logging: make logging independent of platform

"nm-logging.h" is a basic core module that should have few other
dependencies. Instead of letting nm-logging.c directly call a function
from "nm-linux-platform.c", let platform register a handler as needed.

This way, you can build a core library containing nm-logging but no
nm-platform.

src/nm-logging.c

@@ -39,7 +39,6 @@
 
 #include "nm-errors.h"
 #include "NetworkManagerUtils.h"
-#include "nm-linux-platform.h"
 
 typedef enum {
 	LOG_FORMAT_FLAG_NONE                                = 0,
@@ -71,6 +70,8 @@ typedef enum {
 	                                                      LOG_FORMAT_FLAG_ALIGN_LOCATION,
 } LogFormatFlags;
 
+void (*_nm_logging_clear_platform_logging_cache) (void);
+
 static void
 nm_log_handler (const gchar *log_domain,
                 GLogLevelFlags level,
@@ -332,11 +333,12 @@ nm_logging_setup (const char  *level,
 		global.logging[i] = new_logging[i];
 
 	if (   had_platform_debug
+	    && _nm_logging_clear_platform_logging_cache
 	    && !nm_logging_enabled (LOGL_DEBUG, LOGD_PLATFORM)) {
 		/* when debug logging is enabled, platform will cache all access to
 		 * sysctl. When the user disables debug-logging, we want to clear that
 		 * cache right away. */
-		_nm_linux_platform_sysctl_clear_cache ();
+		_nm_logging_clear_platform_logging_cache ();
 	}
 
 	if (unrecognized)

src/nm-logging.h

@@ -243,6 +243,8 @@ void     nm_logging_syslog_openlog (const char *logging_backend);
 #define _LOG2t_err(errsv, ...) G_STMT_START { if (FALSE) { _NMLOG2_err (errsv, LOGL_TRACE, __VA_ARGS__); } } G_STMT_END
 #endif
 
+extern void (*_nm_logging_clear_platform_logging_cache) (void);
+
 /*****************************************************************************/
 
 #endif /* __NETWORKMANAGER_LOGGING_H__ */

src/platform/nm-linux-platform.c

@@ -2520,8 +2520,8 @@ sysctl_set (NMPlatform *platform, const char *path, const char *value)
 
 static GSList *sysctl_clear_cache_list;
 
-void
+static void
-_nm_linux_platform_sysctl_clear_cache (void)
+_nm_logging_clear_platform_logging_cache_impl (void)
 {
 	while (sysctl_clear_cache_list) {
 		NMLinuxPlatformPrivate *priv = NM_LINUX_PLATFORM_GET_PRIVATE (sysctl_clear_cache_list->data);
@@ -2541,6 +2541,7 @@ _log_dbg_sysctl_get_impl (NMPlatform *platform, const char *path, const char *co
 	const char *prev_value = NULL;
 
 	if (!priv->sysctl_get_prev_values) {
+		_nm_logging_clear_platform_logging_cache = _nm_logging_clear_platform_logging_cache_impl;
 		sysctl_clear_cache_list = g_slist_prepend (sysctl_clear_cache_list, platform);
 		priv->sysctl_get_prev_values = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
 	} else

src/platform/nm-linux-platform.h

@@ -50,6 +50,4 @@ GType nm_linux_platform_get_type (void);
 
 void nm_linux_platform_setup (void);
 
-void _nm_linux_platform_sysctl_clear_cache (void);
-
 #endif /* __NETWORKMANAGER_LINUX_PLATFORM_H__ */