drivers/xen/xenbus/xenbus_dev

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This source file includes following definitions.
xenbus_file_read
queue_reply
queue_cleanup
free_watch_adapter
alloc_watch_adapter
watch_fired
xenbus_worker
xenbus_file_free
xenbus_get_transaction
xenbus_dev_queue_reply
xenbus_command_reply
xenbus_write_transaction
xenbus_write_watch
xenbus_file_write
xenbus_file_open
xenbus_file_release
xenbus_file_poll
xenbus_init
   1 /*
   2  * Driver giving user-space access to the kernel's xenbus connection
   3  * to xenstore.
   4  *
   5  * Copyright (c) 2005, Christian Limpach
   6  * Copyright (c) 2005, Rusty Russell, IBM Corporation
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation; or, when distributed
  11  * separately from the Linux kernel or incorporated into other
  12  * software packages, subject to the following license:
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining a copy
  15  * of this source file (the "Software"), to deal in the Software without
  16  * restriction, including without limitation the rights to use, copy, modify,
  17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  18  * and to permit persons to whom the Software is furnished to do so, subject to
  19  * the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  30  * IN THE SOFTWARE.
  31  *
  32  * Changes:
  33  * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
  34  *                              and /proc/xen compatibility mount point.
  35  *                              Turned xenfs into a loadable module.
  36  */
  37 
  38 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  39 
  40 #include <linux/kernel.h>
  41 #include <linux/errno.h>
  42 #include <linux/uio.h>
  43 #include <linux/notifier.h>
  44 #include <linux/wait.h>
  45 #include <linux/fs.h>
  46 #include <linux/poll.h>
  47 #include <linux/mutex.h>
  48 #include <linux/sched.h>
  49 #include <linux/spinlock.h>
  50 #include <linux/mount.h>
  51 #include <linux/pagemap.h>
  52 #include <linux/uaccess.h>
  53 #include <linux/init.h>
  54 #include <linux/namei.h>
  55 #include <linux/string.h>
  56 #include <linux/slab.h>
  57 #include <linux/miscdevice.h>
  58 #include <linux/workqueue.h>
  59 
  60 #include <xen/xenbus.h>
  61 #include <xen/xen.h>
  62 #include <asm/xen/hypervisor.h>
  63 
  64 #include "xenbus.h"
  65 
  66 unsigned int xb_dev_generation_id;
  67 
  68 /*
  69  * An element of a list of outstanding transactions, for which we're
  70  * still waiting a reply.
  71  */
  72 struct xenbus_transaction_holder {
  73         struct list_head list;
  74         struct xenbus_transaction handle;
  75         unsigned int generation_id;
  76 };
  77 
  78 /*
  79  * A buffer of data on the queue.
  80  */
  81 struct read_buffer {
  82         struct list_head list;
  83         unsigned int cons;
  84         unsigned int len;
  85         char msg[];
  86 };
  87 
  88 struct xenbus_file_priv {
  89         /*
  90          * msgbuffer_mutex is held while partial requests are built up
  91          * and complete requests are acted on.  It therefore protects
  92          * the "transactions" and "watches" lists, and the partial
  93          * request length and buffer.
  94          *
  95          * reply_mutex protects the reply being built up to return to
  96          * usermode.  It nests inside msgbuffer_mutex but may be held
  97          * alone during a watch callback.
