1/*
   2 * Copyright (c) 2014 Samsung Electronics Co., Ltd
   3 *
   4 * Permission is hereby granted, free of charge, to any person obtaining a
   5 * copy of this software and associated documentation files (the "Software"),
   6 * to deal in the Software without restriction, including without limitation
   7 * the rights to use, copy, modify, merge, publish, distribute, sub license,
   8 * and/or sell copies of the Software, and to permit persons to whom the
   9 * Software is furnished to do so, subject to the following conditions:
  10 *
  11 * The above copyright notice and this permission notice (including the
  12 * next paragraph) shall be included in all copies or substantial portions
  13 * of the Software.
  14 *
  15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21 * DEALINGS IN THE SOFTWARE.
  22 */
  23
  24#include <linux/err.h>
  25#include <linux/module.h>
  26#include <linux/mutex.h>
  27
  28#include <drm/drm_atomic_state_helper.h>
  29#include <drm/drm_bridge.h>
  30#include <drm/drm_encoder.h>
  31
  32#include "drm_crtc_internal.h"
  33
  34/**
  35 * DOC: overview
  36 *
  37 * &struct drm_bridge represents a device that hangs on to an encoder. These are
  38 * handy when a regular &drm_encoder entity isn't enough to represent the entire
  39 * encoder chain.
  40 *
  41 * A bridge is always attached to a single &drm_encoder at a time, but can be
  42 * either connected to it directly, or through a chain of bridges::
  43 *
  44 *     [ CRTC ---> ] Encoder ---> Bridge A ---> Bridge B
  45 *
  46 * Here, the output of the encoder feeds to bridge A, and that furthers feeds to
  47 * bridge B. Bridge chains can be arbitrarily long, and shall be fully linear:
  48 * Chaining multiple bridges to the output of a bridge, or the same bridge to
  49 * the output of different bridges, is not supported.
  50 *
  51 * Display drivers are responsible for linking encoders with the first bridge
  52 * in the chains. This is done by acquiring the appropriate bridge with
  53 * of_drm_find_bridge() or drm_of_find_panel_or_bridge(), or creating it for a
  54 * panel with drm_panel_bridge_add_typed() (or the managed version
  55 * devm_drm_panel_bridge_add_typed()). Once acquired, the bridge shall be
  56 * attached to the encoder with a call to drm_bridge_attach().
  57 *
  58 * Bridges are responsible for linking themselves with the next bridge in the
  59 * chain, if any. This is done the same way as for encoders, with the call to
  60 * drm_bridge_attach() occurring in the &drm_bridge_funcs.attach operation.
  61 *
  62 * Once these links are created, the bridges can participate along with encoder
  63 * functions to perform mode validation and fixup (through
  64 * drm_bridge_chain_mode_valid() and drm_atomic_bridge_chain_check()), mode
  65 * setting (through drm_bridge_chain_mode_set()), enable (through
  66 * drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_enable())
  67 * and disable (through drm_atomic_bridge_chain_disable() and
  68 * drm_atomic_bridge_chain_post_disable()). Those functions call the
  69 * corresponding operations provided in &drm_bridge_funcs in sequence for all
  70 * bridges in the chain.
  71 *
  72 * For display drivers that use the atomic helpers
  73 * drm_atomic_helper_check_modeset(),
  74 * drm_atomic_helper_commit_modeset_enables() and
  75 * drm_atomic_helper_commit_modeset_disables() (either directly in hand-rolled
  76 * commit check and commit tail handlers, or through the higher-level
  77 * drm_atomic_helper_check() and drm_atomic_helper_commit_tail() or
  78 * drm_atomic_helper_commit_tail_rpm() helpers), this is done transparently and
  79 * requires no intervention from the driver. For other drivers, the relevant
  80 * DRM bridge chain functions shall be called manually.
  81 *
  82 * Bridges also participate in implementing the &drm_connector at the end of
  83 * the bridge chain. Display drivers may use the drm_bridge_connector_init()
  84 * helper to create the &drm_connector, or implement it manually on top of the
  85 * connector-related operations exposed by the bridge (see the overview
  86 * documentation of bridge operations for more details).
  87 *
  88 * &drm_bridge, like &drm_panel, aren't &drm_mode_object entities like planes,
 
 
 
 
 
  89 * CRTCs, encoders or connectors and hence are not visible to userspace. They
  90 * just provide additional hooks to get the desired output at the end of the
  91 * encoder chain.
 
 
 
 
  92 */
  93
  94static DEFINE_MUTEX(bridge_lock);
  95static LIST_HEAD(bridge_list);
  96
  97/**
  98 * drm_bridge_add - add the given bridge to the global bridge list
  99 *
 100 * @bridge: bridge control structure
 101 */
 102void drm_bridge_add(struct drm_bridge *bridge)
 103{
 104	mutex_init(&bridge->hpd_mutex);
 105
 106	mutex_lock(&bridge_lock);
 107	list_add_tail(&bridge->list, &bridge_list);
 108	mutex_unlock(&bridge_lock);
 109}
 110EXPORT_SYMBOL(drm_bridge_add);
 111
 112/**
 113 * drm_bridge_remove - remove the given bridge from the global bridge list
 114 *
 115 * @bridge: bridge control structure
 116 */
 117void drm_bridge_remove(struct drm_bridge *bridge)
 118{
 119	mutex_lock(&bridge_lock);
 120	list_del_init(&bridge->list);
 121	mutex_unlock(&bridge_lock);
 122
 123	mutex_destroy(&bridge->hpd_mutex);
 124}
 125EXPORT_SYMBOL(drm_bridge_remove);
 126
 127static struct drm_private_state *
 128drm_bridge_atomic_duplicate_priv_state(struct drm_private_obj *obj)
 129{
 130	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
 131	struct drm_bridge_state *state;
 132
 133	state = bridge->funcs->atomic_duplicate_state(bridge);
 134	return state ? &state->base : NULL;
 135}
 136
 137static void
 138drm_bridge_atomic_destroy_priv_state(struct drm_private_obj *obj,
 139				     struct drm_private_state *s)
 140{
 141	struct drm_bridge_state *state = drm_priv_to_bridge_state(s);
 142	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
 143
 144	bridge->funcs->atomic_destroy_state(bridge, state);
 145}
 146
 147static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
 148	.atomic_duplicate_state = drm_bridge_atomic_duplicate_priv_state,
 149	.atomic_destroy_state = drm_bridge_atomic_destroy_priv_state,
 150};
 151
 152/**
 153 * drm_bridge_attach - attach the bridge to an encoder's chain
 154 *
 155 * @encoder: DRM encoder
 156 * @bridge: bridge to attach
 157 * @previous: previous bridge in the chain (optional)
 158 * @flags: DRM_BRIDGE_ATTACH_* flags
 159 *
 160 * Called by a kms driver to link the bridge to an encoder's chain. The previous
 161 * argument specifies the previous bridge in the chain. If NULL, the bridge is
 162 * linked directly at the encoder's output. Otherwise it is linked at the
 163 * previous bridge's output.
