[PATCH v3 14/28] hw/xen: add get_frontend_path() method to XenDeviceClass

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

The primary Xen console is special. The guest's side is set up for it by
the toolstack automatically and not by the standard PV init sequence.

Accordingly, its *frontend* doesn't appear in …/device/console/0 either;
instead it appears under …/console in the guest's XenStore node.

To allow the Xen console driver to override the frontend path for the
primary console, add a method to the XenDeviceClass which can be used
instead of the standard xen_device_get_frontend_path()

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 hw/xen/xen-bus.c         | 11 ++++++++++-
 include/hw/xen/xen-bus.h |  2 ++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index ece8ec40cd..12ff782005 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -711,8 +711,17 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp)
 {
     ERRP_GUARD();
     XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
 
-    xendev->frontend_path = xen_device_get_frontend_path(xendev);
+    if (xendev_class->get_frontend_path) {
+        xendev->frontend_path = xendev_class->get_frontend_path(xendev, errp);
+        if (!xendev->frontend_path) {
+            error_prepend(errp, "failed to create frontend: ");
+            return;
+        }
+    } else {
+        xendev->frontend_path = xen_device_get_frontend_path(xendev);
+    }
 
     /*
      * The frontend area may have already been created by a legacy
diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h
index f435898164..eb440880b5 100644
--- a/include/hw/xen/xen-bus.h
+++ b/include/hw/xen/xen-bus.h
@@ -33,6 +33,7 @@ struct XenDevice {
 };
 typedef struct XenDevice XenDevice;
 
+typedef char *(*XenDeviceGetFrontendPath)(XenDevice *xendev, Error **errp);
 typedef char *(*XenDeviceGetName)(XenDevice *xendev, Error **errp);
 typedef void (*XenDeviceRealize)(XenDevice *xendev, Error **errp);
 typedef void (*XenDeviceFrontendChanged)(XenDevice *xendev,
@@ -46,6 +47,7 @@ struct XenDeviceClass {
     /*< public >*/
     const char *backend;
     const char *device;
+    XenDeviceGetFrontendPath get_frontend_path;
     XenDeviceGetName get_name;
     XenDeviceRealize realize;
     XenDeviceFrontendChanged frontend_changed;
-- 
2.40.1