xref: /openbmc/linux/drivers/acpi/scan.c (revision 87c2ce3b)
1 /*
2  * scan.c - support for transforming the ACPI namespace into individual objects
3  */
4 
5 #include <linux/module.h>
6 #include <linux/init.h>
7 #include <linux/acpi.h>
8 
9 #include <acpi/acpi_drivers.h>
10 #include <acpi/acinterp.h>	/* for acpi_ex_eisa_id_to_string() */
11 
12 #define _COMPONENT		ACPI_BUS_COMPONENT
13 ACPI_MODULE_NAME("scan")
14 #define STRUCT_TO_INT(s)	(*((int*)&s))
15 extern struct acpi_device *acpi_root;
16 
17 #define ACPI_BUS_CLASS			"system_bus"
18 #define ACPI_BUS_HID			"ACPI_BUS"
19 #define ACPI_BUS_DRIVER_NAME		"ACPI Bus Driver"
20 #define ACPI_BUS_DEVICE_NAME		"System Bus"
21 
22 static LIST_HEAD(acpi_device_list);
23 DEFINE_SPINLOCK(acpi_device_lock);
24 LIST_HEAD(acpi_wakeup_device_list);
25 
26 static int acpi_bus_trim(struct acpi_device *start, int rmdevice);
27 
28 static void acpi_device_release(struct kobject *kobj)
29 {
30 	struct acpi_device *dev = container_of(kobj, struct acpi_device, kobj);
31 	kfree(dev->pnp.cid_list);
32 	kfree(dev);
33 }
34 
35 struct acpi_device_attribute {
36 	struct attribute attr;
37 	 ssize_t(*show) (struct acpi_device *, char *);
38 	 ssize_t(*store) (struct acpi_device *, const char *, size_t);
39 };
40 
41 typedef void acpi_device_sysfs_files(struct kobject *,
42 				     const struct attribute *);
43 
44 static void setup_sys_fs_device_files(struct acpi_device *dev,
45 				      acpi_device_sysfs_files * func);
46 
47 #define create_sysfs_device_files(dev)	\
48 	setup_sys_fs_device_files(dev, (acpi_device_sysfs_files *)&sysfs_create_file)
49 #define remove_sysfs_device_files(dev)	\
50 	setup_sys_fs_device_files(dev, (acpi_device_sysfs_files *)&sysfs_remove_file)
51 
52 #define to_acpi_device(n) container_of(n, struct acpi_device, kobj)
53 #define to_handle_attr(n) container_of(n, struct acpi_device_attribute, attr);
54 
55 static ssize_t acpi_device_attr_show(struct kobject *kobj,
56 				     struct attribute *attr, char *buf)
57 {
58 	struct acpi_device *device = to_acpi_device(kobj);
59 	struct acpi_device_attribute *attribute = to_handle_attr(attr);
60 	return attribute->show ? attribute->show(device, buf) : -EIO;
61 }
62 static ssize_t acpi_device_attr_store(struct kobject *kobj,
63 				      struct attribute *attr, const char *buf,
64 				      size_t len)
65 {
66 	struct acpi_device *device = to_acpi_device(kobj);
67 	struct acpi_device_attribute *attribute = to_handle_attr(attr);
68 	return attribute->store ? attribute->store(device, buf, len) : -EIO;
69 }
70 
71 static struct sysfs_ops acpi_device_sysfs_ops = {
72 	.show = acpi_device_attr_show,
73 	.store = acpi_device_attr_store,
74 };
75 
76 static struct kobj_type ktype_acpi_ns = {
77 	.sysfs_ops = &acpi_device_sysfs_ops,
78 	.release = acpi_device_release,
79 };
80 
81 static int namespace_uevent(struct kset *kset, struct kobject *kobj,
82 			     char **envp, int num_envp, char *buffer,
83 			     int buffer_size)
84 {
85 	struct acpi_device *dev = to_acpi_device(kobj);
86 	int i = 0;
87 	int len = 0;
88 
89 	if (!dev->driver)
90 		return 0;
91 
92 	if (add_uevent_var(envp, num_envp, &i, buffer, buffer_size, &len,
93 			   "PHYSDEVDRIVER=%s", dev->driver->name))
94 		return -ENOMEM;
95 
96 	envp[i] = NULL;
97 
98 	return 0;
99 }
100 
101 static struct kset_uevent_ops namespace_uevent_ops = {
102 	.uevent = &namespace_uevent,
103 };
104 
105 static struct kset acpi_namespace_kset = {
106 	.kobj = {
107 		 .name = "namespace",
108 		 },
109 	.subsys = &acpi_subsys,
110 	.ktype = &ktype_acpi_ns,
111 	.uevent_ops = &namespace_uevent_ops,
112 };
113 
114 static void acpi_device_register(struct acpi_device *device,
115 				 struct acpi_device *parent)
116 {
117 	/*
118 	 * Linkage
119 	 * -------
120 	 * Link this device to its parent and siblings.
