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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Componentized device handling.
4 *
5 * This is work in progress. We gather up the component devices into a list,
6 * and bind them when instructed. At the moment, we're specific to the DRM
7 * subsystem, and only handles one master device, but this doesn't have to be
8 * the case.
9 */
10#include <linux/component.h>
11#include <linux/device.h>
12#include <linux/kref.h>
13#include <linux/list.h>
14#include <linux/mutex.h>
15#include <linux/slab.h>
16#include <linux/debugfs.h>
17
18/**
19 * DOC: overview
20 *
21 * The component helper allows drivers to collect a pile of sub-devices,
22 * including their bound drivers, into an aggregate driver. Various subsystems
23 * already provide functions to get hold of such components, e.g.
24 * of_clk_get_by_name(). The component helper can be used when such a
25 * subsystem-specific way to find a device is not available: The component
26 * helper fills the niche of aggregate drivers for specific hardware, where
27 * further standardization into a subsystem would not be practical. The common
28 * example is when a logical device (e.g. a DRM display driver) is spread around
29 * the SoC on various components (scanout engines, blending blocks, transcoders
30 * for various outputs and so on).
31 *
32 * The component helper also doesn't solve runtime dependencies, e.g. for system
33 * suspend and resume operations. See also :ref:`device links<device_link>`.
34 *
35 * Components are registered using component_add() and unregistered with
36 * component_del(), usually from the driver's probe and disconnect functions.
37 *
38 * Aggregate drivers first assemble a component match list of what they need
39 * using component_match_add(). This is then registered as an aggregate driver
40 * using component_master_add_with_match(), and unregistered using
41 * component_master_del().
42 */
43
44struct component;
45
46struct component_match_array {
47 void *data;
48 int (*compare)(struct device *, void *);
49 int (*compare_typed)(struct device *, int, void *);
50 void (*release)(struct device *, void *);
51 struct component *component;
52 bool duplicate;
53};
54
55struct component_match {
56 size_t alloc;
57 size_t num;
58 struct component_match_array *compare;
59};
60
61struct master {
62 struct list_head node;
63 bool bound;
64
65 const struct component_master_ops *ops;
66 struct device *parent;
67 struct component_match *match;
68};
69
70struct component {
71 struct list_head node;
72 struct master *master;
73 bool bound;
74
75 const struct component_ops *ops;
76 int subcomponent;
77 struct device *dev;
78};
79
80static DEFINE_MUTEX(component_mutex);
81static LIST_HEAD(component_list);
82static LIST_HEAD(masters);
83
84#ifdef CONFIG_DEBUG_FS
85
86static struct dentry *component_debugfs_dir;
87
88static int component_devices_show(struct seq_file *s, void *data)
89{
90 struct master *m = s->private;
91 struct component_match *match = m->match;
92 size_t i;
93
94 mutex_lock(&component_mutex);
95 seq_printf(s, "%-40s %20s\n", "master name", "status");
96 seq_puts(s, "-------------------------------------------------------------\n");
97 seq_printf(s, "%-40s %20s\n\n",
98 dev_name(m->parent), m->bound ? "bound" : "not bound");
99
100 seq_printf(s, "%-40s %20s\n", "device name", "status");
101 seq_puts(s, "-------------------------------------------------------------\n");
102 for (i = 0; i < match->num; i++) {
103 struct component *component = match->compare[i].component;
104
105 seq_printf(s, "%-40s %20s\n",
106 component ? dev_name(component->dev) : "(unknown)",
107 component ? (component->bound ? "bound" : "not bound") : "not registered");
108 }
109 mutex_unlock(&component_mutex);
110
111 return 0;
112}
113
114DEFINE_SHOW_ATTRIBUTE(component_devices);
115
116static int __init component_debug_init(void)
117{
118 component_debugfs_dir = debugfs_create_dir("device_component", NULL);
119
120 return 0;
121}
122
123core_initcall(component_debug_init);
124
125static void component_master_debugfs_add(struct master *m)
126{
127 debugfs_create_file(dev_name(m->parent), 0444, component_debugfs_dir, m,
128 &component_devices_fops);
129}
130
131static void component_master_debugfs_del(struct master *m)
132{
133 debugfs_remove(debugfs_lookup(dev_name(m->parent), component_debugfs_dir));
134}
135
136#else
137
138static void component_master_debugfs_add(struct master *m)
139{ }
140
141static void component_master_debugfs_del(struct master *m)
142{ }
143
144#endif
145
146static struct master *__master_find(struct device *parent,
147 const struct component_master_ops *ops)
148{
149 struct master *m;
150
151 list_for_each_entry(m, &masters, node)
152 if (m->parent == parent && (!ops || m->ops == ops))
153 return m;
154
155 return NULL;
156}
157
158static struct component *find_component(struct master *master,
159 struct component_match_array *mc)
160{
161 struct component *c;
162
163 list_for_each_entry(c, &component_list, node) {
164 if (c->master && c->master != master)
165 continue;
166
167 if (mc->compare && mc->compare(c->dev, mc->data))
168 return c;
169
170 if (mc->compare_typed &&
171 mc->compare_typed(c->dev, c->subcomponent, mc->data))
172 return c;
173 }
174
175 return NULL;
176}
177
178static int find_components(struct master *master)
179{
180 struct component_match *match = master->match;
181 size_t i;
182 int ret = 0;
183
184 /*
185 * Scan the array of match functions and attach
186 * any components which are found to this master.
