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/list.h>
13 #include <linux/mutex.h>
14 #include <linux/slab.h>
15 #include <linux/debugfs.h>
20 * The component helper allows drivers to collect a pile of sub-devices,
21 * including their bound drivers, into an aggregate driver. Various subsystems
22 * already provide functions to get hold of such components, e.g.
23 * of_clk_get_by_name(). The component helper can be used when such a
24 * subsystem-specific way to find a device is not available: The component
25 * helper fills the niche of aggregate drivers for specific hardware, where
26 * further standardization into a subsystem would not be practical. The common
27 * example is when a logical device (e.g. a DRM display driver) is spread around
28 * the SoC on various components (scanout engines, blending blocks, transcoders
29 * for various outputs and so on).
31 * The component helper also doesn't solve runtime dependencies, e.g. for system
32 * suspend and resume operations. See also :ref:`device links<device_link>`.
34 * Components are registered using component_add() and unregistered with
35 * component_del(), usually from the driver's probe and disconnect functions.
37 * Aggregate drivers first assemble a component match list of what they need
38 * using component_match_add(). This is then registered as an aggregate driver
39 * using component_master_add_with_match(), and unregistered using
40 * component_master_del().
45 struct component_match_array {
47 int (*compare)(struct device *, void *);
48 int (*compare_typed)(struct device *, int, void *);
49 void (*release)(struct device *, void *);
50 struct component *component;
54 struct component_match {
57 struct component_match_array *compare;
61 struct list_head node;
64 const struct component_master_ops *ops;
65 struct device *parent;
66 struct component_match *match;
70 struct list_head node;
71 struct master *master;
74 const struct component_ops *ops;
79 static DEFINE_MUTEX(component_mutex);
80 static LIST_HEAD(component_list);
81 static LIST_HEAD(masters);
83 #ifdef CONFIG_DEBUG_FS
85 static struct dentry *component_debugfs_dir;
87 static int component_devices_show(struct seq_file *s, void *data)
89 struct master *m = s->private;
90 struct component_match *match = m->match;
93 mutex_lock(&component_mutex);
94 seq_printf(s, "%-40s %20s\n", "master name", "status");
95 seq_puts(s, "-------------------------------------------------------------\n");
96 seq_printf(s, "%-40s %20s\n\n",
97 dev_name(m->parent), m->bound ? "bound" : "not bound");
99 seq_printf(s, "%-40s %20s\n", "device name", "status");
100 seq_puts(s, "-------------------------------------------------------------\n");
101 for (i = 0; i < match->num; i++) {
102 struct component *component = match->compare[i].component;
104 seq_printf(s, "%-40s %20s\n",
105 component ? dev_name(component->dev) : "(unknown)",
106 component ? (component->bound ? "bound" : "not bound") : "not registered");
108 mutex_unlock(&component_mutex);
113 DEFINE_SHOW_ATTRIBUTE(component_devices);
115 static int __init component_debug_init(void)
117 component_debugfs_dir = debugfs_create_dir("device_component", NULL);
122 core_initcall(component_debug_init);
124 static void component_master_debugfs_add(struct master *m)
126 debugfs_create_file(dev_name(m->parent), 0444, component_debugfs_dir, m,
127 &component_devices_fops);
130 static void component_master_debugfs_del(struct master *m)
132 debugfs_remove(debugfs_lookup(dev_name(m->parent), component_debugfs_dir));
137 static void component_master_debugfs_add(struct master *m)
140 static void component_master_debugfs_del(struct master *m)
145 static struct master *__master_find(struct device *parent,
146 const struct component_master_ops *ops)
150 list_for_each_entry(m, &masters, node)
151 if (m->parent == parent && (!ops || m->ops == ops))
157 static struct component *find_component(struct master *master,
158 struct component_match_array *mc)
162 list_for_each_entry(c, &component_list, node) {
163 if (c->master && c->master != master)
166 if (mc->compare && mc->compare(c->dev, mc->data))
169 if (mc->compare_typed &&
170 mc->compare_typed(c->dev, c->subcomponent, mc->data))
177 static int find_components(struct master *master)
179 struct component_match *match = master->match;
184 * Scan the array of match functions and attach
185 * any components which are found to this master.