121 	 */
122 	INIT_LIST_HEAD(&device->children);
123 	INIT_LIST_HEAD(&device->node);
124 	INIT_LIST_HEAD(&device->g_list);
125 	INIT_LIST_HEAD(&device->wakeup_list);
126 
127 	spin_lock(&acpi_device_lock);
128 	if (device->parent) {
129 		list_add_tail(&device->node, &device->parent->children);
130 		list_add_tail(&device->g_list, &device->parent->g_list);
131 	} else
132 		list_add_tail(&device->g_list, &acpi_device_list);
133 	if (device->wakeup.flags.valid)
134 		list_add_tail(&device->wakeup_list, &acpi_wakeup_device_list);
135 	spin_unlock(&acpi_device_lock);
136 
137 	strlcpy(device->kobj.name, device->pnp.bus_id, KOBJ_NAME_LEN);
138 	if (parent)
139 		device->kobj.parent = &parent->kobj;
140 	device->kobj.ktype = &ktype_acpi_ns;
141 	device->kobj.kset = &acpi_namespace_kset;
142 	kobject_register(&device->kobj);
143 	create_sysfs_device_files(device);
144 }
145 
146 static int acpi_device_unregister(struct acpi_device *device, int type)
147 {
148 	spin_lock(&acpi_device_lock);
149 	if (device->parent) {
150 		list_del(&device->node);
151 		list_del(&device->g_list);
152 	} else
153 		list_del(&device->g_list);
154 
155 	list_del(&device->wakeup_list);
156 
157 	spin_unlock(&acpi_device_lock);
158 
159 	acpi_detach_data(device->handle, acpi_bus_data_handler);
160 	remove_sysfs_device_files(device);
161 	kobject_unregister(&device->kobj);
162 	return 0;
163 }
164 
165 void acpi_bus_data_handler(acpi_handle handle, u32 function, void *context)
166 {
167 	ACPI_FUNCTION_TRACE("acpi_bus_data_handler");
168 
169 	/* TBD */
170 
171 	return_VOID;
172 }
173 
174 static int acpi_bus_get_power_flags(struct acpi_device *device)
175 {
176 	acpi_status status = 0;
177 	acpi_handle handle = NULL;
178 	u32 i = 0;
179 
180 	ACPI_FUNCTION_TRACE("acpi_bus_get_power_flags");
181 
182 	/*
183 	 * Power Management Flags
184 	 */
185 	status = acpi_get_handle(device->handle, "_PSC", &handle);
186 	if (ACPI_SUCCESS(status))
187 		device->power.flags.explicit_get = 1;
188 	status = acpi_get_handle(device->handle, "_IRC", &handle);
189 	if (ACPI_SUCCESS(status))
190 		device->power.flags.inrush_current = 1;
191 
192 	/*
193 	 * Enumerate supported power management states
194 	 */
195 	for (i = ACPI_STATE_D0; i <= ACPI_STATE_D3; i++) {
196 		struct acpi_device_power_state *ps = &device->power.states[i];
197 		char object_name[5] = { '_', 'P', 'R', '0' + i, '\0' };
198 
199 		/* Evaluate "_PRx" to se if power resources are referenced */
200 		acpi_evaluate_reference(device->handle, object_name, NULL,
201 					&ps->resources);
202 		if (ps->resources.count) {
203 			device->power.flags.power_resources = 1;
204 			ps->flags.valid = 1;
205 		}
206 
207 		/* Evaluate "_PSx" to see if we can do explicit sets */
208 		object_name[2] = 'S';
209 		status = acpi_get_handle(device->handle, object_name, &handle);
210 		if (ACPI_SUCCESS(status)) {
211 			ps->flags.explicit_set = 1;
212 			ps->flags.valid = 1;
213 		}
214 
215 		/* State is valid if we have some power control */
216 		if (ps->resources.count || ps->flags.explicit_set)
217 			ps->flags.valid = 1;
218 
219 		ps->power = -1;	/* Unknown - driver assigned */
220 		ps->latency = -1;	/* Unknown - driver assigned */
221 	}
222 
223 	/* Set defaults for D0 and D3 states (always valid) */
224 	device->power.states[ACPI_STATE_D0].flags.valid = 1;
225 	device->power.states[ACPI_STATE_D0].power = 100;
226 	device->power.states[ACPI_STATE_D3].flags.valid = 1;
227 	device->power.states[ACPI_STATE_D3].power = 0;
228 
229 	/* TBD: System wake support and resource requirements. */
230 
231 	device->power.state = ACPI_STATE_UNKNOWN;
232 
233 	return_VALUE(0);
234 }
235 
236 int acpi_match_ids(struct acpi_device *device, char *ids)
237 {
238 	int error = 0;
239 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
240 
241 	if (device->flags.hardware_id)
242 		if (strstr(ids, device->pnp.hardware_id))
243 			goto Done;
244 
245 	if (device->flags.compatible_ids) {
246 		struct acpi_compatible_id_list *cid_list = device->pnp.cid_list;
247 		int i;
248 
249 		/* compare multiple _CID entries against driver ids */
250 		for (i = 0; i < cid_list->count; i++) {
251 			if (strstr(ids, cid_list->id[i].value))
252 				goto Done;
253 		}
254 	}
255 	error = -ENOENT;
256 
257       Done:
258 	if (buffer.pointer)
259 		acpi_os_free(buffer.pointer);
260 	return error;
261 }
262 
263 static acpi_status
264 acpi_bus_extract_wakeup_device_power_package(struct acpi_device *device,
265 					     union acpi_object *package)
266 {
267 	int i = 0;
268 	union acpi_object *element = NULL;
269 
270 	if (!device || !package || (package->package.count < 2))
271 		return AE_BAD_PARAMETER;
272 
273 	element = &(package->package.elements[0]);
274 	if (!element)
275 		return AE_BAD_PARAMETER;
276 	if (element->type == ACPI_TYPE_PACKAGE) {
277 		if ((element->package.count < 2) ||
278 		    (element->package.elements[0].type !=
279 		     ACPI_TYPE_LOCAL_REFERENCE)
280 		    || (element->package.elements[1].type != ACPI_TYPE_INTEGER))
281 			return AE_BAD_DATA;
282 		device->wakeup.gpe_device =
283 		    element->package.elements[0].reference.handle;
284 		device->wakeup.gpe_number =
285 		    (u32) element->package.elements[1].integer.value;
286 	} else if (element->type == ACPI_TYPE_INTEGER) {
287 		device->wakeup.gpe_number = element->integer.value;
288 	} else
289 		return AE_BAD_DATA;
290 
291 	element = &(package->package.elements[1]);
292 	if (element->type != ACPI_TYPE_INTEGER) {
293 		return AE_BAD_DATA;
294 	}
295 	device->wakeup.sleep_state = element->integer.value;
296 
297 	if ((package->package.count - 2) > ACPI_MAX_HANDLES) {
298 		return AE_NO_MEMORY;
299 	}
300 	device->wakeup.resources.count = package->package.count - 2;
301 	for (i = 0; i < device->wakeup.resources.count; i++) {
302 		element = &(package->package.elements[i + 2]);
303 		if (element->type != ACPI_TYPE_ANY) {
304 			return AE_BAD_DATA;
305 		}
306 
307 		device->wakeup.resources.handles[i] = element->reference.handle;
308 	}
309 
310 	return AE_OK;
311 }
312 
313 static int acpi_bus_get_wakeup_device_flags(struct acpi_device *device)
314 {
315 	acpi_status status = 0;
316 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
