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4bac07c9 JF |
1 | /****************************************************************************** |
2 | * Client-facing interface for the Xenbus driver. In other words, the | |
3 | * interface between the Xenbus and the device-specific code, be it the | |
4 | * frontend or the backend of that driver. | |
5 | * | |
6 | * Copyright (C) 2005 XenSource Ltd | |
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 | ||
33 | #include <linux/types.h> | |
34 | #include <linux/vmalloc.h> | |
35 | #include <asm/xen/hypervisor.h> | |
36 | #include <xen/interface/xen.h> | |
37 | #include <xen/interface/event_channel.h> | |
38 | #include <xen/events.h> | |
39 | #include <xen/grant_table.h> | |
40 | #include <xen/xenbus.h> | |
41 | ||
42 | const char *xenbus_strstate(enum xenbus_state state) | |
43 | { | |
44 | static const char *const name[] = { | |
45 | [ XenbusStateUnknown ] = "Unknown", | |
46 | [ XenbusStateInitialising ] = "Initialising", | |
47 | [ XenbusStateInitWait ] = "InitWait", | |
48 | [ XenbusStateInitialised ] = "Initialised", | |
49 | [ XenbusStateConnected ] = "Connected", | |
50 | [ XenbusStateClosing ] = "Closing", | |
51 | [ XenbusStateClosed ] = "Closed", | |
52 | }; | |
53 | return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID"; | |
54 | } | |
55 | EXPORT_SYMBOL_GPL(xenbus_strstate); | |
56 | ||
57 | /** | |
58 | * xenbus_watch_path - register a watch | |
59 | * @dev: xenbus device | |
60 | * @path: path to watch | |
61 | * @watch: watch to register | |
62 | * @callback: callback to register | |
63 | * | |
64 | * Register a @watch on the given path, using the given xenbus_watch structure | |
65 | * for storage, and the given @callback function as the callback. Return 0 on | |
66 | * success, or -errno on error. On success, the given @path will be saved as | |
67 | * @watch->node, and remains the caller's to free. On error, @watch->node will | |
68 | * be NULL, the device will switch to %XenbusStateClosing, and the error will | |
69 | * be saved in the store. | |
70 | */ | |
71 | int xenbus_watch_path(struct xenbus_device *dev, const char *path, | |
72 | struct xenbus_watch *watch, | |
73 | void (*callback)(struct xenbus_watch *, | |
74 | const char **, unsigned int)) | |
75 | { | |
76 | int err; | |
77 | ||
78 | watch->node = path; | |
79 | watch->callback = callback; | |
80 | ||
81 | err = register_xenbus_watch(watch); | |
82 | ||
83 | if (err) { | |
84 | watch->node = NULL; | |
85 | watch->callback = NULL; | |
86 | xenbus_dev_fatal(dev, err, "adding watch on %s", path); | |
87 | } | |
88 | ||
89 | return err; | |
90 | } | |
91 | EXPORT_SYMBOL_GPL(xenbus_watch_path); | |
92 | ||
93 | ||
94 | /** | |
95 | * xenbus_watch_pathfmt - register a watch on a sprintf-formatted path | |
96 | * @dev: xenbus device | |
97 | * @watch: watch to register | |
98 | * @callback: callback to register | |
99 | * @pathfmt: format of path to watch | |
100 | * | |
101 | * Register a watch on the given @path, using the given xenbus_watch | |
102 | * structure for storage, and the given @callback function as the callback. | |
103 | * Return 0 on success, or -errno on error. On success, the watched path | |
104 | * (@path/@path2) will be saved as @watch->node, and becomes the caller's to | |
105 | * kfree(). On error, watch->node will be NULL, so the caller has nothing to | |
106 | * free, the device will switch to %XenbusStateClosing, and the error will be | |
107 | * saved in the store. | |
108 | */ | |
109 | int xenbus_watch_pathfmt(struct xenbus_device *dev, | |
110 | struct xenbus_watch *watch, | |
111 | void (*callback)(struct xenbus_watch *, | |
112 | const char **, unsigned int), | |
113 | const char *pathfmt, ...) | |
114 | { | |
115 | int err; | |
116 | va_list ap; | |
117 | char *path; | |
118 | ||
119 | va_start(ap, pathfmt); | |
a144ff09 | 120 | path = kvasprintf(GFP_NOIO | __GFP_HIGH, pathfmt, ap); |
4bac07c9 JF |
