Add helpers to lookup the event channel for a domid. This hides some
of the differences between dom0 and stubdom xenstored. Each version
defines its own.
It highlights the different meanings between get_xenbus_evtchn() in a
stubdom, where it looks up dom0's event channel, and dom0, where it
looks up the local event channel.
get_domain_evtchn() replaces get_xenbus_evtchn(), and
get_xenbus_evtchn() is removed from minios.c as it is inlined in the new
function.
The default return 0 will be fine as any other auto-introduced domain
will needs the event channel populated in the grant.
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Jason Andryuk
cec885de7f