  98          */
  99         struct mutex msgbuffer_mutex;
 100 
 101         /* In-progress transactions */
 102         struct list_head transactions;
 103 
 104         /* Active watches. */
 105         struct list_head watches;
 106 
 107         /* Partial request. */
 108         unsigned int len;
 109         union {
 110                 struct xsd_sockmsg msg;
 111                 char buffer[XENSTORE_PAYLOAD_MAX];
 112         } u;
 113 
 114         /* Response queue. */
 115         struct mutex reply_mutex;
 116         struct list_head read_buffers;
 117         wait_queue_head_t read_waitq;
 118 
 119         struct kref kref;
 120 
 121         struct work_struct wq;
 122 };
 123 
 124 /* Read out any raw xenbus messages queued up. */
 125 static ssize_t xenbus_file_read(struct file *filp,
 126                                char __user *ubuf,
 127                                size_t len, loff_t *ppos)
 128 {
 129         struct xenbus_file_priv *u = filp->private_data;
 130         struct read_buffer *rb;
 131         unsigned i;
 132         int ret;
 133 
 134         mutex_lock(&u->reply_mutex);
 135 again:
 136         while (list_empty(&u->read_buffers)) {
 137                 mutex_unlock(&u->reply_mutex);
 138                 if (filp->f_flags & O_NONBLOCK)
 139                         return -EAGAIN;
 140 
 141                 ret = wait_event_interruptible(u->read_waitq,
 142                                                !list_empty(&u->read_buffers));
 143                 if (ret)
 144                         return ret;
 145                 mutex_lock(&u->reply_mutex);
 146         }
 147 
 148         rb = list_entry(u->read_buffers.next, struct read_buffer, list);
 149         i = 0;
 150         while (i < len) {
 151                 unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
 152 
 153                 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
 154 
 155                 i += sz - ret;
 156                 rb->cons += sz - ret;
 157 
 158                 if (ret != 0) {
 159                         if (i == 0)
 160                                 i = -EFAULT;
 161                         goto out;
 162                 }
 163 
 164                 /* Clear out buffer if it has been consumed */
 165                 if (rb->cons == rb->len) {
 166                         list_del(&rb->list);
 167                         kfree(rb);
 168                         if (list_empty(&u->read_buffers))
 169                                 break;
 170                         rb = list_entry(u->read_buffers.next,
 171                                         struct read_buffer, list);
 172                 }
 173         }
 174         if (i == 0)
 175                 goto again;
 176 
 177 out:
 178         mutex_unlock(&u->reply_mutex);
 179         return i;
 180 }
 181 
 182 /*
 183  * Add a buffer to the queue.  Caller must hold the appropriate lock
 184  * if the queue is not local.  (Commonly the caller will build up
 185  * multiple queued buffers on a temporary local list, and then add it
 186  * to the appropriate list under lock once all the buffers have een
 187  * successfully allocated.)
 188  */
 189 static int queue_reply(struct list_head *queue, const void *data, size_t len)
 190 {
 191         struct read_buffer *rb;
 192 
 193         if (len == 0)
 194                 return 0;
 195         if (len > XENSTORE_PAYLOAD_MAX)
 196                 return -EINVAL;
 197 
 198         rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
 199         if (rb == NULL)
 200                 return -ENOMEM;
 201 
 202         rb->cons = 0;
 203         rb->len = len;
 204 
 205         memcpy(rb->msg, data, len);
 206 
 207         list_add_tail(&rb->list, queue);
 208         return 0;
 209 }
 210 
 211 /*
 212  * Free all the read_buffer s on a list.
 213  * Caller must have sole reference to list.
