diff mbox

[v1,1/2] libxl: add PV display device driver interface

Message ID 1491386597-1103-2-git-send-email-al1img@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Oleksandr Grytsov April 5, 2017, 10:03 a.m. UTC
From: Oleksandr Grytsov <oleksandr_grytsov@epam.com>

Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@epam.com>
---
 tools/libxl/Makefile                 |   2 +-
 tools/libxl/libxl.h                  |  21 ++++
 tools/libxl/libxl_create.c           |   3 +
 tools/libxl/libxl_device.c           | 206 ++++++++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h         |  24 ++++
 tools/libxl/libxl_types.idl          |  22 +++-
 tools/libxl/libxl_types_internal.idl |   1 +
 tools/libxl/libxl_usb.c              |   2 +
 tools/libxl/libxl_utils.h            |   4 +
 tools/libxl/libxl_vdispl.c           | 209 +++++++++++++++++++++++++++++++++++
 10 files changed, 491 insertions(+), 3 deletions(-)
 create mode 100644 tools/libxl/libxl_vdispl.c
diff mbox

Patch

diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
index 566b706..3a932e1 100644
--- a/tools/libxl/Makefile
+++ b/tools/libxl/Makefile
@@ -138,7 +138,7 @@  LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
 			libxl_dom_suspend.o libxl_dom_save.o libxl_usb.o \
 			libxl_vtpm.o libxl_nic.o libxl_disk.o libxl_console.o \
 			libxl_cpupool.o libxl_mem.o libxl_sched.o libxl_tmem.o \
-			libxl_domain.o \
+			libxl_domain.o libxl_vdispl.o \
                         $(LIBXL_OBJS-y)
 LIBXL_OBJS += libxl_genid.o
 LIBXL_OBJS += _libxl_types.o libxl_flask.o _libxl_types_internal.o
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 72ec39d..4eff121 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -1833,6 +1833,27 @@  libxl_device_vtpm *libxl_device_vtpm_list(libxl_ctx *ctx, uint32_t domid, int *n
 int libxl_device_vtpm_getinfo(libxl_ctx *ctx, uint32_t domid,
                                libxl_device_vtpm *vtpm, libxl_vtpminfo *vtpminfo);
 
+/* Virtual displays */
+int libxl_device_vdispl_add(libxl_ctx *ctx, uint32_t domid,
+                            libxl_device_vdispl *displ,
+                            const libxl_asyncop_how *ao_how)
+                            LIBXL_EXTERNAL_CALLERS_ONLY;
+int libxl_device_vdispl_remove(libxl_ctx *ctx, uint32_t domid,
+                               libxl_device_vdispl *vdispl,
+                               const libxl_asyncop_how *ao_how)
+                               LIBXL_EXTERNAL_CALLERS_ONLY;
+int libxl_device_vdispl_destroy(libxl_ctx *ctx, uint32_t domid,
+                                libxl_device_vdispl *vdispl,
+                                const libxl_asyncop_how *ao_how)
+                                LIBXL_EXTERNAL_CALLERS_ONLY;
+
+libxl_device_vdispl *libxl_device_vdispl_list(libxl_ctx *ctx, uint32_t domid,
+                                              int *num);
+void libxl_device_vdispl_list_free(libxl_device_vdispl* list, int num);
+int libxl_device_vdispl_getinfo(libxl_ctx *ctx, uint32_t domid,
+                                libxl_device_vdispl *vdispl,
+                                libxl_vdisplinfo *vdisplinfo);
+
 /* Keyboard */
 int libxl_device_vkb_add(libxl_ctx *ctx, uint32_t domid, libxl_device_vkb *vkb,
                          const libxl_asyncop_how *ao_how)
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 25389e1..b36383f 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -1422,6 +1422,8 @@  out:
 
 #define libxl_device_dtdev_list NULL
 #define libxl_device_dtdev_compare NULL
+#define libxl__device_from_dtdev NULL
+#define libxl__device_dtdev_setdefault NULL
 static DEFINE_DEVICE_TYPE_STRUCT(dtdev);
 
 const struct libxl_device_type *device_type_tbl[] = {
@@ -1432,6 +1434,7 @@  const struct libxl_device_type *device_type_tbl[] = {
     &libxl__usbdev_devtype,
     &libxl__pcidev_devtype,
     &libxl__dtdev_devtype,
+    &libxl__vdispl_devtype,
     NULL
 };
 
