1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Power capping class
4  * Copyright (c) 2013, Intel Corporation.
5  */
6 
7 #include <linux/module.h>
8 #include <linux/device.h>
9 #include <linux/err.h>
10 #include <linux/kstrtox.h>
11 #include <linux/slab.h>
12 #include <linux/powercap.h>
13 
14 #define to_powercap_zone(n) container_of(n, struct powercap_zone, dev)
15 #define to_powercap_control_type(n) \
16 			container_of(n, struct powercap_control_type, dev)
17 
18 /* Power zone show function */
19 #define define_power_zone_show(_attr)		\
20 static ssize_t _attr##_show(struct device *dev, \
21 					struct device_attribute *dev_attr,\
22 					char *buf) \
23 { \
24 	u64 value; \
25 	ssize_t len = -EINVAL; \
26 	struct powercap_zone *power_zone = to_powercap_zone(dev); \
27 	\
28 	if (power_zone->ops->get_##_attr) { \
29 		if (!power_zone->ops->get_##_attr(power_zone, &value)) \
30 			len = sprintf(buf, "%lld\n", value); \
31 	} \
32 	\
33 	return len; \
34 }
35 
36 /* The only meaningful input is 0 (reset), others are silently ignored */
37 #define define_power_zone_store(_attr)		\
38 static ssize_t _attr##_store(struct device *dev,\
39 				struct device_attribute *dev_attr, \
40 				const char *buf, size_t count) \
41 { \
42 	int err; \
43 	struct powercap_zone *power_zone = to_powercap_zone(dev); \
44 	u64 value; \
45 	\
46 	err = kstrtoull(buf, 10, &value); \
47 	if (err) \
48 		return -EINVAL; \
49 	if (value) \
50 		return count; \
51 	if (power_zone->ops->reset_##_attr) { \
52 		if (!power_zone->ops->reset_##_attr(power_zone)) \
53 			return count; \
54 	} \
55 	\
56 	return -EINVAL; \
57 }
58 
59 /* Power zone constraint show function */
60 #define define_power_zone_constraint_show(_attr) \
61 static ssize_t show_constraint_##_attr(struct device *dev, \
62 				struct device_attribute *dev_attr,\
63 				char *buf) \
64 { \
65 	u64 value; \
66 	ssize_t len = -ENODATA; \
67 	struct powercap_zone *power_zone = to_powercap_zone(dev); \
68 	int id; \
69 	struct powercap_zone_constraint *pconst;\
70 	\
71 	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
72 		return -EINVAL; \
73 	if (id >= power_zone->const_id_cnt)	\
74 		return -EINVAL; \
75 	pconst = &power_zone->constraints[id]; \
76 	if (pconst && pconst->ops && pconst->ops->get_##_attr) { \
77 		if (!pconst->ops->get_##_attr(power_zone, id, &value)) \
78 			len = sprintf(buf, "%lld\n", value); \
79 	} \
80 	\
81 	return len; \
82 }
83 
84 /* Power zone constraint store function */
85 #define define_power_zone_constraint_store(_attr) \
86 static ssize_t store_constraint_##_attr(struct device *dev,\
87 				struct device_attribute *dev_attr, \
88 				const char *buf, size_t count) \
89 { \
90 	int err; \
91 	u64 value; \
92 	struct powercap_zone *power_zone = to_powercap_zone(dev); \
93 	int id; \
94 	struct powercap_zone_constraint *pconst;\
95 	\
96 	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
97 		return -EINVAL; \
98 	if (id >= power_zone->const_id_cnt)	\
99 		return -EINVAL; \
100 	pconst = &power_zone->constraints[id]; \
101 	err = kstrtoull(buf, 10, &value); \
102 	if (err) \
103 		return -EINVAL; \
104 	if (pconst && pconst->ops && pconst->ops->set_##_attr) { \
105 		if (!pconst->ops->set_##_attr(power_zone, id, value)) \
106 			return count; \
107 	} \
108 	\
109 	return -ENODATA; \
110 }
111 
112 /* Power zone information callbacks */
113 define_power_zone_show(power_uw);
114 define_power_zone_show(max_power_range_uw);
115 define_power_zone_show(energy_uj);
116 define_power_zone_store(energy_uj);
117 define_power_zone_show(max_energy_range_uj);
