Patch: driver->open functions return declined or error status

["Richard W.M. Jones" <rjones@xxxxxxxxxx>]

I want to change the driver->open function so that as well as declining 
a name (returning -1 as now), it may also indicate that it accepts the 
name, but there is an error opening the name (-2).  virConnectOpen fails 
in this second case, rather than going on and trying the next driver in 
sequence.

Rich.

--
Emerging Technologies, Red Hat  http://et.redhat.com/~rjones/
64 Baker Street, London, W1U 7DF     Mobile: +44 7866 314 421
 "[Negative numbers] darken the very whole doctrines of the equations
 and make dark of the things which are in their nature excessively
 obvious and simple" (Francis Maseres FRS, mathematician, 1759)

Index: src/libvirt.c
===================================================================
RCS file: /data/cvs/libvirt/src/libvirt.c,v
retrieving revision 1.58
diff -u -r1.58 libvirt.c
--- src/libvirt.c	23 Feb 2007 08:51:30 -0000	1.58
+++ src/libvirt.c	28 Feb 2007 16:10:26 -0000
@@ -303,16 +305,22 @@
     for (i = 0;i < MAX_DRIVERS;i++) {
         if ((virDriverTab[i] != NULL) && (virDriverTab[i]->open != NULL)) {
 	    res = virDriverTab[i]->open(ret, name, VIR_DRV_OPEN_QUIET);
-	    /*
-	     * For a default connect to Xen make sure we manage to contact
-	     * all related drivers.
-	     */
-	    if ((res < 0) && (for_xen) &&
-	        (!strncasecmp(virDriverTab[i]->name, "xen", 3)) &&
-		(virDriverTab[i]->no != VIR_DRV_XEN_PROXY))
-		goto failed;
-	    if (res == 0)
+	    switch (res)
+	      {
+	      case VIR_DRV_OPEN_ERROR: goto failed;
+	      case VIR_DRV_OPEN_DECLINED:
+		/*
+		 * For a default connect to Xen make sure we manage to contact
+		 * all related drivers.
+		 */
+		if (for_xen &&
+		    strncasecmp(virDriverTab[i]->name, "xen", 3) == 0 &&
+		    virDriverTab[i]->no != VIR_DRV_XEN_PROXY)
+		  goto failed;
+		break;
+	      case VIR_DRV_OPEN_SUCCESS:
 	        ret->drivers[ret->nb_drivers++] = virDriverTab[i];
+	      }
 	}
     }
 
@@ -379,9 +387,13 @@
         if ((virDriverTab[i] != NULL) && (virDriverTab[i]->open != NULL)) {
 	    res = virDriverTab[i]->open(ret, name,
 	                                VIR_DRV_OPEN_QUIET | VIR_DRV_OPEN_RO);
-	    if (res == 0)
-	        ret->drivers[ret->nb_drivers++] = virDriverTab[i];
-
+	    switch (res)
+	      {
+	      case VIR_DRV_OPEN_ERROR: goto failed;
+	      case VIR_DRV_OPEN_DECLINED: break;
+	      case VIR_DRV_OPEN_SUCCESS:
+		ret->drivers[ret->nb_drivers++] = virDriverTab[i];
+	      }
 	}
         if ((virNetworkDriverTab[i] != NULL) && (virNetworkDriverTab[i]->open != NULL) &&
 	    (res = virNetworkDriverTab[i]->open(ret, name, VIR_DRV_OPEN_QUIET)) == 0) {
Index: src/driver.h
===================================================================
RCS file: /data/cvs/libvirt/src/driver.h,v
retrieving revision 1.21
diff -u -r1.21 driver.h
--- src/driver.h	23 Feb 2007 08:51:30 -0000	1.21
+++ src/driver.h	28 Feb 2007 16:10:26 -0000
@@ -32,10 +33,24 @@
     VIR_DRV_OPEN_RO = 2
 } virDrvOpenFlag;
 
-typedef int
-	(*virDrvOpen)			(virConnectPtr conn,
-					 const char *name,
-					 int flags);
+/* Status codes returned from driver open call. */
+typedef enum {
+    /* Opened successfully. */
+    VIR_DRV_OPEN_SUCCESS = 0,
+
+    /* 'name' is not for us. */
+    VIR_DRV_OPEN_DECLINED = -1,
+
+    /* 'name' is for us, but there was some error.  virConnectOpen will
+     * return an error rather than continue probing the other drivers.
+     */
+    VIR_DRV_OPEN_ERROR = -2,
+} virDrvOpenStatus;
+
+typedef virDrvOpenStatus
+    (*virDrvOpen)			(virConnectPtr conn,
+                             const char *name,
+                             int flags);
 typedef int
 	(*virDrvClose)			(virConnectPtr conn);
 typedef const char *

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