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 5e96676..def1859 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -1776,6 +1776,212 @@  out:
     return AO_CREATE_FAIL(rc);
 }
 
+static int device_add_domain_config(libxl__gc *gc, uint32_t domid,
+                                    const struct libxl_device_type *dt,
+                                    void *type)
+{
+    int rc;
+    libxl_domain_config d_config;
+    libxl__domain_userdata_lock *lock = NULL;
+    int *num_dev;
+    int i;
+    void *item = NULL;
+
+    libxl_domain_config_init(&d_config);
+
+    lock = libxl__lock_domain_userdata(gc, domid);
+    if (!lock) {
+        rc = ERROR_LOCK_FAIL; goto out;
+    }
+
+    rc = libxl__get_domain_configuration(gc, domid, &d_config);
+    if (rc) goto out;
+
+    num_dev = libxl__device_type_get_num(dt, &d_config);
+
+    /* Check for existing device */
+    for (i = 0; i < *num_dev; i++) {
+        if (dt->compare(libxl__device_type_get_elem(dt, &d_config, i), type)) {
+            item = libxl__device_type_get_elem(dt, &d_config, i);
+        }
+    }
+
+    if (!item) {
+        void **devs= libxl__device_type_get_ptr(dt, &d_config);
+        *devs = libxl__realloc(NOGC, *devs,
+                               dt->dev_elem_size * (*num_dev + 1));
+        item = libxl__device_type_get_elem(dt, &d_config, *num_dev);
+        (*num_dev)++;
+    } else {
+        dt->dispose(item);
+    }
+
+    dt->init(item);
+    dt->copy(CTX, item, type);
+
+    rc = libxl__dm_check_start(gc, &d_config, domid);
+    if (rc) goto out;
+
+    rc = libxl__set_domain_configuration(gc, domid, &d_config);
+    if (rc) goto out;
+
+    rc = 0;
+
+out:
+    if (lock) libxl__unlock_domain_userdata(lock);
+    libxl_domain_config_dispose(&d_config);
+    return rc;
+}
+
+static int device_add_xen_store(libxl__gc *gc, libxl__device *device,
+                                char **bents, char **fents, char **ro_fents)
+{
+    xs_transaction_t t = XBT_NULL;
+    int rc;
+
+    for (;;) {
+        rc = libxl__xs_transaction_start(gc, &t);
+        if (rc) goto out;
+
+        libxl__device_generic_add(gc, t, device, bents, fents, ro_fents);
+
+        rc = libxl__xs_transaction_commit(gc, &t);
+        if (!rc) break;
+        if (rc < 0) goto out;
+    }
+
+    rc = 0;
+
+out:
+    libxl__xs_transaction_abort(gc, &t);
+    return rc;
+}
+
+void libxl__device_add(libxl__egc *egc, uint32_t domid,
+                       const struct libxl_device_type *dt, void *type,
+                       libxl__ao_device *aodev)
+{
+    STATE_AO_GC(aodev->ao);
+    libxl__device *device;
+    int rc;
+    flexarray_t *front = NULL;
+    flexarray_t *back = NULL;
+
+    rc = dt->set_default(gc, domid, type);
+    if (rc) goto out;
+
+    GCNEW(device);
+    rc = dt->to_device(gc, domid, type, device);
+    if ( rc != 0 ) goto out;
+
+    rc = libxl__device_exists(gc, XBT_NULL, device);
+    if (rc < 0) goto out;
+    if (rc == 1) {              /* already exists in xenstore */
+        LOGD(ERROR, domid, "device already exists in xenstore");
+        aodev->action = LIBXL__DEVICE_ACTION_ADD; /* for error message */
+        rc = ERROR_DEVICE_EXISTS;
+        goto out;
+    }
+
+    if (aodev->update_json) {
+        rc = device_add_domain_config(gc, domid, dt, type);
+        if (rc) goto out;
+    }
+
+    if (dt->set_xenstore_config) {
+        dt->set_xenstore_config(gc, domid, type, &front, &back);
+        rc = device_add_xen_store(gc, device,
+                                  libxl__xs_kvs_of_flexarray(gc, back),
+                                  libxl__xs_kvs_of_flexarray(gc, front),
+                                  NULL);
+        if (rc) goto out;
+    }
+
+    aodev->dev = device;
+    aodev->action = LIBXL__DEVICE_ACTION_ADD;
+    libxl__wait_device_connection(egc, aodev);
+
+    rc = 0;
+
+out:
+    aodev->rc = rc;
+    if(rc) aodev->callback(egc, aodev);
+    return;
+}
+
+void* libxl__device_list(const struct libxl_device_type *dt,
+                         libxl_ctx *ctx, uint32_t domid, int *num)
+{
+    GC_INIT(ctx);
+
+    void *r = NULL;
+    void *list = NULL;
+    void *item = NULL;
+    char *libxl_path;
+    char *be_path;
+    char** dir = NULL;
+    unsigned int ndirs = 0;
+    int rc;
+
+    *num = 0;
+
+    libxl_path = GCSPRINTF("%s/device/%s",
+                           libxl__xs_libxl_path(gc, domid), dt->type);
+
+    dir = libxl__xs_directory(gc, XBT_NULL, libxl_path, &ndirs);
+
+    if (dir && ndirs) {
+        list = malloc(dt->dev_elem_size * ndirs);
+        void *end = (uint8_t*)list + ndirs * dt->dev_elem_size;
+        item = list;
+
+        while(item < end) {
+            be_path = libxl__xs_read(gc, XBT_NULL,
+                                     GCSPRINTF("%s/%s/backend",
+                                     libxl_path, *dir));
+
+            dt->init(item);
+
+            rc = dt->from_xenstore(gc, be_path, atoi(*dir), item);
+            if (rc) goto out;
+
+            item = (uint8_t*)item + dt->dev_elem_size;
+            ++dir;
+        }
+    }
+
+    *num = ndirs;
+    r = list;
+    list = NULL;
+
+out:
+
+    if (list) {
+        *num = 0;
+        while(item >= list) {
+            item = (uint8_t*)item - dt->dev_elem_size;
+            dt->dispose(item);
+        }
+        free(list);
+    }
+
+    GC_FREE;
+
+    return r;
+}
+
+void libxl__device_list_free(const struct libxl_device_type *dt,
+                             void *list, int num)
+{
+    int i;
+
+    for (i = 0; i < num; i++) {
+        dt->dispose((uint8_t*)list + i * dt->dev_elem_size);
+    }
+
+    free(list);
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 25cb08a..c07e280 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3473,11 +3473,18 @@  struct libxl_device_type {
     void (*add)(libxl__egc *, libxl__ao *, uint32_t, libxl_domain_config *,
                 libxl__multidev *);
     void *(*list)(libxl_ctx *, uint32_t, int *);
+    int (*set_default)(libxl__gc *, uint32_t, void *);
+    int (*to_device)(libxl__gc *, uint32_t, void *, libxl__device *);
+    void (*init)(void *);
+    void (*copy)(libxl_ctx *, void *, void *);
     void (*dispose)(void *);
     int (*compare)(void *, void *);
     void (*merge)(libxl_ctx *, void *, void *);
     int (*dm_needed)(void *, unsigned);
     void (*update_config)(libxl__gc *, void *, void *);
+    int (*from_xenstore)(libxl__gc *, const char *, uint32_t, void *);
+    void (*set_xenstore_config)(libxl__gc *, uint32_t, void *,
+                                flexarray_t **, flexarray_t **);
 };
 
