xen: separate out frontend xenbus

Impact: refactor

Make a distinct frontend xenbus, in preparation for adding a backend xenbus.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
[corresponds to 2fd433a4188f in git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
 with adjustments to reflect changes in the code which is moved]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

6 files changed, 367 insertions, 305 deletions

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 4b9359a6f6ca..83c32cb72582 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -464,6 +464,7 @@ config XEN_BLKDEV_FRONTEND
         tristate "Xen virtual block device support"
         depends on XEN
         default y
+        select XEN_XENBUS_FRONTEND
         help
           This driver implements the front-end of the Xen virtual
           block device driver.  It communicates with a back-end driver
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 6e6180ccd726..10b6bef2e217 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -62,6 +62,9 @@ config XEN_SYS_HYPERVISOR
          virtual environment, /sys/hypervisor will still be present,
          but will have no xen contents.
 
+config XEN_XENBUS_FRONTEND
+       tristate
+          
 config XEN_PLATFORM_PCI
         tristate "xen platform pci device driver"
         depends on XEN_PVHVM
diff --git a/drivers/xen/xenbus/Makefile b/drivers/xen/xenbus/Makefile
index 5571f5b84223..33e8cf8149b3 100644
--- a/drivers/xen/xenbus/Makefile
+++ b/drivers/xen/xenbus/Makefile
@@ -5,3 +5,5 @@ xenbus-objs += xenbus_client.o
 xenbus-objs += xenbus_comms.o
 xenbus-objs += xenbus_xs.o
 xenbus-objs += xenbus_probe.o
+
+obj-$(CONFIG_XEN_XENBUS_FRONTEND) += xenbus_probe_frontend.o
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index deb9c4ba3a93..d46205868b88 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -56,7 +56,6 @@
 #include <xen/events.h>
 #include <xen/page.h>
 
-#include <xen/platform_pci.h>
 #include <xen/hvm.h>
 
 #include "xenbus_comms.h"
@@ -73,15 +72,6 @@ static unsigned long xen_store_mfn;
 
 static BLOCKING_NOTIFIER_HEAD(xenstore_chain);
 
-static void wait_for_devices(struct xenbus_driver *xendrv);
-
-static int xenbus_probe_frontend(const char *type, const char *name);
-
-static void xenbus_dev_shutdown(struct device *_dev);
-
-static int xenbus_dev_suspend(struct device *dev, pm_message_t state);
-static int xenbus_dev_resume(struct device *dev);
-
 /* If something in array of ids matches this device, return it. */
 static const struct xenbus_device_id *
 match_device(const struct xenbus_device_id *arr, struct xenbus_device *dev)
@@ -102,8 +92,10 @@ int xenbus_match(struct device *_dev, struct device_driver *_drv)
 
         return match_device(drv->ids, to_xenbus_device(_dev)) != NULL;
 }
+EXPORT_SYMBOL_GPL(xenbus_match);
+
 
-static int xenbus_uevent(struct device *_dev, struct kobj_uevent_env *env)
+int xenbus_uevent(struct device *_dev, struct kobj_uevent_env *env)
 {
         struct xenbus_device *dev = to_xenbus_device(_dev);
 
@@ -112,25 +104,7 @@ static int xenbus_uevent(struct device *_dev, struct kobj_uevent_env *env)
 
         return 0;
 }
-
-/* device/<type>/<id> => <type>-<id> */
-static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
-{
-        nodename = strchr(nodename, '/');
-        if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
-                printk(KERN_WARNING "XENBUS: bad frontend %s\n", nodename);
-                return -EINVAL;
-        }
-
-        strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
-        if (!strchr(bus_id, '/')) {
-                printk(KERN_WARNING "XENBUS: bus_id %s no slash\n", bus_id);
-                return -EINVAL;
-        }
-        *strchr(bus_id, '/') = '-';
-        return 0;
-}
-
+EXPORT_SYMBOL_GPL(xenbus_uevent);
 
 static void free_otherend_details(struct xenbus_device *dev)
 {
@@ -149,7 +123,28 @@ static void free_otherend_watch(struct xenbus_device *dev)
 }
 
