Add a DBus interface for setting the log level.

Lifted almost entirely from similar code in NetworkManager.

BUG=chromium-os:15197
TEST='dbus-send --print-reply --system --dest=org.freedesktop.ModemManager /org/freedesktop/ModemManager org.freedesktop.ModemManager.SetLogging string:DEBUG'
Also try valid log levels 'ERR', 'WARN', 'INFO', and an invalid log level, such as 'ABCDE'.

Change-Id: I2bddcd0319f4966dd293b119f68e7cc1697949b7
Reviewed-on: http://gerrit.chromium.org/gerrit/3134
Tested-by: Nathan J. Williams <njw@chromium.org>
Reviewed-by: Eric Shienbrood <ers@chromium.org>

introspection/org.freedesktop.ModemManager.xml

@@ -23,6 +23,18 @@
       <annotation name="org.freedesktop.DBus.GLib.CSymbol" value="impl_manager_scan_devices"/>
     </method>
 
+    <method name="SetLogging">
+      <annotation name="org.freedesktop.DBus.GLib.CSymbol" value="impl_manager_set_logging"/>
+      <tp:docstring>
+        Set logging verbosity.
+      </tp:docstring>
+      <arg name="level" type="s" direction="in">
+        <tp:docstring>
+          One of [ERR, WARN, INFO, DEBUG].
+        </tp:docstring>
+      </arg>
+    </method>
+
     <signal name="DeviceAdded">
       <tp:docstring>
         A device was added to the system.

src/mm-log.c

@@ -163,14 +163,8 @@ log_handler (const gchar *log_domain,
 }
 
 gboolean
-mm_log_setup (const char *level,
-              const char *log_file,
-              gboolean show_timestamps,
-              gboolean rel_timestamps,
-              GError **error)
+mm_log_set_level (const char *level, GError **error)
 {
-    /* levels */
-    if (level && strlen (level)) {
     gboolean found = FALSE;
     const LogDesc *diter;
 
@@ -181,12 +175,21 @@ mm_log_setup (const char *level,
             break;
         }
     }
-
-        if (!found) {
+    if (!found)
        g_set_error (error, 0, 0, "Unknown log level '%s'", level);
+    return found;
+}
+
+gboolean
+mm_log_setup (const char *level,
+              const char *log_file,
+              gboolean show_timestamps,
+              gboolean rel_timestamps,
+              GError **error)
+{
+    /* levels */
+    if (level && strlen (level) && !mm_log_set_level (level, error))
         return FALSE;
-        }
-    }
 
     if (show_timestamps)
         ts_flags = TS_FLAG_WALL;

src/mm-log.h

@@ -47,6 +47,8 @@ void _mm_log (const char *loc,
               const char *fmt,
               ...)  __attribute__((__format__ (__printf__, 4, 5)));
 
+gboolean mm_log_set_level (const char *level, GError **error);
+
 gboolean mm_log_setup (const char *level,
                        const char *log_file,
                        gboolean show_ts,

src/mm-manager.c

@@ -34,6 +34,10 @@ static gboolean impl_manager_enumerate_devices (MMManager *manager,
 static void impl_manager_scan_devices (MMManager *manager,
                                        DBusGMethodInvocation *context);
 
+static gboolean impl_manager_set_logging (MMManager *manager,
+                                          const char *level,
+                                          GError **error);
+
 #include "mm-manager-glue.h"
 
 G_DEFINE_TYPE (MMManager, mm_manager, G_TYPE_OBJECT)
@@ -1001,6 +1005,19 @@ impl_manager_scan_devices (MMManager *manager,
     }
 }
 
+static gboolean
+impl_manager_set_logging (MMManager *manager,
+                          const char *level,
+                          GError **error)
+{
+	if (mm_log_set_level (level, error)) {
+		mm_info ("logging: level '%s'", level);
+		return TRUE;
+	}
+	return FALSE;
+}
+
+
 void
 mm_manager_start (MMManager *manager)
 {