317 	union acpi_object *package = NULL;
318 
319 	ACPI_FUNCTION_TRACE("acpi_bus_get_wakeup_flags");
320 
321 	/* _PRW */
322 	status = acpi_evaluate_object(device->handle, "_PRW", NULL, &buffer);
323 	if (ACPI_FAILURE(status)) {
324 		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _PRW\n"));
325 		goto end;
326 	}
327 
328 	package = (union acpi_object *)buffer.pointer;
329 	status = acpi_bus_extract_wakeup_device_power_package(device, package);
330 	if (ACPI_FAILURE(status)) {
331 		ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
332 				  "Error extracting _PRW package\n"));
333 		goto end;
334 	}
335 
336 	acpi_os_free(buffer.pointer);
337 
338 	device->wakeup.flags.valid = 1;
339 	/* Power button, Lid switch always enable wakeup */
340 	if (!acpi_match_ids(device, "PNP0C0D,PNP0C0C,PNP0C0E"))
341 		device->wakeup.flags.run_wake = 1;
342 
343       end:
344 	if (ACPI_FAILURE(status))
345 		device->flags.wake_capable = 0;
346 	return_VALUE(0);
347 }
348 
349 /* --------------------------------------------------------------------------
350 		ACPI sysfs device file support
351    -------------------------------------------------------------------------- */
352 static ssize_t acpi_eject_store(struct acpi_device *device,
353 				const char *buf, size_t count);
354 
355 #define ACPI_DEVICE_ATTR(_name,_mode,_show,_store) \
356 static struct acpi_device_attribute acpi_device_attr_##_name = \
357 		__ATTR(_name, _mode, _show, _store)
358 
359 ACPI_DEVICE_ATTR(eject, 0200, NULL, acpi_eject_store);
360 
361 /**
362  * setup_sys_fs_device_files - sets up the device files under device namespace
363  * @dev:	acpi_device object
364  * @func:	function pointer to create or destroy the device file
365  */
366 static void
367 setup_sys_fs_device_files(struct acpi_device *dev,
368 			  acpi_device_sysfs_files * func)
369 {
370 	acpi_status status;
371 	acpi_handle temp = NULL;
372 
373 	/*
374 	 * If device has _EJ0, 'eject' file is created that is used to trigger
375 	 * hot-removal function from userland.
376 	 */
377 	status = acpi_get_handle(dev->handle, "_EJ0", &temp);
378 	if (ACPI_SUCCESS(status))
379 		(*(func)) (&dev->kobj, &acpi_device_attr_eject.attr);
380 }
381 
382 static int acpi_eject_operation(acpi_handle handle, int lockable)
383 {
384 	struct acpi_object_list arg_list;
385 	union acpi_object arg;
386 	acpi_status status = AE_OK;
387 
388 	/*
389 	 * TBD: evaluate _PS3?
390 	 */
391 
392 	if (lockable) {
393 		arg_list.count = 1;
394 		arg_list.pointer = &arg;
395 		arg.type = ACPI_TYPE_INTEGER;
396 		arg.integer.value = 0;
397 		acpi_evaluate_object(handle, "_LCK", &arg_list, NULL);
398 	}
399 
400 	arg_list.count = 1;
401 	arg_list.pointer = &arg;
402 	arg.type = ACPI_TYPE_INTEGER;
403 	arg.integer.value = 1;
404 
405 	/*
406 	 * TBD: _EJD support.
407 	 */
408 
409 	status = acpi_evaluate_object(handle, "_EJ0", &arg_list, NULL);
410 	if (ACPI_FAILURE(status)) {
411 		return (-ENODEV);
412 	}
413 
414 	return (0);
415 }
416 
417 static ssize_t
418 acpi_eject_store(struct acpi_device *device, const char *buf, size_t count)
419 {
420 	int result;
421 	int ret = count;
422 	int islockable;
423 	acpi_status status;
424 	acpi_handle handle;
425 	acpi_object_type type = 0;
426 
427 	if ((!count) || (buf[0] != '1')) {
428 		return -EINVAL;
429 	}
430 #ifndef FORCE_EJECT
431 	if (device->driver == NULL) {
432 		ret = -ENODEV;
433 		goto err;
434 	}
435 #endif
436 	status = acpi_get_type(device->handle, &type);
437 	if (ACPI_FAILURE(status) || (!device->flags.ejectable)) {
438 		ret = -ENODEV;
439 		goto err;
440 	}
441 
442 	islockable = device->flags.lockable;
443 	handle = device->handle;
444 
445 	if (type == ACPI_TYPE_PROCESSOR)
446 		result = acpi_bus_trim(device, 0);
447 	else
448 		result = acpi_bus_trim(device, 1);
449 
450 	if (!result)
451 		result = acpi_eject_operation(handle, islockable);
452 
453 	if (result) {
454 		ret = -EBUSY;
455 	}
456       err:
457 	return ret;
458 }
459 
460 /* --------------------------------------------------------------------------
461                               Performance Management
462    -------------------------------------------------------------------------- */
463 
464 static int acpi_bus_get_perf_flags(struct acpi_device *device)
465 {
466 	device->performance.state = ACPI_STATE_UNKNOWN;
467 	return 0;
468 }
469 
470 /* --------------------------------------------------------------------------
471                                  Driver Management
472    -------------------------------------------------------------------------- */
473 
474 static LIST_HEAD(acpi_bus_drivers);
475 static DECLARE_MUTEX(acpi_bus_drivers_lock);
476 
477 /**
478  * acpi_bus_match - match device IDs to driver's supported IDs
479  * @device: the device that we are trying to match to a driver
480  * @driver: driver whose device id table is being checked
481  *
482  * Checks the device's hardware (_HID) or compatible (_CID) ids to see if it
483  * matches the specified driver's criteria.
484  */
485 static int
486 acpi_bus_match(struct acpi_device *device, struct acpi_driver *driver)
487 {
488 	if (driver && driver->ops.match)
489 		return driver->ops.match(device, driver);
490 	return acpi_match_ids(device, driver->ids);
491 }
492 
493 /**
494  * acpi_bus_driver_init - add a device to a driver
495  * @device: the device to add and initialize
496  * @driver: driver for the device
497  *
498  * Used to initialize a device via its device driver.  Called whenever a
499  * driver is bound to a device.  Invokes the driver's add() and start() ops.
500  */
501 static int
502 acpi_bus_driver_init(struct acpi_device *device, struct acpi_driver *driver)
503 {
504 	int result = 0;
505 
506 	ACPI_FUNCTION_TRACE("acpi_bus_driver_init");
507 
508 	if (!device || !driver)
509 		return_VALUE(-EINVAL);
510 
511 	if (!driver->ops.add)
512 		return_VALUE(-ENOSYS);
513 
514 	result = driver->ops.add(device);
515 	if (result) {
516 		device->driver = NULL;
517 		acpi_driver_data(device) = NULL;
518 		return_VALUE(result);
519 	}
520 
521 	device->driver = driver;
522 
523 	/*
524 	 * TBD - Configuration Management: Assign resources to device based
525 	 * upon possible configuration and currently allocated resources.
