drivers/xen/xenbus/xenbus_probe_backend.c

   1 /******************************************************************************
   2  * Talks to Xen Store to figure out what devices we have (backend half).
   3  *
   4  * Copyright (C) 2005 Rusty Russell, IBM Corporation
   5  * Copyright (C) 2005 Mike Wray, Hewlett-Packard
   6  * Copyright (C) 2005, 2006 XenSource Ltd
   7  * Copyright (C) 2007 Solarflare Communications, Inc.
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License version 2
  11  * as published by the Free Software Foundation; or, when distributed
  12  * separately from the Linux kernel or incorporated into other
  13  * software packages, subject to the following license:
  14  *
  15  * Permission is hereby granted, free of charge, to any person obtaining a copy
  16  * of this source file (the "Software"), to deal in the Software without
  17  * restriction, including without limitation the rights to use, copy, modify,
  18  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  19  * and to permit persons to whom the Software is furnished to do so, subject to
  20  * the following conditions:
  21  *
  22  * The above copyright notice and this permission notice shall be included in
  23  * all copies or substantial portions of the Software.
  24  *
  25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  26  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  27  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  28  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  29  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  30  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  31  * IN THE SOFTWARE.
  32  */
  33
  34 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  35
  36 #define DPRINTK(fmt, ...)                               \
  37         pr_debug("(%s:%d) " fmt "\n",                   \
  38                  __func__, __LINE__, ##__VA_ARGS__)
  39
  40 #include <linux/kernel.h>
  41 #include <linux/err.h>
  42 #include <linux/string.h>
  43 #include <linux/ctype.h>
  44 #include <linux/fcntl.h>
  45 #include <linux/mm.h>
  46 #include <linux/notifier.h>
  47 #include <linux/export.h>
  48
  49 #include <asm/page.h>
  50 #include <asm/pgtable.h>
  51 #include <asm/xen/hypervisor.h>
  52 #include <asm/hypervisor.h>
  53 #include <xen/xenbus.h>
  54 #include <xen/features.h>
  55
  56 #include "xenbus.h"
  57
  58 /* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
  59 static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  60 {
  61         int domid, err;
  62         const char *devid, *type, *frontend;
  63         unsigned int typelen;
  64
  65         type = strchr(nodename, '/');
  66         if (!type)
  67                 return -EINVAL;
  68         type++;
  69         typelen = strcspn(type, "/");
  70         if (!typelen || type[typelen] != '/')
  71                 return -EINVAL;
  72
  73         devid = strrchr(nodename, '/') + 1;
  74
  75         err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
  76                             "frontend", NULL, &frontend,
  77                             NULL);
  78         if (err)
  79                 return err;
  80         if (strlen(frontend) == 0)
  81                 err = -ERANGE;
  82         if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
  83                 err = -ENOENT;
  84         kfree(frontend);
  85
  86         if (err)
  87                 return err;
  88
  89         if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
  90                      typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
  91                 return -ENOSPC;
  92         return 0;
  93 }
  94
  95 static int xenbus_uevent_backend(struct device *dev,
  96                                  struct kobj_uevent_env *env)
  97 {
  98         struct xenbus_device *xdev;
  99         struct xenbus_driver *drv;
 100         struct xen_bus_type *bus;
 101
 102         DPRINTK("");
 103
 104         if (dev == NULL)
 105                 return -ENODEV;
 106
 107         xdev = to_xenbus_device(dev);
 108         bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
 109
 110         if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
 111                 return -ENOMEM;
 112
 113         /* stuff we want to pass to /sbin/hotplug */
 114         if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
 115                 return -ENOMEM;
 116
 117         if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
 118                 return -ENOMEM;
 119
 120         if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
 121                 return -ENOMEM;
 122
 123         if (dev->driver) {
 124                 drv = to_xenbus_driver(dev->driver);
 125                 if (drv && drv->uevent)
