New training

Linux graphics course

New training

Linux graphics course

Bootlin logo

Elixir Cross Referencer

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
/*
 * Copyright (c) 2006-2008 Intel Corporation
 * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
 *
 * DRM core CRTC related functions
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 *
 * Authors:
 *      Keith Packard
 *	Eric Anholt <eric@anholt.net>
 *      Dave Airlie <airlied@linux.ie>
 *      Jesse Barnes <jesse.barnes@intel.com>
 */

#include <linux/export.h>
#include <linux/moduleparam.h>

#include <drm/drmP.h>
#include <drm/drm_client.h>
#include <drm/drm_crtc.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_edid.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_probe_helper.h>

#include "drm_crtc_helper_internal.h"

/**
 * DOC: output probing helper overview
 *
 * This library provides some helper code for output probing. It provides an
 * implementation of the core &drm_connector_funcs.fill_modes interface with
 * drm_helper_probe_single_connector_modes().
 *
 * It also provides support for polling connectors with a work item and for
 * generic hotplug interrupt handling where the driver doesn't or cannot keep
 * track of a per-connector hpd interrupt.
 *
 * This helper library can be used independently of the modeset helper library.
 * Drivers can also overwrite different parts e.g. use their own hotplug
 * handling code to avoid probing unrelated outputs.
 *
 * The probe helpers share the function table structures with other display
 * helper libraries. See &struct drm_connector_helper_funcs for the details.
 */

static bool drm_kms_helper_poll = true;
module_param_named(poll, drm_kms_helper_poll, bool, 0600);

static enum drm_mode_status
drm_mode_validate_flag(const struct drm_display_mode *mode,
		       int flags)
{
	if ((mode->flags & DRM_MODE_FLAG_INTERLACE) &&
	    !(flags & DRM_MODE_FLAG_INTERLACE))
		return MODE_NO_INTERLACE;

	if ((mode->flags & DRM_MODE_FLAG_DBLSCAN) &&
	    !(flags & DRM_MODE_FLAG_DBLSCAN))
		return MODE_NO_DBLESCAN;

	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) &&
	    !(flags & DRM_MODE_FLAG_3D_MASK))
		return MODE_NO_STEREO;

	return MODE_OK;
}

static enum drm_mode_status
drm_mode_validate_pipeline(struct drm_display_mode *mode,
			    struct drm_connector *connector)
{
	struct drm_device *dev = connector->dev;
	enum drm_mode_status ret = MODE_OK;
	struct drm_encoder *encoder;
	int i;

	/* Step 1: Validate against connector */
	ret = drm_connector_mode_valid(connector, mode);
	if (ret != MODE_OK)
		return ret;

	/* Step 2: Validate against encoders and crtcs */
	drm_connector_for_each_possible_encoder(connector, encoder, i) {
		struct drm_crtc *crtc;

		ret = drm_encoder_mode_valid(encoder, mode);
		if (ret != MODE_OK) {
			/* No point in continuing for crtc check as this encoder
			 * will not accept the mode anyway. If all encoders
			 * reject the mode then, at exit, ret will not be
			 * MODE_OK. */
			continue;
		}

		ret = drm_bridge_mode_valid(encoder->bridge, mode);
		if (ret != MODE_OK) {
			/* There is also no point in continuing for crtc check
			 * here. */
			continue;
		}

		drm_for_each_crtc(crtc, dev) {
			if (!drm_encoder_crtc_ok(encoder, crtc))
				continue;

			ret = drm_crtc_mode_valid(crtc, mode);
			if (ret == MODE_OK) {
				/* If we get to this point there is at least
				 * one combination of encoder+crtc that works
				 * for this mode. Lets return now. */
				return ret;
			}
		}
	}

	return ret;
}

static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
{
	struct drm_cmdline_mode *cmdline_mode;
	struct drm_display_mode *mode;

	cmdline_mode = &connector->cmdline_mode;
	if (!cmdline_mode->specified)
		return 0;