526 	 */
527 
528 	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
529 			  "Driver successfully bound to device\n"));
530 	return_VALUE(0);
531 }
532 
533 static int acpi_start_single_object(struct acpi_device *device)
534 {
535 	int result = 0;
536 	struct acpi_driver *driver;
537 
538 	ACPI_FUNCTION_TRACE("acpi_start_single_object");
539 
540 	if (!(driver = device->driver))
541 		return_VALUE(0);
542 
543 	if (driver->ops.start) {
544 		result = driver->ops.start(device);
545 		if (result && driver->ops.remove)
546 			driver->ops.remove(device, ACPI_BUS_REMOVAL_NORMAL);
547 	}
548 
549 	return_VALUE(result);
550 }
551 
552 static int acpi_driver_attach(struct acpi_driver *drv)
553 {
554 	struct list_head *node, *next;
555 	int count = 0;
556 
557 	ACPI_FUNCTION_TRACE("acpi_driver_attach");
558 
559 	spin_lock(&acpi_device_lock);
560 	list_for_each_safe(node, next, &acpi_device_list) {
561 		struct acpi_device *dev =
562 		    container_of(node, struct acpi_device, g_list);
563 
564 		if (dev->driver || !dev->status.present)
565 			continue;
566 		spin_unlock(&acpi_device_lock);
567 
568 		if (!acpi_bus_match(dev, drv)) {
569 			if (!acpi_bus_driver_init(dev, drv)) {
570 				acpi_start_single_object(dev);
571 				atomic_inc(&drv->references);
572 				count++;
573 				ACPI_DEBUG_PRINT((ACPI_DB_INFO,
574 						  "Found driver [%s] for device [%s]\n",
575 						  drv->name, dev->pnp.bus_id));
576 			}
577 		}
578 		spin_lock(&acpi_device_lock);
579 	}
580 	spin_unlock(&acpi_device_lock);
581 	return_VALUE(count);
582 }
583 
584 static int acpi_driver_detach(struct acpi_driver *drv)
585 {
586 	struct list_head *node, *next;
587 
588 	ACPI_FUNCTION_TRACE("acpi_driver_detach");
589 
590 	spin_lock(&acpi_device_lock);
591 	list_for_each_safe(node, next, &acpi_device_list) {
592 		struct acpi_device *dev =
593 		    container_of(node, struct acpi_device, g_list);
594 
595 		if (dev->driver == drv) {
596 			spin_unlock(&acpi_device_lock);
597 			if (drv->ops.remove)
598 				drv->ops.remove(dev, ACPI_BUS_REMOVAL_NORMAL);
599 			spin_lock(&acpi_device_lock);
600 			dev->driver = NULL;
601 			dev->driver_data = NULL;
602 			atomic_dec(&drv->references);
603 		}
604 	}
605 	spin_unlock(&acpi_device_lock);
606 	return_VALUE(0);
607 }
608 
609 /**
610  * acpi_bus_register_driver - register a driver with the ACPI bus
611  * @driver: driver being registered
612  *
613  * Registers a driver with the ACPI bus.  Searches the namespace for all
614  * devices that match the driver's criteria and binds.  Returns the
615  * number of devices that were claimed by the driver, or a negative
616  * error status for failure.
617  */
618 int acpi_bus_register_driver(struct acpi_driver *driver)
619 {
620 	int count;
621 
622 	ACPI_FUNCTION_TRACE("acpi_bus_register_driver");
623 
624 	if (acpi_disabled)
625 		return_VALUE(-ENODEV);
626 
627 	if (!driver)
628 		return_VALUE(-EINVAL);
629 
630 	spin_lock(&acpi_device_lock);
631 	list_add_tail(&driver->node, &acpi_bus_drivers);
632 	spin_unlock(&acpi_device_lock);
633 	count = acpi_driver_attach(driver);
634 
635 	return_VALUE(count);
636 }
637 
638 EXPORT_SYMBOL(acpi_bus_register_driver);
639 
640 /**
641  * acpi_bus_unregister_driver - unregisters a driver with the APIC bus
642  * @driver: driver to unregister
643  *
644  * Unregisters a driver with the ACPI bus.  Searches the namespace for all
645  * devices that match the driver's criteria and unbinds.
646  */
647 int acpi_bus_unregister_driver(struct acpi_driver *driver)
648 {
649 	int error = 0;
650 
651 	ACPI_FUNCTION_TRACE("acpi_bus_unregister_driver");
652 
653 	if (driver) {
654 		acpi_driver_detach(driver);
655 
656 		if (!atomic_read(&driver->references)) {
657 			spin_lock(&acpi_device_lock);
658 			list_del_init(&driver->node);
659 			spin_unlock(&acpi_device_lock);
660 		}
661 	} else
662 		error = -EINVAL;
663 	return_VALUE(error);
664 }
665 
666 EXPORT_SYMBOL(acpi_bus_unregister_driver);
667 
668 /**
669  * acpi_bus_find_driver - check if there is a driver installed for the device
670  * @device: device that we are trying to find a supporting driver for
671  *
672  * Parses the list of registered drivers looking for a driver applicable for
673  * the specified device.
