[libvirt] [PATCHv2 1/3] virdbus: Add virDBusHasSystemBus()

[Daniel P. Berrange]

On Mon, Aug 19, 2013 at 12:32:05PM +0200, Peter Krempa wrote:
> 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       | 34 +++++++++++++++++++++++++++++++---
>  src/util/virdbus.h       |  1 +
>  3 files changed, 33 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..1ef78ce 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 +82,33 @@ 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;
> +}
> +
> +
> +DBusConnection *virDBusHasSystemBus(void)
> +{
> +    DBusConnection *bus;
> +
> +    if (!(bus = virDBusGetSystemBusInternal()))
> +        VIR_DEBUG("System DBus not available: %s", NULLSTR(systemdbuserr.message));
> +
> +    return bus;
>  }
> 
> 
> @@ -1195,6 +1215,14 @@ DBusConnection *virDBusGetSystemBus(void)
>      return NULL;
>  }
> 
> +
> +DBusConnection *virDBusHasSystemBus(void)
> +{
> +    VIR_DEBUG("DBus support not compiled into this binary");
> +    return NULL;
> +}
> +
> +
>  DBusConnection *virDBusGetSessionBus(void)
>  {
>      virReportError(VIR_ERR_INTERNAL_ERROR,
> diff --git a/src/util/virdbus.h b/src/util/virdbus.h
> index 39de479..63908fe 100644
> --- a/src/util/virdbus.h
> +++ b/src/util/virdbus.h
> @@ -32,6 +32,7 @@
>  # include "internal.h"
> 
>  DBusConnection *virDBusGetSystemBus(void);
> +DBusConnection *virDBusHasSystemBus(void);

This should be a returning a 'bool' IMHO. eg usage would be 


   if (virDBusHasSystemBus()) {
      DBusConnection conn = virDBusGetSystemBus()
      ....dbus code path...
   } else {
      ... non-dbus code path...
   }


Daniel
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