187 */
188 for (i = 0; i < match->num; i++) {
189 struct component_match_array *mc = &match->compare[i];
190 struct component *c;
191
192 dev_dbg(master->parent, "Looking for component %zu\n", i);
193
194 if (match->compare[i].component)
195 continue;
196
197 c = find_component(master, mc);
198 if (!c) {
199 ret = -ENXIO;
200 break;
201 }
202
203 dev_dbg(master->parent, "found component %s, duplicate %u\n", dev_name(c->dev), !!c->master);
204
205 /* Attach this component to the master */
206 match->compare[i].duplicate = !!c->master;
207 match->compare[i].component = c;
208 c->master = master;
209 }
210 return ret;
211}
212
213/* Detach component from associated master */
214static void remove_component(struct master *master, struct component *c)
215{
216 size_t i;
217
218 /* Detach the component from this master. */
219 for (i = 0; i < master->match->num; i++)
220 if (master->match->compare[i].component == c)
221 master->match->compare[i].component = NULL;
222}
223
224/*
225 * Try to bring up a master. If component is NULL, we're interested in
226 * this master, otherwise it's a component which must be present to try
227 * and bring up the master.
228 *
229 * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
230 */
231static int try_to_bring_up_master(struct master *master,
232 struct component *component)
233{
234 int ret;
235
236 dev_dbg(master->parent, "trying to bring up master\n");
237
238 if (find_components(master)) {
239 dev_dbg(master->parent, "master has incomplete components\n");
240 return 0;
241 }
242
243 if (component && component->master != master) {
244 dev_dbg(master->parent, "master is not for this component (%s)\n",
245 dev_name(component->dev));
246 return 0;
247 }
248
249 if (!devres_open_group(master->parent, NULL, GFP_KERNEL))
250 return -ENOMEM;
251
252 /* Found all components */
253 ret = master->ops->bind(master->parent);
254 if (ret < 0) {
255 devres_release_group(master->parent, NULL);
256 if (ret != -EPROBE_DEFER)
257 dev_info(master->parent, "master bind failed: %d\n", ret);
258 return ret;
259 }
260
261 master->bound = true;
262 return 1;
263}
264
265static int try_to_bring_up_masters(struct component *component)
266{
267 struct master *m;
268 int ret = 0;
269
270 list_for_each_entry(m, &masters, node) {
271 if (!m->bound) {
272 ret = try_to_bring_up_master(m, component);
273 if (ret != 0)
274 break;
275 }
276 }
277
278 return ret;
279}
280
281static void take_down_master(struct master *master)
282{
283 if (master->bound) {
284 master->ops->unbind(master->parent);
285 devres_release_group(master->parent, NULL);
286 master->bound = false;
287 }
288}
289
290static void devm_component_match_release(struct device *parent, void *res)
291{
292 struct component_match *match = res;
293 unsigned int i;
294
295 for (i = 0; i < match->num; i++) {
296 struct component_match_array *mc = &match->compare[i];
297
298 if (mc->release)
299 mc->release(parent, mc->data);
300 }
301
302 kfree(match->compare);
303}
304
305static int component_match_realloc(struct component_match *match, size_t num)
306{
307 struct component_match_array *new;
308
309 if (match->alloc == num)
310 return 0;
311
312 new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
313 if (!new)
314 return -ENOMEM;
315
316 if (match->compare) {
317 memcpy(new, match->compare, sizeof(*new) *
318 min(match->num, num));
319 kfree(match->compare);
320 }
321 match->compare = new;
322 match->alloc = num;
323
324 return 0;
325}
326
327static void __component_match_add(struct device *master,
328 struct component_match **matchptr,
329 void (*release)(struct device *, void *),
330 int (*compare)(struct device *, void *),
331 int (*compare_typed)(struct device *, int, void *),
332 void *compare_data)
333{
334 struct component_match *match = *matchptr;
335
336 if (IS_ERR(match))
337 return;
338
339 if (!match) {
340 match = devres_alloc(devm_component_match_release,
341 sizeof(*match), GFP_KERNEL);
342 if (!match) {
343 *matchptr = ERR_PTR(-ENOMEM);
344 return;
345 }
346
347 devres_add(master, match);
348
349 *matchptr = match;
350 }