121 | va_end(ap); |
122 | ||
123 | if (!path) { | |
124 | xenbus_dev_fatal(dev, -ENOMEM, "allocating path for watch"); | |
125 | return -ENOMEM; | |
126 | } | |
127 | err = xenbus_watch_path(dev, path, watch, callback); | |
128 | ||
129 | if (err) | |
130 | kfree(path); | |
131 | return err; | |
132 | } | |
133 | EXPORT_SYMBOL_GPL(xenbus_watch_pathfmt); | |
134 | ||
135 | ||
136 | /** | |
137 | * xenbus_switch_state | |
138 | * @dev: xenbus device | |
4bac07c9 JF |
139 | * @state: new state |
140 | * | |
141 | * Advertise in the store a change of the given driver to the given new_state. | |
142 | * Return 0 on success, or -errno on error. On error, the device will switch | |
143 | * to XenbusStateClosing, and the error will be saved in the store. | |
144 | */ | |
145 | int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state) | |
146 | { | |
147 | /* We check whether the state is currently set to the given value, and | |
148 | if not, then the state is set. We don't want to unconditionally | |
149 | write the given state, because we don't want to fire watches | |
150 | unnecessarily. Furthermore, if the node has gone, we don't write | |
151 | to it, as the device will be tearing down, and we don't want to | |
152 | resurrect that directory. | |
153 | ||
154 | Note that, because of this cached value of our state, this function | |
155 | will not work inside a Xenstore transaction (something it was | |
156 | trying to in the past) because dev->state would not get reset if | |
157 | the transaction was aborted. | |
158 | ||
159 | */ | |
160 | ||
161 | int current_state; | |
162 | int err; | |
163 | ||
164 | if (state == dev->state) | |
165 | return 0; | |
166 | ||
167 | err = xenbus_scanf(XBT_NIL, dev->nodename, "state", "%d", | |
168 | ¤t_state); | |
169 | if (err != 1) | |
170 | return 0; | |
171 | ||
172 | err = xenbus_printf(XBT_NIL, dev->nodename, "state", "%d", state); | |
173 | if (err) { | |
174 | if (state != XenbusStateClosing) /* Avoid looping */ | |
175 | xenbus_dev_fatal(dev, err, "writing new state"); | |
176 | return err; | |
177 | } | |
178 | ||
179 | dev->state = state; | |
180 | ||
181 | return 0; | |
182 | } | |
183 | EXPORT_SYMBOL_GPL(xenbus_switch_state); | |
184 | ||
185 | int xenbus_frontend_closed(struct xenbus_device *dev) | |
186 | { | |
187 | xenbus_switch_state(dev, XenbusStateClosed); | |
188 | complete(&dev->down); | |
189 | return 0; | |
190 | } | |
191 | EXPORT_SYMBOL_GPL(xenbus_frontend_closed); | |
192 | ||
193 | /** | |
194 | * Return the path to the error node for the given device, or NULL on failure. | |
195 | * If the value returned is non-NULL, then it is the caller's to kfree. | |
196 | */ | |
197 | static char *error_path(struct xenbus_device *dev) | |
198 | { | |
199 | return kasprintf(GFP_KERNEL, "error/%s", dev->nodename); | |
200 | } | |
201 | ||
202 | ||
203 | static void xenbus_va_dev_error(struct xenbus_device *dev, int err, | |
204 | const char *fmt, va_list ap) | |
205 | { | |
206 | int ret; | |
207 | unsigned int len; | |
208 | char *printf_buffer = NULL; | |
209 | char *path_buffer = NULL; | |
210 | ||
211 | #define PRINTF_BUFFER_SIZE 4096 | |
212 | printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL); | |
213 | if (printf_buffer == NULL) | |
214 | goto fail; | |
215 | ||
216 | len = sprintf(printf_buffer, "%i ", -err); | |
217 | ret = vsnprintf(printf_buffer+len, PRINTF_BUFFER_SIZE-len, fmt, ap); | |
218 | ||
219 | BUG_ON(len + ret > PRINTF_BUFFER_SIZE-1); | |
220 | ||
221 | dev_err(&dev->dev, "%s\n", printf_buffer); | |
222 | ||
223 | path_buffer = error_path(dev); | |
224 | ||
225 | if (path_buffer == NULL) { | |
226 | dev_err(&dev->dev, "failed to write error node for %s (%s)\n", | |
227 | dev->nodename, printf_buffer); | |
228 | goto fail; | |
229 | } | |
230 | ||
231 | if (xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer) != 0) { | |
232 | dev_err(&dev->dev, "failed to write error node for %s (%s)\n", | |