 214  */
 215 static void queue_cleanup(struct list_head *list)
 216 {
 217         struct read_buffer *rb;
 218 
 219         while (!list_empty(list)) {
 220                 rb = list_entry(list->next, struct read_buffer, list);
 221                 list_del(list->next);
 222                 kfree(rb);
 223         }
 224 }
 225 
 226 struct watch_adapter {
 227         struct list_head list;
 228         struct xenbus_watch watch;
 229         struct xenbus_file_priv *dev_data;
 230         char *token;
 231 };
 232 
 233 static void free_watch_adapter(struct watch_adapter *watch)
 234 {
 235         kfree(watch->watch.node);
 236         kfree(watch->token);
 237         kfree(watch);
 238 }
 239 
 240 static struct watch_adapter *alloc_watch_adapter(const char *path,
 241                                                  const char *token)
 242 {
 243         struct watch_adapter *watch;
 244 
 245         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 246         if (watch == NULL)
 247                 goto out_fail;
 248 
 249         watch->watch.node = kstrdup(path, GFP_KERNEL);
 250         if (watch->watch.node == NULL)
 251                 goto out_free;
 252 
 253         watch->token = kstrdup(token, GFP_KERNEL);
 254         if (watch->token == NULL)
 255                 goto out_free;
 256 
 257         return watch;
 258 
 259 out_free:
 260         free_watch_adapter(watch);
 261 
 262 out_fail:
 263         return NULL;
 264 }
 265 
 266 static void watch_fired(struct xenbus_watch *watch,
 267                         const char *path,
 268                         const char *token)
 269 {
 270         struct watch_adapter *adap;
 271         struct xsd_sockmsg hdr;
 272         const char *token_caller;
 273         int path_len, tok_len, body_len;
 274         int ret;
 275         LIST_HEAD(staging_q);
 276 
 277         adap = container_of(watch, struct watch_adapter, watch);
 278 
 279         token_caller = adap->token;
 280 
 281         path_len = strlen(path) + 1;
 282         tok_len = strlen(token_caller) + 1;
 283         body_len = path_len + tok_len;
 284 
 285         hdr.type = XS_WATCH_EVENT;
 286         hdr.len = body_len;
 287 
 288         mutex_lock(&adap->dev_data->reply_mutex);
 289 
 290         ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
 291         if (!ret)
 292                 ret = queue_reply(&staging_q, path, path_len);
 293         if (!ret)
 294                 ret = queue_reply(&staging_q, token_caller, tok_len);
 295 
 296         if (!ret) {
 297                 /* success: pass reply list onto watcher */
 298                 list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
 299                 wake_up(&adap->dev_data->read_waitq);
 300         } else
 301                 queue_cleanup(&staging_q);
 302 
 303         mutex_unlock(&adap->dev_data->reply_mutex);
 304 }
 305 
 306 static void xenbus_worker(struct work_struct *wq)
 307 {
 308         struct xenbus_file_priv *u;
 309         struct xenbus_transaction_holder *trans, *tmp;
 310         struct watch_adapter *watch, *tmp_watch;
 311         struct read_buffer *rb, *tmp_rb;
 312 
 313         u = container_of(wq, struct xenbus_file_priv, wq);
 314 
 315         /*
 316          * No need for locking here because there are no other users,
 317          * by definition.
 318          */
 319 
 320         list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
 321                 xenbus_transaction_end(trans->handle, 1);
 322                 list_del(&trans->list);
 323                 kfree(trans);
 324         }
 325 
 326         list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
 327                 unregister_xenbus_watch(&watch->watch);
 328                 list_del(&watch->list);
 329                 free_watch_adapter(watch);
 330         }
 331 
 332         list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
 333                 list_del(&rb->list);
 334                 kfree(rb);
 335         }
 336         kfree(u);
 337 }
 338 
 339 static void xenbus_file_free(struct kref *kref)
 340 {
 341         struct xenbus_file_priv *u;
 342 
 343         /*
 344          * We might be called in xenbus_thread().
 345          * Use workqueue to avoid deadlock.