 #define DEFINE_DEVICE_TYPE_STRUCT_X(name, sname, ...)                          \
@@ -3489,6 +3496,14 @@  struct libxl_device_type {
         .add           = libxl__add_ ## name ## s,                             \
         .list          = (void *(*)(libxl_ctx *, uint32_t, int *))             \
                          libxl_device_ ## sname ## _list,                      \
+        .set_default   = (int (*)(libxl__gc *, uint32_t, void *))              \
+                         libxl__device_ ## sname ## _setdefault,               \
+        .to_device     = (int (*)(libxl__gc *, uint32_t,                       \
+                                  void *, libxl__device *))                    \
+                         libxl__device_from_ ## name,                          \
+        .init          = (void (*)(void *))libxl_device_ ## sname ## _init,    \
+        .copy          = (void (*)(libxl_ctx *, void *, void *))               \
+                         libxl_device_ ## sname ## _copy,                      \
         .dispose       = (void (*)(void *))libxl_device_ ## sname ## _dispose, \
         .compare       = (int (*)(void *, void *))                             \
                          libxl_device_ ## sname ## _compare,                   \
@@ -3523,6 +3538,7 @@  extern const struct libxl_device_type libxl__vtpm_devtype;
 extern const struct libxl_device_type libxl__usbctrl_devtype;
 extern const struct libxl_device_type libxl__usbdev_devtype;
 extern const struct libxl_device_type libxl__pcidev_devtype;
+extern const struct libxl_device_type libxl__vdispl_devtype;
 
 extern const struct libxl_device_type *device_type_tbl[];
 