233 | dev->nodename, printf_buffer); | |
234 | goto fail; | |
235 | } | |
236 | ||
237 | fail: | |
238 | kfree(printf_buffer); | |
239 | kfree(path_buffer); | |
240 | } | |
241 | ||
242 | ||
243 | /** | |
244 | * xenbus_dev_error | |
245 | * @dev: xenbus device | |
246 | * @err: error to report | |
247 | * @fmt: error message format | |
248 | * | |
249 | * Report the given negative errno into the store, along with the given | |
250 | * formatted message. | |
251 | */ | |
252 | void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...) | |
253 | { | |
254 | va_list ap; | |
255 | ||
256 | va_start(ap, fmt); | |
257 | xenbus_va_dev_error(dev, err, fmt, ap); | |
258 | va_end(ap); | |
259 | } | |
260 | EXPORT_SYMBOL_GPL(xenbus_dev_error); | |
261 | ||
262 | /** | |
263 | * xenbus_dev_fatal | |
264 | * @dev: xenbus device | |
265 | * @err: error to report | |
266 | * @fmt: error message format | |
267 | * | |
268 | * Equivalent to xenbus_dev_error(dev, err, fmt, args), followed by | |
d8220347 | 269 | * xenbus_switch_state(dev, XenbusStateClosing) to schedule an orderly |
4bac07c9 JF |
270 | * closedown of this driver and its peer. |
271 | */ | |
272 | ||
273 | void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...) | |
274 | { | |
275 | va_list ap; | |
276 | ||
277 | va_start(ap, fmt); | |
278 | xenbus_va_dev_error(dev, err, fmt, ap); | |
279 | va_end(ap); | |
280 | ||
281 | xenbus_switch_state(dev, XenbusStateClosing); | |
282 | } | |
283 | EXPORT_SYMBOL_GPL(xenbus_dev_fatal); | |
284 | ||
285 | /** | |
286 | * xenbus_grant_ring | |
287 | * @dev: xenbus device | |
288 | * @ring_mfn: mfn of ring to grant | |
289 | ||
290 | * Grant access to the given @ring_mfn to the peer of the given device. Return | |
291 | * 0 on success, or -errno on error. On error, the device will switch to | |
292 | * XenbusStateClosing, and the error will be saved in the store. | |
293 | */ | |
294 | int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn) | |
295 | { | |
296 | int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0); | |
297 | if (err < 0) | |
298 | xenbus_dev_fatal(dev, err, "granting access to ring page"); | |
299 | return err; | |
300 | } | |
301 | EXPORT_SYMBOL_GPL(xenbus_grant_ring); | |
302 | ||
303 | ||
304 | /** | |
305 | * Allocate an event channel for the given xenbus_device, assigning the newly | |
306 | * created local port to *port. Return 0 on success, or -errno on error. On | |
307 | * error, the device will switch to XenbusStateClosing, and the error will be | |
308 | * saved in the store. | |
309 | */ | |
310 | int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port) | |
311 | { | |
312 | struct evtchn_alloc_unbound alloc_unbound; | |
313 | int err; | |
314 | ||
315 | alloc_unbound.dom = DOMID_SELF; | |
316 | alloc_unbound.remote_dom = dev->otherend_id; | |
317 | ||
318 | err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, | |
319 | &alloc_unbound); | |
320 | if (err) | |
321 | xenbus_dev_fatal(dev, err, "allocating event channel"); | |
322 | else | |
323 | *port = alloc_unbound.port; | |
324 | ||
325 | return err; | |
326 | } | |
327 | EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn); | |
328 | ||
329 | ||
330 | /** | |
331 | * Bind to an existing interdomain event channel in another domain. Returns 0 | |
332 | * on success and stores the local port in *port. On error, returns -errno, | |
333 | * switches the device to XenbusStateClosing, and saves the error in XenStore. | |
334 | */ | |
335 | int xenbus_bind_evtchn(struct xenbus_device *dev, int remote_port, int *port) | |
336 | { | |
337 | struct evtchn_bind_interdomain bind_interdomain; | |
338 | int err; | |
339 | ||
340 | bind_interdomain.remote_dom = dev->otherend_id; | |
341 | bind_interdomain.remote_port = remote_port; | |
342 | ||
343 | err = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain, | |
344 | &bind_interdomain); | |
345 | if (err) | |
346 | xenbus_dev_fatal(dev, err, | |