187 for (i = 0; i < match->num; i++) {
188 struct component_match_array *mc = &match->compare[i];
191 dev_dbg(master->parent, "Looking for component %zu\n", i);
193 if (match->compare[i].component)
196 c = find_component(master, mc);
202 dev_dbg(master->parent, "found component %s, duplicate %u\n", dev_name(c->dev), !!c->master);
204 /* Attach this component to the master */
205 match->compare[i].duplicate = !!c->master;
206 match->compare[i].component = c;
212 /* Detach component from associated master */
213 static void remove_component(struct master *master, struct component *c)
217 /* Detach the component from this master. */
218 for (i = 0; i < master->match->num; i++)
219 if (master->match->compare[i].component == c)
220 master->match->compare[i].component = NULL;
224 * Try to bring up a master. If component is NULL, we're interested in
225 * this master, otherwise it's a component which must be present to try
226 * and bring up the master.
228 * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
230 static int try_to_bring_up_master(struct master *master,
231 struct component *component)
235 dev_dbg(master->parent, "trying to bring up master\n");
237 if (find_components(master)) {
238 dev_dbg(master->parent, "master has incomplete components\n");
242 if (component && component->master != master) {
243 dev_dbg(master->parent, "master is not for this component (%s)\n",
244 dev_name(component->dev));
248 if (!devres_open_group(master->parent, master, GFP_KERNEL))
251 /* Found all components */
252 ret = master->ops->bind(master->parent);
254 devres_release_group(master->parent, NULL);
255 if (ret != -EPROBE_DEFER)
256 dev_info(master->parent, "master bind failed: %d\n", ret);
260 devres_close_group(master->parent, NULL);
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->parent);
285 devres_release_group(master->parent, master);
286 master->bound = false;
290 static void devm_component_match_release(struct device *parent, void *res)
292 struct component_match *match = res;
295 for (i = 0; i < match->num; i++) {
296 struct component_match_array *mc = &match->compare[i];
299 mc->release(parent, mc->data);
302 kfree(match->compare);
305 static int component_match_realloc(struct component_match *match, size_t num)
307 struct component_match_array *new;
309 if (match->alloc == num)
312 new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
316 if (match->compare) {
317 memcpy(new, match->compare, sizeof(*new) *
318 min(match->num, num));
319 kfree(match->compare);
321 match->compare = new;
327 static 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 *),
334 struct component_match *match = *matchptr;
340 match = devres_alloc(devm_component_match_release,
341 sizeof(*match), GFP_KERNEL);
343 *matchptr = ERR_PTR(-ENOMEM);
347 devres_add(master, match);
352 if (match->num == match->alloc) {
353 size_t new_size = match->alloc + 16;
356 ret = component_match_realloc(match, new_size);
358 *matchptr = ERR_PTR(ret);
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;
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
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().
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().
389 * See also component_match_add() and component_match_add_typed().
391 void 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)
396 __component_match_add(master, matchptr, release, compare, NULL,
399 EXPORT_SYMBOL(component_match_add_release);
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
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().
413 * The allocated match list in @matchptr is automatically released using devm
416 * See also component_match_add_release() and component_match_add_typed().
418 void component_match_add_typed(struct device *master,
419 struct component_match **matchptr,
420 int (*compare_typed)(struct device *, int, void *), void *compare_data)
422 __component_match_add(master, matchptr, NULL, NULL, compare_typed,
425 EXPORT_SYMBOL(component_match_add_typed);
427 static void free_master(struct master *master)
429 struct component_match *match = master->match;
432 component_master_debugfs_del(master);
433 list_del(&master->node);
436 for (i = 0; i < match->num; i++) {
437 struct component *c = match->compare[i].component;
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
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().
458 int component_master_add_with_match(struct device *parent,
459 const struct component_master_ops *ops,
460 struct component_match *match)
462 struct master *master;
465 /* Reallocate the match array for its true size */
466 ret = component_match_realloc(match, match->num);
470 master = kzalloc(sizeof(*master), GFP_KERNEL);
474 master->parent = parent;
476 master->match = match;
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);
483 ret = try_to_bring_up_master(master, NULL);
488 mutex_unlock(&component_mutex);
490 return ret < 0 ? ret : 0;
492 EXPORT_SYMBOL_GPL(component_master_add_with_match);
495 * component_master_del - unregister an aggregate driver
496 * @parent: parent device of the aggregate driver
497 * @ops: callbacks for the aggregate driver
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.