	/* Only add a GTF mode if we find no matching probed modes */
	list_for_each_entry(mode, &connector->probed_modes, head) {
		if (mode->hdisplay != cmdline_mode->xres ||
		    mode->vdisplay != cmdline_mode->yres)
			continue;

		if (cmdline_mode->refresh_specified) {
			/* The probed mode's vrefresh is set until later */
			if (drm_mode_vrefresh(mode) != cmdline_mode->refresh)
				continue;
		}

		return 0;
	}

	mode = drm_mode_create_from_cmdline_mode(connector->dev,
						 cmdline_mode);
	if (mode == NULL)
		return 0;

	drm_mode_probed_add(connector, mode);
	return 1;
}

enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
					 const struct drm_display_mode *mode)
{
	const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;

	if (!crtc_funcs || !crtc_funcs->mode_valid)
		return MODE_OK;

	return crtc_funcs->mode_valid(crtc, mode);
}

enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
					    const struct drm_display_mode *mode)
{
	const struct drm_encoder_helper_funcs *encoder_funcs =
		encoder->helper_private;

	if (!encoder_funcs || !encoder_funcs->mode_valid)
		return MODE_OK;

	return encoder_funcs->mode_valid(encoder, mode);
}

enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
					      struct drm_display_mode *mode)
{
	const struct drm_connector_helper_funcs *connector_funcs =
		connector->helper_private;

	if (!connector_funcs || !connector_funcs->mode_valid)
		return MODE_OK;

	return connector_funcs->mode_valid(connector, mode);
}

#define DRM_OUTPUT_POLL_PERIOD (10*HZ)
/**
 * drm_kms_helper_poll_enable - re-enable output polling.
 * @dev: drm_device
 *
 * This function re-enables the output polling work, after it has been
 * temporarily disabled using drm_kms_helper_poll_disable(), for example over
 * suspend/resume.
 *
 * Drivers can call this helper from their device resume implementation. It is
 * not an error to call this even when output polling isn't enabled.
 *
 * Note that calls to enable and disable polling must be strictly ordered, which
 * is automatically the case when they're only call from suspend/resume
 * callbacks.
 */
void drm_kms_helper_poll_enable(struct drm_device *dev)
{
	bool poll = false;
	struct drm_connector *connector;
	struct drm_connector_list_iter conn_iter;
	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;

	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
		return;

	drm_connector_list_iter_begin(dev, &conn_iter);
	drm_for_each_connector_iter(connector, &conn_iter) {
		if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
					 DRM_CONNECTOR_POLL_DISCONNECT))
			poll = true;
	}
	drm_connector_list_iter_end(&conn_iter);

	if (dev->mode_config.delayed_event) {
		/*
		 * FIXME:
		 *
		 * Use short (1s) delay to handle the initial delayed event.
		 * This delay should not be needed, but Optimus/nouveau will
		 * fail in a mysterious way if the delayed event is handled as
		 * soon as possible like it is done in
		 * drm_helper_probe_single_connector_modes() in case the poll
		 * was enabled before.
		 */
		poll = true;
		delay = HZ;
	}

	if (poll)
		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
}
EXPORT_SYMBOL(drm_kms_helper_poll_enable);

static enum drm_connector_status
drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
{
	const struct drm_connector_helper_funcs *funcs = connector->helper_private;
	struct drm_modeset_acquire_ctx ctx;
	int ret;

	drm_modeset_acquire_init(&ctx, 0);

retry:
	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
	if (!ret) {
		if (funcs->detect_ctx)
			ret = funcs->detect_ctx(connector, &ctx, force);
		else if (connector->funcs->detect)
			ret = connector->funcs->detect(connector, force);
		else
			ret = connector_status_connected;
	}

	if (ret == -EDEADLK) {
		drm_modeset_backoff(&ctx);
		goto retry;
	}

	if (WARN_ON(ret < 0))
		ret = connector_status_unknown;

	drm_modeset_drop_locks(&ctx);
	drm_modeset_acquire_fini(&ctx);

	return ret;
}

/**
 * drm_helper_probe_detect - probe connector status
 * @connector: connector to probe
 * @ctx: acquire_ctx, or NULL to let this function handle locking.
 * @force: Whether destructive probe operations should be performed.
 *
 * This function calls the detect callbacks of the connector.
 * This function returns &drm_connector_status, or
 * if @ctx is set, it might also return -EDEADLK.
 */
int
drm_helper_probe_detect(struct drm_connector *connector,
			struct drm_modeset_acquire_ctx *ctx,
			bool force)
{
	const struct drm_connector_helper_funcs *funcs = connector->helper_private;
	struct drm_device *dev = connector->dev;
	int ret;

	if (!ctx)
		return drm_helper_probe_detect_ctx(connector, force);

	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
	if (ret)
		return ret;

	if (funcs->detect_ctx)
		return funcs->detect_ctx(connector, ctx, force);
	else if (connector->funcs->detect)
		return connector->funcs->detect(connector, force);
	else
		return connector_status_connected;
}
EXPORT_SYMBOL(drm_helper_probe_detect);

