xen: register legacy backends via xen_backend_init

It is okay to register legacy backends in the middle of xen_bus_init().
All that the registration does is record the existence of the backend
in xenstore.

This makes it possible to remove them from the build without introducing
undefined symbols in xen_be_init().  It also removes the need for the
backend_register callback, whose only purpose is to avoid registering
nonfunctional backends.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240509170044.190795-8-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 0 insertions, 16 deletions

diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 124dd5f..6f0b300 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -622,27 +622,11 @@ void xen_be_init(void)
     qbus_set_bus_hotplug_handler(xen_sysbus);
 
     xen_set_dynamic_sysbus();
-
-    xen_be_register("vkbd", &xen_kbdmouse_ops);
-#ifdef CONFIG_VIRTFS
-    xen_be_register("9pfs", &xen_9pfs_ops);
-#endif
-#ifdef CONFIG_USB_LIBUSB
-    xen_be_register("qusb", &xen_usb_ops);
-#endif
 }
 
 int xen_be_register(const char *type, struct XenDevOps *ops)
 {
     char path[50];
-    int rc;
-
-    if (ops->backend_register) {
-        rc = ops->backend_register();
-        if (rc) {
-            return rc;
-        }
-    }
 
     snprintf(path, sizeof(path), "device-model/%u/backends/%s", xen_domid,
              type);