 126                         return drv->uevent(xdev, env);
 127         }
 128
 129         return 0;
 130 }
 131
 132 /* backend/<typename>/<frontend-uuid>/<name> */
 133 static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
 134                                      const char *dir,
 135                                      const char *type,
 136                                      const char *name)
 137 {
 138         char *nodename;
 139         int err;
 140
 141         nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
 142         if (!nodename)
 143                 return -ENOMEM;
 144
 145         DPRINTK("%s\n", nodename);
 146
 147         err = xenbus_probe_node(bus, type, nodename);
 148         kfree(nodename);
 149         return err;
 150 }
 151
 152 /* backend/<typename>/<frontend-domid> */
 153 static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
 154                                 const char *domid)
 155 {
 156         char *nodename;
 157         int err = 0;
 158         char **dir;
 159         unsigned int i, dir_n = 0;
 160
 161         DPRINTK("");
 162
 163         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
 164         if (!nodename)
 165                 return -ENOMEM;
 166
 167         dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
 168         if (IS_ERR(dir)) {
 169                 kfree(nodename);
 170                 return PTR_ERR(dir);
 171         }
 172
 173         for (i = 0; i < dir_n; i++) {
 174                 err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
 175                 if (err)
 176                         break;
 177         }
 178         kfree(dir);
 179         kfree(nodename);
 180         return err;
 181 }
 182
 183 static void frontend_changed(struct xenbus_watch *watch,
 184                              const char *path, const char *token)
 185 {
 186         xenbus_otherend_changed(watch, path, token, 0);
 187 }
 188
 189 static struct xen_bus_type xenbus_backend = {
 190         .root = "backend",
 191         .levels = 3,            /* backend/type/<frontend>/<id> */
 192         .get_bus_id = backend_bus_id,
 193         .probe = xenbus_probe_backend,
 194         .otherend_changed = frontend_changed,
 195         .bus = {
 196                 .name           = "xen-backend",
 197                 .match          = xenbus_match,
 198                 .uevent         = xenbus_uevent_backend,
 199                 .probe          = xenbus_dev_probe,
 200                 .remove         = xenbus_dev_remove,
 201                 .shutdown       = xenbus_dev_shutdown,
 202                 .dev_groups     = xenbus_dev_groups,
 203         },
 204 };
 205
 206 static void backend_changed(struct xenbus_watch *watch,
 207                             const char *path, const char *token)
 208 {
 209         DPRINTK("");
 210
 211         xenbus_dev_changed(path, &xenbus_backend);
 212 }
 213
 214 static struct xenbus_watch be_watch = {
 215         .node = "backend",
 216         .callback = backend_changed,
 217 };
 218
 219 static int read_frontend_details(struct xenbus_device *xendev)
 220 {
 221         return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
 222 }
 223
 224 int xenbus_dev_is_online(struct xenbus_device *dev)
 225 {
 226         return !!xenbus_read_unsigned(dev->nodename, "online", 0);
 227 }
 228 EXPORT_SYMBOL_GPL(xenbus_dev_is_online);
 229
 230 int __xenbus_register_backend(struct xenbus_driver *drv, struct module *owner,
 231                               const char *mod_name)
 232 {
 233         drv->read_otherend_details = read_frontend_details;
 234
 235         return xenbus_register_driver_common(drv, &xenbus_backend,
 236                                              owner, mod_name);
 237 }
 238 EXPORT_SYMBOL_GPL(__xenbus_register_backend);
 239
 240 static int backend_probe_and_watch(struct notifier_block *notifier,
 241                                    unsigned long event,
 242                                    void *data)
 243 {
 244         /* Enumerate devices in xenstore and watch for changes. */
 245         xenbus_probe_devices(&xenbus_backend);
 246         register_xenbus_watch(&be_watch);
 247
 248         return NOTIFY_DONE;
 249 }
 250
 251 static int __init xenbus_probe_backend_init(void)
 252 {
 253         static struct notifier_block xenstore_notifier = {
 254                 .notifier_call = backend_probe_and_watch
 255         };
 256         int err;
 257
 258         DPRINTK("");
 259
 260         /* Register ourselves with the kernel bus subsystem */
 261         err = bus_register(&xenbus_backend.bus);
 262         if (err)
 263                 return err;
 264
 265         register_xenstore_notifier(&xenstore_notifier);
 266
 267         return 0;
 268 }
 269 subsys_initcall(xenbus_probe_backend_init);