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_comms.h"
  57 #include "xenbus_probe.h"
  58
  59 /* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
  60 static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  61 {
  62         int domid, err;
  63         const char *devid, *type, *frontend;
  64         unsigned int typelen;
  65
  66         type = strchr(nodename, '/');
  67         if (!type)
  68                 return -EINVAL;
  69         type++;
  70         typelen = strcspn(type, "/");
  71         if (!typelen || type[typelen] != '/')
  72                 return -EINVAL;
  73
  74         devid = strrchr(nodename, '/') + 1;
  75
  76         err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
  77                             "frontend", NULL, &frontend,
  78                             NULL);
  79         if (err)
  80                 return err;
  81         if (strlen(frontend) == 0)
  82                 err = -ERANGE;
  83         if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
  84                 err = -ENOENT;
  85         kfree(frontend);
  86
  87         if (err)
  88                 return err;
  89
  90         if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
  91                      typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
  92                 return -ENOSPC;
  93         return 0;
  94 }
  95
  96 static int xenbus_uevent_backend(struct device *dev,
  97                                  struct kobj_uevent_env *env)
  98 {
  99         struct xenbus_device *xdev;
 100         struct xenbus_driver *drv;
 101         struct xen_bus_type *bus;
 102
 103         DPRINTK("");
 104
 105         if (dev == NULL)
 106                 return -ENODEV;
 107
 108         xdev = to_xenbus_device(dev);
 109         bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
 110
 111         if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
 112                 return -ENOMEM;
 113
 114         /* stuff we want to pass to /sbin/hotplug */
 115         if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
 116                 return -ENOMEM;
 117
 118         if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
 119                 return -ENOMEM;
 120
 121         if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
 122                 return -ENOMEM;
 123
 124         if (dev->driver) {
 125                 drv = to_xenbus_driver(dev->driver);
 126                 if (drv && drv->uevent)
 127                         return drv->uevent(xdev, env);
 128         }
 129
 130         return 0;
 131 }
 132
 133 /* backend/<typename>/<frontend-uuid>/<name> */
 134 static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
 135                                      const char *dir,
 136                                      const char *type,
 137                                      const char *name)
 138 {
 139         char *nodename;
 140         int err;
 141
 142         nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
 143         if (!nodename)
 144                 return -ENOMEM;
 145
 146         DPRINTK("%s\n", nodename);
 147
 148         err = xenbus_probe_node(bus, type, nodename);
 149         kfree(nodename);
 150         return err;
 151 }
 152
 153 /* backend/<typename>/<frontend-domid> */
 154 static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
 155                                 const char *domid)
 156 {
 157         char *nodename;
 158         int err = 0;
 159         char **dir;
 160         unsigned int i, dir_n = 0;
 161
 162         DPRINTK("");
 163
 164         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
 165         if (!nodename)
 166                 return -ENOMEM;
 167
 168         dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
 169         if (IS_ERR(dir)) {
 170                 kfree(nodename);
 171                 return PTR_ERR(dir);
 172         }
 173
 174         for (i = 0; i < dir_n; i++) {
 175                 err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
 176                 if (err)
 177                         break;
 178         }
 179         kfree(dir);
 180         kfree(nodename);
 181         return err;
 182 }
 183
 184 static void frontend_changed(struct xenbus_watch *watch,
 185                             const char **vec, unsigned int len)
 186 {
 187         xenbus_otherend_changed(watch, vec, len, 0);
 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_groups     = xenbus_dev_groups,
 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, struct module *owner,
 238                               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);