devices: disk: Add change_bus()

Taken from virt-manager code. Move it here because it is strictly
an XML operation, and it will be easier to unit test

Signed-off-by: Cole Robinson <crobinso@redhat.com>

tests/data/xmlparse/disk-change-bus-in.xml

@@ -0,0 +1,25 @@
+<domain type='kvm'>
+  <name>f30</name>
+  <memory unit='KiB'>8294400</memory>
+  <os>
+    <type arch='x86_64'>hvm</type>
+  </os>
+  <devices>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='qcow2'/>
+      <source file='/mnt/data/devel/images/f30.qcow2'/>
+      <target dev='vda' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
+    </disk>
+    <disk type='file' device='cdrom'>
+      <target dev='hda' bus='ide'/>
+    </disk>
+    <disk type='file' device='cdrom'>
+      <driver name='qemu' type='raw'/>
+      <target dev='sda' bus='sata'/>
+      <readonly/>
+      <address type='drive' controller='0' bus='0' target='0' unit='3'/>
+    </disk>
+  </devices>
+</domain>
+

tests/data/xmlparse/disk-change-bus-out.xml

@@ -0,0 +1,22 @@
+<domain type="kvm">
+  <name>f30</name>
+  <memory unit="KiB">8294400</memory>
+  <os>
+    <type arch="x86_64">hvm</type>
+  </os>
+  <devices>
+    <disk type="file" device="disk">
+      <driver name="qemu" type="qcow2"/>
+      <source file="/mnt/data/devel/images/f30.qcow2"/>
+      <target dev="hdb" bus="ide"/>
+    </disk>
+    <disk type="file" device="cdrom">
+      <target dev="hda" bus="ide"/>
+    </disk>
+    <disk type="file" device="cdrom">
+      <driver name="qemu" type="raw"/>
+      <target dev="sda" bus="scsi"/>
+      <readonly/>
+    </disk>
+  </devices>
+</domain>

tests/test_xmlparse.py

@@ -1206,6 +1206,22 @@ class XMLParseTest(unittest.TestCase):
 
         self._alter_compare(guest.get_xml(), outfile)
 
+    def testDiskChangeBus(self):
+        guest, outfile = self._get_test_content("disk-change-bus")
+
+        disk = guest.devices.disk[0]
+
+        # Same bus is a no-op
+        origxml = disk.get_xml()
+        disk.change_bus(guest, "virtio")
+        assert origxml == disk.get_xml()
+        disk.change_bus(guest, "ide")
+
+        disk = guest.devices.disk[2]
+        disk.change_bus(guest, "scsi")
+
+        self._alter_compare(guest.get_xml(), outfile)
+
 
     ##################
     # Snapshot tests #

virtManager/object/domain.py

@@ -648,31 +648,6 @@ class vmmDomain(vmmLibvirtObject):
         if not editdev:
             return
 
-        def _change_bus():
-            oldprefix = editdev.get_target_prefix()[0]
-            oldbus = editdev.bus
-            editdev.bus = bus
-
-            if oldbus == bus:
-                return
-
-            editdev.address.clear()
-
-            if oldprefix == editdev.get_target_prefix()[0]:
-                return
-
-            used = []
-            disks = (self.xmlobj.devices.disk +
-                     self.get_xmlobj(inactive=True).devices.disk)
-            for d in disks:
-                used.append(d.target)
-
-            if editdev.target:
-                used.remove(editdev.target)
-
-            editdev.target = None
-            editdev.generate_target(used)
-
         if path != _SENTINEL:
             editdev.path = path
             if not do_hotplug:
@@ -693,7 +668,7 @@ class vmmDomain(vmmLibvirtObject):
             editdev.driver_detect_zeroes = detect_zeroes or None
 
         if bus != _SENTINEL:
-            _change_bus()
+            editdev.change_bus(self.xmlobj, bus)
 
         if do_hotplug:
             self.hotplug(device=editdev)

virtinst/devices/disk.py

@@ -890,6 +890,30 @@ class DeviceDisk(Device):
         raise ValueError(_("Only %s disks for bus '%s' are supported"
                            % (maxnode, self.bus)))
 
+    def change_bus(self, guest, newbus):
+        """
+        Change the bus value for an existing disk, which has some
+        follow on side effects.
+        """
+        if self.bus == newbus:
+            return
+
+        oldprefix = self.get_target_prefix()[0]
+        self.bus = newbus
+
+        self.address.clear()
+
+        if oldprefix == self.get_target_prefix()[0]:
+            return
+
+        used = [disk.target for disk in guest.devices.disk]
+
+        if self.target:
+            used.remove(self.target)
+
+        self.target = None
+        self.generate_target(used)
+
 
     ##################
     # Default config #