[libvirt] virStoragePoolGetXMLDesc - how to specify format type

[Sharadha Prabhakar (3P)]

Hi,
I'm trying to write virStoragePoolGetXMLDesc() for XenAPI remote storage.
I'd like to produce an XML similar to this

<pool type="netfs">
  <name>....</name>
  <uuid>....</uuid>
  <source>
    <format type="nfs"/>
    <host name="telos"/>
    <dir path="/images"/>
  </source>
</pool>

I'm trying to fill in the virStoragePoolDefPtr for this.
I need to know if struct _virStoragePoolSource->format
Is the one to fill for format type="nfs".
It's seemingly an integer. Is there any enum for format types for
Nfs and ext3? I couldn't find any in storage_conf.h

My next query is, when would I have to fill in device path? What is it used for
And which pool types use it for remote storage? 
Could someone explain?
Regards,
Sharadha