118 
119 /* Power zone attributes */
120 static DEVICE_ATTR_RO(max_power_range_uw);
121 static DEVICE_ATTR_RO(power_uw);
122 static DEVICE_ATTR_RO(max_energy_range_uj);
123 static DEVICE_ATTR_RW(energy_uj);
124 
125 /* Power zone constraint attributes callbacks */
126 define_power_zone_constraint_show(power_limit_uw);
127 define_power_zone_constraint_store(power_limit_uw);
128 define_power_zone_constraint_show(time_window_us);
129 define_power_zone_constraint_store(time_window_us);
130 define_power_zone_constraint_show(max_power_uw);
131 define_power_zone_constraint_show(min_power_uw);
132 define_power_zone_constraint_show(max_time_window_us);
133 define_power_zone_constraint_show(min_time_window_us);
134 
135 /* For one time seeding of constraint device attributes */
136 struct powercap_constraint_attr {
137 	struct device_attribute power_limit_attr;
138 	struct device_attribute time_window_attr;
139 	struct device_attribute max_power_attr;
140 	struct device_attribute min_power_attr;
141 	struct device_attribute max_time_window_attr;
142 	struct device_attribute min_time_window_attr;
143 	struct device_attribute name_attr;
144 };
145 
146 static struct powercap_constraint_attr
147 				constraint_attrs[MAX_CONSTRAINTS_PER_ZONE];
148 
149 /* A list of powercap control_types */
150 static LIST_HEAD(powercap_cntrl_list);
151 /* Mutex to protect list of powercap control_types */
152 static DEFINE_MUTEX(powercap_cntrl_list_lock);
153 
154 #define POWERCAP_CONSTRAINT_NAME_LEN	30 /* Some limit to avoid overflow */
155 static ssize_t show_constraint_name(struct device *dev,
156 				struct device_attribute *dev_attr,
157 				char *buf)
158 {
159 	const char *name;
160 	struct powercap_zone *power_zone = to_powercap_zone(dev);
161 	int id;
162 	ssize_t len = -ENODATA;
163 	struct powercap_zone_constraint *pconst;
164 
165 	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id))
166 		return -EINVAL;
167 	if (id >= power_zone->const_id_cnt)
168 		return -EINVAL;
169 	pconst = &power_zone->constraints[id];
170 
171 	if (pconst && pconst->ops && pconst->ops->get_name) {
172 		name = pconst->ops->get_name(power_zone, id);
173 		if (name) {
174 			sprintf(buf, "%.*s\n", POWERCAP_CONSTRAINT_NAME_LEN - 1,
175 				name);
176 			len = strlen(buf);
177 		}
178 	}
179 
180 	return len;
181 }
182 
183 static int create_constraint_attribute(int id, const char *name,
184 				int mode,
185 				struct device_attribute *dev_attr,
186 				ssize_t (*show)(struct device *,
187 					struct device_attribute *, char *),
188 				ssize_t (*store)(struct device *,
189 					struct device_attribute *,
190 				const char *, size_t)
191 				)
192 {
193 
194 	dev_attr->attr.name = kasprintf(GFP_KERNEL, "constraint_%d_%s",
195 								id, name);
196 	if (!dev_attr->attr.name)
197 		return -ENOMEM;
198 	dev_attr->attr.mode = mode;
199 	dev_attr->show = show;
200 	dev_attr->store = store;
201 
202 	return 0;
203 }
204 
205 static void free_constraint_attributes(void)
206 {
207 	int i;
208 
209 	for (i = 0; i < MAX_CONSTRAINTS_PER_ZONE; ++i) {
210 		kfree(constraint_attrs[i].power_limit_attr.attr.name);
211 		kfree(constraint_attrs[i].time_window_attr.attr.name);
212 		kfree(constraint_attrs[i].name_attr.attr.name);
213 		kfree(constraint_attrs[i].max_power_attr.attr.name);
214 		kfree(constraint_attrs[i].min_power_attr.attr.name);
215 		kfree(constraint_attrs[i].max_time_window_attr.attr.name);
216 		kfree(constraint_attrs[i].min_time_window_attr.attr.name);
217 	}
218 }
219 
220 static int seed_constraint_attributes(void)
