xen/9pfs: introduce Xen 9pfs backend

Introduce the Xen 9pfs backend: add struct XenDevOps to register as a
Xen backend and add struct V9fsTransport to register as v9fs transport.

All functions are empty stubs for now.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Greg Kurz <groug@kaod.org>

hw/9pfs/xen-9p-backend.c

@@ -0,0 +1,96 @@
+/*
+ * Xen 9p backend
+ *
+ * Copyright Aporeto 2017
+ *
+ * Authors:
+ *  Stefano Stabellini <stefano@aporeto.com>
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include "hw/hw.h"
+#include "hw/9pfs/9p.h"
+#include "hw/xen/xen_backend.h"
+#include "hw/9pfs/xen-9pfs.h"
+#include "qemu/config-file.h"
+#include "fsdev/qemu-fsdev.h"
+
+typedef struct Xen9pfsDev {
+    struct XenDevice xendev;  /* must be first */
+} Xen9pfsDev;
+
+static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
+                                     size_t offset,
+                                     const char *fmt,
+                                     va_list ap)
+{
+    return 0;
+}
+
+static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
+                                       size_t offset,
+                                       const char *fmt,
+                                       va_list ap)
+{
+    return 0;
+}
+
+static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
+                                           struct iovec **piov,
+                                           unsigned int *pniov)
+{
+}
+
+static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
+                                          struct iovec **piov,
+                                          unsigned int *pniov,
+                                          size_t size)
+{
+}
+
+static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
+{
+}
+
+static const struct V9fsTransport xen_9p_transport = {
+    .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
+    .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
+    .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
+    .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
+    .push_and_notify = xen_9pfs_push_and_notify,
+};
+
+static int xen_9pfs_init(struct XenDevice *xendev)
+{
+    return 0;
+}
+
+static int xen_9pfs_free(struct XenDevice *xendev)
+{
+    return -1;
+}
+
+static int xen_9pfs_connect(struct XenDevice *xendev)
+{
+    return 0;
+}
+
+static void xen_9pfs_alloc(struct XenDevice *xendev)
+{
+}
+
+static void xen_9pfs_disconnect(struct XenDevice *xendev)
+{
+}
+
+struct XenDevOps xen_9pfs_ops = {
+    .size       = sizeof(Xen9pfsDev),
+    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
+    .alloc      = xen_9pfs_alloc,
+    .init       = xen_9pfs_init,
+    .initialise = xen_9pfs_connect,
+    .disconnect = xen_9pfs_disconnect,
+    .free       = xen_9pfs_free,
+};

hw/9pfs/xen-9pfs.h

@@ -0,0 +1,21 @@
+/*
+ * Xen 9p backend
+ *
+ * Copyright Aporeto 2017
+ *
+ * Authors:
+ *  Stefano Stabellini <stefano@aporeto.com>
+ *
+ * This work is licensed under the terms of the GNU GPL version 2 or
+ * later. See the COPYING file in the top-level directory.
+ *
+ */
+
+#include <xen/io/protocols.h>
+#include "hw/xen/io/ring.h"
+
+/*
+ * Do not merge into xen-9p-backend.c: clang doesn't allow unused static
+ * inline functions in c files.
+ */
+DEFINE_XEN_FLEX_RING_AND_INTF(xen_9pfs);