xtensa/esp/ws2812: Add the lower-half WS2812 driver based on RMT

This lower-half WS2812 LED driver uses the RMT peripheral of the
Espressif's SoCs to drive the RGB addressable LEDs. Compared to
the SPI-based implementation, it is faster!

arch/xtensa/src/common/espressif/esp_ws2812.h

@@ -0,0 +1,101 @@
+/****************************************************************************
+ * arch/xtensa/src/common/espressif/esp_ws2812.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __ARCH_XTENSA_SRC_COMMON_ESPRESSIF_ESP_WS2812_H
+#define __ARCH_XTENSA_SRC_COMMON_ESPRESSIF_ESP_WS2812_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <debug.h>
+#include <stdbool.h>
+
+#ifndef __ASSEMBLY__
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+#ifdef CONFIG_WS2812
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: esp_ws2812_setup
+ *
+ * Description:
+ *   This function sets up a WS2812 device instance. It allocates memory for
+ *   the device structures, initializes the device with the provided
+ *   parameters, and registers the device with the system.
+ *
+ * Input Parameters:
+ *   path         - The device path.
+ *   rmt          - Pointer to the RMT device structure.
+ *   pixel_count  - The number of pixels in the WS2812 strip.
+ *   has_white    - Flag indicating if the WS2812 strip includes a white LED.
+ *
+ * Returned Value:
+ *   Returns a pointer to the WS2812 device structure on successful setup;
+ *   NULL is returned on any failure, with errno set appropriately.
+ *
+ ****************************************************************************/
+
+struct ws2812_dev_s *esp_ws2812_setup(const char *path,
+                                        struct rmt_dev_s *rmt,
+                                        uint16_t    pixel_count,
+                                        bool        has_white);
+
+/****************************************************************************
+ * Name: esp_ws2812_release
+ *
+ * Description:
+ *   This function releases a previously opened WS2812 device instance. It
+ *   checks if the device is currently open, and if not, it frees the private
+ *   data structure and sets the private field of the device to NULL. If the
+ *   device is still open, it returns an error.
+ *
+ * Input Parameters:
+ *   driver - Pointer to the instance of the WS2812 device driver to be
+ *            released.
+ *
+ * Returned Value:
+ *   Returns OK on successful release of the device; a negated errno value
+ *   is returned on any failure.
+ *
+ ****************************************************************************/
+
+int esp_ws2812_release(void * driver);
+
+#endif
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* __ARCH_XTENSA_SRC_COMMON_ESPRESSIF_ESP_WS2812_H */