 346          */
 347         u = container_of(kref, struct xenbus_file_priv, kref);
 348         schedule_work(&u->wq);
 349 }
 350 
 351 static struct xenbus_transaction_holder *xenbus_get_transaction(
 352         struct xenbus_file_priv *u, uint32_t tx_id)
 353 {
 354         struct xenbus_transaction_holder *trans;
 355 
 356         list_for_each_entry(trans, &u->transactions, list)
 357                 if (trans->handle.id == tx_id)
 358                         return trans;
 359 
 360         return NULL;
 361 }
 362 
 363 void xenbus_dev_queue_reply(struct xb_req_data *req)
 364 {
 365         struct xenbus_file_priv *u = req->par;
 366         struct xenbus_transaction_holder *trans = NULL;
 367         int rc;
 368         LIST_HEAD(staging_q);
 369 
 370         xs_request_exit(req);
 371 
 372         mutex_lock(&u->msgbuffer_mutex);
 373 
 374         if (req->type == XS_TRANSACTION_START) {
 375                 trans = xenbus_get_transaction(u, 0);
 376                 if (WARN_ON(!trans))
 377                         goto out;
 378                 if (req->msg.type == XS_ERROR) {
 379                         list_del(&trans->list);
 380                         kfree(trans);
 381                 } else {
 382                         rc = kstrtou32(req->body, 10, &trans->handle.id);
 383                         if (WARN_ON(rc))
 384                                 goto out;
 385                 }
 386         } else if (req->type == XS_TRANSACTION_END) {
 387                 trans = xenbus_get_transaction(u, req->msg.tx_id);
 388                 if (WARN_ON(!trans))
 389                         goto out;
 390                 list_del(&trans->list);
 391                 kfree(trans);
 392         }
 393 
 394         mutex_unlock(&u->msgbuffer_mutex);
 395 
 396         mutex_lock(&u->reply_mutex);
 397         rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg));
 398         if (!rc)
 399                 rc = queue_reply(&staging_q, req->body, req->msg.len);
 400         if (!rc) {
 401                 list_splice_tail(&staging_q, &u->read_buffers);
 402                 wake_up(&u->read_waitq);
 403         } else {
 404                 queue_cleanup(&staging_q);
 405         }
 406         mutex_unlock(&u->reply_mutex);
 407 
 408         kfree(req->body);
 409         kfree(req);
 410 
 411         kref_put(&u->kref, xenbus_file_free);
 412 
 413         return;
 414 
 415  out:
 416         mutex_unlock(&u->msgbuffer_mutex);
 417 }
 418 
 419 static int xenbus_command_reply(struct xenbus_file_priv *u,
 420                                 unsigned int msg_type, const char *reply)
 421 {
 422         struct {
 423                 struct xsd_sockmsg hdr;
 424                 char body[16];
 425         } msg;
 426         int rc;
 427 
 428         msg.hdr = u->u.msg;
 429         msg.hdr.type = msg_type;
 430         msg.hdr.len = strlen(reply) + 1;
 431         if (msg.hdr.len > sizeof(msg.body))
 432                 return -E2BIG;
 433         memcpy(&msg.body, reply, msg.hdr.len);
 434 
 435         mutex_lock(&u->reply_mutex);
 436         rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
 437         wake_up(&u->read_waitq);
 438         mutex_unlock(&u->reply_mutex);
 439 
 440         if (!rc)
 441                 kref_put(&u->kref, xenbus_file_free);
 442 
 443         return rc;
 444 }
 445 
 446 static int xenbus_write_transaction(unsigned msg_type,
 447                                     struct xenbus_file_priv *u)
 448 {
 449         int rc;
 450         struct xenbus_transaction_holder *trans = NULL;
 451         struct {
 452                 struct xsd_sockmsg hdr;
 453                 char body[];
 454         } *msg = (void *)u->u.buffer;
 455 
 456         if (msg_type == XS_TRANSACTION_START) {
 457                 trans = kzalloc(sizeof(*trans), GFP_KERNEL);
 458                 if (!trans) {
 459                         rc = -ENOMEM;
 460                         goto out;
 461                 }
 462                 trans->generation_id = xb_dev_generation_id;
 463                 list_add(&trans->list, &u->transactions);
 464         } else if (msg->hdr.tx_id != 0 &&
 465                    !xenbus_get_transaction(u, msg->hdr.tx_id))
 466                 return xenbus_command_reply(u, XS_ERROR, "ENOENT");
 467         else if (msg_type == XS_TRANSACTION_END &&
 468                  !(msg->hdr.len == 2 &&
 469                    (!strcmp(msg->body, "T") || !strcmp(msg->body, "F"))))
 470                 return xenbus_command_reply(u, XS_ERROR, "EINVAL");
 471         else if (msg_type == XS_TRANSACTION_END) {
 472                 trans = xenbus_get_transaction(u, msg->hdr.tx_id);
 473                 if (trans && trans->generation_id != xb_dev_generation_id) {
 474                         list_del(&trans->list);
 475                         kfree(trans);
 476                         if (!strcmp(msg->body, "T"))
 477                                 return xenbus_command_reply(u, XS_ERROR,
 478                                                             "EAGAIN");
 479                         else
