1 // SPDX-License-Identifier: GPL-2.0
3 * Componentized device handling.
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
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>
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).
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>`.
35 * Components are registered using component_add() and unregistered with
36 * component_del(), usually from the driver's probe and disconnect functions.
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().
46 struct component_match_array {
48 int (*compare)(struct device *, void *);
49 int (*compare_typed)(struct device *, int, void *);
50 void (*release)(struct device *, void *);
51 struct component *component;
55 struct component_match {
58 struct component_match_array *compare;
62 struct list_head node;
65 const struct component_master_ops *ops;
67 struct component_match *match;
71 struct list_head node;
72 struct master *master;
75 const struct component_ops *ops;
80 static DEFINE_MUTEX(component_mutex);
81 static LIST_HEAD(component_list);
82 static LIST_HEAD(masters);
84 #ifdef CONFIG_DEBUG_FS
86 static struct dentry *component_debugfs_dir;
88 static int component_devices_show(struct seq_file *s, void *data)
90 struct master *m = s->private;
91 struct component_match *match = m->match;
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->dev), m->bound ? "bound" : "not bound");
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;
105 seq_printf(s, "%-40s %20s\n",
106 component ? dev_name(component->dev) : "(unknown)",
107 component ? (component->bound ? "bound" : "not bound") : "not registered");
109 mutex_unlock(&component_mutex);
114 DEFINE_SHOW_ATTRIBUTE(component_devices);
116 static int __init component_debug_init(void)
118 component_debugfs_dir = debugfs_create_dir("device_component", NULL);
123 core_initcall(component_debug_init);
125 static void component_master_debugfs_add(struct master *m)
127 debugfs_create_file(dev_name(m->dev), 0444, component_debugfs_dir, m,
128 &component_devices_fops);
131 static void component_master_debugfs_del(struct master *m)
133 debugfs_remove(debugfs_lookup(dev_name(m->dev), component_debugfs_dir));
138 static void component_master_debugfs_add(struct master *m)
141 static void component_master_debugfs_del(struct master *m)
146 static struct master *__master_find(struct device *dev,
147 const struct component_master_ops *ops)
151 list_for_each_entry(m, &masters, node)
152 if (m->dev == dev && (!ops || m->ops == ops))
158 static struct component *find_component(struct master *master,
159 struct component_match_array *mc)
163 list_for_each_entry(c, &component_list, node) {
164 if (c->master && c->master != master)
167 if (mc->compare && mc->compare(c->dev, mc->data))
170 if (mc->compare_typed &&
171 mc->compare_typed(c->dev, c->subcomponent, mc->data))
178 static int find_components(struct master *master)
180 struct component_match *match = master->match;
185 * Scan the array of match functions and attach
186 * any components which are found to this master.
188 for (i = 0; i < match->num; i++) {
189 struct component_match_array *mc = &match->compare[i];
192 dev_dbg(master->dev, "Looking for component %zu\n", i);
194 if (match->compare[i].component)
197 c = find_component(master, mc);
203 dev_dbg(master->dev, "found component %s, duplicate %u\n", dev_name(c->dev), !!c->master);
205 /* Attach this component to the master */
206 match->compare[i].duplicate = !!c->master;
207 match->compare[i].component = c;
213 /* Detach component from associated master */
214 static void remove_component(struct master *master, struct component *c)
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;
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.
