Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-2.6.git] / drivers / block / xen-blkback / xenbus.c
1 /*  Xenbus code for blkif backend
2     Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
3     Copyright (C) 2005 XenSource Ltd
4
5     This program is free software; you can redistribute it and/or modify
6     it under the terms of the GNU General Public License as published by
7     the Free Software Foundation; either version 2 of the License, or
8     (at your option) any later version.
9
10     This program is distributed in the hope that it will be useful,
11     but WITHOUT ANY WARRANTY; without even the implied warranty of
12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13     GNU General Public License for more details.
14
15 */
16
17 #include <stdarg.h>
18 #include <linux/module.h>
19 #include <linux/kthread.h>
20 #include <xen/events.h>
21 #include <xen/grant_table.h>
22 #include "common.h"
23
24 struct backend_info {
25         struct xenbus_device    *dev;
26         struct xen_blkif        *blkif;
27         struct xenbus_watch     backend_watch;
28         unsigned                major;
29         unsigned                minor;
30         char                    *mode;
31 };
32
33 static struct kmem_cache *xen_blkif_cachep;
34 static void connect(struct backend_info *);
35 static int connect_ring(struct backend_info *);
36 static void backend_changed(struct xenbus_watch *, const char **,
37                             unsigned int);
38
39 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
40 {
41         return be->dev;
42 }
43
44 static int blkback_name(struct xen_blkif *blkif, char *buf)
45 {
46         char *devpath, *devname;
47         struct xenbus_device *dev = blkif->be->dev;
48
49         devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
50         if (IS_ERR(devpath))
51                 return PTR_ERR(devpath);
52
53         devname = strstr(devpath, "/dev/");
54         if (devname != NULL)
55                 devname += strlen("/dev/");
56         else
57                 devname  = devpath;
58
59         snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
60         kfree(devpath);
61
62         return 0;
63 }
64
65 static void xen_update_blkif_status(struct xen_blkif *blkif)
66 {
67         int err;
68         char name[TASK_COMM_LEN];
69
70         /* Not ready to connect? */
71         if (!blkif->irq || !blkif->vbd.bdev)
72                 return;
73
74         /* Already connected? */
75         if (blkif->be->dev->state == XenbusStateConnected)
76                 return;
77
78         /* Attempt to connect: exit if we fail to. */
79         connect(blkif->be);
80         if (blkif->be->dev->state != XenbusStateConnected)
81                 return;
82
83         err = blkback_name(blkif, name);
84         if (err) {
85                 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
86                 return;
87         }
88
89         err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
90         if (err) {
91                 xenbus_dev_error(blkif->be->dev, err, "block flush");
92                 return;
93         }
94         invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
95
96         blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, name);
97         if (IS_ERR(blkif->xenblkd)) {
98                 err = PTR_ERR(blkif->xenblkd);
99                 blkif->xenblkd = NULL;
100                 xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
101         }
102 }
103
104 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
105 {
106         struct xen_blkif *blkif;
107
108         blkif = kmem_cache_alloc(xen_blkif_cachep, GFP_KERNEL);
109         if (!blkif)
110                 return ERR_PTR(-ENOMEM);
111
112         memset(blkif, 0, sizeof(*blkif));
113         blkif->domid = domid;
114         spin_lock_init(&blkif->blk_ring_lock);
115         atomic_set(&blkif->refcnt, 1);
116         init_waitqueue_head(&blkif->wq);
117         blkif->st_print = jiffies;
118         init_waitqueue_head(&blkif->waiting_to_free);
119
120         return blkif;
121 }
122
123 static int map_frontend_page(struct xen_blkif *blkif, unsigned long shared_page)
124 {
125         struct gnttab_map_grant_ref op;
126
127         gnttab_set_map_op(&op, (unsigned long)blkif->blk_ring_area->addr,
128                           GNTMAP_host_map, shared_page, blkif->domid);
129
130         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
131                 BUG();
132
133         if (op.status) {
134                 DPRINTK("Grant table operation failure !\n");
135                 return op.status;
136         }
137
138         blkif->shmem_ref = shared_page;
139         blkif->shmem_handle = op.handle;
140
141         return 0;
142 }
143
144 static void unmap_frontend_page(struct xen_blkif *blkif)
145 {
146         struct gnttab_unmap_grant_ref op;
147
148         gnttab_set_unmap_op(&op, (unsigned long)blkif->blk_ring_area->addr,
149                             GNTMAP_host_map, blkif->shmem_handle);
150
151         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
152                 BUG();
153 }
154
155 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
156                          unsigned int evtchn)
157 {
158         int err;
159
160         /* Already connected through? */
161         if (blkif->irq)
162                 return 0;
163