351
352 if (match->num == match->alloc) {
353 size_t new_size = match->alloc + 16;
354 int ret;
355
356 ret = component_match_realloc(match, new_size);
357 if (ret) {
358 *matchptr = ERR_PTR(ret);
359 return;
360 }
361 }
362
363 match->compare[match->num].compare = compare;
364 match->compare[match->num].compare_typed = compare_typed;
365 match->compare[match->num].release = release;
366 match->compare[match->num].data = compare_data;
367 match->compare[match->num].component = NULL;
368 match->num++;
369}
370
371/**
372 * component_match_add_release - add a component match entry with release callback
373 * @master: device with the aggregate driver
374 * @matchptr: pointer to the list of component matches
375 * @release: release function for @compare_data
376 * @compare: compare function to match against all components
377 * @compare_data: opaque pointer passed to the @compare function
378 *
379 * Adds a new component match to the list stored in @matchptr, which the @master
380 * aggregate driver needs to function. The list of component matches pointed to
381 * by @matchptr must be initialized to NULL before adding the first match. This
382 * only matches against components added with component_add().
383 *
384 * The allocated match list in @matchptr is automatically released using devm
385 * actions, where upon @release will be called to free any references held by
386 * @compare_data, e.g. when @compare_data is a &device_node that must be
387 * released with of_node_put().
388 *
389 * See also component_match_add() and component_match_add_typed().
390 */
391void component_match_add_release(struct device *master,
392 struct component_match **matchptr,
393 void (*release)(struct device *, void *),
394 int (*compare)(struct device *, void *), void *compare_data)
395{
396 __component_match_add(master, matchptr, release, compare, NULL,
397 compare_data);
398}
399EXPORT_SYMBOL(component_match_add_release);
400
401/**
402 * component_match_add_typed - add a component match entry for a typed component
403 * @master: device with the aggregate driver
404 * @matchptr: pointer to the list of component matches
405 * @compare_typed: compare function to match against all typed components
406 * @compare_data: opaque pointer passed to the @compare function
407 *
408 * Adds a new component match to the list stored in @matchptr, which the @master
409 * aggregate driver needs to function. The list of component matches pointed to
410 * by @matchptr must be initialized to NULL before adding the first match. This
411 * only matches against components added with component_add_typed().
412 *
413 * The allocated match list in @matchptr is automatically released using devm
414 * actions.
415 *
416 * See also component_match_add_release() and component_match_add_typed().
417 */
418void component_match_add_typed(struct device *master,
419 struct component_match **matchptr,
420 int (*compare_typed)(struct device *, int, void *), void *compare_data)
421{
422 __component_match_add(master, matchptr, NULL, NULL, compare_typed,
423 compare_data);
424}
425EXPORT_SYMBOL(component_match_add_typed);
426
427static void free_master(struct master *master)
428{
429 struct component_match *match = master->match;
430 int i;
431
432 component_master_debugfs_del(master);
433 list_del(&master->node);
434
435 if (match) {
436 for (i = 0; i < match->num; i++) {
437 struct component *c = match->compare[i].component;
438 if (c)
439 c->master = NULL;
440 }
441 }
442
443 kfree(master);
444}
445
446/**
447 * component_master_add_with_match - register an aggregate driver
448 * @parent: parent device of the aggregate driver
449 * @ops: callbacks for the aggregate driver
450 * @match: component match list for the aggregate driver
451 *
452 * Registers a new aggregate driver consisting of the components added to @match
453 * by calling one of the component_match_add() functions. Once all components in
454 * @match are available, it will be assembled by calling
455 * &component_master_ops.bind from @ops. Must be unregistered by calling
456 * component_master_del().