 164 *
 165 * If non-NULL the previous bridge must be already attached by a call to this
 166 * function.
 167 *
 168 * Note that bridges attached to encoders are auto-detached during encoder
 169 * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
 170 * *not* be balanced with a drm_bridge_detach() in driver code.
 171 *
 172 * RETURNS:
 173 * Zero on success, error code on failure
 174 */
 175int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
 176		      struct drm_bridge *previous,
 177		      enum drm_bridge_attach_flags flags)
 178{
 179	int ret;
 180
 181	if (!encoder || !bridge)
 182		return -EINVAL;
 183
 184	if (previous && (!previous->dev || previous->encoder != encoder))
 185		return -EINVAL;
 186
 187	if (bridge->dev)
 188		return -EBUSY;
 189
 190	bridge->dev = encoder->dev;
 191	bridge->encoder = encoder;
 192
 193	if (previous)
 194		list_add(&bridge->chain_node, &previous->chain_node);
 195	else
 196		list_add(&bridge->chain_node, &encoder->bridge_chain);
 197
 198	if (bridge->funcs->attach) {
 199		ret = bridge->funcs->attach(bridge, flags);
 200		if (ret < 0)
 201			goto err_reset_bridge;
 202	}
 203
 204	if (bridge->funcs->atomic_reset) {
 205		struct drm_bridge_state *state;
 206
 207		state = bridge->funcs->atomic_reset(bridge);
 208		if (IS_ERR(state)) {
 209			ret = PTR_ERR(state);
 210			goto err_detach_bridge;
 211		}
 212
 213		drm_atomic_private_obj_init(bridge->dev, &bridge->base,
 214					    &state->base,
 215					    &drm_bridge_priv_state_funcs);
 216	}
 217
 218	return 0;
 219
 220err_detach_bridge:
 221	if (bridge->funcs->detach)
 222		bridge->funcs->detach(bridge);
 223
 224err_reset_bridge:
 225	bridge->dev = NULL;
 226	bridge->encoder = NULL;
 227	list_del(&bridge->chain_node);
 228	return ret;
 229}
 230EXPORT_SYMBOL(drm_bridge_attach);
 231
 232void drm_bridge_detach(struct drm_bridge *bridge)
 233{
 234	if (WARN_ON(!bridge))
 235		return;
 236
 237	if (WARN_ON(!bridge->dev))
 238		return;
 239
 240	if (bridge->funcs->atomic_reset)
 241		drm_atomic_private_obj_fini(&bridge->base);
 242
 243	if (bridge->funcs->detach)
 244		bridge->funcs->detach(bridge);
 245
 246	list_del(&bridge->chain_node);
 247	bridge->dev = NULL;
 248}
 249
 250/**
 251 * DOC: bridge operations
 252 *
 253 * Bridge drivers expose operations through the &drm_bridge_funcs structure.
 254 * The DRM internals (atomic and CRTC helpers) use the helpers defined in
 255 * drm_bridge.c to call bridge operations. Those operations are divided in
 256 * three big categories to support different parts of the bridge usage.
 257 *
 258 * - The encoder-related operations support control of the bridges in the
 259 *   chain, and are roughly counterparts to the &drm_encoder_helper_funcs
 260 *   operations. They are used by the legacy CRTC and the atomic modeset
 261 *   helpers to perform mode validation, fixup and setting, and enable and
 262 *   disable the bridge automatically.
 263 *
 264 *   The enable and disable operations are split in
 265 *   &drm_bridge_funcs.pre_enable, &drm_bridge_funcs.enable,
 266 *   &drm_bridge_funcs.disable and &drm_bridge_funcs.post_disable to provide
 267 *   finer-grained control.
 268 *
 269 *   Bridge drivers may implement the legacy version of those operations, or
 270 *   the atomic version (prefixed with atomic\_), in which case they shall also
 271 *   implement the atomic state bookkeeping operations
 272 *   (&drm_bridge_funcs.atomic_duplicate_state,
 273 *   &drm_bridge_funcs.atomic_destroy_state and &drm_bridge_funcs.reset).
 274 *   Mixing atomic and non-atomic versions of the operations is not supported.
 275 *
 276 * - The bus format negotiation operations
 277 *   &drm_bridge_funcs.atomic_get_output_bus_fmts and
 278 *   &drm_bridge_funcs.atomic_get_input_bus_fmts allow bridge drivers to
 279 *   negotiate the formats transmitted between bridges in the chain when
 280 *   multiple formats are supported. Negotiation for formats is performed
 281 *   transparently for display drivers by the atomic modeset helpers. Only
 282 *   atomic versions of those operations exist, bridge drivers that need to
 283 *   implement them shall thus also implement the atomic version of the
 284 *   encoder-related operations. This feature is not supported by the legacy
 285 *   CRTC helpers.