164         blkif->blk_ring_area = alloc_vm_area(PAGE_SIZE);
165         if (!blkif->blk_ring_area)
166                 return -ENOMEM;
167
168         err = map_frontend_page(blkif, shared_page);
169         if (err) {
170                 free_vm_area(blkif->blk_ring_area);
171                 return err;
172         }
173
174         switch (blkif->blk_protocol) {
175         case BLKIF_PROTOCOL_NATIVE:
176         {
177                 struct blkif_sring *sring;
178                 sring = (struct blkif_sring *)blkif->blk_ring_area->addr;
179                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
180                 break;
181         }
182         case BLKIF_PROTOCOL_X86_32:
183         {
184                 struct blkif_x86_32_sring *sring_x86_32;
185                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring_area->addr;
186                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
187                 break;
188         }
189         case BLKIF_PROTOCOL_X86_64:
190         {
191                 struct blkif_x86_64_sring *sring_x86_64;
192                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;
193                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
194                 break;
195         }
196         default:
197                 BUG();
198         }
199
200         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
201                                                     xen_blkif_be_int, 0,
202                                                     "blkif-backend", blkif);
203         if (err < 0) {
204                 unmap_frontend_page(blkif);
205                 free_vm_area(blkif->blk_ring_area);
206                 blkif->blk_rings.common.sring = NULL;
207                 return err;
208         }
209         blkif->irq = err;
210
211         return 0;
212 }
213
214 static void xen_blkif_disconnect(struct xen_blkif *blkif)
215 {
216         if (blkif->xenblkd) {
217                 kthread_stop(blkif->xenblkd);
218                 blkif->xenblkd = NULL;
219         }
220
221         atomic_dec(&blkif->refcnt);
222         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
223         atomic_inc(&blkif->refcnt);
224
225         if (blkif->irq) {
226                 unbind_from_irqhandler(blkif->irq, blkif);
227                 blkif->irq = 0;
228         }
229
230         if (blkif->blk_rings.common.sring) {
231                 unmap_frontend_page(blkif);
232                 free_vm_area(blkif->blk_ring_area);
233                 blkif->blk_rings.common.sring = NULL;
234         }
235 }
236
237 void xen_blkif_free(struct xen_blkif *blkif)
238 {
239         if (!atomic_dec_and_test(&blkif->refcnt))
240                 BUG();
241         kmem_cache_free(xen_blkif_cachep, blkif);
242 }
243
244 int __init xen_blkif_interface_init(void)
245 {
246         xen_blkif_cachep = kmem_cache_create("blkif_cache",
247                                              sizeof(struct xen_blkif),
248                                              0, 0, NULL);
249         if (!xen_blkif_cachep)
250                 return -ENOMEM;
251
252         return 0;
253 }
254
255 /*
256  *  sysfs interface for VBD I/O requests
257  */
258
259 #define VBD_SHOW(name, format, args...)                                 \
260         static ssize_t show_##name(struct device *_dev,                 \
261                                    struct device_attribute *attr,       \
262                                    char *buf)                           \
263         {                                                               \
264                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
265                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
266                                                                         \
267                 return sprintf(buf, format, ##args);                    \
268         }                                                               \
269         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
270
271 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
272 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
273 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
274 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
275 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
276 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
277
278 static struct attribute *xen_vbdstat_attrs[] = {
279         &dev_attr_oo_req.attr,
280         &dev_attr_rd_req.attr,
281         &dev_attr_wr_req.attr,
282         &dev_attr_f_req.attr,
283         &dev_attr_rd_sect.attr,
284         &dev_attr_wr_sect.attr,
285         NULL
286 };
287
288 static struct attribute_group xen_vbdstat_group = {
289         .name = "statistics",
290         .attrs = xen_vbdstat_attrs,
291 };
292
293 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
294 VBD_SHOW(mode, "%s\n", be->mode);
295
296 int xenvbd_sysfs_addif(struct xenbus_device *dev)
297 {
298         int error;
299
300         error = device_create_file(&dev->dev, &dev_attr_physical_device);
301         if (error)
302                 goto fail1;
303
304         error = device_create_file(&dev->dev, &dev_attr_mode);
305         if (error)
306                 goto fail2;
307
308         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
309         if (error)
310                 goto fail3;
311
312         return 0;
