Split px4_layer into kernel and userspace parts for nuttx protected build

Split the px4_layer into user and kernel space libraries. Add some stubs for
user-space (e.g. version) where an interface to the kernel needs to be added

Use posix-versions for cpuload.cpp and print_load.cpp for userspace; these link to nuttx internals. This functinality could be built on top of posix (e.g. procfs) interfaces

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

platforms/nuttx/src/px4/common/console_buffer_usr.cpp

@@ -0,0 +1,65 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2021 Technology Innovation Institute. 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.
+ *
+ ****************************************************************************/
+
+#include <px4_platform_common/px4_config.h>
+#include <px4_platform_common/console_buffer.h>
+#include <px4_platform_common/defines.h>
+#include <px4_platform_common/sem.h>
+#include <pthread.h>
+#include <string.h>
+#include <fcntl.h>
+
+#ifdef BOARD_ENABLE_CONSOLE_BUFFER
+#ifndef BOARD_CONSOLE_BUFFER_SIZE
+# define BOARD_CONSOLE_BUFFER_SIZE (1024*4) // default buffer size
+#endif
+
+
+// TODO: User side implementation of px4_console_buffer
+
+int px4_console_buffer_init()
+{
+	return 0;
+}
+
+int px4_console_buffer_size()
+{
+	return 0;
+}
+
+int px4_console_buffer_read(char *buffer, int buffer_length, int *offset)
+{
+	return 0;
+}
+
+#endif /* BOARD_ENABLE_CONSOLE_BUFFER */