@@ -4339,6 +4355,14 @@  static inline bool libxl__acpi_defbool_val(const libxl_domain_build_info *b_info
     return libxl_defbool_val(b_info->acpi) &&
            libxl_defbool_val(b_info->u.hvm.acpi);
 }
+
+void libxl__device_add(libxl__egc *egc, uint32_t domid,
+                       const struct libxl_device_type *dt, void *type,
+                       libxl__ao_device *aodev);
+void* libxl__device_list(const struct libxl_device_type *dt,
+                         libxl_ctx *ctx, uint32_t domid, int *num);
+void libxl__device_list_free(const struct libxl_device_type *dt,
+                             void *list, int num);
 #endif
 
 /*
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 2475a4d..a4ff837 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -738,7 +738,14 @@  libxl_device_vtpm = Struct("device_vtpm", [
     ("backend_domname",  string),
     ("devid",            libxl_devid),
     ("uuid",             libxl_uuid),
-])
+    ])
+
+libxl_device_vdispl = Struct("device_vdispl", [
+    ("backend_domid", libxl_domid),
+    ("backend_domname", string),
+    ("devid", libxl_devid),
+    ("be_alloc", bool),
+    ])
 
 libxl_device_channel = Struct("device_channel", [
     ("backend_domid", libxl_domid),
@@ -750,7 +757,7 @@  libxl_device_channel = Struct("device_channel", [
             ("pty", None),
             ("socket", Struct(None, [("path", string)])),
            ])),
-])
+    ])
 
 libxl_domain_config = Struct("domain_config", [
     ("c_info", libxl_domain_create_info),
@@ -764,6 +771,7 @@  libxl_domain_config = Struct("domain_config", [
     ("vfbs", Array(libxl_device_vfb, "num_vfbs")),
     ("vkbs", Array(libxl_device_vkb, "num_vkbs")),
     ("vtpms", Array(libxl_device_vtpm, "num_vtpms")),
+    ("vdispls", Array(libxl_device_vdispl, "num_vdispls")),
     # a channel manifests as a console with a name,
     # see docs/misc/channels.txt
     ("channels", Array(libxl_device_channel, "num_channels")),
@@ -860,6 +868,16 @@  libxl_physinfo = Struct("physinfo", [
     ("cap_hvm_directio", bool),
     ], dir=DIR_OUT)
 
+libxl_vdisplinfo = Struct("vdisplinfo", [
+    ("backend", string),
+    ("backend_id", uint32),
+    ("frontend", string),
+    ("frontend_id", uint32),
+    ("devid", libxl_devid),
+    ("state", integer),
+    ("be_alloc", bool),
+    ], dir=DIR_OUT)
+
 # NUMA node characteristics: size and free are how much memory it has, and how
 # much of it is free, respectively. dists is an array of distances from this
 # node to each other node.
diff --git a/tools/libxl/libxl_types_internal.idl b/tools/libxl/libxl_types_internal.idl
index 82e5c07..cdef4d3 100644
--- a/tools/libxl/libxl_types_internal.idl
+++ b/tools/libxl/libxl_types_internal.idl
@@ -25,6 +25,7 @@  libxl__device_kind = Enumeration("device_kind", [
     (8, "VTPM"),
     (9, "VUSB"),
     (10, "QUSB"),
+    (11, "VDISPL")
     ])
 
 libxl__console_backend = Enumeration("console_backend", [
diff --git a/tools/libxl/libxl_usb.c b/tools/libxl/libxl_usb.c
index d8948d5..d1ec28f 100644
--- a/tools/libxl/libxl_usb.c
+++ b/tools/libxl/libxl_usb.c
@@ -1968,6 +1968,8 @@  void libxl_device_usbdev_list_free(libxl_device_usbdev *list, int nr)
 DEFINE_DEVICE_TYPE_STRUCT(usbctrl,
     .dm_needed = libxl_device_usbctrl_dm_needed
 );
+
+#define libxl__device_from_usbdev NULL
 DEFINE_DEVICE_TYPE_STRUCT(usbdev);
 