 
-int read_otherend_details(struct xenbus_device *xendev,
+static int talk_to_otherend(struct xenbus_device *dev)
+{
+        struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
+
+        free_otherend_watch(dev);
+        free_otherend_details(dev);
+
+        return drv->read_otherend_details(dev);
+}
+
+
+
+static int watch_otherend(struct xenbus_device *dev)
+{
+        struct xen_bus_type *bus = container_of(dev->dev.bus, struct xen_bus_type, bus);
+
+        return xenbus_watch_pathfmt(dev, &dev->otherend_watch, bus->otherend_changed,
+                                    "%s/%s", dev->otherend, "state");
+}
+
+
+int xenbus_read_otherend_details(struct xenbus_device *xendev,
                                  char *id_node, char *path_node)
 {
         int err = xenbus_gather(XBT_NIL, xendev->nodename,
@@ -174,39 +169,11 @@ int read_otherend_details(struct xenbus_device *xendev,
 
         return 0;
 }
+EXPORT_SYMBOL_GPL(xenbus_read_otherend_details);
 
-
-static int read_backend_details(struct xenbus_device *xendev)
-{
-        return read_otherend_details(xendev, "backend-id", "backend");
-}
-
-static struct device_attribute xenbus_dev_attrs[] = {
-        __ATTR_NULL
-};
-
-/* Bus type for frontend drivers. */
-static struct xen_bus_type xenbus_frontend = {
-        .root = "device",
-        .levels = 2,            /* device/type/<id> */
-        .get_bus_id = frontend_bus_id,
-        .probe = xenbus_probe_frontend,
-        .bus = {
-                .name      = "xen",
-                .match     = xenbus_match,
-                .uevent    = xenbus_uevent,
-                .probe     = xenbus_dev_probe,
-                .remove    = xenbus_dev_remove,
-                .shutdown  = xenbus_dev_shutdown,
-                .dev_attrs = xenbus_dev_attrs,
-
-                .suspend   = xenbus_dev_suspend,
-                .resume    = xenbus_dev_resume,
-        },
-};
-
-static void otherend_changed(struct xenbus_watch *watch,
-                             const char **vec, unsigned int len)
+void xenbus_otherend_changed(struct xenbus_watch *watch,
+                             const char **vec, unsigned int len,
+                             int ignore_on_shutdown)
 {
         struct xenbus_device *dev =
                 container_of(watch, struct xenbus_device, otherend_watch);
@@ -234,11 +201,7 @@ static void otherend_changed(struct xenbus_watch *watch,
          * work that can fail e.g., when the rootfs is gone.
          */
         if (system_state > SYSTEM_RUNNING) {
-                struct xen_bus_type *bus = bus;
-                bus = container_of(dev->dev.bus, struct xen_bus_type, bus);
-                /* If we're frontend, drive the state machine to Closed. */
-                /* This should cause the backend to release our resources. */
-                if ((bus == &xenbus_frontend) && (state == XenbusStateClosing))
+                if (ignore_on_shutdown && (state == XenbusStateClosing))
                         xenbus_frontend_closed(dev);
                 return;
         }
@@ -246,25 +209,7 @@ static void otherend_changed(struct xenbus_watch *watch,
         if (drv->otherend_changed)
                 drv->otherend_changed(dev, state);
 }
-
-
-static int talk_to_otherend(struct xenbus_device *dev)
-{
-        struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
-
-        free_otherend_watch(dev);
-        free_otherend_details(dev);
-
-        return drv->read_otherend_details(dev);
-}
-
-
-static int watch_otherend(struct xenbus_device *dev)
-{
-        return xenbus_watch_pathfmt(dev, &dev->otherend_watch, otherend_changed,
-                                    "%s/%s", dev->otherend, "state");
-}
-
+EXPORT_SYMBOL_GPL(xenbus_otherend_changed);
 