457 */
458int component_master_add_with_match(struct device *parent,
459 const struct component_master_ops *ops,
460 struct component_match *match)
461{
462 struct master *master;
463 int ret;
464
465 /* Reallocate the match array for its true size */
466 ret = component_match_realloc(match, match->num);
467 if (ret)
468 return ret;
469
470 master = kzalloc(sizeof(*master), GFP_KERNEL);
471 if (!master)
472 return -ENOMEM;
473
474 master->parent = parent;
475 master->ops = ops;
476 master->match = match;
477
478 component_master_debugfs_add(master);
479 /* Add to the list of available masters. */
480 mutex_lock(&component_mutex);
481 list_add(&master->node, &masters);
482
483 ret = try_to_bring_up_master(master, NULL);
484
485 if (ret < 0)
486 free_master(master);
487
488 mutex_unlock(&component_mutex);
489
490 return ret < 0 ? ret : 0;
491}
492EXPORT_SYMBOL_GPL(component_master_add_with_match);
493
494/**
495 * component_master_del - unregister an aggregate driver
496 * @parent: parent device of the aggregate driver
497 * @ops: callbacks for the aggregate driver
498 *
499 * Unregisters an aggregate driver registered with
500 * component_master_add_with_match(). If necessary the aggregate driver is first
501 * disassembled by calling &component_master_ops.unbind from @ops.
502 */
503void component_master_del(struct device *parent,
504 const struct component_master_ops *ops)
505{
506 struct master *master;
507
508 mutex_lock(&component_mutex);
509 master = __master_find(parent, ops);
510 if (master) {
511 take_down_master(master);
512 free_master(master);
513 }
514 mutex_unlock(&component_mutex);
515}
516EXPORT_SYMBOL_GPL(component_master_del);
517
518static void component_unbind(struct component *component,
519 struct master *master, void *data)
520{
521 WARN_ON(!component->bound);
522
523 if (component->ops && component->ops->unbind)
524 component->ops->unbind(component->dev, master->parent, data);
525 component->bound = false;
526
527 /* Release all resources claimed in the binding of this component */
528 devres_release_group(component->dev, component);
529}
530
531/**
532 * component_unbind_all - unbind all components of an aggregate driver
533 * @parent: parent device of the aggregate driver
534 * @data: opaque pointer, passed to all components
535 *
536 * Unbinds all components of the aggregate device by passing @data to their
537 * &component_ops.unbind functions. Should be called from
538 * &component_master_ops.unbind.
539 */
540void component_unbind_all(struct device *parent, void *data)
541{
542 struct master *master;
543 struct component *c;
544 size_t i;
545
546 WARN_ON(!mutex_is_locked(&component_mutex));
547
548 master = __master_find(parent, NULL);
549 if (!master)
550 return;
551
552 /* Unbind components in reverse order */
553 for (i = master->match->num; i--; )
554 if (!master->match->compare[i].duplicate) {
555 c = master->match->compare[i].component;
556 component_unbind(c, master, data);
557 }
558}
559EXPORT_SYMBOL_GPL(component_unbind_all);
560
561static int component_bind(struct component *component, struct master *master,
562 void *data)
563{
564 int ret;
565
566 /*
567 * Each component initialises inside its own devres group.
568 * This allows us to roll-back a failed component without
569 * affecting anything else.
570 */
571 if (!devres_open_group(master->parent, NULL, GFP_KERNEL))
572 return -ENOMEM;
573
574 /*
575 * Also open a group for the device itself: this allows us
576 * to release the resources claimed against the sub-device
577 * at the appropriate moment.
578 */
579 if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
580 devres_release_group(master->parent, NULL);
581 return -ENOMEM;
582 }
583
584 dev_dbg(master->parent, "binding %s (ops %ps)\n",
585 dev_name(component->dev), component->ops);
586
587 ret = component->ops->bind(component->dev, master->parent, data);
588 if (!ret) {
589 component->bound = true;
590
591 /*
592 * Close the component device's group so that resources
593 * allocated in the binding are encapsulated for removal
594 * at unbind. Remove the group on the DRM device as we
595 * can clean those resources up independently.
596 */
597 devres_close_group(component->dev, NULL);
598 devres_remove_group(master->parent, NULL);
599
600 dev_info(master->parent, "bound %s (ops %ps)\n",
601 dev_name(component->dev), component->ops);
602 } else {
603 devres_release_group(component->dev, NULL);
604 devres_release_group(master->parent, NULL);
605
606 if (ret != -EPROBE_DEFER)
607 dev_err(master->parent, "failed to bind %s (ops %ps): %d\n",
608 dev_name(component->dev), component->ops, ret);
609 }
610
611 return ret;
612}
613
614/**
615 * component_bind_all - bind all components of an aggregate driver
616 * @parent: parent device of the aggregate driver
617 * @data: opaque pointer, passed to all components
618 *
619 * Binds all components of the aggregate @dev by passing @data to their
620 * &component_ops.bind functions. Should be called from
621 * &component_master_ops.bind.