 286 *
 287 * - The connector-related operations support implementing a &drm_connector
 288 *   based on a chain of bridges. DRM bridges traditionally create a
 289 *   &drm_connector for bridges meant to be used at the end of the chain. This
 290 *   puts additional burden on bridge drivers, especially for bridges that may
 291 *   be used in the middle of a chain or at the end of it. Furthermore, it
 292 *   requires all operations of the &drm_connector to be handled by a single
 293 *   bridge, which doesn't always match the hardware architecture.
 294 *
 295 *   To simplify bridge drivers and make the connector implementation more
 296 *   flexible, a new model allows bridges to unconditionally skip creation of
 297 *   &drm_connector and instead expose &drm_bridge_funcs operations to support
 298 *   an externally-implemented &drm_connector. Those operations are
 299 *   &drm_bridge_funcs.detect, &drm_bridge_funcs.get_modes,
 300 *   &drm_bridge_funcs.get_edid, &drm_bridge_funcs.hpd_notify,
 301 *   &drm_bridge_funcs.hpd_enable and &drm_bridge_funcs.hpd_disable. When
 302 *   implemented, display drivers shall create a &drm_connector instance for
 303 *   each chain of bridges, and implement those connector instances based on
 304 *   the bridge connector operations.
 305 *
 306 *   Bridge drivers shall implement the connector-related operations for all
 307 *   the features that the bridge hardware support. For instance, if a bridge
 308 *   supports reading EDID, the &drm_bridge_funcs.get_edid shall be
 309 *   implemented. This however doesn't mean that the DDC lines are wired to the
 310 *   bridge on a particular platform, as they could also be connected to an I2C
 311 *   controller of the SoC. Support for the connector-related operations on the
 312 *   running platform is reported through the &drm_bridge.ops flags. Bridge
 313 *   drivers shall detect which operations they can support on the platform
 314 *   (usually this information is provided by ACPI or DT), and set the
 315 *   &drm_bridge.ops flags for all supported operations. A flag shall only be
 316 *   set if the corresponding &drm_bridge_funcs operation is implemented, but
 317 *   an implemented operation doesn't necessarily imply that the corresponding
 318 *   flag will be set. Display drivers shall use the &drm_bridge.ops flags to
 319 *   decide which bridge to delegate a connector operation to. This mechanism
 320 *   allows providing a single static const &drm_bridge_funcs instance in
 321 *   bridge drivers, improving security by storing function pointers in
 322 *   read-only memory.
 323 *
 324 *   In order to ease transition, bridge drivers may support both the old and
 325 *   new models by making connector creation optional and implementing the
 326 *   connected-related bridge operations. Connector creation is then controlled
 327 *   by the flags argument to the drm_bridge_attach() function. Display drivers
 328 *   that support the new model and create connectors themselves shall set the
 329 *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag, and bridge drivers shall then skip
 330 *   connector creation. For intermediate bridges in the chain, the flag shall
 331 *   be passed to the drm_bridge_attach() call for the downstream bridge.
 332 *   Bridge drivers that implement the new model only shall return an error
 333 *   from their &drm_bridge_funcs.attach handler when the
 334 *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is not set. New display drivers
 335 *   should use the new model, and convert the bridge drivers they use if
 336 *   needed, in order to gradually transition to the new model.
 337 */
 338
 339/**
 340 * drm_bridge_chain_mode_fixup - fixup proposed mode for all bridges in the
 341 *				 encoder chain
 342 * @bridge: bridge control structure
 343 * @mode: desired mode to be set for the bridge
 344 * @adjusted_mode: updated mode that works for this bridge
 345 *
 346 * Calls &drm_bridge_funcs.mode_fixup for all the bridges in the
 347 * encoder chain, starting from the first bridge to the last.
 348 *
 349 * Note: the bridge passed should be the one closest to the encoder
 350 *
 351 * RETURNS:
 352 * true on success, false on failure
 353 */
 354bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
 355				 const struct drm_display_mode *mode,
 356				 struct drm_display_mode *adjusted_mode)
 357{
 358	struct drm_encoder *encoder;
 359
 360	if (!bridge)
 361		return true;
 362
 363	encoder = bridge->encoder;
 364	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 365		if (!bridge->funcs->mode_fixup)
 366			continue;
 367
 368		if (!bridge->funcs->mode_fixup(bridge, mode, adjusted_mode))
 369			return false;
 370	}
 371
 372	return true;
 373}
 374EXPORT_SYMBOL(drm_bridge_chain_mode_fixup);
 375
 376/**
 377 * drm_bridge_chain_mode_valid - validate the mode against all bridges in the
 378 *				 encoder chain.
 379 * @bridge: bridge control structure
 380 * @info: display info against which the mode shall be validated
 381 * @mode: desired mode to be validated
 382 *
 383 * Calls &drm_bridge_funcs.mode_valid for all the bridges in the encoder
 384 * chain, starting from the first bridge to the last. If at least one bridge
 385 * does not accept the mode the function returns the error code.
 386 *
 387 * Note: the bridge passed should be the one closest to the encoder.
 388 *
 389 * RETURNS:
 390 * MODE_OK on success, drm_mode_status Enum error code on failure
 391 */
 392enum drm_mode_status
 393drm_bridge_chain_mode_valid(struct drm_bridge *bridge,
 394			    const struct drm_display_info *info,
 395			    const struct drm_display_mode *mode)
 396{
 397	struct drm_encoder *encoder;
 398
 399	if (!bridge)
 400		return MODE_OK;
 401
 402	encoder = bridge->encoder;
 403	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 404		enum drm_mode_status ret;
 405
 406		if (!bridge->funcs->mode_valid)
 407			continue;
 408
 409		ret = bridge->funcs->mode_valid(bridge, info, mode);
 410		if (ret != MODE_OK)
 411			return ret;
 412	}
 413
 414	return MODE_OK;
 415}
 416EXPORT_SYMBOL(drm_bridge_chain_mode_valid);
 417
 418/**
 419 * drm_bridge_chain_disable - disables all bridges in the encoder chain
 420 * @bridge: bridge control structure
 421 *
 422 * Calls &drm_bridge_funcs.disable op for all the bridges in the encoder
 423 * chain, starting from the last bridge to the first. These are called before
 424 * calling the encoder's prepare op.