 int xenbus_dev_probe(struct device *_dev)
 {
@@ -310,6 +255,7 @@ fail:
         xenbus_switch_state(dev, XenbusStateClosed);
         return -ENODEV;
 }
+EXPORT_SYMBOL_GPL(xenbus_dev_probe);
 
 int xenbus_dev_remove(struct device *_dev)
 {
@@ -327,8 +273,9 @@ int xenbus_dev_remove(struct device *_dev)
         xenbus_switch_state(dev, XenbusStateClosed);
         return 0;
 }
+EXPORT_SYMBOL_GPL(xenbus_dev_remove);
 
-static void xenbus_dev_shutdown(struct device *_dev)
+void xenbus_dev_shutdown(struct device *_dev)
 {
         struct xenbus_device *dev = to_xenbus_device(_dev);
         unsigned long timeout = 5*HZ;
@@ -349,6 +296,7 @@ static void xenbus_dev_shutdown(struct device *_dev)
  out:
         put_device(&dev->dev);
 }
+EXPORT_SYMBOL_GPL(xenbus_dev_shutdown);
 
 int xenbus_register_driver_common(struct xenbus_driver *drv,
                                   struct xen_bus_type *bus,
@@ -362,25 +310,7 @@ int xenbus_register_driver_common(struct xenbus_driver *drv,
 
         return driver_register(&drv->driver);
 }
-
-int __xenbus_register_frontend(struct xenbus_driver *drv,
-                               struct module *owner, const char *mod_name)
-{
-        int ret;
-
-        drv->read_otherend_details = read_backend_details;
-
-        ret = xenbus_register_driver_common(drv, &xenbus_frontend,
-                                            owner, mod_name);
-        if (ret)
-                return ret;
-
-        /* If this driver is loaded as a module wait for devices to attach. */
-        wait_for_devices(drv);
-
-        return 0;
-}
-EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
+EXPORT_SYMBOL_GPL(xenbus_register_driver_common);
 
 void xenbus_unregister_driver(struct xenbus_driver *drv)
 {
@@ -551,24 +481,7 @@ fail:
         kfree(xendev);
         return err;
 }
-
-/* device/<typename>/<name> */
-static int xenbus_probe_frontend(const char *type, const char *name)
-{
-        char *nodename;
-        int err;
-
-        nodename = kasprintf(GFP_KERNEL, "%s/%s/%s",
-                             xenbus_frontend.root, type, name);
-        if (!nodename)
-                return -ENOMEM;
-
-        DPRINTK("%s", nodename);
-
-        err = xenbus_probe_node(&xenbus_frontend, type, nodename);
-        kfree(nodename);
-        return err;
-}
+EXPORT_SYMBOL_GPL(xenbus_probe_node);
 
 static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
 {
@@ -577,15 +490,23 @@ static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
         unsigned int dir_n = 0;
         int i;
 
+        printk(KERN_CRIT "%s type %s\n", __func__, type);
+
         dir = xenbus_directory(XBT_NIL, bus->root, type, &dir_n);
-        if (IS_ERR(dir))
+        if (IS_ERR(dir)) {
+                printk(KERN_CRIT "%s failed xenbus_directory\n", __func__);
                 return PTR_ERR(dir);
+        }
 
         for (i = 0; i < dir_n; i++) {
-                err = bus->probe(type, dir[i]);
-                if (err)
+                printk(KERN_CRIT "%s %d/%d %s\n", __func__, i+1,dir_n, dir[i]);
+                err = bus->probe(bus, type, dir[i]);
+                if (err) {
+                        printk(KERN_CRIT "%s failed\n", __func__);
                         break;
+                }
         }
+        printk("%s done\n", __func__);
         kfree(dir);
         return err;
 }
@@ -596,18 +517,27 @@ int xenbus_probe_devices(struct xen_bus_type *bus)
         char **dir;
         unsigned int i, dir_n;
 
