Initial version of log history support.

platforms/common/include/px4_platform_common/log.h

@@ -130,6 +130,7 @@ __EXPORT void px4_log_modulename(int level, const char *moduleName, const char *
 __attribute__((format(printf, 3, 4)));
 __EXPORT void px4_log_raw(int level, const char *fmt, ...)
 __attribute__((format(printf, 2, 3)));
+__EXPORT void px4_log_history(FILE *out);
 
 #if __GNUC__
 // Allow empty format strings.

platforms/common/include/px4_platform_common/log_history.h

@@ -0,0 +1,68 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2022 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include <px4_platform_common/px4_config.h>
+
+#if defined(BOARD_ENABLE_LOG_HISTORY)
+#include <stdio.h>
+#include <px4_platform_common/sem.h>
+
+#ifndef BOARD_LOG_HISTORY_SIZE
+#define BOARD_LOG_HISTORY_SIZE (1024*4) // default buffer size
+#endif
+
+class LogHistory
+{
+public:
+	LogHistory() { px4_sem_init(&_lock, 0, 1); }
+	~LogHistory() { px4_sem_destroy(&_lock); }
+
+	void write(const char *buffer);
+	void print(FILE *out);
+
+private:
+	void lock() { do {} while (px4_sem_wait(&_lock) != 0); }
+	void unlock() { px4_sem_post(&_lock); }
+
+	int size();
+	int read(char *buffer, int buffer_length, int *offset);
+
+	char _log_history[BOARD_LOG_HISTORY_SIZE];
+	int _head{0};
+	int _tail{0};
+	px4_sem_t _lock;
+};
+
+#endif