674  */
675 static int acpi_bus_find_driver(struct acpi_device *device)
676 {
677 	int result = 0;
678 	struct list_head *node, *next;
679 
680 	ACPI_FUNCTION_TRACE("acpi_bus_find_driver");
681 
682 	spin_lock(&acpi_device_lock);
683 	list_for_each_safe(node, next, &acpi_bus_drivers) {
684 		struct acpi_driver *driver =
685 		    container_of(node, struct acpi_driver, node);
686 
687 		atomic_inc(&driver->references);
688 		spin_unlock(&acpi_device_lock);
689 		if (!acpi_bus_match(device, driver)) {
690 			result = acpi_bus_driver_init(device, driver);
691 			if (!result)
692 				goto Done;
693 		}
694 		atomic_dec(&driver->references);
695 		spin_lock(&acpi_device_lock);
696 	}
697 	spin_unlock(&acpi_device_lock);
698 
699       Done:
700 	return_VALUE(result);
701 }
702 
703 /* --------------------------------------------------------------------------
704                                  Device Enumeration
705    -------------------------------------------------------------------------- */
706 
707 static int acpi_bus_get_flags(struct acpi_device *device)
708 {
709 	acpi_status status = AE_OK;
710 	acpi_handle temp = NULL;
711 
712 	ACPI_FUNCTION_TRACE("acpi_bus_get_flags");
713 
714 	/* Presence of _STA indicates 'dynamic_status' */
715 	status = acpi_get_handle(device->handle, "_STA", &temp);
716 	if (ACPI_SUCCESS(status))
717 		device->flags.dynamic_status = 1;
718 
719 	/* Presence of _CID indicates 'compatible_ids' */
720 	status = acpi_get_handle(device->handle, "_CID", &temp);
721 	if (ACPI_SUCCESS(status))
722 		device->flags.compatible_ids = 1;
723 
724 	/* Presence of _RMV indicates 'removable' */
725 	status = acpi_get_handle(device->handle, "_RMV", &temp);
726 	if (ACPI_SUCCESS(status))
727 		device->flags.removable = 1;
728 
729 	/* Presence of _EJD|_EJ0 indicates 'ejectable' */
730 	status = acpi_get_handle(device->handle, "_EJD", &temp);
731 	if (ACPI_SUCCESS(status))
732 		device->flags.ejectable = 1;
733 	else {
734 		status = acpi_get_handle(device->handle, "_EJ0", &temp);
735 		if (ACPI_SUCCESS(status))
736 			device->flags.ejectable = 1;
737 	}
738 
739 	/* Presence of _LCK indicates 'lockable' */
740 	status = acpi_get_handle(device->handle, "_LCK", &temp);
741 	if (ACPI_SUCCESS(status))
742 		device->flags.lockable = 1;
743 
744 	/* Presence of _PS0|_PR0 indicates 'power manageable' */
745 	status = acpi_get_handle(device->handle, "_PS0", &temp);
746 	if (ACPI_FAILURE(status))
747 		status = acpi_get_handle(device->handle, "_PR0", &temp);
748 	if (ACPI_SUCCESS(status))
749 		device->flags.power_manageable = 1;
750 
751 	/* Presence of _PRW indicates wake capable */
752 	status = acpi_get_handle(device->handle, "_PRW", &temp);
753 	if (ACPI_SUCCESS(status))
754 		device->flags.wake_capable = 1;
755 
756 	/* TBD: Peformance management */
757 
758 	return_VALUE(0);
759 }
760 
761 static void acpi_device_get_busid(struct acpi_device *device,
762 				  acpi_handle handle, int type)
763 {
764 	char bus_id[5] = { '?', 0 };
765 	struct acpi_buffer buffer = { sizeof(bus_id), bus_id };
766 	int i = 0;
767 
768 	/*
769 	 * Bus ID
770 	 * ------
771 	 * The device's Bus ID is simply the object name.
772 	 * TBD: Shouldn't this value be unique (within the ACPI namespace)?
773 	 */
774 	switch (type) {
775 	case ACPI_BUS_TYPE_SYSTEM:
776 		strcpy(device->pnp.bus_id, "ACPI");
777 		break;
778 	case ACPI_BUS_TYPE_POWER_BUTTON:
779 		strcpy(device->pnp.bus_id, "PWRF");
780 		break;
781 	case ACPI_BUS_TYPE_SLEEP_BUTTON:
782 		strcpy(device->pnp.bus_id, "SLPF");
783 		break;
784 	default:
785 		acpi_get_name(handle, ACPI_SINGLE_NAME, &buffer);
786 		/* Clean up trailing underscores (if any) */
787 		for (i = 3; i > 1; i--) {
788 			if (bus_id[i] == '_')
789 				bus_id[i] = '\0';
790 			else
791 				break;
792 		}
793 		strcpy(device->pnp.bus_id, bus_id);
794 		break;
795 	}
796 }
797 
798 static void acpi_device_set_id(struct acpi_device *device,
799 			       struct acpi_device *parent, acpi_handle handle,
800 			       int type)
801 {
802 	struct acpi_device_info *info;
803 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
804 	char *hid = NULL;
805 	char *uid = NULL;
806 	struct acpi_compatible_id_list *cid_list = NULL;
807 	acpi_status status;
808 
809 	switch (type) {
810 	case ACPI_BUS_TYPE_DEVICE:
811 		status = acpi_get_object_info(handle, &buffer);
812 		if (ACPI_FAILURE(status)) {
813 			printk("%s: Error reading device info\n", __FUNCTION__);
814 			return;
815 		}
816 
817 		info = buffer.pointer;
818 		if (info->valid & ACPI_VALID_HID)
819 			hid = info->hardware_id.value;
820 		if (info->valid & ACPI_VALID_UID)
821 			uid = info->unique_id.value;
822 		if (info->valid & ACPI_VALID_CID)
823 			cid_list = &info->compatibility_id;
824 		if (info->valid & ACPI_VALID_ADR) {
825 			device->pnp.bus_address = info->address;
826 			device->flags.bus_address = 1;
827 		}
828 		break;
829 	case ACPI_BUS_TYPE_POWER:
830 		hid = ACPI_POWER_HID;
831 		break;
832 	case ACPI_BUS_TYPE_PROCESSOR:
833 		hid = ACPI_PROCESSOR_HID;
834 		break;
835 	case ACPI_BUS_TYPE_SYSTEM:
836 		hid = ACPI_SYSTEM_HID;
837 		break;
838 	case ACPI_BUS_TYPE_THERMAL:
839 		hid = ACPI_THERMAL_HID;
840 		break;
841 	case ACPI_BUS_TYPE_POWER_BUTTON:
842 		hid = ACPI_BUTTON_HID_POWERF;
843 		break;
844 	case ACPI_BUS_TYPE_SLEEP_BUTTON:
845 		hid = ACPI_BUTTON_HID_SLEEPF;
846 		break;
847 	}
848 
849 	/*
850 	 * \_SB
851 	 * ----
852 	 * Fix for the system root bus device -- the only root-level device.
853 	 */
854 	if ((parent == ACPI_ROOT_OBJECT) && (type == ACPI_BUS_TYPE_DEVICE)) {
855 		hid = ACPI_BUS_HID;
856 		strcpy(device->pnp.device_name, ACPI_BUS_DEVICE_NAME);
857 		strcpy(device->pnp.device_class, ACPI_BUS_CLASS);
858 	}
859 
860 	if (hid) {
861 		strcpy(device->pnp.hardware_id, hid);
862 		device->flags.hardware_id = 1;
863 	}
864 	if (uid) {
865 		strcpy(device->pnp.unique_id, uid);
866 		device->flags.unique_id = 1;
867 	}
868 	if (cid_list) {
869 		device->pnp.cid_list = kmalloc(cid_list->size, GFP_KERNEL);
870 		if (device->pnp.cid_list)
871 			memcpy(device->pnp.cid_list, cid_list, cid_list->size);
872 		else
873 			printk(KERN_ERR "Memory allocation error\n");
874 	}
875 
876 	acpi_os_free(buffer.pointer);
877 }
878 
879 static int acpi_device_set_context(struct acpi_device *device, int type)
880 {
881 	acpi_status status = AE_OK;
882 	int result = 0;
883 	/*
884 	 * Context
885 	 * -------
886 	 * Attach this 'struct acpi_device' to the ACPI object.  This makes
887 	 * resolutions from handle->device very efficient.  Note that we need
888 	 * to be careful with fixed-feature devices as they all attach to the
889 	 * root object.
890 	 */
891 	if (type != ACPI_BUS_TYPE_POWER_BUTTON &&
892 	    type != ACPI_BUS_TYPE_SLEEP_BUTTON) {
893 		status = acpi_attach_data(device->handle,
894 					  acpi_bus_data_handler, device);
895 
896 		if (ACPI_FAILURE(status)) {
897 			printk("Error attaching device data\n");
898 			result = -ENODEV;
899 		}
900 	}
901 	return result;
902 }
903 
904 static void acpi_device_get_debug_info(struct acpi_device *device,
905 				       acpi_handle handle, int type)
906 {
907 #ifdef CONFIG_ACPI_DEBUG_OUTPUT
908 	char *type_string = NULL;
909 	char name[80] = { '?', '\0' };
910 	struct acpi_buffer buffer = { sizeof(name), name };
911 
912 	switch (type) {
913 	case ACPI_BUS_TYPE_DEVICE:
914 		type_string = "Device";
915 		acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
916 		break;
917 	case ACPI_BUS_TYPE_POWER:
918 		type_string = "Power Resource";
919 		acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
920 		break;
921 	case ACPI_BUS_TYPE_PROCESSOR:
922 		type_string = "Processor";
923 		acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
924 		break;
925 	case ACPI_BUS_TYPE_SYSTEM:
926 		type_string = "System";
927 		acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
928 		break;
929 	case ACPI_BUS_TYPE_THERMAL:
930 		type_string = "Thermal Zone";
931 		acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
932 		break;
933 	case ACPI_BUS_TYPE_POWER_BUTTON:
934 		type_string = "Power Button";
935 		sprintf(name, "PWRB");
936 		break;
937 	case ACPI_BUS_TYPE_SLEEP_BUTTON:
938 		type_string = "Sleep Button";
939 		sprintf(name, "SLPB");
940 		break;
941 	}
942 
943 	printk(KERN_DEBUG "Found %s %s [%p]\n", type_string, name, handle);
944 #endif				/*CONFIG_ACPI_DEBUG_OUTPUT */
945 }
946 
947 static int acpi_bus_remove(struct acpi_device *dev, int rmdevice)
948 {
949 	int result = 0;
950 	struct acpi_driver *driver;
951 
952 	ACPI_FUNCTION_TRACE("acpi_bus_remove");
953 
954 	if (!dev)
955 		return_VALUE(-EINVAL);
956 
957 	driver = dev->driver;
958 
959 	if ((driver) && (driver->ops.remove)) {
960 
961 		if (driver->ops.stop) {
962 			result = driver->ops.stop(dev, ACPI_BUS_REMOVAL_EJECT);
963 			if (result)
964 				return_VALUE(result);
965 		}
966 
967 		result = dev->driver->ops.remove(dev, ACPI_BUS_REMOVAL_EJECT);
968 		if (result) {
969 			return_VALUE(result);
970 		}
971 
972 		atomic_dec(&dev->driver->references);
973 		dev->driver = NULL;
974 		acpi_driver_data(dev) = NULL;
975 	}
976 
977 	if (!rmdevice)
978 		return_VALUE(0);
979 
980 	if (dev->flags.bus_address) {
981 		if ((dev->parent) && (dev->parent->ops.unbind))
982 			dev->parent->ops.unbind(dev);
983 	}
984 
985 	acpi_device_unregister(dev, ACPI_BUS_REMOVAL_EJECT);
986 
987 	return_VALUE(0);
988 }
989 
990 static int
991 acpi_add_single_object(struct acpi_device **child,
992 		       struct acpi_device *parent, acpi_handle handle, int type)
993 {
994 	int result = 0;
995 	struct acpi_device *device = NULL;
996 
997 	ACPI_FUNCTION_TRACE("acpi_add_single_object");
998 
999 	if (!child)
1000 		return_VALUE(-EINVAL);
1001 
1002 	device = kmalloc(sizeof(struct acpi_device), GFP_KERNEL);
1003 	if (!device) {
1004 		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Memory allocation error\n"));
1005 		return_VALUE(-ENOMEM);
1006 	}
1007 	memset(device, 0, sizeof(struct acpi_device));
1008 
1009 	device->handle = handle;
1010 	device->parent = parent;
1011 
1012 	acpi_device_get_busid(device, handle, type);
1013 
1014 	/*
1015 	 * Flags
1016 	 * -----
1017 	 * Get prior to calling acpi_bus_get_status() so we know whether
1018 	 * or not _STA is present.  Note that we only look for object
1019 	 * handles -- cannot evaluate objects until we know the device is
1020 	 * present and properly initialized.
1021 	 */
1022 	result = acpi_bus_get_flags(device);
1023 	if (result)
1024 		goto end;
1025 
1026 	/*
1027 	 * Status
1028 	 * ------
1029 	 * See if the device is present.  We always assume that non-Device
1030 	 * and non-Processor objects (e.g. thermal zones, power resources,
1031 	 * etc.) are present, functioning, etc. (at least when parent object
1032 	 * is present).  Note that _STA has a different meaning for some
1033 	 * objects (e.g. power resources) so we need to be careful how we use
1034 	 * it.