+        printk(KERN_CRIT "%s %s\n", __func__, bus->root);
+
         dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
-        if (IS_ERR(dir))
+        if (IS_ERR(dir)) {
+                printk(KERN_CRIT "%s failed xenbus_directory\n", __func__);
                 return PTR_ERR(dir);
+        }
 
         for (i = 0; i < dir_n; i++) {
+                printk(KERN_CRIT "%s %d/%d %s\n", __func__, i+1,dir_n, dir[i]);
                 err = xenbus_probe_device_type(bus, dir[i]);
-                if (err)
+                if (err) {
+                        printk(KERN_CRIT "%s failed\n", __func__);
                         break;
+                }
         }
+        printk("%s done\n", __func__);
         kfree(dir);
         return err;
 }
+EXPORT_SYMBOL_GPL(xenbus_probe_devices);
 
 static unsigned int char_count(const char *str, char c)
 {
@@ -670,32 +600,17 @@ void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_changed);
 
-static void frontend_changed(struct xenbus_watch *watch,
-                             const char **vec, unsigned int len)
-{
-        DPRINTK("");
-
-        xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
-}
-
-/* We watch for devices appearing and vanishing. */
-static struct xenbus_watch fe_watch = {
-        .node = "device",
-        .callback = frontend_changed,
-};
-
-static int xenbus_dev_suspend(struct device *dev, pm_message_t state)
+int xenbus_dev_suspend(struct device *dev, pm_message_t state)
 {
         int err = 0;
         struct xenbus_driver *drv;
-        struct xenbus_device *xdev;
+        struct xenbus_device *xdev = container_of(dev, struct xenbus_device, dev);
 
-        DPRINTK("");
+        DPRINTK("%s", xdev->nodename);
 
         if (dev->driver == NULL)
                 return 0;
         drv = to_xenbus_driver(dev->driver);
-        xdev = container_of(dev, struct xenbus_device, dev);
         if (drv->suspend)
                 err = drv->suspend(xdev, state);
         if (err)
@@ -703,21 +618,19 @@ static int xenbus_dev_suspend(struct device *dev, pm_message_t state)
                        "xenbus: suspend %s failed: %i\n", dev_name(dev), err);
         return 0;
 }
+EXPORT_SYMBOL_GPL(xenbus_dev_suspend);
 
-static int xenbus_dev_resume(struct device *dev)
+int xenbus_dev_resume(struct device *dev)
 {
         int err;
         struct xenbus_driver *drv;
-        struct xenbus_device *xdev;
+        struct xenbus_device *xdev = container_of(dev, struct xenbus_device, dev);
 
-        DPRINTK("");
+        DPRINTK("%s", xdev->nodename);
 
         if (dev->driver == NULL)
                 return 0;
-
         drv = to_xenbus_driver(dev->driver);
-        xdev = container_of(dev, struct xenbus_device, dev);
-
         err = talk_to_otherend(xdev);
         if (err) {
                 printk(KERN_WARNING
@@ -748,6 +661,7 @@ static int xenbus_dev_resume(struct device *dev)
 
         return 0;
 }
+EXPORT_SYMBOL_GPL(xenbus_dev_resume);
 
 /* A flag to determine if xenstored is 'ready' (i.e. has started) */
 int xenstored_ready = 0;
@@ -776,11 +690,6 @@ void xenbus_probe(struct work_struct *unused)
 {
         xenstored_ready = 1;
 
-        /* Enumerate devices in xenstore and watch for changes. */
-        xenbus_probe_devices(&xenbus_frontend);
-        register_xenbus_watch(&fe_watch);
-        xenbus_backend_probe_and_watch();
-
         /* Notify others that xenstore is up */
         blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
 }
@@ -811,15 +720,6 @@ static int __init xenbus_init(void)
         if (!xen_domain())
                 goto out_error;
 
