[PATCH] Allow modifying existing block device, making virDomainAttachDevice modify the device if it already exists

[Hugh Brock <hbrock@xxxxxxxxxx>]

The attached patch adds code to xend_internal.c:xenDomainAttachDevice 
that checks to see if the device mentioned in the passed-in XML already 
exists, and if so calls op_device_configure to modify the device. It is 
particularly useful for connecting and disconnecting a hardware cdrom 
device to an FV guest.

I considered making new API a la virDomainModifyDevice, but decided 
overloading virDomainAttachDevice was cleaner (and didn't change 
existing API).

I have tested the patch on f7 with xen 3.1 and a windows 2000 guest. 
Since the patch merely wraps Xen's device_configure call, we're not 
adding much risk of breakage.

Please ACK.


Take care,
--Hugh


--
Red Hat Virtualization Group http://redhat.com/virtualization
Hugh Brock           | virt-manager http://virt-manager.org
hbrock@xxxxxxxxxx    | virtualization library http://libvirt.org

diff -ruN libvirt.orig/src/xend_internal.c libvirt/src/xend_internal.c
--- libvirt.orig/src/xend_internal.c	2007-09-06 11:28:05.000000000 -0400
+++ libvirt/src/xend_internal.c	2007-09-06 10:47:25.000000000 -0400
@@ -3087,6 +3087,7 @@
     char *sexpr, *conf, *str;
     int hvm = 0, ret;
     xenUnifiedPrivatePtr priv;
+    char class[8], ref[80];
 
     if ((domain == NULL) || (domain->conn == NULL) || (domain->name == NULL)) {
         virXendError((domain ? domain->conn : NULL), VIR_ERR_INVALID_ARG,
@@ -3116,8 +3117,16 @@
         *(conf + strlen(conf) -1) = 0; /* suppress final ) */
     }
     else conf = sexpr;
-    ret = xend_op(domain->conn, domain->name, "op", "device_create",
-        "config", conf, NULL);
+    if (virDomainXMLDevID(domain, xml, class, ref)) {
+        /* device doesn't exist, define it */
+        ret = xend_op(domain->conn, domain->name, "op", "device_create",
+                      "config", conf, NULL);
+    } 
+    else {
+        /* device exists, attempt to modify it */
+        ret = xend_op(domain->conn, domain->name, "op", "device_configure", 
+                      "config", conf, "dev", ref, NULL);
+    }
     free(sexpr);
     return ret;
 }

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