/**
 * drm_helper_probe_single_connector_modes - get complete set of display modes
 * @connector: connector to probe
 * @maxX: max width for modes
 * @maxY: max height for modes
 *
 * Based on the helper callbacks implemented by @connector in struct
 * &drm_connector_helper_funcs try to detect all valid modes.  Modes will first
 * be added to the connector's probed_modes list, then culled (based on validity
 * and the @maxX, @maxY parameters) and put into the normal modes list.
 *
 * Intended to be used as a generic implementation of the
 * &drm_connector_funcs.fill_modes() vfunc for drivers that use the CRTC helpers
 * for output mode filtering and detection.
 *
 * The basic procedure is as follows
 *
 * 1. All modes currently on the connector's modes list are marked as stale
 *
 * 2. New modes are added to the connector's probed_modes list with
 *    drm_mode_probed_add(). New modes start their life with status as OK.
 *    Modes are added from a single source using the following priority order.
 *
 *    - &drm_connector_helper_funcs.get_modes vfunc
 *    - if the connector status is connector_status_connected, standard
 *      VESA DMT modes up to 1024x768 are automatically added
 *      (drm_add_modes_noedid())
 *
 *    Finally modes specified via the kernel command line (video=...) are
 *    added in addition to what the earlier probes produced
 *    (drm_helper_probe_add_cmdline_mode()). These modes are generated
 *    using the VESA GTF/CVT formulas.
 *
 * 3. Modes are moved from the probed_modes list to the modes list. Potential
 *    duplicates are merged together (see drm_connector_list_update()).
 *    After this step the probed_modes list will be empty again.
 *
 * 4. Any non-stale mode on the modes list then undergoes validation
 *
 *    - drm_mode_validate_basic() performs basic sanity checks
 *    - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
 *      (if specified)
 *    - drm_mode_validate_flag() checks the modes against basic connector
 *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
 *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
 *      driver and/or sink specific checks
 *    - the optional &drm_crtc_helper_funcs.mode_valid,
 *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
 *      helpers can perform driver and/or source specific checks which are also
 *      enforced by the modeset/atomic helpers
 *
 * 5. Any mode whose status is not OK is pruned from the connector's modes list,
 *    accompanied by a debug message indicating the reason for the mode's
 *    rejection (see drm_mode_prune_invalid()).
 *
 * Returns:
 * The number of modes found on @connector.
 */
int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
					    uint32_t maxX, uint32_t maxY)
{
	struct drm_device *dev = connector->dev;
	struct drm_display_mode *mode;
	const struct drm_connector_helper_funcs *connector_funcs =
		connector->helper_private;
	int count = 0, ret;
	int mode_flags = 0;
	bool verbose_prune = true;
	enum drm_connector_status old_status;
	struct drm_modeset_acquire_ctx ctx;

	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

	drm_modeset_acquire_init(&ctx, 0);

	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
			connector->name);

retry:
	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
	if (ret == -EDEADLK) {
		drm_modeset_backoff(&ctx);
		goto retry;
	} else
		WARN_ON(ret < 0);

	/* set all old modes to the stale state */
	list_for_each_entry(mode, &connector->modes, head)
		mode->status = MODE_STALE;

	old_status = connector->status;

	if (connector->force) {
		if (connector->force == DRM_FORCE_ON ||
		    connector->force == DRM_FORCE_ON_DIGITAL)
			connector->status = connector_status_connected;
		else
			connector->status = connector_status_disconnected;
		if (connector->funcs->force)
			connector->funcs->force(connector);
	} else {
		ret = drm_helper_probe_detect(connector, &ctx, true);

		if (ret == -EDEADLK) {
			drm_modeset_backoff(&ctx);
			goto retry;
		} else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
			ret = connector_status_unknown;

		connector->status = ret;
	}

	/*
	 * Normally either the driver's hpd code or the poll loop should
	 * pick up any changes and fire the hotplug event. But if
	 * userspace sneaks in a probe, we might miss a change. Hence
	 * check here, and if anything changed start the hotplug code.
	 */
	if (old_status != connector->status) {
		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
			      connector->base.id,
			      connector->name,
			      drm_get_connector_status_name(old_status),
			      drm_get_connector_status_name(connector->status));

		/*
		 * The hotplug event code might call into the fb
		 * helpers, and so expects that we do not hold any
		 * locks. Fire up the poll struct instead, it will
		 * disable itself again.
		 */
		dev->mode_config.delayed_event = true;
		if (dev->mode_config.poll_enabled)
			schedule_delayed_work(&dev->mode_config.output_poll_work,
					      0);
	}