 /*
diff --git a/tools/libxl/libxl_utils.h b/tools/libxl/libxl_utils.h
index 25773d8..9e743dc 100644
--- a/tools/libxl/libxl_utils.h
+++ b/tools/libxl/libxl_utils.h
@@ -78,6 +78,10 @@  int libxl_devid_to_device_vtpm(libxl_ctx *ctx, uint32_t domid,
                                int devid, libxl_device_vtpm *vtpm);
 int libxl_devid_to_device_usbctrl(libxl_ctx *ctx, uint32_t domid,
                                   int devid, libxl_device_usbctrl *usbctrl);
+
+int libxl_devid_to_device_vdispl(libxl_ctx *ctx, uint32_t domid,
+                                 int devid, libxl_device_vdispl *vdispl);
+
 int libxl_ctrlport_to_device_usbdev(libxl_ctx *ctx, uint32_t domid,
                                     int ctrl, int port,
                                     libxl_device_usbdev *usbdev);
diff --git a/tools/libxl/libxl_vdispl.c b/tools/libxl/libxl_vdispl.c
new file mode 100644
index 0000000..85b20db
--- /dev/null
+++ b/tools/libxl/libxl_vdispl.c
@@ -0,0 +1,209 @@ 
+/*
+ * Copyright (C) 2016 EPAM Systems Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include "libxl_osdeps.h"
+
+#include "libxl_internal.h"
+
+static int libxl__device_vdispl_setdefault(libxl__gc *gc, uint32_t domid,
+                                           libxl_device_vdispl *vdispl)
+{
+    int rc;
+
+    rc = libxl__resolve_domid(gc, vdispl->backend_domname,
+                              &vdispl->backend_domid);
+
+    if (vdispl->devid == -1) {
+        vdispl->devid = libxl__device_nextid(gc, domid, "vdispl");
+    }
+
+    return rc;
+}
+
+static int libxl__from_xenstore_vdispl(libxl__gc *gc, const char *be_path,
+                                       uint32_t devid,
+                                       libxl_device_vdispl *vdispl)
+{
+    vdispl->devid = devid;
+
+    return libxl__backendpath_parse_domid(gc, be_path, &vdispl->backend_domid);
+}
+
+static int libxl__device_from_vdispl(libxl__gc *gc, uint32_t domid,
+                                     libxl_device_vdispl *vdispl,
+                                     libxl__device *device)
+{
+   device->backend_devid   = vdispl->devid;
+   device->backend_domid   = vdispl->backend_domid;
+   device->backend_kind    = LIBXL__DEVICE_KIND_VDISPL;
+   device->devid           = vdispl->devid;
+   device->domid           = domid;
+   device->kind            = LIBXL__DEVICE_KIND_VDISPL;
+
+   return 0;
+}
+
+static void libxl__set_xenstore_vdispl(libxl__gc *gc, uint32_t domid,
+                                       libxl_device_vdispl *vdispl,
+                                       flexarray_t **front, flexarray_t **back)
+{
+    *front = flexarray_make(gc, 16, 1);
+    *back = flexarray_make(gc, 16, 1);
+
+    flexarray_append(*back, "frontend-id");
+    flexarray_append(*back, GCSPRINTF("%d", domid));
+    flexarray_append(*back, "online");
+    flexarray_append(*back, "1");
+    flexarray_append(*back, "state");
+    flexarray_append(*back, GCSPRINTF("%d", XenbusStateInitialising));
+    flexarray_append(*back, "handle");
+    flexarray_append(*back, GCSPRINTF("%d", vdispl->devid));
+
+    flexarray_append(*front, "backend-id");
+    flexarray_append(*front, GCSPRINTF("%d", vdispl->backend_domid));
+    flexarray_append(*front, "state");
+    flexarray_append(*front, GCSPRINTF("%d", XenbusStateInitialising));
+    flexarray_append(*front, "handle");
+    flexarray_append(*front, GCSPRINTF("%d", vdispl->devid));
+    flexarray_append(*front, "be_alloc");
+    flexarray_append(*front, GCSPRINTF("%d", vdispl->be_alloc));
+}
+
+static void libxl__update_config_vdispl(libxl__gc *gc,
+                                        libxl_device_vdispl *dst,
+                                        libxl_device_vdispl *src)
+{