347 | "binding to event channel %d from domain %d", | |
348 | remote_port, dev->otherend_id); | |
349 | else | |
350 | *port = bind_interdomain.local_port; | |
351 | ||
352 | return err; | |
353 | } | |
354 | EXPORT_SYMBOL_GPL(xenbus_bind_evtchn); | |
355 | ||
356 | ||
357 | /** | |
358 | * Free an existing event channel. Returns 0 on success or -errno on error. | |
359 | */ | |
360 | int xenbus_free_evtchn(struct xenbus_device *dev, int port) | |
361 | { | |
362 | struct evtchn_close close; | |
363 | int err; | |
364 | ||
365 | close.port = port; | |
366 | ||
367 | err = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close); | |
368 | if (err) | |
369 | xenbus_dev_error(dev, err, "freeing event channel %d", port); | |
370 | ||
371 | return err; | |
372 | } | |
373 | EXPORT_SYMBOL_GPL(xenbus_free_evtchn); | |
374 | ||
375 | ||
376 | /** | |
377 | * xenbus_map_ring_valloc | |
378 | * @dev: xenbus device | |
379 | * @gnt_ref: grant reference | |
380 | * @vaddr: pointer to address to be filled out by mapping | |
381 | * | |
382 | * Based on Rusty Russell's skeleton driver's map_page. | |
383 | * Map a page of memory into this domain from another domain's grant table. | |
384 | * xenbus_map_ring_valloc allocates a page of virtual address space, maps the | |
385 | * page to that address, and sets *vaddr to that address. | |
386 | * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h) | |
387 | * or -ENOMEM on error. If an error is returned, device will switch to | |
388 | * XenbusStateClosing and the error message will be saved in XenStore. | |
389 | */ | |
390 | int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr) | |
391 | { | |
392 | struct gnttab_map_grant_ref op = { | |
393 | .flags = GNTMAP_host_map, | |
394 | .ref = gnt_ref, | |
395 | .dom = dev->otherend_id, | |
396 | }; | |
397 | struct vm_struct *area; | |
398 | ||
399 | *vaddr = NULL; | |
400 | ||
5f0ababb | 401 | area = xen_alloc_vm_area(PAGE_SIZE); |
4bac07c9 JF |
402 | if (!area) |
403 | return -ENOMEM; | |
404 | ||
405 | op.host_addr = (unsigned long)area->addr; | |
406 | ||
407 | if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1)) | |
408 | BUG(); | |
409 | ||
410 | if (op.status != GNTST_okay) { | |
5f0ababb | 411 | xen_free_vm_area(area); |
4bac07c9 JF |
412 | xenbus_dev_fatal(dev, op.status, |
413 | "mapping in shared page %d from domain %d", | |
414 | gnt_ref, dev->otherend_id); | |
415 | return op.status; | |
416 | } | |
417 | ||
418 | /* Stuff the handle in an unused field */ | |
419 | area->phys_addr = (unsigned long)op.handle; | |
420 | ||
421 | *vaddr = area->addr; | |
422 | return 0; | |
423 | } | |
424 | EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc); | |
425 | ||
426 | ||
427 | /** | |
428 | * xenbus_map_ring | |
429 | * @dev: xenbus device | |
430 | * @gnt_ref: grant reference | |
431 | * @handle: pointer to grant handle to be filled | |
432 | * @vaddr: address to be mapped to | |
433 | * | |
434 | * Map a page of memory into this domain from another domain's grant table. | |
435 | * xenbus_map_ring does not allocate the virtual address space (you must do | |
436 | * this yourself!). It only maps in the page to the specified address. | |
437 | * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h) | |
438 | * or -ENOMEM on error. If an error is returned, device will switch to | |
439 | * XenbusStateClosing and the error message will be saved in XenStore. | |
440 | */ | |
441 | int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref, | |
442 | grant_handle_t *handle, void *vaddr) | |
443 | { | |
444 | struct gnttab_map_grant_ref op = { | |
445 | .host_addr = (unsigned long)vaddr, | |
446 | .flags = GNTMAP_host_map, | |
447 | .ref = gnt_ref, | |
448 | .dom = dev->otherend_id, | |
449 | }; | |
450 | ||
451 | if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1)) | |
452 | BUG(); | |
453 | ||
454 | if (op.status != GNTST_okay) { | |
455 | xenbus_dev_fatal(dev, op.status, | |