 425 *
 426 * Note: the bridge passed should be the one closest to the encoder
 427 */
 428void drm_bridge_chain_disable(struct drm_bridge *bridge)
 429{
 430	struct drm_encoder *encoder;
 431	struct drm_bridge *iter;
 432
 433	if (!bridge)
 434		return;
 435
 436	encoder = bridge->encoder;
 437	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
 438		if (iter->funcs->disable)
 439			iter->funcs->disable(iter);
 440
 441		if (iter == bridge)
 442			break;
 443	}
 444}
 445EXPORT_SYMBOL(drm_bridge_chain_disable);
 446
 447/**
 448 * drm_bridge_chain_post_disable - cleans up after disabling all bridges in the
 449 *				   encoder chain
 450 * @bridge: bridge control structure
 451 *
 452 * Calls &drm_bridge_funcs.post_disable op for all the bridges in the
 453 * encoder chain, starting from the first bridge to the last. These are called
 454 * after completing the encoder's prepare op.
 455 *
 456 * Note: the bridge passed should be the one closest to the encoder
 457 */
 458void drm_bridge_chain_post_disable(struct drm_bridge *bridge)
 459{
 460	struct drm_encoder *encoder;
 461
 462	if (!bridge)
 463		return;
 464
 465	encoder = bridge->encoder;
 466	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 467		if (bridge->funcs->post_disable)
 468			bridge->funcs->post_disable(bridge);
 469	}
 470}
 471EXPORT_SYMBOL(drm_bridge_chain_post_disable);
 472
 473/**
 474 * drm_bridge_chain_mode_set - set proposed mode for all bridges in the
 475 *			       encoder chain
 476 * @bridge: bridge control structure
 477 * @mode: desired mode to be set for the encoder chain
 478 * @adjusted_mode: updated mode that works for this encoder chain
 479 *
 480 * Calls &drm_bridge_funcs.mode_set op for all the bridges in the
 481 * encoder chain, starting from the first bridge to the last.
 482 *
 483 * Note: the bridge passed should be the one closest to the encoder
 484 */
 485void drm_bridge_chain_mode_set(struct drm_bridge *bridge,
 486			       const struct drm_display_mode *mode,
 487			       const struct drm_display_mode *adjusted_mode)
 488{
 489	struct drm_encoder *encoder;
 490
 491	if (!bridge)
 492		return;
 493
 494	encoder = bridge->encoder;
 495	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 496		if (bridge->funcs->mode_set)
 497			bridge->funcs->mode_set(bridge, mode, adjusted_mode);
 498	}
 499}
 500EXPORT_SYMBOL(drm_bridge_chain_mode_set);
 501
 502/**
 503 * drm_bridge_chain_pre_enable - prepares for enabling all bridges in the
 504 *				 encoder chain
 505 * @bridge: bridge control structure
 506 *
 507 * Calls &drm_bridge_funcs.pre_enable op for all the bridges in the encoder
 508 * chain, starting from the last bridge to the first. These are called
 509 * before calling the encoder's commit op.
 510 *
 511 * Note: the bridge passed should be the one closest to the encoder
 512 */
 513void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
 514{
 515	struct drm_encoder *encoder;
 516	struct drm_bridge *iter;
 517
 518	if (!bridge)
 519		return;
 520
 521	encoder = bridge->encoder;
 522	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
 523		if (iter->funcs->pre_enable)
 524			iter->funcs->pre_enable(iter);
 525	}
 526}
 527EXPORT_SYMBOL(drm_bridge_chain_pre_enable);
 528
 529/**
 530 * drm_bridge_chain_enable - enables all bridges in the encoder chain
 531 * @bridge: bridge control structure
 532 *
 533 * Calls &drm_bridge_funcs.enable op for all the bridges in the encoder
 534 * chain, starting from the first bridge to the last. These are called
 535 * after completing the encoder's commit op.
 536 *
 537 * Note that the bridge passed should be the one closest to the encoder
 538 */
 539void drm_bridge_chain_enable(struct drm_bridge *bridge)
 540{
 541	struct drm_encoder *encoder;
 542
 543	if (!bridge)
 544		return;
 545
 546	encoder = bridge->encoder;
 547	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 548		if (bridge->funcs->enable)
 549			bridge->funcs->enable(bridge);
 550	}
 551}
 552EXPORT_SYMBOL(drm_bridge_chain_enable);
 553
 554/**
 555 * drm_atomic_bridge_chain_disable - disables all bridges in the encoder chain
 556 * @bridge: bridge control structure
 557 * @old_state: old atomic state
 558 *
 559 * Calls &drm_bridge_funcs.atomic_disable (falls back on
 560 * &drm_bridge_funcs.disable) op for all the bridges in the encoder chain,
 561 * starting from the last bridge to the first. These are called before calling
 562 * &drm_encoder_helper_funcs.atomic_disable
 563 *
 564 * Note: the bridge passed should be the one closest to the encoder
 565 */
 566void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
 567				     struct drm_atomic_state *old_state)
 568{
 569	struct drm_encoder *encoder;
 570	struct drm_bridge *iter;
 571
 572	if (!bridge)
 573		return;
 574
 575	encoder = bridge->encoder;
 576	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
 577		if (iter->funcs->atomic_disable) {
 578			struct drm_bridge_state *old_bridge_state;
 579
 580			old_bridge_state =
 581				drm_atomic_get_old_bridge_state(old_state,
 582								iter);
 583			if (WARN_ON(!old_bridge_state))
 584				return;
 585
 586			iter->funcs->atomic_disable(iter, old_bridge_state);
 587		} else if (iter->funcs->disable) {
 588			iter->funcs->disable(iter);
 589		}
 590
 591		if (iter == bridge)
 592			break;
 593	}
 
 594}
 595EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
 596
 597/**
 598 * drm_atomic_bridge_chain_post_disable - cleans up after disabling all bridges
 599 *					  in the encoder chain