-        /* Register ourselves with the kernel bus subsystem */
-        err = bus_register(&xenbus_frontend.bus);
-        if (err)
-                goto out_error;
-
-        err = xenbus_backend_bus_register();
-        if (err)
-                goto out_unreg_front;
-
         /*
          * Domain0 doesn't have a store_evtchn or store_mfn yet.
          */
@@ -874,7 +774,7 @@ static int __init xenbus_init(void)
         if (err) {
                 printk(KERN_WARNING
                        "XENBUS: Error initializing xenstore comms: %i\n", err);
-                goto out_unreg_back;
+                goto out_error;
         }
 
 #ifdef CONFIG_XEN_COMPAT_XENFS
@@ -885,135 +785,16 @@ static int __init xenbus_init(void)
         proc_mkdir("xen", NULL);
 #endif
 
+        printk(KERN_CRIT "%s ok\n", __func__);
         return 0;
 
-  out_unreg_back:
-        xenbus_backend_bus_unregister();
-
-  out_unreg_front:
-        bus_unregister(&xenbus_frontend.bus);
-
   out_error:
         if (page != 0)
                 free_page(page);
+
         return err;
 }
 
 postcore_initcall(xenbus_init);
 
 MODULE_LICENSE("GPL");
-
-static int is_device_connecting(struct device *dev, void *data)
-{
-        struct xenbus_device *xendev = to_xenbus_device(dev);
-        struct device_driver *drv = data;
-        struct xenbus_driver *xendrv;
-
-        /*
-         * A device with no driver will never connect. We care only about
-         * devices which should currently be in the process of connecting.
-         */
-        if (!dev->driver)
-                return 0;
-
-        /* Is this search limited to a particular driver? */
-        if (drv && (dev->driver != drv))
-                return 0;
-
-        xendrv = to_xenbus_driver(dev->driver);
-        return (xendev->state < XenbusStateConnected ||
-                (xendev->state == XenbusStateConnected &&
-                 xendrv->is_ready && !xendrv->is_ready(xendev)));
-}
-
-static int exists_connecting_device(struct device_driver *drv)
-{
-        return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
-                                is_device_connecting);
-}
-
-static int print_device_status(struct device *dev, void *data)
-{
-        struct xenbus_device *xendev = to_xenbus_device(dev);
-        struct device_driver *drv = data;
-
-        /* Is this operation limited to a particular driver? */
-        if (drv && (dev->driver != drv))
-                return 0;
-
-        if (!dev->driver) {
-                /* Information only: is this too noisy? */
-                printk(KERN_INFO "XENBUS: Device with no driver: %s\n",
-                       xendev->nodename);
-        } else if (xendev->state < XenbusStateConnected) {
-                enum xenbus_state rstate = XenbusStateUnknown;
-                if (xendev->otherend)
-                        rstate = xenbus_read_driver_state(xendev->otherend);
-                printk(KERN_WARNING "XENBUS: Timeout connecting "
-                       "to device: %s (local state %d, remote state %d)\n",
-                       xendev->nodename, xendev->state, rstate);
-        }
-
-        return 0;
-}
-
-/* We only wait for device setup after most initcalls have run. */
-static int ready_to_wait_for_devices;
-
-/*
- * On a 5-minute timeout, wait for all devices currently configured.  We need
- * to do this to guarantee that the filesystems and / or network devices
- * needed for boot are available, before we can allow the boot to proceed.
- *
- * This needs to be on a late_initcall, to happen after the frontend device
- * drivers have been initialised, but before the root fs is mounted.
- *
- * A possible improvement here would be to have the tools add a per-device
- * flag to the store entry, indicating whether it is needed at boot time.
- * This would allow people who knew what they were doing to accelerate their
- * boot slightly, but of course needs tools or manual intervention to set up
- * those flags correctly.
- */
-static void wait_for_devices(struct xenbus_driver *xendrv)
-{
-        unsigned long start = jiffies;
-        struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
-        unsigned int seconds_waited = 0;
-
-        if (!ready_to_wait_for_devices || !xen_domain())
-                return;
-
-        while (exists_connecting_device(drv)) {
-                if (time_after(jiffies, start + (seconds_waited+5)*HZ)) {
-                        if (!seconds_waited)
-                                printk(KERN_WARNING "XENBUS: Waiting for "
-                                       "devices to initialise: ");
-                        seconds_waited += 5;
-                        printk("%us...", 300 - seconds_waited);
-                        if (seconds_waited == 300)
-                                break;
-                }
-
-                schedule_timeout_interruptible(HZ/10);
-        }
-
-        if (seconds_waited)
-                printk("\n");
-
-        bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
-                         print_device_status);
-}
-
-#ifndef MODULE
-static int __init boot_wait_for_devices(void)
-{
-        if (xen_hvm_domain() && !xen_platform_pci_unplug)
-                return -ENODEV;
-
-        ready_to_wait_for_devices = 1;
-        wait_for_devices(NULL);
-        return 0;
-}
-
-late_initcall(boot_wait_for_devices);
-#endif
diff --git a/drivers/xen/xenbus/xenbus_probe.h b/drivers/xen/xenbus/xenbus_probe.h
index 6c5e3185a6a2..be390cef329f 100644
--- a/drivers/xen/xenbus/xenbus_probe.h
+++ b/drivers/xen/xenbus/xenbus_probe.h
@@ -36,26 +36,13 @@
 