221 {
222 	int i;
223 	int ret;
224 
225 	for (i = 0; i < MAX_CONSTRAINTS_PER_ZONE; ++i) {
226 		ret = create_constraint_attribute(i, "power_limit_uw",
227 					S_IWUSR | S_IRUGO,
228 					&constraint_attrs[i].power_limit_attr,
229 					show_constraint_power_limit_uw,
230 					store_constraint_power_limit_uw);
231 		if (ret)
232 			goto err_alloc;
233 		ret = create_constraint_attribute(i, "time_window_us",
234 					S_IWUSR | S_IRUGO,
235 					&constraint_attrs[i].time_window_attr,
236 					show_constraint_time_window_us,
237 					store_constraint_time_window_us);
238 		if (ret)
239 			goto err_alloc;
240 		ret = create_constraint_attribute(i, "name", S_IRUGO,
241 				&constraint_attrs[i].name_attr,
242 				show_constraint_name,
243 				NULL);
244 		if (ret)
245 			goto err_alloc;
246 		ret = create_constraint_attribute(i, "max_power_uw", S_IRUGO,
247 				&constraint_attrs[i].max_power_attr,
248 				show_constraint_max_power_uw,
249 				NULL);
250 		if (ret)
251 			goto err_alloc;
252 		ret = create_constraint_attribute(i, "min_power_uw", S_IRUGO,
253 				&constraint_attrs[i].min_power_attr,
254 				show_constraint_min_power_uw,
255 				NULL);
256 		if (ret)
257 			goto err_alloc;
258 		ret = create_constraint_attribute(i, "max_time_window_us",
259 				S_IRUGO,
260 				&constraint_attrs[i].max_time_window_attr,
261 				show_constraint_max_time_window_us,
262 				NULL);
263 		if (ret)
264 			goto err_alloc;
265 		ret = create_constraint_attribute(i, "min_time_window_us",
266 				S_IRUGO,
267 				&constraint_attrs[i].min_time_window_attr,
268 				show_constraint_min_time_window_us,
269 				NULL);
270 		if (ret)
271 			goto err_alloc;
272 
273 	}
274 
275 	return 0;
276 
277 err_alloc:
278 	free_constraint_attributes();
279 
280 	return ret;
281 }
282 
283 static int create_constraints(struct powercap_zone *power_zone,
284 			int nr_constraints,
285 			const struct powercap_zone_constraint_ops *const_ops)
286 {
287 	int i;
288 	int ret = 0;
289 	int count;
290 	struct powercap_zone_constraint *pconst;
291 
292 	if (!power_zone || !const_ops || !const_ops->get_power_limit_uw ||
293 					!const_ops->set_power_limit_uw ||
294 					!const_ops->get_time_window_us ||
295 					!const_ops->set_time_window_us)
296 		return -EINVAL;
297 
298 	count = power_zone->zone_attr_count;
299 	for (i = 0; i < nr_constraints; ++i) {
300 		pconst = &power_zone->constraints[i];
301 		pconst->ops = const_ops;
302 		pconst->id = power_zone->const_id_cnt;
303 		power_zone->const_id_cnt++;
304 		power_zone->zone_dev_attrs[count++] =
305 				&constraint_attrs[i].power_limit_attr.attr;
306 		power_zone->zone_dev_attrs[count++] =
307 				&constraint_attrs[i].time_window_attr.attr;
308 		if (pconst->ops->get_name)
309 			power_zone->zone_dev_attrs[count++] =
310 				&constraint_attrs[i].name_attr.attr;
311 		if (pconst->ops->get_max_power_uw)
312 			power_zone->zone_dev_attrs[count++] =
313 				&constraint_attrs[i].max_power_attr.attr;
314 		if (pconst->ops->get_min_power_uw)
315 			power_zone->zone_dev_attrs[count++] =
316 				&constraint_attrs[i].min_power_attr.attr;
317 		if (pconst->ops->get_max_time_window_us)
318 			power_zone->zone_dev_attrs[count++] =
319 				&constraint_attrs[i].max_time_window_attr.attr;
320 		if (pconst->ops->get_min_time_window_us)
321 			power_zone->zone_dev_attrs[count++] =
322 				&constraint_attrs[i].min_time_window_attr.attr;
323 	}
324 	power_zone->zone_attr_count = count;
325 
326 	return ret;
327 }
328 
329 static bool control_type_valid(void *control_type)
330 {
331 	struct powercap_control_type *pos = NULL;