 600 * @bridge: bridge control structure
 601 * @old_state: old atomic state
 602 *
 603 * Calls &drm_bridge_funcs.atomic_post_disable (falls back on
 604 * &drm_bridge_funcs.post_disable) op for all the bridges in the encoder chain,
 605 * starting from the first bridge to the last. These are called after completing
 606 * &drm_encoder_helper_funcs.atomic_disable
 607 *
 608 * Note: the bridge passed should be the one closest to the encoder
 609 */
 610void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
 611					  struct drm_atomic_state *old_state)
 612{
 613	struct drm_encoder *encoder;
 614
 615	if (!bridge)
 616		return;
 617
 618	encoder = bridge->encoder;
 619	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 620		if (bridge->funcs->atomic_post_disable) {
 621			struct drm_bridge_state *old_bridge_state;
 622
 623			old_bridge_state =
 624				drm_atomic_get_old_bridge_state(old_state,
 625								bridge);
 626			if (WARN_ON(!old_bridge_state))
 627				return;
 628
 629			bridge->funcs->atomic_post_disable(bridge,
 630							   old_bridge_state);
 631		} else if (bridge->funcs->post_disable) {
 632			bridge->funcs->post_disable(bridge);
 633		}
 634	}
 635}
 636EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
 637
 638/**
 639 * drm_atomic_bridge_chain_pre_enable - prepares for enabling all bridges in
 640 *					the encoder chain
 641 * @bridge: bridge control structure
 642 * @old_state: old atomic state
 643 *
 644 * Calls &drm_bridge_funcs.atomic_pre_enable (falls back on
 645 * &drm_bridge_funcs.pre_enable) op for all the bridges in the encoder chain,
 646 * starting from the last bridge to the first. These are called before calling
 647 * &drm_encoder_helper_funcs.atomic_enable
 648 *
 649 * Note: the bridge passed should be the one closest to the encoder
 650 */
 651void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
 652					struct drm_atomic_state *old_state)
 653{
 654	struct drm_encoder *encoder;
 655	struct drm_bridge *iter;
 656
 657	if (!bridge)
 658		return;
 659
 660	encoder = bridge->encoder;
 661	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
 662		if (iter->funcs->atomic_pre_enable) {
 663			struct drm_bridge_state *old_bridge_state;
 664
 665			old_bridge_state =
 666				drm_atomic_get_old_bridge_state(old_state,
 667								iter);
 668			if (WARN_ON(!old_bridge_state))
 669				return;
 670
 671			iter->funcs->atomic_pre_enable(iter, old_bridge_state);
 672		} else if (iter->funcs->pre_enable) {
 673			iter->funcs->pre_enable(iter);
 674		}
 675
 676		if (iter == bridge)
 677			break;
 678	}
 
 679}
 680EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
 681
 682/**
 683 * drm_atomic_bridge_chain_enable - enables all bridges in the encoder chain
 684 * @bridge: bridge control structure
 685 * @old_state: old atomic state
 686 *
 687 * Calls &drm_bridge_funcs.atomic_enable (falls back on
 688 * &drm_bridge_funcs.enable) op for all the bridges in the encoder chain,
 689 * starting from the first bridge to the last. These are called after completing
 690 * &drm_encoder_helper_funcs.atomic_enable
 691 *
 692 * Note: the bridge passed should be the one closest to the encoder
 693 */
 694void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
 695				    struct drm_atomic_state *old_state)
 696{
 697	struct drm_encoder *encoder;
 698
 699	if (!bridge)
 700		return;
 701
 702	encoder = bridge->encoder;
 703	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
 704		if (bridge->funcs->atomic_enable) {
 705			struct drm_bridge_state *old_bridge_state;
 706
 707			old_bridge_state =
 708				drm_atomic_get_old_bridge_state(old_state,
 709								bridge);
 710			if (WARN_ON(!old_bridge_state))
 711				return;
 712
 713			bridge->funcs->atomic_enable(bridge, old_bridge_state);
 714		} else if (bridge->funcs->enable) {
 715			bridge->funcs->enable(bridge);
 716		}
 717	}
 718}
 719EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
 720
 721static int drm_atomic_bridge_check(struct drm_bridge *bridge,
 722				   struct drm_crtc_state *crtc_state,
 723				   struct drm_connector_state *conn_state)
 724{
 725	if (bridge->funcs->atomic_check) {
 726		struct drm_bridge_state *bridge_state;
 727		int ret;
 728
 729		bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
 730							       bridge);
 731		if (WARN_ON(!bridge_state))
 732			return -EINVAL;
 733
 734		ret = bridge->funcs->atomic_check(bridge, bridge_state,
 735						  crtc_state, conn_state);
 736		if (ret)
 737			return ret;
 738	} else if (bridge->funcs->mode_fixup) {
 739		if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
 740					       &crtc_state->adjusted_mode))
 741			return -EINVAL;
 742	}
 743
 744	return 0;
 745}
 746
 747static int select_bus_fmt_recursive(struct drm_bridge *first_bridge,
 748				    struct drm_bridge *cur_bridge,
 749				    struct drm_crtc_state *crtc_state,
 750				    struct drm_connector_state *conn_state,
 751				    u32 out_bus_fmt)
 752{
 753	struct drm_bridge_state *cur_state;
 754	unsigned int num_in_bus_fmts, i;
 755	struct drm_bridge *prev_bridge;
 756	u32 *in_bus_fmts;
 757	int ret;
 758
 759	prev_bridge = drm_bridge_get_prev_bridge(cur_bridge);
 760	cur_state = drm_atomic_get_new_bridge_state(crtc_state->state,
 761						    cur_bridge);
 762
 763	/*
 764	 * If bus format negotiation is not supported by this bridge, let's
 765	 * pass MEDIA_BUS_FMT_FIXED to the previous bridge in the chain and
 766	 * hope that it can handle this situation gracefully (by providing
 767	 * appropriate default values).