+    dst->devid = src->devid;
+    dst->be_alloc = src->be_alloc;
+}
+
+static int libxl_device_vdispl_compare(libxl_device_vdispl *d1,
+                                       libxl_device_vdispl *d2)
+{
+    return COMPARE_DEVID(d1, d2);
+}
+
+static void libxl__device_vdispl_add(libxl__egc *egc, uint32_t domid,
+                                     libxl_device_vdispl *vdispl,
+                                     libxl__ao_device *aodev)
+{
+    libxl__device_add(egc, domid, &libxl__vdispl_devtype, vdispl, aodev);
+}
+
+libxl_device_vdispl *libxl_device_vdispl_list(libxl_ctx *ctx, uint32_t domid,
+                                              int *num)
+{
+    return libxl__device_list(&libxl__vdispl_devtype, ctx, domid, num);
+}
+
+void libxl_device_vdispl_list_free(libxl_device_vdispl* list, int num)
+{
+    libxl__device_list_free(&libxl__vdispl_devtype, list, num);
+}
+
+int libxl_device_vdispl_getinfo(libxl_ctx *ctx, uint32_t domid,
+                                libxl_device_vdispl *vdispl,
+                                libxl_vdisplinfo *info)
+{
+    GC_INIT(ctx);
+    char *libxl_path, *dompath, *devpath;
+    char *val;
+    int rc;
+
+    libxl_vdisplinfo_init(info);
+    dompath = libxl__xs_get_dompath(gc, domid);
+    info->devid = vdispl->devid;
+
+    devpath = GCSPRINTF("%s/device/vdispl/%d", dompath, info->devid);
+    libxl_path = GCSPRINTF("%s/device/vdispl/%d",
+                           libxl__xs_libxl_path(gc, domid),
+                           info->devid);
+    info->backend = xs_read(ctx->xsh, XBT_NULL,
+                            GCSPRINTF("%s/backend", libxl_path),
+                            NULL);
+    if (!info->backend) { rc = ERROR_FAIL; goto out; }
+
+    rc = libxl__backendpath_parse_domid(gc, info->backend, &info->backend_id);
+    if (rc) { goto out; }
+
+    val = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/state", devpath));
+    info->state = val ? strtoul(val, NULL, 10) : -1;
+
+    info->frontend = xs_read(ctx->xsh, XBT_NULL,
+                             GCSPRINTF("%s/frontend", libxl_path),
+                             NULL);
+    info->frontend_id = domid;
+
+    val = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/be_alloc", libxl_path));
+    info->be_alloc = val ? strtoul(val, NULL, 10) : 0;
+
+    rc = 0;
+
+out:
+     GC_FREE;
+     return rc;
+}
+
+int libxl_devid_to_device_vdispl(libxl_ctx *ctx, uint32_t domid,
+                                 int devid, libxl_device_vdispl *vdispl)
+{
+    libxl_device_vdispl *vdispls = NULL;
+    int n, i;
+    int rc;
+
+    libxl_device_vdispl_init(vdispl);
+
+    vdispls = libxl_device_vdispl_list(ctx, domid, &n);
+
+    if (!vdispls) { rc = ERROR_NOTFOUND; goto out; }
+
+    for (i = 0; i < n; ++i) {
+        if (devid == vdispls[i].devid) {
+            libxl_device_vdispl_copy(ctx, vdispl, &vdispls[i]);
+            rc = 0;
+            goto out;
+        }
+    }
+
+    rc = ERROR_NOTFOUND;
+
+out:
+
+    if (vdispls) {
+        libxl_device_vdispl_list_free(vdispls, n);
+    }
+    return rc;
+}
+
+LIBXL_DEFINE_DEVICE_ADD(vdispl)
+static LIBXL_DEFINE_DEVICES_ADD(vdispl)
+LIBXL_DEFINE_DEVICE_REMOVE(vdispl)
+
+DEFINE_DEVICE_TYPE_STRUCT(vdispl,
+    .update_config = (void (*)(libxl__gc *, void *, void *))
+                     libxl__update_config_vdispl,
+    .from_xenstore = (int (*)(libxl__gc *, const char *, uint32_t, void *))
+                     libxl__from_xenstore_vdispl,
+    .set_xenstore_config = (void (*)(libxl__gc *, uint32_t, void *,
+                           flexarray_t **, flexarray_t **))
+                           libxl__set_xenstore_vdispl
+);
+
+/*
+ * Local variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */