[PATCHv3 1/3] virdbus: Add virDBusHasSystemBus()

[Peter Krempa <pkrempa@xxxxxxxxxx>]

Some systems may not use DBus in their system. Add a method to check if
the system bus is available that doesn't print error messages so that
code can later check for this condition and use an alternative approach.
---
 src/libvirt_private.syms |  1 +
 src/util/virdbus.c       | 33 ++++++++++++++++++++++++++++++---
 src/util/virdbus.h       |  1 +
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index a958d94..c25a61f 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1294,6 +1294,7 @@ virConfWriteMem;
 virDBusCallMethod;
 virDBusGetSessionBus;
 virDBusGetSystemBus;
+virDBusHasSystemBus;
 virDBusMessageDecode;
 virDBusMessageEncode;
 virDBusMessageRead;
diff --git a/src/util/virdbus.c b/src/util/virdbus.c
index e88dc26..1370a5d 100644
--- a/src/util/virdbus.c
+++ b/src/util/virdbus.c
@@ -73,7 +73,8 @@ static void virDBusSystemBusInit(void)
     systembus = virDBusBusInit(DBUS_BUS_SYSTEM, &systemdbuserr);
 }

-DBusConnection *virDBusGetSystemBus(void)
+static DBusConnection
+*virDBusGetSystemBusInternal(void)
 {
     if (virOnce(&systemonce, virDBusSystemBusInit) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -81,14 +82,32 @@ DBusConnection *virDBusGetSystemBus(void)
         return NULL;
     }

-    if (!systembus) {
+    return systembus;
+}
+
+
+DBusConnection *virDBusGetSystemBus(void)
+{
+    DBusConnection *bus;
+
+    if (!(bus = virDBusGetSystemBusInternal())) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        _("Unable to get DBus system bus connection: %s"),
                        systemdbuserr.message ? systemdbuserr.message : "watch setup failed");
         return NULL;
     }

-    return systembus;
+    return bus;
+}
+
+
+bool virDBusHasSystemBus(void)
+{
+    if (virDBusGetSystemBusInternal())
+        return true;
+
+    VIR_DEBUG("System DBus not available: %s", NULLSTR(systemdbuserr.message));
+    return false;
 }


@@ -1195,6 +1214,14 @@ DBusConnection *virDBusGetSystemBus(void)
     return NULL;
 }

+
+bool virDBusHasSystemBus(void)
+{
+    VIR_DEBUG("DBus support not compiled into this binary");
+    return false;
+}
+
+
 DBusConnection *virDBusGetSessionBus(void)
 {
     virReportError(VIR_ERR_INTERNAL_ERROR,
diff --git a/src/util/virdbus.h b/src/util/virdbus.h
index 39de479..a5aab56 100644
--- a/src/util/virdbus.h
+++ b/src/util/virdbus.h
@@ -32,6 +32,7 @@
 # include "internal.h"

 DBusConnection *virDBusGetSystemBus(void);
+bool virDBusHasSystemBus(void);
 DBusConnection *virDBusGetSessionBus(void);

 int virDBusCallMethod(DBusConnection *conn,
-- 
1.8.3.2

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