313
314 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
315 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
316 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
317         return error;
318 }
319
320 void xenvbd_sysfs_delif(struct xenbus_device *dev)
321 {
322         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
323         device_remove_file(&dev->dev, &dev_attr_mode);
324         device_remove_file(&dev->dev, &dev_attr_physical_device);
325 }
326
327
328 static void xen_vbd_free(struct xen_vbd *vbd)
329 {
330         if (vbd->bdev)
331                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
332         vbd->bdev = NULL;
333 }
334
335 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
336                           unsigned major, unsigned minor, int readonly,
337                           int cdrom)
338 {
339         struct xen_vbd *vbd;
340         struct block_device *bdev;
341         struct request_queue *q;
342
343         vbd = &blkif->vbd;
344         vbd->handle   = handle;
345         vbd->readonly = readonly;
346         vbd->type     = 0;
347
348         vbd->pdevice  = MKDEV(major, minor);
349
350         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
351                                  FMODE_READ : FMODE_WRITE, NULL);
352
353         if (IS_ERR(bdev)) {
354                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
355                         vbd->pdevice);
356                 return -ENOENT;
357         }
358
359         vbd->bdev = bdev;
360         if (vbd->bdev->bd_disk == NULL) {
361                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
362                         vbd->pdevice);
363                 xen_vbd_free(vbd);
364                 return -ENOENT;
365         }
366         vbd->size = vbd_sz(vbd);
367
368         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
369                 vbd->type |= VDISK_CDROM;
370         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
371                 vbd->type |= VDISK_REMOVABLE;
372
373         q = bdev_get_queue(bdev);
374         if (q && q->flush_flags)
375                 vbd->flush_support = true;
376
377         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
378                 handle, blkif->domid);
379         return 0;
380 }
381 static int xen_blkbk_remove(struct xenbus_device *dev)
382 {
383         struct backend_info *be = dev_get_drvdata(&dev->dev);
384
385         DPRINTK("");
386
387         if (be->major || be->minor)
388                 xenvbd_sysfs_delif(dev);
389
390         if (be->backend_watch.node) {
391                 unregister_xenbus_watch(&be->backend_watch);
392                 kfree(be->backend_watch.node);
393                 be->backend_watch.node = NULL;
394         }
395
396         if (be->blkif) {
397                 xen_blkif_disconnect(be->blkif);
398                 xen_vbd_free(&be->blkif->vbd);
399                 xen_blkif_free(be->blkif);
400                 be->blkif = NULL;
401         }
402
403         kfree(be);
404         dev_set_drvdata(&dev->dev, NULL);
405         return 0;
406 }
407
408 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
409                               struct backend_info *be, int state)
410 {
411         struct xenbus_device *dev = be->dev;
412         int err;
413
414         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
415                             "%d", state);
416         if (err)
417                 xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
418
419         return err;
420 }
421
422 /*
423  * Entry point to this code when a new device is created.  Allocate the basic
424  * structures, and watch the store waiting for the hotplug scripts to tell us
425  * the device's physical major and minor numbers.  Switch to InitWait.
426  */
427 static int xen_blkbk_probe(struct xenbus_device *dev,
428                            const struct xenbus_device_id *id)
429 {
430         int err;
431         struct backend_info *be = kzalloc(sizeof(struct backend_info),
432                                           GFP_KERNEL);
433         if (!be) {
434                 xenbus_dev_fatal(dev, -ENOMEM,
435                                  "allocating backend structure");
436                 return -ENOMEM;
437         }
438         be->dev = dev;
439         dev_set_drvdata(&dev->dev, be);
440
441         be->blkif = xen_blkif_alloc(dev->otherend_id);
442         if (IS_ERR(be->blkif)) {
443                 err = PTR_ERR(be->blkif);
444                 be->blkif = NULL;
445                 xenbus_dev_fatal(dev, err, "creating block interface");
446                 goto fail;
447         }
448
449         /* setup back pointer */
450         be->blkif->be = be;
451
452         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
453                                    "%s/%s", dev->nodename, "physical-device");
454         if (err)
455                 goto fail;
456
457         err = xenbus_switch_state(dev, XenbusStateInitWait);
458         if (err)
459                 goto fail;
460
461         return 0;
462
463 fail:
464         DPRINTK("failed");
465         xen_blkbk_remove(dev);
466         return err;
467 }
468
469
470 /*
471  * Callback received when the hotplug scripts have placed the physical-device
472  * node.  Read it and the mode node, and create a vbd.  If the frontend is
473  * ready, connect.
474  */
475 static void backend_changed(struct xenbus_watch *watch,
476                             const char **vec, unsigned int len)
477 {
478         int err;
479         unsigned major;
480         unsigned minor;
481         struct backend_info *be
482                 = container_of(watch, struct backend_info, backend_watch);
483         struct xenbus_device *dev = be->dev;
484         int cdrom = 0;
485         char *device_type;
486
487         DPRINTK("");
488
489         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
490                            &major, &minor);
491         if (XENBUS_EXIST_ERR(err)) {
492                 /*
493                  * Since this watch will fire once immediately after it is
494                  * registered, we expect this.  Ignore it, and wait for the
495                  * hotplug scripts.
496                  */
497                 return;
498         }
499         if (err != 2) {
500                 xenbus_dev_fatal(dev, err, "reading physical-device");
501                 return;
502         }
503
504         if ((be->major || be->minor) &&
505             ((be->major != major) || (be->minor != minor))) {
506                 pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
507                         be->major, be->minor, major, minor);
508                 return;
509         }
510
511         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
512         if (IS_ERR(be->mode)) {
513                 err = PTR_ERR(be->mode);
514                 be->mode = NULL;
515                 xenbus_dev_fatal(dev, err, "reading mode");
516                 return;
517         }
518
519         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
520         if (!IS_ERR(device_type)) {
521                 cdrom = strcmp(device_type, "cdrom") == 0;
522                 kfree(device_type);
523         }
524
525         if (be->major == 0 && be->minor == 0) {
526                 /* Front end dir is a number, which is used as the handle. */
527
528                 char *p = strrchr(dev->otherend, '/') + 1;
529                 long handle;
530                 err = strict_strtoul(p, 0, &handle);
531                 if (err)
532                         return;
533
534                 be->major = major;
535                 be->minor = minor;
536
537                 err = xen_vbd_create(be->blkif, handle, major, minor,
538                                  (NULL == strchr(be->mode, 'w')), cdrom);
539                 if (err) {
540                         be->major = 0;
541                         be->minor = 0;
542                         xenbus_dev_fatal(dev, err, "creating vbd structure");
543                         return;
544                 }
545
546                 err = xenvbd_sysfs_addif(dev);
547                 if (err) {
548                         xen_vbd_free(&be->blkif->vbd);
549                         be->major = 0;
550                         be->minor = 0;
551                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
552                         return;
553                 }
554
555                 /* We're potentially connected now */
556                 xen_update_blkif_status(be->blkif);
557         }
558 }
559
560
561 /*
562  * Callback received when the frontend's state changes.
563  */
564 static void frontend_changed(struct xenbus_device *dev,
565                              enum xenbus_state frontend_state)
566 {
567         struct backend_info *be = dev_get_drvdata(&dev->dev);
568         int err;
569
570         DPRINTK("%s", xenbus_strstate(frontend_state));
571
572         switch (frontend_state) {
573         case XenbusStateInitialising:
574                 if (dev->state == XenbusStateClosed) {
575                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
576                                 dev->nodename);
577                         xenbus_switch_state(dev, XenbusStateInitWait);
578                 }
579                 break;
580
581         case XenbusStateInitialised:
582         case XenbusStateConnected:
583                 /*
584                  * Ensure we connect even when two watches fire in
585                  * close successsion and we miss the intermediate value
586                  * of frontend_state.
587                  */
588                 if (dev->state == XenbusStateConnected)
589                         break;
590
591                 /*
592                  * Enforce precondition before potential leak point.
593                  * blkif_disconnect() is idempotent.
594                  */
595                 xen_blkif_disconnect(be->blkif);
596
597                 err = connect_ring(be);
598                 if (err)
599                         break;
600                 xen_update_blkif_status(be->blkif);
601                 break;
602
603         case XenbusStateClosing:
604                 xen_blkif_disconnect(be->blkif);
605                 xenbus_switch_state(dev, XenbusStateClosing);
606                 break;
607
608         case XenbusStateClosed:
609                 xenbus_switch_state(dev, XenbusStateClosed);
610                 if (xenbus_dev_is_online(dev))
611                         break;
612                 /* fall through if not online */
613         case XenbusStateUnknown:
614                 /* implies blkif_disconnect() via blkback_remove() */
615                 device_unregister(&dev->dev);
616                 break;
617
618         default:
619                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
620                                  frontend_state);
621                 break;
622         }
623 }
624
625
626 /* ** Connection ** */
627
628
629 /*
630  * Write the physical details regarding the block device to the store, and
631  * switch to Connected state.
632  */
633 static void connect(struct backend_info *be)
634 {
635         struct xenbus_transaction xbt;
636         int err;
637         struct xenbus_device *dev = be->dev;
638
639         DPRINTK("%s", dev->otherend);
640
641         /* Supply the information about the device the frontend needs */
642 again:
643         err = xenbus_transaction_start(&xbt);
644         if (err) {
645                 xenbus_dev_fatal(dev, err, "starting transaction");
646                 return;
647         }
648
649         err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
650         if (err)
651                 goto abort;
652
653         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
654                             (unsigned long long)vbd_sz(&be->blkif->vbd));
655         if (err) {
656                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
657                                  dev->nodename);
658                 goto abort;
659         }
660
661         /* FIXME: use a typename instead */
662         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
663                             be->blkif->vbd.type |
664                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
665         if (err) {
666                 xenbus_dev_fatal(dev, err, "writing %s/info",
667                                  dev->nodename);
668                 goto abort;
669         }
670         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
671                             (unsigned long)
672                             bdev_logical_block_size(be->blkif->vbd.bdev));
673         if (err) {
674                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
675                                  dev->nodename);
676                 goto abort;
677         }
678
679         err = xenbus_transaction_end(xbt, 0);
680         if (err == -EAGAIN)
681                 goto again;
682         if (err)
683                 xenbus_dev_fatal(dev, err, "ending transaction");
684
685         err = xenbus_switch_state(dev, XenbusStateConnected);
686         if (err)
687                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
688                                  dev->nodename);
689
690         return;
691  abort:
692         xenbus_transaction_end(xbt, 1);
693 }
694
695
696 static int connect_ring(struct backend_info *be)
697 {
698         struct xenbus_device *dev = be->dev;
699         unsigned long ring_ref;
700         unsigned int evtchn;
701         char protocol[64] = "";
702         int err;
703
704         DPRINTK("%s", dev->otherend);
705
706         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
707                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
708         if (err) {
709                 xenbus_dev_fatal(dev, err,
710                                  "reading %s/ring-ref and event-channel",
711                                  dev->otherend);
712                 return err;
713         }
714
715         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
716         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
717                             "%63s", protocol, NULL);
718         if (err)
719                 strcpy(protocol, "unspecified, assuming native");
720         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
721                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
722         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
723                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
724         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
725                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
726         else {
727                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
728                 return -1;
729         }
730         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s)\n",
731                 ring_ref, evtchn, be->blkif->blk_protocol, protocol);
732
733         /* Map the shared frame, irq etc. */
734         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
735         if (err) {
736                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
737                                  ring_ref, evtchn);
738                 return err;
739         }
740
741         return 0;
742 }
743
744
745 /* ** Driver Registration ** */
746
747
748 static const struct xenbus_device_id xen_blkbk_ids[] = {
749         { "vbd" },
750         { "" }
751 };
752
753
754 static struct xenbus_driver xen_blkbk = {
755         .name = "vbd",
756         .owner = THIS_MODULE,
757         .ids = xen_blkbk_ids,
758         .probe = xen_blkbk_probe,
759         .remove = xen_blkbk_remove,
760         .otherend_changed = frontend_changed
761 };
762
763
764 int xen_blkif_xenbus_init(void)
765 {
766         return xenbus_register_backend(&xen_blkbk);
767 }