229 * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
231 static int try_to_bring_up_master(struct master *master,
232 struct component *component)
236 dev_dbg(master->dev, "trying to bring up master\n");
238 if (find_components(master)) {
239 dev_dbg(master->dev, "master has incomplete components\n");
243 if (component && component->master != master) {
244 dev_dbg(master->dev, "master is not for this component (%s)\n",
245 dev_name(component->dev));
249 if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
252 /* Found all components */
253 ret = master->ops->bind(master->dev);
255 devres_release_group(master->dev, NULL);
256 if (ret != -EPROBE_DEFER)
257 dev_info(master->dev, "master bind failed: %d\n", ret);
261 master->bound = true;
265 static int try_to_bring_up_masters(struct component *component)
270 list_for_each_entry(m, &masters, node) {
272 ret = try_to_bring_up_master(m, component);
281 static void take_down_master(struct master *master)
284 master->ops->unbind(master->dev);
285 devres_release_group(master->dev, NULL);
286 master->bound = false;
290 static void component_match_release(struct device *master,
291 struct component_match *match)
295 for (i = 0; i < match->num; i++) {
296 struct component_match_array *mc = &match->compare[i];
299 mc->release(master, mc->data);
302 kfree(match->compare);
305 static void devm_component_match_release(struct device *dev, void *res)
307 component_match_release(dev, res);
310 static int component_match_realloc(struct device *dev,
311 struct component_match *match, size_t num)
313 struct component_match_array *new;
315 if (match->alloc == num)
318 new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
322 if (match->compare) {
323 memcpy(new, match->compare, sizeof(*new) *
324 min(match->num, num));
325 kfree(match->compare);
327 match->compare = new;
333 static void __component_match_add(struct device *master,
334 struct component_match **matchptr,
335 void (*release)(struct device *, void *),
336 int (*compare)(struct device *, void *),
337 int (*compare_typed)(struct device *, int, void *),
340 struct component_match *match = *matchptr;
346 match = devres_alloc(devm_component_match_release,
347 sizeof(*match), GFP_KERNEL);
349 *matchptr = ERR_PTR(-ENOMEM);
353 devres_add(master, match);
358 if (match->num == match->alloc) {
359 size_t new_size = match->alloc + 16;
362 ret = component_match_realloc(master, match, new_size);
364 *matchptr = ERR_PTR(ret);
369 match->compare[match->num].compare = compare;
370 match->compare[match->num].compare_typed = compare_typed;
371 match->compare[match->num].release = release;
372 match->compare[match->num].data = compare_data;
373 match->compare[match->num].component = NULL;
378 * component_match_add_release - add a component match entry with release callback
379 * @master: device with the aggregate driver
380 * @matchptr: pointer to the list of component matches
381 * @release: release function for @compare_data
382 * @compare: compare function to match against all components
383 * @compare_data: opaque pointer passed to the @compare function
385 * Adds a new component match to the list stored in @matchptr, which the @master
386 * aggregate driver needs to function. The list of component matches pointed to
387 * by @matchptr must be initialized to NULL before adding the first match. This
388 * only matches against components added with component_add().
390 * The allocated match list in @matchptr is automatically released using devm
391 * actions, where upon @release will be called to free any references held by
392 * @compare_data, e.g. when @compare_data is a &device_node that must be
393 * released with of_node_put().
395 * See also component_match_add() and component_match_add_typed().
397 void component_match_add_release(struct device *master,
398 struct component_match **matchptr,
399 void (*release)(struct device *, void *),
400 int (*compare)(struct device *, void *), void *compare_data)
402 __component_match_add(master, matchptr, release, compare, NULL,
405 EXPORT_SYMBOL(component_match_add_release);
408 * component_match_add_typed - add a component match entry for a typed component
409 * @master: device with the aggregate driver
410 * @matchptr: pointer to the list of component matches
411 * @compare_typed: compare function to match against all typed components
412 * @compare_data: opaque pointer passed to the @compare function
414 * Adds a new component match to the list stored in @matchptr, which the @master
415 * aggregate driver needs to function. The list of component matches pointed to
416 * by @matchptr must be initialized to NULL before adding the first match. This
417 * only matches against components added with component_add_typed().
419 * The allocated match list in @matchptr is automatically released using devm
422 * See also component_match_add_release() and component_match_add_typed().
424 void component_match_add_typed(struct device *master,
425 struct component_match **matchptr,
426 int (*compare_typed)(struct device *, int, void *), void *compare_data)
428 __component_match_add(master, matchptr, NULL, NULL, compare_typed,
431 EXPORT_SYMBOL(component_match_add_typed);
433 static void free_master(struct master *master)
435 struct component_match *match = master->match;
438 component_master_debugfs_del(master);
439 list_del(&master->node);
442 for (i = 0; i < match->num; i++) {
443 struct component *c = match->compare[i].component;
453 * component_master_add_with_match - register an aggregate driver
454 * @dev: device with the aggregate driver
455 * @ops: callbacks for the aggregate driver
456 * @match: component match list for the aggregate driver
458 * Registers a new aggregate driver consisting of the components added to @match
459 * by calling one of the component_match_add() functions. Once all components in
460 * @match are available, it will be assembled by calling
461 * &component_master_ops.bind from @ops. Must be unregistered by calling
462 * component_master_del().
464 int component_master_add_with_match(struct device *dev,
465 const struct component_master_ops *ops,
466 struct component_match *match)
468 struct master *master;
471 /* Reallocate the match array for its true size */
472 ret = component_match_realloc(dev, match, match->num);
476 master = kzalloc(sizeof(*master), GFP_KERNEL);
482 master->match = match;
484 component_master_debugfs_add(master);
485 /* Add to the list of available masters. */
486 mutex_lock(&component_mutex);
487 list_add(&master->node, &masters);
489 ret = try_to_bring_up_master(master, NULL);
494 mutex_unlock(&component_mutex);
496 return ret < 0 ? ret : 0;
498 EXPORT_SYMBOL_GPL(component_master_add_with_match);
501 * component_master_del - unregister an aggregate driver
502 * @dev: device with the aggregate driver
503 * @ops: callbacks for the aggregate driver
505 * Unregisters an aggregate driver registered with
506 * component_master_add_with_match(). If necessary the aggregate driver is first
507 * disassembled by calling &component_master_ops.unbind from @ops.
509 void component_master_del(struct device *dev,
510 const struct component_master_ops *ops)
512 struct master *master;
514 mutex_lock(&component_mutex);
515 master = __master_find(dev, ops);
517 take_down_master(master);
520 mutex_unlock(&component_mutex);
522 EXPORT_SYMBOL_GPL(component_master_del);
524 static void component_unbind(struct component *component,
525 struct master *master, void *data)
527 WARN_ON(!component->bound);
529 if (component->ops && component->ops->unbind)
530 component->ops->unbind(component->dev, master->dev, data);
531 component->bound = false;
533 /* Release all resources claimed in the binding of this component */
534 devres_release_group(component->dev, component);
538 * component_unbind_all - unbind all components of an aggregate driver
539 * @master_dev: device with the aggregate driver
540 * @data: opaque pointer, passed to all components
542 * Unbinds all components of the aggregate @dev by passing @data to their
543 * &component_ops.unbind functions. Should be called from
544 * &component_master_ops.unbind.
546 void component_unbind_all(struct device *master_dev, void *data)
548 struct master *master;
552 WARN_ON(!mutex_is_locked(&component_mutex));
554 master = __master_find(master_dev, NULL);
558 /* Unbind components in reverse order */
559 for (i = master->match->num; i--; )
560 if (!master->match->compare[i].duplicate) {
561 c = master->match->compare[i].component;
562 component_unbind(c, master, data);
565 EXPORT_SYMBOL_GPL(component_unbind_all);
567 static int component_bind(struct component *component, struct master *master,
573 * Each component initialises inside its own devres group.
574 * This allows us to roll-back a failed component without
575 * affecting anything else.
577 if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
581 * Also open a group for the device itself: this allows us
582 * to release the resources claimed against the sub-device
583 * at the appropriate moment.
585 if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
586 devres_release_group(master->dev, NULL);
590 dev_dbg(master->dev, "binding %s (ops %ps)\n",
591 dev_name(component->dev), component->ops);
593 ret = component->ops->bind(component->dev, master->dev, data);
595 component->bound = true;
598 * Close the component device's group so that resources
599 * allocated in the binding are encapsulated for removal
600 * at unbind. Remove the group on the DRM device as we
601 * can clean those resources up independently.