332 	bool found = false;
333 
334 	mutex_lock(&powercap_cntrl_list_lock);
335 
336 	list_for_each_entry(pos, &powercap_cntrl_list, node) {
337 		if (pos == control_type) {
338 			found = true;
339 			break;
340 		}
341 	}
342 	mutex_unlock(&powercap_cntrl_list_lock);
343 
344 	return found;
345 }
346 
347 static ssize_t name_show(struct device *dev,
348 				struct device_attribute *attr,
349 				char *buf)
350 {
351 	struct powercap_zone *power_zone = to_powercap_zone(dev);
352 
353 	return sprintf(buf, "%s\n", power_zone->name);
354 }
355 
356 static DEVICE_ATTR_RO(name);
357 
358 /* Create zone and attributes in sysfs */
359 static void create_power_zone_common_attributes(
360 					struct powercap_zone *power_zone)
361 {
362 	int count = 0;
363 
364 	power_zone->zone_dev_attrs[count++] = &dev_attr_name.attr;
365 	if (power_zone->ops->get_max_energy_range_uj)
366 		power_zone->zone_dev_attrs[count++] =
367 					&dev_attr_max_energy_range_uj.attr;
368 	if (power_zone->ops->get_energy_uj) {
369 		if (power_zone->ops->reset_energy_uj)
370 			dev_attr_energy_uj.attr.mode = S_IWUSR | S_IRUSR;
371 		else
372 			dev_attr_energy_uj.attr.mode = S_IRUSR;
373 		power_zone->zone_dev_attrs[count++] =
374 					&dev_attr_energy_uj.attr;
375 	}
376 	if (power_zone->ops->get_power_uw)
377 		power_zone->zone_dev_attrs[count++] =
378 					&dev_attr_power_uw.attr;
379 	if (power_zone->ops->get_max_power_range_uw)
380 		power_zone->zone_dev_attrs[count++] =
381 					&dev_attr_max_power_range_uw.attr;
382 	power_zone->zone_dev_attrs[count] = NULL;
383 	power_zone->zone_attr_count = count;
384 }
385 
386 static void powercap_release(struct device *dev)
387 {
388 	bool allocated;
389 
390 	if (dev->parent) {
391 		struct powercap_zone *power_zone = to_powercap_zone(dev);
392 
393 		/* Store flag as the release() may free memory */
394 		allocated = power_zone->allocated;
395 		/* Remove id from parent idr struct */
396 		idr_remove(power_zone->parent_idr, power_zone->id);
397 		/* Destroy idrs allocated for this zone */
398 		idr_destroy(&power_zone->idr);
399 		kfree(power_zone->name);
400 		kfree(power_zone->zone_dev_attrs);
401 		kfree(power_zone->constraints);
402 		if (power_zone->ops->release)
403 			power_zone->ops->release(power_zone);
404 		if (allocated)
405 			kfree(power_zone);
406 	} else {
407 		struct powercap_control_type *control_type =
408 						to_powercap_control_type(dev);
409 
410 		/* Store flag as the release() may free memory */
411 		allocated = control_type->allocated;
412 		idr_destroy(&control_type->idr);
413 		mutex_destroy(&control_type->lock);
414 		if (control_type->ops && control_type->ops->release)
415 			control_type->ops->release(control_type);
416 		if (allocated)
417 			kfree(control_type);
418 	}
419 }
420 
421 static ssize_t enabled_show(struct device *dev,
422 				struct device_attribute *attr,
423 				char *buf)
424 {
425 	bool mode = true;
426 
427 	/* Default is enabled */
428 	if (dev->parent) {
429 		struct powercap_zone *power_zone = to_powercap_zone(dev);
430 		if (power_zone->ops->get_enable)
431 			if (power_zone->ops->get_enable(power_zone, &mode))
432 				mode = false;
433 	} else {
434 		struct powercap_control_type *control_type =
435 						to_powercap_control_type(dev);
436 		if (control_type->ops && control_type->ops->get_enable)
437 			if (control_type->ops->get_enable(control_type, &mode))
438 				mode = false;
439 	}
440 
441 	return sprintf(buf, "%d\n", mode);
442 }
443 
444 static ssize_t enabled_store(struct device *dev,
445 				struct device_attribute *attr,