 480                                 return xenbus_command_reply(u,
 481                                                             XS_TRANSACTION_END,
 482                                                             "OK");
 483                 }
 484         }
 485 
 486         rc = xenbus_dev_request_and_reply(&msg->hdr, u);
 487         if (rc && trans) {
 488                 list_del(&trans->list);
 489                 kfree(trans);
 490         }
 491 
 492 out:
 493         return rc;
 494 }
 495 
 496 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
 497 {
 498         struct watch_adapter *watch;
 499         char *path, *token;
 500         int err, rc;
 501 
 502         path = u->u.buffer + sizeof(u->u.msg);
 503         token = memchr(path, 0, u->u.msg.len);
 504         if (token == NULL) {
 505                 rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
 506                 goto out;
 507         }
 508         token++;
 509         if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
 510                 rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
 511                 goto out;
 512         }
 513 
 514         if (msg_type == XS_WATCH) {
 515                 watch = alloc_watch_adapter(path, token);
 516                 if (watch == NULL) {
 517                         rc = -ENOMEM;
 518                         goto out;
 519                 }
 520 
 521                 watch->watch.callback = watch_fired;
 522                 watch->dev_data = u;
 523 
 524                 err = register_xenbus_watch(&watch->watch);
 525                 if (err) {
 526                         free_watch_adapter(watch);
 527                         rc = err;
 528                         goto out;
 529                 }
 530                 list_add(&watch->list, &u->watches);
 531         } else {
 532                 list_for_each_entry(watch, &u->watches, list) {
 533                         if (!strcmp(watch->token, token) &&
 534                             !strcmp(watch->watch.node, path)) {
 535                                 unregister_xenbus_watch(&watch->watch);
 536                                 list_del(&watch->list);
 537                                 free_watch_adapter(watch);
 538                                 break;
 539                         }
 540                 }
 541         }
 542 
 543         /* Success.  Synthesize a reply to say all is OK. */
 544         rc = xenbus_command_reply(u, msg_type, "OK");
 545 
 546 out:
 547         return rc;
 548 }
 549 
 550 static ssize_t xenbus_file_write(struct file *filp,
 551                                 const char __user *ubuf,
 552                                 size_t len, loff_t *ppos)
 553 {
 554         struct xenbus_file_priv *u = filp->private_data;
 555         uint32_t msg_type;
 556         int rc = len;
 557         int ret;
 558 
 559         /*
 560          * We're expecting usermode to be writing properly formed
 561          * xenbus messages.  If they write an incomplete message we
 562          * buffer it up.  Once it is complete, we act on it.
 563          */
 564 
 565         /*
 566          * Make sure concurrent writers can't stomp all over each
 567          * other's messages and make a mess of our partial message
 568          * buffer.  We don't make any attemppt to stop multiple
 569          * writers from making a mess of each other's incomplete
 570          * messages; we're just trying to guarantee our own internal
 571          * consistency and make sure that single writes are handled
 572          * atomically.
 573          */
 574         mutex_lock(&u->msgbuffer_mutex);
 575 
 576         /* Get this out of the way early to avoid confusion */
 577         if (len == 0)
 578                 goto out;
 579 
 580         /* Can't write a xenbus message larger we can buffer */
 581         if (len > sizeof(u->u.buffer) - u->len) {
 582                 /* On error, dump existing buffer */
 583                 u->len = 0;
 584                 rc = -EINVAL;
 585                 goto out;
 586         }
 587 
 588         ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
 589 
 590         if (ret != 0) {
 591                 rc = -EFAULT;
 592                 goto out;
 593         }
 594 
 595         /* Deal with a partial copy. */
 596         len -= ret;
 597         rc = len;
 598 
 599         u->len += len;
 600 
 601         /* Return if we haven't got a full message yet */
 602         if (u->len < sizeof(u->u.msg))
 603                 goto out;       /* not even the header yet */
 604 
 605         /* If we're expecting a message that's larger than we can
 606            possibly send, dump what we have and return an error. */
 607         if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
 608                 rc = -E2BIG;
 609                 u->len = 0;
 610                 goto out;
 611         }
 612 
 613         if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
 614                 goto out;       /* incomplete data portion */
 615 
 616         /*
 617          * OK, now we have a complete message.  Do something with it.