 768	 */
 769	if (!cur_bridge->funcs->atomic_get_input_bus_fmts) {
 770		if (cur_bridge != first_bridge) {
 771			ret = select_bus_fmt_recursive(first_bridge,
 772						       prev_bridge, crtc_state,
 773						       conn_state,
 774						       MEDIA_BUS_FMT_FIXED);
 775			if (ret)
 776				return ret;
 777		}
 778
 779		/*
 780		 * Driver does not implement the atomic state hooks, but that's
 781		 * fine, as long as it does not access the bridge state.
 782		 */
 783		if (cur_state) {
 784			cur_state->input_bus_cfg.format = MEDIA_BUS_FMT_FIXED;
 785			cur_state->output_bus_cfg.format = out_bus_fmt;
 786		}
 787
 788		return 0;
 789	}
 790
 791	/*
 792	 * If the driver implements ->atomic_get_input_bus_fmts() it
 793	 * should also implement the atomic state hooks.
 794	 */
 795	if (WARN_ON(!cur_state))
 796		return -EINVAL;
 797
 798	in_bus_fmts = cur_bridge->funcs->atomic_get_input_bus_fmts(cur_bridge,
 799							cur_state,
 800							crtc_state,
 801							conn_state,
 802							out_bus_fmt,
 803							&num_in_bus_fmts);
 804	if (!num_in_bus_fmts)
 805		return -ENOTSUPP;
 806	else if (!in_bus_fmts)
 807		return -ENOMEM;
 808
 809	if (first_bridge == cur_bridge) {
 810		cur_state->input_bus_cfg.format = in_bus_fmts[0];
 811		cur_state->output_bus_cfg.format = out_bus_fmt;
 812		kfree(in_bus_fmts);
 813		return 0;
 814	}
 815
 816	for (i = 0; i < num_in_bus_fmts; i++) {
 817		ret = select_bus_fmt_recursive(first_bridge, prev_bridge,
 818					       crtc_state, conn_state,
 819					       in_bus_fmts[i]);
 820		if (ret != -ENOTSUPP)
 821			break;
 822	}
 823
 824	if (!ret) {
 825		cur_state->input_bus_cfg.format = in_bus_fmts[i];
 826		cur_state->output_bus_cfg.format = out_bus_fmt;
 827	}
 828
 829	kfree(in_bus_fmts);
 830	return ret;
 831}
 832
 833/*
 834 * This function is called by &drm_atomic_bridge_chain_check() just before
 835 * calling &drm_bridge_funcs.atomic_check() on all elements of the chain.
 836 * It performs bus format negotiation between bridge elements. The negotiation
 837 * happens in reverse order, starting from the last element in the chain up to
 838 * @bridge.
 839 *
 840 * Negotiation starts by retrieving supported output bus formats on the last
 841 * bridge element and testing them one by one. The test is recursive, meaning
 842 * that for each tested output format, the whole chain will be walked backward,
 843 * and each element will have to choose an input bus format that can be
 844 * transcoded to the requested output format. When a bridge element does not
 845 * support transcoding into a specific output format -ENOTSUPP is returned and
 846 * the next bridge element will have to try a different format. If none of the
 847 * combinations worked, -ENOTSUPP is returned and the atomic modeset will fail.
 848 *
 849 * This implementation is relying on
 850 * &drm_bridge_funcs.atomic_get_output_bus_fmts() and
 851 * &drm_bridge_funcs.atomic_get_input_bus_fmts() to gather supported
 852 * input/output formats.
 853 *
 854 * When &drm_bridge_funcs.atomic_get_output_bus_fmts() is not implemented by
 855 * the last element of the chain, &drm_atomic_bridge_chain_select_bus_fmts()
 856 * tries a single format: &drm_connector.display_info.bus_formats[0] if
 857 * available, MEDIA_BUS_FMT_FIXED otherwise.
 858 *
 859 * When &drm_bridge_funcs.atomic_get_input_bus_fmts() is not implemented,
 860 * &drm_atomic_bridge_chain_select_bus_fmts() skips the negotiation on the
 861 * bridge element that lacks this hook and asks the previous element in the
 862 * chain to try MEDIA_BUS_FMT_FIXED. It's up to bridge drivers to decide what
 863 * to do in that case (fail if they want to enforce bus format negotiation, or
 864 * provide a reasonable default if they need to support pipelines where not
 865 * all elements support bus format negotiation).
 866 */
 867static int
 868drm_atomic_bridge_chain_select_bus_fmts(struct drm_bridge *bridge,
 869					struct drm_crtc_state *crtc_state,
 870					struct drm_connector_state *conn_state)
 871{
 872	struct drm_connector *conn = conn_state->connector;
 873	struct drm_encoder *encoder = bridge->encoder;
 874	struct drm_bridge_state *last_bridge_state;
 875	unsigned int i, num_out_bus_fmts;
 876	struct drm_bridge *last_bridge;
 877	u32 *out_bus_fmts;
 878	int ret = 0;
 879
 880	last_bridge = list_last_entry(&encoder->bridge_chain,
 881				      struct drm_bridge, chain_node);
 882	last_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
 883							    last_bridge);
 884
 885	if (last_bridge->funcs->atomic_get_output_bus_fmts) {
 886		const struct drm_bridge_funcs *funcs = last_bridge->funcs;
 887
 888		/*
 889		 * If the driver implements ->atomic_get_output_bus_fmts() it
 890		 * should also implement the atomic state hooks.