503 void component_master_del(struct device *parent,
504 const struct component_master_ops *ops)
506 struct master *master;
508 mutex_lock(&component_mutex);
509 master = __master_find(parent, ops);
511 take_down_master(master);
514 mutex_unlock(&component_mutex);
516 EXPORT_SYMBOL_GPL(component_master_del);
518 static void component_unbind(struct component *component,
519 struct master *master, void *data)
521 WARN_ON(!component->bound);
523 if (component->ops && component->ops->unbind)
524 component->ops->unbind(component->dev, master->parent, data);
525 component->bound = false;
527 /* Release all resources claimed in the binding of this component */
528 devres_release_group(component->dev, component);
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
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.
540 void component_unbind_all(struct device *parent, void *data)
542 struct master *master;
546 WARN_ON(!mutex_is_locked(&component_mutex));
548 master = __master_find(parent, NULL);
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);
559 EXPORT_SYMBOL_GPL(component_unbind_all);
561 static int component_bind(struct component *component, struct master *master,
567 * Each component initialises inside its own devres group.
568 * This allows us to roll-back a failed component without
569 * affecting anything else.
571 if (!devres_open_group(master->parent, NULL, GFP_KERNEL))
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.
579 if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
580 devres_release_group(master->parent, NULL);
584 dev_dbg(master->parent, "binding %s (ops %ps)\n",
585 dev_name(component->dev), component->ops);
587 ret = component->ops->bind(component->dev, master->parent, data);
589 component->bound = true;
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.
597 devres_close_group(component->dev, NULL);
598 devres_remove_group(master->parent, NULL);
600 dev_info(master->parent, "bound %s (ops %ps)\n",
601 dev_name(component->dev), component->ops);
603 devres_release_group(component->dev, NULL);
604 devres_release_group(master->parent, NULL);
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);
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
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.
623 int component_bind_all(struct device *parent, void *data)
625 struct master *master;
630 WARN_ON(!mutex_is_locked(&component_mutex));
632 master = __master_find(parent, NULL);
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);
647 if (!master->match->compare[i - 1].duplicate) {
648 c = master->match->compare[i - 1].component;
649 component_unbind(c, master, data);
655 EXPORT_SYMBOL_GPL(component_bind_all);
657 static int __component_add(struct device *dev, const struct component_ops *ops,
660 struct component *component;
663 component = kzalloc(sizeof(*component), GFP_KERNEL);
667 component->ops = ops;
668 component->dev = dev;
669 component->subcomponent = subcomponent;
671 dev_dbg(dev, "adding component (ops %ps)\n", ops);
673 mutex_lock(&component_mutex);
674 list_add_tail(&component->node, &component_list);
676 ret = try_to_bring_up_masters(component);
678 if (component->master)
679 remove_component(component->master, component);
680 list_del(&component->node);
684 mutex_unlock(&component_mutex);
686 return ret < 0 ? ret : 0;
690 * component_add_typed - register a component
691 * @dev: component device
692 * @ops: component callbacks
693 * @subcomponent: nonzero identifier for subcomponents
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.
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().
703 * The component needs to be unregistered at driver unload/disconnect by
704 * calling component_del().
706 * See also component_add().
708 int component_add_typed(struct device *dev, const struct component_ops *ops,
711 if (WARN_ON(subcomponent == 0))
714 return __component_add(dev, ops, subcomponent);
716 EXPORT_SYMBOL_GPL(component_add_typed);
719 * component_add - register a component
720 * @dev: component device
721 * @ops: component callbacks
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.
727 * The component needs to be unregistered at driver unload/disconnect by
728 * calling component_del().
730 * See also component_add_typed() for a variant that allows multipled different
731 * components on the same device.
733 int component_add(struct device *dev, const struct component_ops *ops)
735 return __component_add(dev, ops, 0);
737 EXPORT_SYMBOL_GPL(component_add);
740 * component_del - unregister a component
741 * @dev: component device
742 * @ops: component callbacks
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.
748 void component_del(struct device *dev, const struct component_ops *ops)
750 struct component *c, *component = NULL;
752 mutex_lock(&component_mutex);
753 list_for_each_entry(c, &component_list, node)
754 if (c->dev == dev && c->ops == ops) {
760 if (component && component->master) {
761 take_down_master(component->master);
762 remove_component(component->master, component);
765 mutex_unlock(&component_mutex);
770 EXPORT_SYMBOL_GPL(component_del);