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