 891		 */
 892		if (WARN_ON(!last_bridge_state))
 893			return -EINVAL;
 894
 895		out_bus_fmts = funcs->atomic_get_output_bus_fmts(last_bridge,
 896							last_bridge_state,
 897							crtc_state,
 898							conn_state,
 899							&num_out_bus_fmts);
 900		if (!num_out_bus_fmts)
 901			return -ENOTSUPP;
 902		else if (!out_bus_fmts)
 903			return -ENOMEM;
 904	} else {
 905		num_out_bus_fmts = 1;
 906		out_bus_fmts = kmalloc(sizeof(*out_bus_fmts), GFP_KERNEL);
 907		if (!out_bus_fmts)
 908			return -ENOMEM;
 909
 910		if (conn->display_info.num_bus_formats &&
 911		    conn->display_info.bus_formats)
 912			out_bus_fmts[0] = conn->display_info.bus_formats[0];
 913		else
 914			out_bus_fmts[0] = MEDIA_BUS_FMT_FIXED;
 915	}
 916
 917	for (i = 0; i < num_out_bus_fmts; i++) {
 918		ret = select_bus_fmt_recursive(bridge, last_bridge, crtc_state,
 919					       conn_state, out_bus_fmts[i]);
 920		if (ret != -ENOTSUPP)
 921			break;
 922	}
 923
 924	kfree(out_bus_fmts);
 925
 926	return ret;
 927}
 928
 929static void
 930drm_atomic_bridge_propagate_bus_flags(struct drm_bridge *bridge,
 931				      struct drm_connector *conn,
 932				      struct drm_atomic_state *state)
 933{
 934	struct drm_bridge_state *bridge_state, *next_bridge_state;
 935	struct drm_bridge *next_bridge;
 936	u32 output_flags = 0;
 937
 938	bridge_state = drm_atomic_get_new_bridge_state(state, bridge);
 939
 940	/* No bridge state attached to this bridge => nothing to propagate. */
 941	if (!bridge_state)
 942		return;
 943
 944	next_bridge = drm_bridge_get_next_bridge(bridge);
 945
 946	/*
 947	 * Let's try to apply the most common case here, that is, propagate
 948	 * display_info flags for the last bridge, and propagate the input
 949	 * flags of the next bridge element to the output end of the current
 950	 * bridge when the bridge is not the last one.
 951	 * There are exceptions to this rule, like when signal inversion is
 952	 * happening at the board level, but that's something drivers can deal
 953	 * with from their &drm_bridge_funcs.atomic_check() implementation by
 954	 * simply overriding the flags value we've set here.
 955	 */
 956	if (!next_bridge) {
 957		output_flags = conn->display_info.bus_flags;
 958	} else {
 959		next_bridge_state = drm_atomic_get_new_bridge_state(state,
 960								next_bridge);
 961		/*
 962		 * No bridge state attached to the next bridge, just leave the
 963		 * flags to 0.
 964		 */
 965		if (next_bridge_state)
 966			output_flags = next_bridge_state->input_bus_cfg.flags;
 967	}
 968
 969	bridge_state->output_bus_cfg.flags = output_flags;
 970
 971	/*
 972	 * Propage the output flags to the input end of the bridge. Again, it's
 973	 * not necessarily what all bridges want, but that's what most of them
 974	 * do, and by doing that by default we avoid forcing drivers to
 975	 * duplicate the "dummy propagation" logic.
 976	 */
 977	bridge_state->input_bus_cfg.flags = output_flags;
 978}
 979
 980/**
 981 * drm_atomic_bridge_chain_check() - Do an atomic check on the bridge chain
 982 * @bridge: bridge control structure
 983 * @crtc_state: new CRTC state
 984 * @conn_state: new connector state
 985 *
 986 * First trigger a bus format negotiation before calling
 987 * &drm_bridge_funcs.atomic_check() (falls back on
 988 * &drm_bridge_funcs.mode_fixup()) op for all the bridges in the encoder chain,
 989 * starting from the last bridge to the first. These are called before calling
 990 * &drm_encoder_helper_funcs.atomic_check()
 991 *
 992 * RETURNS:
 993 * 0 on success, a negative error code on failure
 994 */
 995int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
 996				  struct drm_crtc_state *crtc_state,
 997				  struct drm_connector_state *conn_state)
 998{
 999	struct drm_connector *conn = conn_state->connector;
1000	struct drm_encoder *encoder;
1001	struct drm_bridge *iter;
1002	int ret;
1003
1004	if (!bridge)
1005		return 0;
1006
1007	ret = drm_atomic_bridge_chain_select_bus_fmts(bridge, crtc_state,
1008						      conn_state);
1009	if (ret)
1010		return ret;
1011
1012	encoder = bridge->encoder;
1013	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
1014		int ret;
1015
1016		/*
1017		 * Bus flags are propagated by default. If a bridge needs to
1018		 * tweak the input bus flags for any reason, it should happen
1019		 * in its &drm_bridge_funcs.atomic_check() implementation such
1020		 * that preceding bridges in the chain can propagate the new
1021		 * bus flags.
1022		 */
1023		drm_atomic_bridge_propagate_bus_flags(iter, conn,
1024						      crtc_state->state);
1025
1026		ret = drm_atomic_bridge_check(iter, crtc_state, conn_state);
1027		if (ret)
1028			return ret;
1029
1030		if (iter == bridge)
1031			break;
1032	}
1033
1034	return 0;
1035}
1036EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
1037
1038/**
1039 * drm_bridge_detect - check if anything is attached to the bridge output
1040 * @bridge: bridge control structure
1041 *
1042 * If the bridge supports output detection, as reported by the
1043 * DRM_BRIDGE_OP_DETECT bridge ops flag, call &drm_bridge_funcs.detect for the
1044 * bridge and return the connection status. Otherwise return
1045 * connector_status_unknown.
1046 *
1047 * RETURNS:
1048 * The detection status on success, or connector_status_unknown if the bridge
1049 * doesn't support output detection.