 618          */
 619 
 620         kref_get(&u->kref);
 621 
 622         msg_type = u->u.msg.type;
 623 
 624         switch (msg_type) {
 625         case XS_WATCH:
 626         case XS_UNWATCH:
 627                 /* (Un)Ask for some path to be watched for changes */
 628                 ret = xenbus_write_watch(msg_type, u);
 629                 break;
 630 
 631         default:
 632                 /* Send out a transaction */
 633                 ret = xenbus_write_transaction(msg_type, u);
 634                 break;
 635         }
 636         if (ret != 0) {
 637                 rc = ret;
 638                 kref_put(&u->kref, xenbus_file_free);
 639         }
 640 
 641         /* Buffered message consumed */
 642         u->len = 0;
 643 
 644  out:
 645         mutex_unlock(&u->msgbuffer_mutex);
 646         return rc;
 647 }
 648 
 649 static int xenbus_file_open(struct inode *inode, struct file *filp)
 650 {
 651         struct xenbus_file_priv *u;
 652 
 653         if (xen_store_evtchn == 0)
 654                 return -ENOENT;
 655 
 656         stream_open(inode, filp);
 657 
 658         u = kzalloc(sizeof(*u), GFP_KERNEL);
 659         if (u == NULL)
 660                 return -ENOMEM;
 661 
 662         kref_init(&u->kref);
 663 
 664         INIT_LIST_HEAD(&u->transactions);
 665         INIT_LIST_HEAD(&u->watches);
 666         INIT_LIST_HEAD(&u->read_buffers);
 667         init_waitqueue_head(&u->read_waitq);
 668         INIT_WORK(&u->wq, xenbus_worker);
 669 
 670         mutex_init(&u->reply_mutex);
 671         mutex_init(&u->msgbuffer_mutex);
 672 
 673         filp->private_data = u;
 674 
 675         return 0;
 676 }
 677 
 678 static int xenbus_file_release(struct inode *inode, struct file *filp)
 679 {
 680         struct xenbus_file_priv *u = filp->private_data;
 681 
 682         kref_put(&u->kref, xenbus_file_free);
 683 
 684         return 0;
 685 }
 686 
 687 static __poll_t xenbus_file_poll(struct file *file, poll_table *wait)
 688 {
 689         struct xenbus_file_priv *u = file->private_data;
 690 
 691         poll_wait(file, &u->read_waitq, wait);
 692         if (!list_empty(&u->read_buffers))
 693                 return EPOLLIN | EPOLLRDNORM;
 694         return 0;
 695 }
 696 
 697 const struct file_operations xen_xenbus_fops = {
 698         .read = xenbus_file_read,
 699         .write = xenbus_file_write,
 700         .open = xenbus_file_open,
 701         .release = xenbus_file_release,
 702         .poll = xenbus_file_poll,
 703         .llseek = no_llseek,
 704 };
 705 EXPORT_SYMBOL_GPL(xen_xenbus_fops);
 706 
 707 static struct miscdevice xenbus_dev = {
 708         .minor = MISC_DYNAMIC_MINOR,
 709         .name = "xen/xenbus",
 710         .fops = &xen_xenbus_fops,
 711 };
 712 
 713 static int __init xenbus_init(void)
 714 {
 715         int err;
 716 
 717         if (!xen_domain())
 718                 return -ENODEV;
 719 
 720         err = misc_register(&xenbus_dev);
 721         if (err)
 722                 pr_err("Could not register xenbus frontend device\n");
 723         return err;
 724 }
 725 device_initcall(xenbus_init);
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/xen/xenbus/xenbus_dev_frontend.c

DEFINITIONS
