From: Gerd Hoffmann <kraxel@redhat.com>
Subject: [RHEL-5.1 PATCH 3/10] xen: bimodal drivers, blkfront driver
Date: Fri, 15 Jun 2007 10:30:27 +0200
Bugzilla: 222128
Message-Id: <46724E23.9080108@redhat.com>
Changelog: [xen] bimodal drivers, blkfront driver


  Hi,

Starting with Xen 3.1 the 64bit hypervisor can run 32bit-pae paravirtual 
guests.  Some paravirtual drivers have different data structures in 
32bit vs. 64bit mode.  Thus the backend drivers must be bimodal, i.e.

  (a) must be able to deal with multiple protocols.
  (b) need to know which protocol the frontend driver speaks.

This patch makes the block device frontend driver signal the protocol it 
speaks by adding a node to xenstore.

cheers,
  Gerd

# HG changeset patch
# User kfraser@localhost.localdomain
# Date 1169563722 0
# Node ID c545932a18f33b27e5c889e6e51759b23bd08f12
# Parent  b9ffa4b49d9711edba34d490a2263fd909b2acfe
bimodal blkfront: Create a new node "protocol" in xenstore, add the
protocol name it speaks there.

Signed-off-by: Gerd Hoffmann <kraxel@suse.de>

---
 drivers/xen/blkfront/blkfront.c |    7 +++++++
 1 file changed, 7 insertions(+)

Index: linux-2.6.18.noarch/drivers/xen/blkfront/blkfront.c
===================================================================
--- linux-2.6.18.noarch.orig/drivers/xen/blkfront/blkfront.c
+++ linux-2.6.18.noarch/drivers/xen/blkfront/blkfront.c
@@ -44,6 +44,7 @@
 #include <xen/evtchn.h>
 #include <xen/xenbus.h>
 #include <xen/interface/grant_table.h>
+#include <xen/interface/io/protocols.h>
 #include <xen/gnttab.h>
 #include <asm/hypervisor.h>
 #include <asm/maddr.h>
@@ -176,6 +177,12 @@ again:
 		message = "writing event-channel";
 		goto abort_transaction;
 	}
+	err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
+			    XEN_IO_PROTO_ABI_NATIVE);
+	if (err) {
+		message = "writing protocol";
+		goto abort_transaction;
+	}
 
 	err = xenbus_transaction_end(xbt, 0);
 	if (err) {