 #define XEN_BUS_ID_SIZE                 20
 
-#ifdef CONFIG_XEN_BACKEND
-extern void xenbus_backend_suspend(int (*fn)(struct device *, void *));
-extern void xenbus_backend_resume(int (*fn)(struct device *, void *));
-extern void xenbus_backend_probe_and_watch(void);
-extern int xenbus_backend_bus_register(void);
-extern void xenbus_backend_bus_unregister(void);
-#else
-static inline void xenbus_backend_suspend(int (*fn)(struct device *, void *)) {}
-static inline void xenbus_backend_resume(int (*fn)(struct device *, void *)) {}
-static inline void xenbus_backend_probe_and_watch(void) {}
-static inline int xenbus_backend_bus_register(void) { return 0; }
-static inline void xenbus_backend_bus_unregister(void) {}
-#endif
-
 struct xen_bus_type
 {
         char *root;
         unsigned int levels;
         int (*get_bus_id)(char bus_id[XEN_BUS_ID_SIZE], const char *nodename);
-        int (*probe)(const char *type, const char *dir);
+        int (*probe)(struct xen_bus_type *bus, const char *type, const char *dir);
+        void (*otherend_changed)(struct xenbus_watch *watch, const char **vec, unsigned int len);
         struct bus_type bus;
 };
 
@@ -73,4 +60,17 @@ extern int xenbus_probe_devices(struct xen_bus_type *bus);
 
 extern void xenbus_dev_changed(const char *node, struct xen_bus_type *bus);
 