1050 */
1051enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge)
1052{
1053	if (!(bridge->ops & DRM_BRIDGE_OP_DETECT))
1054		return connector_status_unknown;
1055
1056	return bridge->funcs->detect(bridge);
1057}
1058EXPORT_SYMBOL_GPL(drm_bridge_detect);
1059
1060/**
1061 * drm_bridge_get_modes - fill all modes currently valid for the sink into the
1062 * @connector
1063 * @bridge: bridge control structure
1064 * @connector: the connector to fill with modes
1065 *
1066 * If the bridge supports output modes retrieval, as reported by the
1067 * DRM_BRIDGE_OP_MODES bridge ops flag, call &drm_bridge_funcs.get_modes to
1068 * fill the connector with all valid modes and return the number of modes
1069 * added. Otherwise return 0.
1070 *
1071 * RETURNS:
1072 * The number of modes added to the connector.
1073 */
1074int drm_bridge_get_modes(struct drm_bridge *bridge,
1075			 struct drm_connector *connector)
1076{
1077	if (!(bridge->ops & DRM_BRIDGE_OP_MODES))
1078		return 0;
1079
1080	return bridge->funcs->get_modes(bridge, connector);
1081}
1082EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
1083
1084/**
1085 * drm_bridge_get_edid - get the EDID data of the connected display
1086 * @bridge: bridge control structure
1087 * @connector: the connector to read EDID for
1088 *
1089 * If the bridge supports output EDID retrieval, as reported by the
1090 * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
1091 * get the EDID and return it. Otherwise return NULL.
1092 *
1093 * RETURNS:
1094 * The retrieved EDID on success, or NULL otherwise.
1095 */
1096struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
1097				 struct drm_connector *connector)
1098{
1099	if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
1100		return NULL;
1101
1102	return bridge->funcs->get_edid(bridge, connector);
1103}
1104EXPORT_SYMBOL_GPL(drm_bridge_get_edid);
1105
1106/**
1107 * drm_bridge_hpd_enable - enable hot plug detection for the bridge
1108 * @bridge: bridge control structure
1109 * @cb: hot-plug detection callback
1110 * @data: data to be passed to the hot-plug detection callback
1111 *
1112 * Call &drm_bridge_funcs.hpd_enable if implemented and register the given @cb
1113 * and @data as hot plug notification callback. From now on the @cb will be
1114 * called with @data when an output status change is detected by the bridge,
1115 * until hot plug notification gets disabled with drm_bridge_hpd_disable().
1116 *
1117 * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
1118 * bridge->ops. This function shall not be called when the flag is not set.
1119 *
1120 * Only one hot plug detection callback can be registered at a time, it is an
1121 * error to call this function when hot plug detection is already enabled for
1122 * the bridge.
1123 */
1124void drm_bridge_hpd_enable(struct drm_bridge *bridge,
1125			   void (*cb)(void *data,
1126				      enum drm_connector_status status),
1127			   void *data)
1128{
1129	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
1130		return;
1131
1132	mutex_lock(&bridge->hpd_mutex);
1133
1134	if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n"))
1135		goto unlock;
1136
1137	bridge->hpd_cb = cb;
1138	bridge->hpd_data = data;
1139
1140	if (bridge->funcs->hpd_enable)
1141		bridge->funcs->hpd_enable(bridge);
1142
1143unlock:
1144	mutex_unlock(&bridge->hpd_mutex);
1145}
1146EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable);
1147
1148/**
1149 * drm_bridge_hpd_disable - disable hot plug detection for the bridge
1150 * @bridge: bridge control structure
1151 *
1152 * Call &drm_bridge_funcs.hpd_disable if implemented and unregister the hot
1153 * plug detection callback previously registered with drm_bridge_hpd_enable().
1154 * Once this function returns the callback will not be called by the bridge
1155 * when an output status change occurs.
1156 *
1157 * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
1158 * bridge->ops. This function shall not be called when the flag is not set.
1159 */
1160void drm_bridge_hpd_disable(struct drm_bridge *bridge)
1161{
1162	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
1163		return;
1164
1165	mutex_lock(&bridge->hpd_mutex);
1166	if (bridge->funcs->hpd_disable)
1167		bridge->funcs->hpd_disable(bridge);
1168
1169	bridge->hpd_cb = NULL;
1170	bridge->hpd_data = NULL;
1171	mutex_unlock(&bridge->hpd_mutex);
1172}
1173EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);
1174
1175/**
1176 * drm_bridge_hpd_notify - notify hot plug detection events
1177 * @bridge: bridge control structure
1178 * @status: output connection status
1179 *
1180 * Bridge drivers shall call this function to report hot plug events when they
1181 * detect a change in the output status, when hot plug detection has been
1182 * enabled by drm_bridge_hpd_enable().
1183 *
1184 * This function shall be called in a context that can sleep.
1185 */
1186void drm_bridge_hpd_notify(struct drm_bridge *bridge,
1187			   enum drm_connector_status status)
1188{
1189	mutex_lock(&bridge->hpd_mutex);
1190	if (bridge->hpd_cb)
1191		bridge->hpd_cb(bridge->hpd_data, status);
1192	mutex_unlock(&bridge->hpd_mutex);
1193}
1194EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
1195
1196#ifdef CONFIG_OF
1197/**
1198 * of_drm_find_bridge - find the bridge corresponding to the device node in
1199 *			the global bridge list
1200 *
1201 * @np: device node
1202 *
1203 * RETURNS:
1204 * drm_bridge control struct on success, NULL on failure
1205 */
1206struct drm_bridge *of_drm_find_bridge(struct device_node *np)
1207{
1208	struct drm_bridge *bridge;
1209
1210	mutex_lock(&bridge_lock);
1211
1212	list_for_each_entry(bridge, &bridge_list, list) {
1213		if (bridge->of_node == np) {
1214			mutex_unlock(&bridge_lock);
1215			return bridge;
1216		}
1217	}
1218
1219	mutex_unlock(&bridge_lock);
1220	return NULL;
1221}
1222EXPORT_SYMBOL(of_drm_find_bridge);
1223#endif
1224
1225MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@samsung.com>");
1226MODULE_DESCRIPTION("DRM bridge infrastructure");
1227MODULE_LICENSE("GPL and additional rights");