libcamera: logging: add logging API for applications

Currently the log file and the log level can only be set via environment
variables, but applications may also want to set the log file and the
log level at run time. Provide an API for this.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/logging.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * logging.h - Logging infrastructure
+ */
+#ifndef __LIBCAMERA_LOGGING_H__
+#define __LIBCAMERA_LOGGING_H__
+
+namespace libcamera {
+
+void logSetFile(const char *file);
+int logSetLevel(const char *category, const char *level);
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_LOGGING_H__ */