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 DPRINTK(fmt, args...)                           \
  35         pr_debug("xenbus_probe (%s:%d) " fmt ".\n",     \
  36                  __func__, __LINE__, ##args)
  37
  38 #include <linux/kernel.h>
  39 #include <linux/err.h>
  40 #include <linux/string.h>
  41 #include <linux/ctype.h>
  42 #include <linux/fcntl.h>
  43 #include <linux/mm.h>
  44 #include <linux/notifier.h>
  45
  46 #include <asm/page.h>
  47 #include <asm/pgtable.h>
  48 #include <asm/xen/hypervisor.h>
  49 #include <asm/hypervisor.h>
  50 #include <xen/xenbus.h>
  51 #include <xen/features.h>
  52
  53 #include "xenbus_comms.h"
  54 #include "xenbus_probe.h"
  55
  56 /* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
  57 static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  58 {
  59         int domid, err;
  60         const char *devid, *type, *frontend;
  61         unsigned int typelen;
  62
  63         type = strchr(nodename, '/');
  64         if (!type)
  65                 return -EINVAL;
  66         type++;
  67         typelen = strcspn(type, "/");
  68         if (!typelen || type[typelen] != '/')
  69                 return -EINVAL;
  70
  71         devid = strrchr(nodename, '/') + 1;
  72
  73         err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
  74                             "frontend", NULL, &frontend,
  75                             NULL);
  76         if (err)
  77                 return err;
  78         if (strlen(frontend) == 0)
  79                 err = -ERANGE;
  80         if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
  81                 err = -ENOENT;
  82         kfree(frontend);
  83
  84         if (err)
  85                 return err;
  86
  87         if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
  88                      typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
  89                 return -ENOSPC;
  90         return 0;
  91 }
  92
  93 static int xenbus_uevent_backend(struct device *dev,
  94                                  struct kobj_uevent_env *env)
  95 {
  96         struct xenbus_device *xdev;
  97         struct xenbus_driver *drv;
  98         struct xen_bus_type *bus;
  99
 100         DPRINTK("");
 101
 102         if (dev == NULL)
 103                 return -ENODEV;
 104
 105         xdev = to_xenbus_device(dev);
 106         bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
 107         if (xdev == NULL)
 108                 return -ENODEV;
 109
 110         /* stuff we want to pass to /sbin/hotplug */
 111         if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
 112                 return -ENOMEM;
 113
 114         if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
 115                 return -ENOMEM;
 116
 117         if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
 118                 return -ENOMEM;
 119
 120         if (dev->driver) {
 121                 drv = to_xenbus_driver(dev->driver);
 122                 if (drv && drv->uevent)
 123                         return drv->uevent(xdev, env);
 124         }
 125
 126         return 0;
 127 }
 128
 129 /* backend/<typename>/<frontend-uuid>/<name> */
 130 static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
 131                                      const char *dir,
 132                                      const char *type,
 133                                      const char *name)
 134 {
 135         char *nodename;
 136         int err;
 137
 138         nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
 139         if (!nodename)
 140                 return -ENOMEM;
 141
 142         DPRINTK("%s\n", nodename);
 143
 144         err = xenbus_probe_node(bus, type, nodename);
 145         kfree(nodename);
 146         return err;
 147 }
 148
 149 /* backend/<typename>/<frontend-domid> */
 150 static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
 151                                 const char *domid)
 152 {
 153         char *nodename;
 154         int err = 0;
 155         char **dir;
 156         unsigned int i, dir_n = 0;
 157
 158         DPRINTK("");
 159
 160         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
 161         if (!nodename)
 162                 return -ENOMEM;
 163
 164         dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
 165         if (IS_ERR(dir)) {
 166                 kfree(nodename);
 167                 return PTR_ERR(dir);
 168         }
 169
 170         for (i = 0; i < dir_n; i++) {
 171                 err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
 172                 if (err)
 173                         break;
 174         }
 175         kfree(dir);
 176         kfree(nodename);
 177         return err;
 178 }
 179
 180 static void frontend_changed(struct xenbus_watch *watch,
 181                             const char **vec, unsigned int len)
 182 {
 183         xenbus_otherend_changed(watch, vec, len, 0);
 184 }
 185
 186 static struct device_attribute xenbus_backend_dev_attrs[] = {
 187         __ATTR_NULL
 188 };
 189
 190 static struct xen_bus_type xenbus_backend = {
 191         .root = "backend",
 192         .levels = 3,            /* backend/type/<frontend>/<id> */
 193         .get_bus_id = backend_bus_id,
 194         .probe = xenbus_probe_backend,
 195         .otherend_changed = frontend_changed,
 196         .bus = {
 197                 .name           = "xen-backend",
 198                 .match          = xenbus_match,
 199                 .uevent         = xenbus_uevent_backend,
 200                 .probe          = xenbus_dev_probe,
 201                 .remove         = xenbus_dev_remove,
 202                 .shutdown       = xenbus_dev_shutdown,
 203                 .dev_attrs      = xenbus_backend_dev_attrs,
 204         },
 205 };
 206
 207 static void backend_changed(struct xenbus_watch *watch,
 208                             const char **vec, unsigned int len)
 209 {
 210         DPRINTK("");
 211
 212         xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_backend);
 213 }
 214
 215 static struct xenbus_watch be_watch = {
 216         .node = "backend",
 217         .callback = backend_changed,
 218 };
 219
 220 static int read_frontend_details(struct xenbus_device *xendev)
 221 {
 222         return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
 223 }
 224
 225 int xenbus_dev_is_online(struct xenbus_device *dev)
 226 {
 227         int rc, val;
 228
 229         rc = xenbus_scanf(XBT_NIL, dev->nodename, "online", "%d", &val);
 230         if (rc != 1)
 231                 val = 0; /* no online node present */
 232
 233         return val;
 234 }
 235 EXPORT_SYMBOL_GPL(xenbus_dev_is_online);
 236
 237 int __xenbus_register_backend(struct xenbus_driver *drv,
 238                               struct module *owner, const char *mod_name)
 239 {
 240         drv->read_otherend_details = read_frontend_details;
 241
 242         return xenbus_register_driver_common(drv, &xenbus_backend,
 243                                              owner, mod_name);
 244 }
 245 EXPORT_SYMBOL_GPL(__xenbus_register_backend);
 246
 247 static int backend_probe_and_watch(struct notifier_block *notifier,
 248                                    unsigned long event,
 249                                    void *data)
 250 {
 251         /* Enumerate devices in xenstore and watch for changes. */
 252         xenbus_probe_devices(&xenbus_backend);
 253         register_xenbus_watch(&be_watch);
 254
 255         return NOTIFY_DONE;
 256 }
 257
 258 static int __init xenbus_probe_backend_init(void)
 259 {
 260         static struct notifier_block xenstore_notifier = {
 261                 .notifier_call = backend_probe_and_watch
 262         };
 263         int err;
 264
 265         DPRINTK("");
 266
 267         /* Register ourselves with the kernel bus subsystem */
 268         err = bus_register(&xenbus_backend.bus);
 269         if (err)
 270                 return err;
 271
 272         register_xenstore_notifier(&xenstore_notifier);
 273
 274         return 0;
 275 }
 276 subsys_initcall(xenbus_probe_backend_init);