1035 	 */
1036 	switch (type) {
1037 	case ACPI_BUS_TYPE_PROCESSOR:
1038 	case ACPI_BUS_TYPE_DEVICE:
1039 		result = acpi_bus_get_status(device);
1040 		if (ACPI_FAILURE(result) || !device->status.present) {
1041 			result = -ENOENT;
1042 			goto end;
1043 		}
1044 		break;
1045 	default:
1046 		STRUCT_TO_INT(device->status) = 0x0F;
1047 		break;
1048 	}
1049 
1050 	/*
1051 	 * Initialize Device
1052 	 * -----------------
1053 	 * TBD: Synch with Core's enumeration/initialization process.
1054 	 */
1055 
1056 	/*
1057 	 * Hardware ID, Unique ID, & Bus Address
1058 	 * -------------------------------------
1059 	 */
1060 	acpi_device_set_id(device, parent, handle, type);
1061 
1062 	/*
1063 	 * Power Management
1064 	 * ----------------
1065 	 */
1066 	if (device->flags.power_manageable) {
1067 		result = acpi_bus_get_power_flags(device);
1068 		if (result)
1069 			goto end;
1070 	}
1071 
1072 	/*
1073 	 * Wakeup device management
1074 	 *-----------------------
1075 	 */
1076 	if (device->flags.wake_capable) {
1077 		result = acpi_bus_get_wakeup_device_flags(device);
1078 		if (result)
1079 			goto end;
1080 	}
1081 
1082 	/*
1083 	 * Performance Management
1084 	 * ----------------------
1085 	 */
1086 	if (device->flags.performance_manageable) {
1087 		result = acpi_bus_get_perf_flags(device);
1088 		if (result)
1089 			goto end;
1090 	}
1091 
1092 	if ((result = acpi_device_set_context(device, type)))
1093 		goto end;
1094 
1095 	acpi_device_get_debug_info(device, handle, type);
1096 
1097 	acpi_device_register(device, parent);
1098 
1099 	/*
1100 	 * Bind _ADR-Based Devices
1101 	 * -----------------------
1102 	 * If there's a a bus address (_ADR) then we utilize the parent's
1103 	 * 'bind' function (if exists) to bind the ACPI- and natively-
1104 	 * enumerated device representations.
1105 	 */
1106 	if (device->flags.bus_address) {
1107 		if (device->parent && device->parent->ops.bind)
1108 			device->parent->ops.bind(device);
1109 	}
1110 
1111 	/*
1112 	 * Locate & Attach Driver
1113 	 * ----------------------
1114 	 * If there's a hardware id (_HID) or compatible ids (_CID) we check
1115 	 * to see if there's a driver installed for this kind of device.  Note
1116 	 * that drivers can install before or after a device is enumerated.
1117 	 *
1118 	 * TBD: Assumes LDM provides driver hot-plug capability.
1119 	 */
1120 	acpi_bus_find_driver(device);
1121 
1122       end:
1123 	if (!result)
1124 		*child = device;
1125 	else {
1126 		kfree(device->pnp.cid_list);
1127 		kfree(device);
1128 	}
1129 
1130 	return_VALUE(result);
1131 }
1132 
1133 static int acpi_bus_scan(struct acpi_device *start, struct acpi_bus_ops *ops)
1134 {
1135 	acpi_status status = AE_OK;
1136 	struct acpi_device *parent = NULL;
1137 	struct acpi_device *child = NULL;
1138 	acpi_handle phandle = NULL;
1139 	acpi_handle chandle = NULL;
1140 	acpi_object_type type = 0;
1141 	u32 level = 1;
1142 
1143 	ACPI_FUNCTION_TRACE("acpi_bus_scan");
1144 
1145 	if (!start)
1146 		return_VALUE(-EINVAL);
1147 
1148 	parent = start;
1149 	phandle = start->handle;
1150 
1151 	/*
1152 	 * Parse through the ACPI namespace, identify all 'devices', and
1153 	 * create a new 'struct acpi_device' for each.
1154 	 */
1155 	while ((level > 0) && parent) {
1156 
1157 		status = acpi_get_next_object(ACPI_TYPE_ANY, phandle,
1158 					      chandle, &chandle);
1159 
1160 		/*
1161 		 * If this scope is exhausted then move our way back up.
1162 		 */
1163 		if (ACPI_FAILURE(status)) {
1164 			level--;
1165 			chandle = phandle;
1166 			acpi_get_parent(phandle, &phandle);
1167 			if (parent->parent)
1168 				parent = parent->parent;
1169 			continue;
1170 		}
1171 
1172 		status = acpi_get_type(chandle, &type);
1173 		if (ACPI_FAILURE(status))
1174 			continue;
1175 
1176 		/*
1177 		 * If this is a scope object then parse it (depth-first).
1178 		 */
1179 		if (type == ACPI_TYPE_LOCAL_SCOPE) {
1180 			level++;
1181 			phandle = chandle;
1182 			chandle = NULL;
1183 			continue;
1184 		}
1185 
1186 		/*
1187 		 * We're only interested in objects that we consider 'devices'.
1188 		 */
1189 		switch (type) {
1190 		case ACPI_TYPE_DEVICE:
1191 			type = ACPI_BUS_TYPE_DEVICE;
1192 			break;
1193 		case ACPI_TYPE_PROCESSOR:
1194 			type = ACPI_BUS_TYPE_PROCESSOR;
1195 			break;
1196 		case ACPI_TYPE_THERMAL:
1197 			type = ACPI_BUS_TYPE_THERMAL;
1198 			break;
1199 		case ACPI_TYPE_POWER:
1200 			type = ACPI_BUS_TYPE_POWER;
1201 			break;
1202 		default:
1203 			continue;
1204 		}
1205 
1206 		if (ops->acpi_op_add)
1207 			status = acpi_add_single_object(&child, parent,
1208 							chandle, type);
1209 		else
1210 			status = acpi_bus_get_device(chandle, &child);
1211 
1212 		if (ACPI_FAILURE(status))
1213 			continue;
1214 
1215 		if (ops->acpi_op_start) {
1216 			status = acpi_start_single_object(child);
1217 			if (ACPI_FAILURE(status))
1218 				continue;
1219 		}
1220 
1221 		/*
1222 		 * If the device is present, enabled, and functioning then
1223 		 * parse its scope (depth-first).  Note that we need to
1224 		 * represent absent devices to facilitate PnP notifications
1225 		 * -- but only the subtree head (not all of its children,
1226 		 * which will be enumerated when the parent is inserted).
