ret);
+		return LV_RESULT_INVALID;
+	}
+
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_thread_sync_signal(lv_thread_sync_t *sync)
+{
+	k_sem_give(sync);
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_thread_sync_signal_isr(lv_thread_sync_t *sync)
+{
+	k_sem_give(sync);
+	return LV_RESULT_OK;
+}
+
+lv_result_t lv_thread_sync_delete(lv_thread_sync_t *sync)
+{
+	ARG_UNUSED(sync);
+	return LV_RESULT_OK;
+}
+
+void thread_entry(void *thread, void *cb, void *user_data)
+{
+	__ASSERT_NO_MSG(cb != NULL);
+	lv_thread_entry entry_cb = (lv_thread_entry)cb;
+
+	entry_cb(user_data);
+	lv_thread_delete((lv_thread_t *)thread);
+}