+extern int xenbus_uevent(struct device *_dev, struct kobj_uevent_env *env);
+extern void xenbus_dev_shutdown(struct device *_dev);
+
+extern int xenbus_dev_suspend(struct device *dev, pm_message_t state);
+extern int xenbus_dev_resume(struct device *dev);
+
+extern void xenbus_otherend_changed(struct xenbus_watch *watch,
+                                    const char **vec, unsigned int len,
+                                    int ignore_on_shutdown);
+
+extern int xenbus_read_otherend_details(struct xenbus_device *xendev,
+                                        char *id_node, char *path_node);
+
 #endif
diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
new file mode 100644
index 000000000000..04c4f0123521
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -0,0 +1,275 @@
+#define DPRINTK(fmt, args...)                           \
+        pr_debug("xenbus_probe (%s:%d) " fmt ".\n",     \
+                 __func__, __LINE__, ##args)
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/fcntl.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/notifier.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include <linux/io.h>
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/page.h>
+
+#include <xen/platform_pci.h>
+
+#include "xenbus_comms.h"
+#include "xenbus_probe.h"
+
+
+/* device/<type>/<id> => <type>-<id> */
+static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
+{
+        nodename = strchr(nodename, '/');
+        if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
+                printk(KERN_WARNING "XENBUS: bad frontend %s\n", nodename);
+                return -EINVAL;
+        }
+
+        strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
+        if (!strchr(bus_id, '/')) {
+                printk(KERN_WARNING "XENBUS: bus_id %s no slash\n", bus_id);
+                return -EINVAL;
+        }
+        *strchr(bus_id, '/') = '-';
+        return 0;
+}
+
+/* device/<typename>/<name> */
+static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type, const char *name)
+{
+        char *nodename;
+        int err;
+
+        nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
+        if (!nodename)
+                return -ENOMEM;
+
+        DPRINTK("%s", nodename);
+
+        err = xenbus_probe_node(bus, type, nodename);
+        kfree(nodename);
+        return err;
+}
+
+static void backend_changed(struct xenbus_watch *watch,
+                            const char **vec, unsigned int len)
+{
+        xenbus_otherend_changed(watch, vec, len, 1);
+}
+
+static struct device_attribute xenbus_frontend_dev_attrs[] = {
+        __ATTR_NULL
+};
+
+static struct xen_bus_type xenbus_frontend = {
+        .root = "device",
+        .levels = 2,            /* device/type/<id> */
+        .get_bus_id = frontend_bus_id,
+        .probe = xenbus_probe_frontend,
+        .otherend_changed = backend_changed,
+        .bus = {
+                .name     = "xen",
+                .match    = xenbus_match,
+                .uevent   = xenbus_uevent,
+                .probe    = xenbus_dev_probe,
+                .remove   = xenbus_dev_remove,
+                .shutdown = xenbus_dev_shutdown,
+                .dev_attrs= xenbus_frontend_dev_attrs,
+
+                .suspend  = xenbus_dev_suspend,
+                .resume   = xenbus_dev_resume,
+        },
+};
+
+static void frontend_changed(struct xenbus_watch *watch,
+                             const char **vec, unsigned int len)
+{
+        DPRINTK("");
+
+        xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
+}
+
+
+/* We watch for devices appearing and vanishing. */
+static struct xenbus_watch fe_watch = {
+        .node = "device",
+        .callback = frontend_changed,
+};
+
+static int read_backend_details(struct xenbus_device *xendev)
+{
+        return xenbus_read_otherend_details(xendev, "backend-id", "backend");
+}
+
+static int is_device_connecting(struct device *dev, void *data)
+{
+        struct xenbus_device *xendev = to_xenbus_device(dev);
+        struct device_driver *drv = data;
+        struct xenbus_driver *xendrv;
+
+        /*
+         * A device with no driver will never connect. We care only about
+         * devices which should currently be in the process of connecting.
+         */
+        if (!dev->driver)
+                return 0;
+
+        /* Is this search limited to a particular driver? */
+        if (drv && (dev->driver != drv))
+                return 0;
+
+        xendrv = to_xenbus_driver(dev->driver);
+        return (xendev->state < XenbusStateConnected ||
+                (xendev->state == XenbusStateConnected &&
+                 xendrv->is_ready && !xendrv->is_ready(xendev)));
+}
+
+static int exists_connecting_device(struct device_driver *drv)
+{