1227 		 *
1228 		 * TBD: Need notifications and other detection mechanisms
1229 		 *      in place before we can fully implement this.
1230 		 */
1231 		if (child->status.present) {
1232 			status = acpi_get_next_object(ACPI_TYPE_ANY, chandle,
1233 						      NULL, NULL);
1234 			if (ACPI_SUCCESS(status)) {
1235 				level++;
1236 				phandle = chandle;
1237 				chandle = NULL;
1238 				parent = child;
1239 			}
1240 		}
1241 	}
1242 
1243 	return_VALUE(0);
1244 }
1245 
1246 int
1247 acpi_bus_add(struct acpi_device **child,
1248 	     struct acpi_device *parent, acpi_handle handle, int type)
1249 {
1250 	int result;
1251 	struct acpi_bus_ops ops;
1252 
1253 	ACPI_FUNCTION_TRACE("acpi_bus_add");
1254 
1255 	result = acpi_add_single_object(child, parent, handle, type);
1256 	if (!result) {
1257 		memset(&ops, 0, sizeof(ops));
1258 		ops.acpi_op_add = 1;
1259 		result = acpi_bus_scan(*child, &ops);
1260 	}
1261 	return_VALUE(result);
1262 }
1263 
1264 EXPORT_SYMBOL(acpi_bus_add);
1265 
1266 int acpi_bus_start(struct acpi_device *device)
1267 {
1268 	int result;
1269 	struct acpi_bus_ops ops;
1270 
1271 	ACPI_FUNCTION_TRACE("acpi_bus_start");
1272 
1273 	if (!device)
1274 		return_VALUE(-EINVAL);
1275 
1276 	result = acpi_start_single_object(device);
1277 	if (!result) {
1278 		memset(&ops, 0, sizeof(ops));
1279 		ops.acpi_op_start = 1;
1280 		result = acpi_bus_scan(device, &ops);
1281 	}
1282 	return_VALUE(result);
1283 }
1284 
1285 EXPORT_SYMBOL(acpi_bus_start);
1286 
1287 static int acpi_bus_trim(struct acpi_device *start, int rmdevice)
1288 {
1289 	acpi_status status;
1290 	struct acpi_device *parent, *child;
1291 	acpi_handle phandle, chandle;
1292 	acpi_object_type type;
1293 	u32 level = 1;
1294 	int err = 0;
1295 
1296 	parent = start;
1297 	phandle = start->handle;
1298 	child = chandle = NULL;
1299 
1300 	while ((level > 0) && parent && (!err)) {
1301 		status = acpi_get_next_object(ACPI_TYPE_ANY, phandle,
1302 					      chandle, &chandle);
1303 
1304 		/*
1305 		 * If this scope is exhausted then move our way back up.
1306 		 */
1307 		if (ACPI_FAILURE(status)) {
1308 			level--;
1309 			chandle = phandle;
1310 			acpi_get_parent(phandle, &phandle);
1311 			child = parent;
1312 			parent = parent->parent;
1313 
1314 			if (level == 0)
1315 				err = acpi_bus_remove(child, rmdevice);
1316 			else
1317 				err = acpi_bus_remove(child, 1);
1318 
1319 			continue;
1320 		}
1321 
1322 		status = acpi_get_type(chandle, &type);
1323 		if (ACPI_FAILURE(status)) {
1324 			continue;
1325 		}
1326 		/*
1327 		 * If there is a device corresponding to chandle then
1328 		 * parse it (depth-first).
1329 		 */
1330 		if (acpi_bus_get_device(chandle, &child) == 0) {
1331 			level++;
1332 			phandle = chandle;
1333 			chandle = NULL;
1334 			parent = child;
1335 		}
1336 		continue;
1337 	}
1338 	return err;
1339 }
1340 
1341 static int acpi_bus_scan_fixed(struct acpi_device *root)
1342 {
1343 	int result = 0;
1344 	struct acpi_device *device = NULL;
1345 
1346 	ACPI_FUNCTION_TRACE("acpi_bus_scan_fixed");
1347 
1348 	if (!root)
1349 		return_VALUE(-ENODEV);
1350 
1351 	/*
1352 	 * Enumerate all fixed-feature devices.
1353 	 */
1354 	if (acpi_fadt.pwr_button == 0) {
1355 		result = acpi_add_single_object(&device, acpi_root,
1356 						NULL,
1357 						ACPI_BUS_TYPE_POWER_BUTTON);
1358 		if (!result)
1359 			result = acpi_start_single_object(device);
1360 	}
1361 
1362 	if (acpi_fadt.sleep_button == 0) {
1363 		result = acpi_add_single_object(&device, acpi_root,
1364 						NULL,
1365 						ACPI_BUS_TYPE_SLEEP_BUTTON);
1366 		if (!result)
1367 			result = acpi_start_single_object(device);
1368 	}
1369 
1370 	return_VALUE(result);
1371 }
1372 
1373 static int __init acpi_scan_init(void)
1374 {
1375 	int result;
1376 	struct acpi_bus_ops ops;
1377 
1378 	ACPI_FUNCTION_TRACE("acpi_scan_init");
1379 
1380 	if (acpi_disabled)
1381 		return_VALUE(0);
1382 
1383 	kset_register(&acpi_namespace_kset);
1384 
1385 	/*
1386 	 * Create the root device in the bus's device tree
1387 	 */
1388 	result = acpi_add_single_object(&acpi_root, NULL, ACPI_ROOT_OBJECT,
1389 					ACPI_BUS_TYPE_SYSTEM);
1390 	if (result)
1391 		goto Done;
1392 
1393 	result = acpi_start_single_object(acpi_root);
1394 
1395 	/*
1396 	 * Enumerate devices in the ACPI namespace.
1397 	 */
1398 	result = acpi_bus_scan_fixed(acpi_root);
1399 	if (!result) {
1400 		memset(&ops, 0, sizeof(ops));
1401 		ops.acpi_op_add = 1;
1402 		ops.acpi_op_start = 1;
1403 		result = acpi_bus_scan(acpi_root, &ops);
1404 	}
1405 
1406 	if (result)
1407 		acpi_device_unregister(acpi_root, ACPI_BUS_REMOVAL_NORMAL);
1408 
1409       Done:
1410 	return_VALUE(result);
1411 }
1412 
1413 subsys_initcall(acpi_scan_init);
1414