446 				const char *buf,  size_t len)
447 {
448 	bool mode;
449 
450 	if (kstrtobool(buf, &mode))
451 		return -EINVAL;
452 	if (dev->parent) {
453 		struct powercap_zone *power_zone = to_powercap_zone(dev);
454 		if (power_zone->ops->set_enable)
455 			if (!power_zone->ops->set_enable(power_zone, mode))
456 				return len;
457 	} else {
458 		struct powercap_control_type *control_type =
459 						to_powercap_control_type(dev);
460 		if (control_type->ops && control_type->ops->set_enable)
461 			if (!control_type->ops->set_enable(control_type, mode))
462 				return len;
463 	}
464 
465 	return -ENOSYS;
466 }
467 
468 static DEVICE_ATTR_RW(enabled);
469 
470 static struct attribute *powercap_attrs[] = {
471 	&dev_attr_enabled.attr,
472 	NULL,
473 };
474 ATTRIBUTE_GROUPS(powercap);
475 
476 static struct class powercap_class = {
477 	.name = "powercap",
478 	.dev_release = powercap_release,
479 	.dev_groups = powercap_groups,
480 };
481 
482 struct powercap_zone *powercap_register_zone(
483 			struct powercap_zone *power_zone,
484 			struct powercap_control_type *control_type,
485 			const char *name,
486 			struct powercap_zone *parent,
487 			const struct powercap_zone_ops *ops,
488 			int nr_constraints,
489 			const struct powercap_zone_constraint_ops *const_ops)
490 {
491 	int result;
492 	int nr_attrs;
493 
494 	if (!name || !control_type || !ops ||
495 			nr_constraints > MAX_CONSTRAINTS_PER_ZONE ||
496 			(!ops->get_energy_uj && !ops->get_power_uw) ||
497 			!control_type_valid(control_type))
498 		return ERR_PTR(-EINVAL);
499 
500 	if (power_zone) {
501 		if (!ops->release)
502 			return ERR_PTR(-EINVAL);
503 		memset(power_zone, 0, sizeof(*power_zone));
504 	} else {
505 		power_zone = kzalloc(sizeof(*power_zone), GFP_KERNEL);
506 		if (!power_zone)
507 			return ERR_PTR(-ENOMEM);
508 		power_zone->allocated = true;
509 	}
510 	power_zone->ops = ops;
511 	power_zone->control_type_inst = control_type;
512 	if (!parent) {
513 		power_zone->dev.parent = &control_type->dev;
514 		power_zone->parent_idr = &control_type->idr;
515 	} else {
516 		power_zone->dev.parent = &parent->dev;
517 		power_zone->parent_idr = &parent->idr;
518 	}
519 	power_zone->dev.class = &powercap_class;
520 
521 	mutex_lock(&control_type->lock);
522 	/* Using idr to get the unique id */
523 	result = idr_alloc(power_zone->parent_idr, NULL, 0, 0, GFP_KERNEL);
524 	if (result < 0)
525 		goto err_idr_alloc;
526 
527 	power_zone->id = result;
528 	idr_init(&power_zone->idr);
529 	result = -ENOMEM;
530 	power_zone->name = kstrdup(name, GFP_KERNEL);
531 	if (!power_zone->name)
532 		goto err_name_alloc;
533 	dev_set_name(&power_zone->dev, "%s:%x",
534 					dev_name(power_zone->dev.parent),
535 					power_zone->id);
536 	power_zone->constraints = kcalloc(nr_constraints,
537 					  sizeof(*power_zone->constraints),
538 					  GFP_KERNEL);
539 	if (!power_zone->constraints)
540 		goto err_const_alloc;
541 
542 	nr_attrs = nr_constraints * POWERCAP_CONSTRAINTS_ATTRS +
543 						POWERCAP_ZONE_MAX_ATTRS + 1;
544 	power_zone->zone_dev_attrs = kcalloc(nr_attrs, sizeof(void *),
545 					     GFP_KERNEL);
546 	if (!power_zone->zone_dev_attrs)
547 		goto err_attr_alloc;
548 	create_power_zone_common_attributes(power_zone);
549 	result = create_constraints(power_zone, nr_constraints, const_ops);
550 	if (result)
551 		goto err_dev_ret;
552 
553 	power_zone->zone_dev_attrs[power_zone->zone_attr_count] = NULL;
554 	power_zone->dev_zone_attr_group.attrs = power_zone->zone_dev_attrs;
555 	power_zone->dev_attr_groups[0] = &power_zone->dev_zone_attr_group;