456 | "mapping in shared page %d from domain %d", | |
457 | gnt_ref, dev->otherend_id); | |
458 | } else | |
459 | *handle = op.handle; | |
460 | ||
461 | return op.status; | |
462 | } | |
463 | EXPORT_SYMBOL_GPL(xenbus_map_ring); | |
464 | ||
465 | ||
466 | /** | |
467 | * xenbus_unmap_ring_vfree | |
468 | * @dev: xenbus device | |
469 | * @vaddr: addr to unmap | |
470 | * | |
471 | * Based on Rusty Russell's skeleton driver's unmap_page. | |
472 | * Unmap a page of memory in this domain that was imported from another domain. | |
473 | * Use xenbus_unmap_ring_vfree if you mapped in your memory with | |
474 | * xenbus_map_ring_valloc (it will free the virtual address space). | |
475 | * Returns 0 on success and returns GNTST_* on error | |
476 | * (see xen/include/interface/grant_table.h). | |
477 | */ | |
478 | int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr) | |
479 | { | |
480 | struct vm_struct *area; | |
481 | struct gnttab_unmap_grant_ref op = { | |
482 | .host_addr = (unsigned long)vaddr, | |
483 | }; | |
484 | ||
485 | /* It'd be nice if linux/vmalloc.h provided a find_vm_area(void *addr) | |
486 | * method so that we don't have to muck with vmalloc internals here. | |
487 | * We could force the user to hang on to their struct vm_struct from | |
488 | * xenbus_map_ring_valloc, but these 6 lines considerably simplify | |
489 | * this API. | |
490 | */ | |
491 | read_lock(&vmlist_lock); | |
492 | for (area = vmlist; area != NULL; area = area->next) { | |
493 | if (area->addr == vaddr) | |
494 | break; | |
495 | } | |
496 | read_unlock(&vmlist_lock); | |
497 | ||
498 | if (!area) { | |
499 | xenbus_dev_error(dev, -ENOENT, | |
500 | "can't find mapped virtual address %p", vaddr); | |
501 | return GNTST_bad_virt_addr; | |
502 | } | |
503 | ||
504 | op.handle = (grant_handle_t)area->phys_addr; | |
505 | ||
506 | if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1)) | |
507 | BUG(); | |
508 | ||
509 | if (op.status == GNTST_okay) | |
5f0ababb | 510 | xen_free_vm_area(area); |
4bac07c9 JF |
511 | else |
512 | xenbus_dev_error(dev, op.status, | |
513 | "unmapping page at handle %d error %d", | |
514 | (int16_t)area->phys_addr, op.status); | |
515 | ||
516 | return op.status; | |
517 | } | |
518 | EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree); | |
519 | ||
520 | ||
521 | /** | |
522 | * xenbus_unmap_ring | |
523 | * @dev: xenbus device | |
524 | * @handle: grant handle | |
525 | * @vaddr: addr to unmap | |
526 | * | |
527 | * Unmap a page of memory in this domain that was imported from another domain. | |
528 | * Returns 0 on success and returns GNTST_* on error | |
529 | * (see xen/include/interface/grant_table.h). | |
530 | */ | |
531 | int xenbus_unmap_ring(struct xenbus_device *dev, | |
532 | grant_handle_t handle, void *vaddr) | |
533 | { | |
534 | struct gnttab_unmap_grant_ref op = { | |
535 | .host_addr = (unsigned long)vaddr, | |
536 | .handle = handle, | |
537 | }; | |
538 | ||
539 | if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1)) | |
540 | BUG(); | |
541 | ||
542 | if (op.status != GNTST_okay) | |
543 | xenbus_dev_error(dev, op.status, | |
544 | "unmapping page at handle %d error %d", | |
545 | handle, op.status); | |
546 | ||
547 | return op.status; | |
548 | } | |
549 | EXPORT_SYMBOL_GPL(xenbus_unmap_ring); | |
550 | ||
551 | ||
552 | /** | |
553 | * xenbus_read_driver_state | |
554 | * @path: path for driver | |
555 | * | |
556 | * Return the state of the driver rooted at the given store path, or | |
557 | * XenbusStateUnknown if no state can be read. | |
558 | */ | |
559 | enum xenbus_state xenbus_read_driver_state(const char *path) | |
560 | { | |
561 | enum xenbus_state result; | |
562 | int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL); | |
563 | if (err) | |
564 | result = XenbusStateUnknown; | |
565 | ||
566 | return result; | |
567 | } | |
568 | EXPORT_SYMBOL_GPL(xenbus_read_driver_state); |