622 */
623int component_bind_all(struct device *parent, void *data)
624{
625 struct master *master;
626 struct component *c;
627 size_t i;
628 int ret = 0;
629
630 WARN_ON(!mutex_is_locked(&component_mutex));
631
632 master = __master_find(parent, NULL);
633 if (!master)
634 return -EINVAL;
635
636 /* Bind components in match order */
637 for (i = 0; i < master->match->num; i++)
638 if (!master->match->compare[i].duplicate) {
639 c = master->match->compare[i].component;
640 ret = component_bind(c, master, data);
641 if (ret)
642 break;
643 }
644
645 if (ret != 0) {
646 for (; i > 0; i--)
647 if (!master->match->compare[i - 1].duplicate) {
648 c = master->match->compare[i - 1].component;
649 component_unbind(c, master, data);
650 }
651 }
652
653 return ret;
654}
655EXPORT_SYMBOL_GPL(component_bind_all);
656
657static int __component_add(struct device *dev, const struct component_ops *ops,
658 int subcomponent)
659{
660 struct component *component;
661 int ret;
662
663 component = kzalloc(sizeof(*component), GFP_KERNEL);
664 if (!component)
665 return -ENOMEM;
666
667 component->ops = ops;
668 component->dev = dev;
669 component->subcomponent = subcomponent;
670
671 dev_dbg(dev, "adding component (ops %ps)\n", ops);
672
673 mutex_lock(&component_mutex);
674 list_add_tail(&component->node, &component_list);
675
676 ret = try_to_bring_up_masters(component);
677 if (ret < 0) {
678 if (component->master)
679 remove_component(component->master, component);
680 list_del(&component->node);
681
682 kfree(component);
683 }
684 mutex_unlock(&component_mutex);
685
686 return ret < 0 ? ret : 0;
687}
688
689/**
690 * component_add_typed - register a component
691 * @dev: component device
692 * @ops: component callbacks
693 * @subcomponent: nonzero identifier for subcomponents
694 *
695 * Register a new component for @dev. Functions in @ops will be call when the
696 * aggregate driver is ready to bind the overall driver by calling
697 * component_bind_all(). See also &struct component_ops.
698 *
699 * @subcomponent must be nonzero and is used to differentiate between multiple
700 * components registerd on the same device @dev. These components are match
701 * using component_match_add_typed().
702 *
703 * The component needs to be unregistered at driver unload/disconnect by
704 * calling component_del().
705 *
706 * See also component_add().
707 */
708int component_add_typed(struct device *dev, const struct component_ops *ops,
709 int subcomponent)
710{
711 if (WARN_ON(subcomponent == 0))
712 return -EINVAL;
713
714 return __component_add(dev, ops, subcomponent);
715}
716EXPORT_SYMBOL_GPL(component_add_typed);
717
718/**
719 * component_add - register a component
720 * @dev: component device
721 * @ops: component callbacks
722 *
723 * Register a new component for @dev. Functions in @ops will be called when the
724 * aggregate driver is ready to bind the overall driver by calling
725 * component_bind_all(). See also &struct component_ops.
726 *
727 * The component needs to be unregistered at driver unload/disconnect by
728 * calling component_del().
729 *
730 * See also component_add_typed() for a variant that allows multipled different
731 * components on the same device.
732 */
733int component_add(struct device *dev, const struct component_ops *ops)
734{
735 return __component_add(dev, ops, 0);
736}
737EXPORT_SYMBOL_GPL(component_add);
738
739/**
740 * component_del - unregister a component
741 * @dev: component device
742 * @ops: component callbacks
743 *
744 * Unregister a component added with component_add(). If the component is bound
745 * into an aggregate driver, this will force the entire aggregate driver, including
746 * all its components, to be unbound.
747 */
748void component_del(struct device *dev, const struct component_ops *ops)
749{
750 struct component *c, *component = NULL;
751
752 mutex_lock(&component_mutex);
753 list_for_each_entry(c, &component_list, node)
754 if (c->dev == dev && c->ops == ops) {
755 list_del(&c->node);
756 component = c;
757 break;
758 }
759
760 if (component && component->master) {
761 take_down_master(component->master);
762 remove_component(component->master, component);
763 }
764
765 mutex_unlock(&component_mutex);
766
767 WARN_ON(!component);
768 kfree(component);
769}
770EXPORT_SYMBOL_GPL(component_del);