556 	power_zone->dev_attr_groups[1] = NULL;
557 	power_zone->dev.groups = power_zone->dev_attr_groups;
558 	result = device_register(&power_zone->dev);
559 	if (result)
560 		goto err_dev_ret;
561 
562 	control_type->nr_zones++;
563 	mutex_unlock(&control_type->lock);
564 
565 	return power_zone;
566 
567 err_dev_ret:
568 	kfree(power_zone->zone_dev_attrs);
569 err_attr_alloc:
570 	kfree(power_zone->constraints);
571 err_const_alloc:
572 	kfree(power_zone->name);
573 err_name_alloc:
574 	idr_remove(power_zone->parent_idr, power_zone->id);
575 err_idr_alloc:
576 	if (power_zone->allocated)
577 		kfree(power_zone);
578 	mutex_unlock(&control_type->lock);
579 
580 	return ERR_PTR(result);
581 }
582 EXPORT_SYMBOL_GPL(powercap_register_zone);
583 
584 int powercap_unregister_zone(struct powercap_control_type *control_type,
585 				struct powercap_zone *power_zone)
586 {
587 	if (!power_zone || !control_type)
588 		return -EINVAL;
589 
590 	mutex_lock(&control_type->lock);
591 	control_type->nr_zones--;
592 	mutex_unlock(&control_type->lock);
593 
594 	device_unregister(&power_zone->dev);
595 
596 	return 0;
597 }
598 EXPORT_SYMBOL_GPL(powercap_unregister_zone);
599 
600 struct powercap_control_type *powercap_register_control_type(
601 				struct powercap_control_type *control_type,
602 				const char *name,
603 				const struct powercap_control_type_ops *ops)
604 {
605 	int result;
606 
607 	if (!name)
608 		return ERR_PTR(-EINVAL);
609 	if (control_type) {
610 		if (!ops || !ops->release)
611 			return ERR_PTR(-EINVAL);
612 		memset(control_type, 0, sizeof(*control_type));
613 	} else {
614 		control_type = kzalloc(sizeof(*control_type), GFP_KERNEL);
615 		if (!control_type)
616 			return ERR_PTR(-ENOMEM);
617 		control_type->allocated = true;
618 	}
619 	mutex_init(&control_type->lock);
620 	control_type->ops = ops;
621 	INIT_LIST_HEAD(&control_type->node);
622 	control_type->dev.class = &powercap_class;
623 	dev_set_name(&control_type->dev, "%s", name);
624 	result = device_register(&control_type->dev);
625 	if (result) {
626 		if (control_type->allocated)
627 			kfree(control_type);
628 		return ERR_PTR(result);
629 	}
630 	idr_init(&control_type->idr);
631 
632 	mutex_lock(&powercap_cntrl_list_lock);
633 	list_add_tail(&control_type->node, &powercap_cntrl_list);
634 	mutex_unlock(&powercap_cntrl_list_lock);
635 
636 	return control_type;
637 }
638 EXPORT_SYMBOL_GPL(powercap_register_control_type);
639 
640 int powercap_unregister_control_type(struct powercap_control_type *control_type)
641 {
642 	struct powercap_control_type *pos = NULL;
643 
644 	if (control_type->nr_zones) {
645 		dev_err(&control_type->dev, "Zones of this type still not freed\n");
646 		return -EINVAL;
647 	}
648 	mutex_lock(&powercap_cntrl_list_lock);
649 	list_for_each_entry(pos, &powercap_cntrl_list, node) {
650 		if (pos == control_type) {
651 			list_del(&control_type->node);
652 			mutex_unlock(&powercap_cntrl_list_lock);
653 			device_unregister(&control_type->dev);
654 			return 0;
655 		}
656 	}
657 	mutex_unlock(&powercap_cntrl_list_lock);
658 
659 	return -ENODEV;
660 }
661 EXPORT_SYMBOL_GPL(powercap_unregister_control_type);
662 
663 static int __init powercap_init(void)
664 {
665 	int result;
666 
667 	result = seed_constraint_attributes();
668 	if (result)
669 		return result;
670 
671 	return class_register(&powercap_class);
672 }
673 
674 fs_initcall(powercap_init);
675 
676 MODULE_DESCRIPTION("PowerCap sysfs Driver");
677 MODULE_AUTHOR("Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>");
678 MODULE_LICENSE("GPL v2");
679