+        return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
+                                is_device_connecting);
+}
+
+static int print_device_status(struct device *dev, void *data)
+{
+        struct xenbus_device *xendev = to_xenbus_device(dev);
+        struct device_driver *drv = data;
+
+        /* Is this operation limited to a particular driver? */
+        if (drv && (dev->driver != drv))
+                return 0;
+
+        if (!dev->driver) {
+                /* Information only: is this too noisy? */
+                printk(KERN_INFO "XENBUS: Device with no driver: %s\n",
+                       xendev->nodename);
+        } else if (xendev->state < XenbusStateConnected) {
+                enum xenbus_state rstate = XenbusStateUnknown;
+                if (xendev->otherend)
+                        rstate = xenbus_read_driver_state(xendev->otherend);
+                printk(KERN_WARNING "XENBUS: Timeout connecting "
+                       "to device: %s (local state %d, remote state %d)\n",
+                       xendev->nodename, xendev->state, rstate);
+        }
+
+        return 0;
+}
+
+/* We only wait for device setup after most initcalls have run. */
+static int ready_to_wait_for_devices;
+
+/*
+ * On a 5-minute timeout, wait for all devices currently configured.  We need
+ * to do this to guarantee that the filesystems and / or network devices
+ * needed for boot are available, before we can allow the boot to proceed.
+ *
+ * This needs to be on a late_initcall, to happen after the frontend device
+ * drivers have been initialised, but before the root fs is mounted.
+ *
+ * A possible improvement here would be to have the tools add a per-device
+ * flag to the store entry, indicating whether it is needed at boot time.
+ * This would allow people who knew what they were doing to accelerate their
+ * boot slightly, but of course needs tools or manual intervention to set up
+ * those flags correctly.
+ */
+static void wait_for_devices(struct xenbus_driver *xendrv)
+{
+        unsigned long start = jiffies;
+        struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
+        unsigned int seconds_waited = 0;
+
+        if (!ready_to_wait_for_devices || !xen_domain())
+                return;
+
+        while (exists_connecting_device(drv)) {
+                if (time_after(jiffies, start + (seconds_waited+5)*HZ)) {
+                        if (!seconds_waited)
+                                printk(KERN_WARNING "XENBUS: Waiting for "
+                                       "devices to initialise: ");
+                        seconds_waited += 5;
+                        printk("%us...", 300 - seconds_waited);
+                        if (seconds_waited == 300)
+                                break;
+                }
+
+                schedule_timeout_interruptible(HZ/10);
+        }
+
+        if (seconds_waited)
+                printk("\n");
+
+        bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
+                         print_device_status);
+}
+
+int __xenbus_register_frontend(struct xenbus_driver *drv,
+                               struct module *owner, const char *mod_name)
+{
+        int ret;
+
+        drv->read_otherend_details = read_backend_details;
+
+        ret = xenbus_register_driver_common(drv, &xenbus_frontend,
+                                            owner, mod_name);
+        if (ret)
+                return ret;
+
+        /* If this driver is loaded as a module wait for devices to attach. */
+        wait_for_devices(drv);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
+
+static int __init xenbus_probe_frontend_init(void)
+{
+        int err;
+
+        DPRINTK("");
+
+        /* Register ourselves with the kernel bus subsystem */
+        err = bus_register(&xenbus_frontend.bus);
+        if (err) {
+                printk(KERN_CRIT "%s didn't register bus!\n", __func__);
+                return err;
+        }
+        printk(KERN_CRIT "%s bus registered ok\n", __func__);
+
+        if (!xen_initial_domain()) {
+                /* Enumerate devices in xenstore and watch for changes. */
+                xenbus_probe_devices(&xenbus_frontend);
+                printk(KERN_CRIT "%s devices probed ok\n", __func__);
+                register_xenbus_watch(&fe_watch);
+                printk(KERN_CRIT "%s watch add ok ok\n", __func__);
+                printk(KERN_CRIT "%s all done\n", __func__);
+        }
+
+        return 0;
+}
+
+module_init(xenbus_probe_frontend_init);
+
+#ifndef MODULE
+static int __init boot_wait_for_devices(void)
+{
+        if (xen_hvm_domain() && !xen_platform_pci_unplug)
+                return -ENODEV;
+
+        ready_to_wait_for_devices = 1;
+        wait_for_devices(NULL);
+        return 0;
+}
+
+late_initcall(boot_wait_for_devices);
+#endif