603 devres_close_group(component->dev, NULL);
604 devres_remove_group(master->dev, NULL);
606 dev_info(master->dev, "bound %s (ops %ps)\n",
607 dev_name(component->dev), component->ops);
609 devres_release_group(component->dev, NULL);
610 devres_release_group(master->dev, NULL);
612 if (ret != -EPROBE_DEFER)
613 dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
614 dev_name(component->dev), component->ops, ret);
621 * component_bind_all - bind all components of an aggregate driver
622 * @master_dev: device with the aggregate driver
623 * @data: opaque pointer, passed to all components
625 * Binds all components of the aggregate @dev by passing @data to their
626 * &component_ops.bind functions. Should be called from
627 * &component_master_ops.bind.
629 int component_bind_all(struct device *master_dev, void *data)
631 struct master *master;
636 WARN_ON(!mutex_is_locked(&component_mutex));
638 master = __master_find(master_dev, NULL);
642 /* Bind components in match order */
643 for (i = 0; i < master->match->num; i++)
644 if (!master->match->compare[i].duplicate) {
645 c = master->match->compare[i].component;
646 ret = component_bind(c, master, data);
653 if (!master->match->compare[i - 1].duplicate) {
654 c = master->match->compare[i - 1].component;
655 component_unbind(c, master, data);
661 EXPORT_SYMBOL_GPL(component_bind_all);
663 static int __component_add(struct device *dev, const struct component_ops *ops,
666 struct component *component;
669 component = kzalloc(sizeof(*component), GFP_KERNEL);
673 component->ops = ops;
674 component->dev = dev;
675 component->subcomponent = subcomponent;
677 dev_dbg(dev, "adding component (ops %ps)\n", ops);
679 mutex_lock(&component_mutex);
680 list_add_tail(&component->node, &component_list);
682 ret = try_to_bring_up_masters(component);
684 if (component->master)
685 remove_component(component->master, component);
686 list_del(&component->node);
690 mutex_unlock(&component_mutex);
692 return ret < 0 ? ret : 0;
696 * component_add_typed - register a component
697 * @dev: component device
698 * @ops: component callbacks
699 * @subcomponent: nonzero identifier for subcomponents
701 * Register a new component for @dev. Functions in @ops will be call when the
702 * aggregate driver is ready to bind the overall driver by calling
703 * component_bind_all(). See also &struct component_ops.
705 * @subcomponent must be nonzero and is used to differentiate between multiple
706 * components registerd on the same device @dev. These components are match
707 * using component_match_add_typed().
709 * The component needs to be unregistered at driver unload/disconnect by
710 * calling component_del().
712 * See also component_add().
714 int component_add_typed(struct device *dev, const struct component_ops *ops,
717 if (WARN_ON(subcomponent == 0))
720 return __component_add(dev, ops, subcomponent);
722 EXPORT_SYMBOL_GPL(component_add_typed);
725 * component_add - register a component
726 * @dev: component device
727 * @ops: component callbacks
729 * Register a new component for @dev. Functions in @ops will be called when the
730 * aggregate driver is ready to bind the overall driver by calling
731 * component_bind_all(). See also &struct component_ops.
733 * The component needs to be unregistered at driver unload/disconnect by
734 * calling component_del().
736 * See also component_add_typed() for a variant that allows multipled different
737 * components on the same device.
739 int component_add(struct device *dev, const struct component_ops *ops)
741 return __component_add(dev, ops, 0);
743 EXPORT_SYMBOL_GPL(component_add);
746 * component_del - unregister a component
747 * @dev: component device
748 * @ops: component callbacks
750 * Unregister a component added with component_add(). If the component is bound
751 * into an aggregate driver, this will force the entire aggregate driver, including
752 * all its components, to be unbound.
754 void component_del(struct device *dev, const struct component_ops *ops)
756 struct component *c, *component = NULL;
758 mutex_lock(&component_mutex);
759 list_for_each_entry(c, &component_list, node)
760 if (c->dev == dev && c->ops == ops) {
766 if (component && component->master) {
767 take_down_master(component->master);
768 remove_component(component->master, component);
771 mutex_unlock(&component_mutex);
776 EXPORT_SYMBOL_GPL(component_del);