	/* Re-enable polling in case the global poll config changed. */
	if (drm_kms_helper_poll != dev->mode_config.poll_running)
		drm_kms_helper_poll_enable(dev);

	dev->mode_config.poll_running = drm_kms_helper_poll;

	if (connector->status == connector_status_disconnected) {
		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
			connector->base.id, connector->name);
		drm_connector_update_edid_property(connector, NULL);
		verbose_prune = false;
		goto prune;
	}

	count = (*connector_funcs->get_modes)(connector);

	/*
	 * Fallback for when DDC probe failed in drm_get_edid() and thus skipped
	 * override/firmware EDID.
	 */
	if (count == 0 && connector->status == connector_status_connected)
		count = drm_add_override_edid_modes(connector);

	if (count == 0 && connector->status == connector_status_connected)
		count = drm_add_modes_noedid(connector, 1024, 768);
	count += drm_helper_probe_add_cmdline_mode(connector);
	if (count == 0)
		goto prune;

	drm_connector_list_update(connector);

	if (connector->interlace_allowed)
		mode_flags |= DRM_MODE_FLAG_INTERLACE;
	if (connector->doublescan_allowed)
		mode_flags |= DRM_MODE_FLAG_DBLSCAN;
	if (connector->stereo_allowed)
		mode_flags |= DRM_MODE_FLAG_3D_MASK;

	list_for_each_entry(mode, &connector->modes, head) {
		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_driver(dev, mode);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_size(mode, maxX, maxY);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_flag(mode, mode_flags);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_pipeline(mode,
								  connector);

		if (mode->status == MODE_OK)
			mode->status = drm_mode_validate_ycbcr420(mode,
								  connector);
	}

prune:
	drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);

	drm_modeset_drop_locks(&ctx);
	drm_modeset_acquire_fini(&ctx);

	if (list_empty(&connector->modes))
		return 0;

	list_for_each_entry(mode, &connector->modes, head)
		mode->vrefresh = drm_mode_vrefresh(mode);

	drm_mode_sort(&connector->modes);

	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] probed modes :\n", connector->base.id,
			connector->name);
	list_for_each_entry(mode, &connector->modes, head) {
		drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
		drm_mode_debug_printmodeline(mode);
	}

	return count;
}
EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);

/**
 * drm_kms_helper_hotplug_event - fire off KMS hotplug events
 * @dev: drm_device whose connector state changed
 *
 * This function fires off the uevent for userspace and also calls the
 * output_poll_changed function, which is most commonly used to inform the fbdev
 * emulation code and allow it to update the fbcon output configuration.
 *
 * Drivers should call this from their hotplug handling code when a change is
 * detected. Note that this function does not do any output detection of its
 * own, like drm_helper_hpd_irq_event() does - this is assumed to be done by the
 * driver already.
 *
 * This function must be called from process context with no mode
 * setting locks held.
 */
void drm_kms_helper_hotplug_event(struct drm_device *dev)
{
	/* send a uevent + call fbdev */
	drm_sysfs_hotplug_event(dev);
	if (dev->mode_config.funcs->output_poll_changed)
		dev->mode_config.funcs->output_poll_changed(dev);

	drm_client_dev_hotplug(dev);
}
EXPORT_SYMBOL(drm_kms_helper_hotplug_event);

static void output_poll_execute(struct work_struct *work)
{
	struct delayed_work *delayed_work = to_delayed_work(work);
	struct drm_device *dev = container_of(delayed_work, struct drm_device, mode_config.output_poll_work);
	struct drm_connector *connector;
	struct drm_connector_list_iter conn_iter;
	enum drm_connector_status old_status;
	bool repoll = false, changed;

	/* Pick up any changes detected by the probe functions. */
	changed = dev->mode_config.delayed_event;
	dev->mode_config.delayed_event = false;

	if (!drm_kms_helper_poll)
		goto out;

	if (!mutex_trylock(&dev->mode_config.mutex)) {
		repoll = true;
		goto out;
	}

	drm_connector_list_iter_begin(dev, &conn_iter);
	drm_for_each_connector_iter(connector, &conn_iter) {
		/* Ignore forced connectors. */
		if (connector->force)
			continue;

		/* Ignore HPD capable connectors and connectors where we don't
		 * want any hotplug detection at all for polling. */
		if (!connector->polled || connector->polled == DRM_CONNECTOR_POLL_HPD)
			continue;

		old_status = connector->status;
		/* if we are connected and don't want to poll for disconnect
		   skip it */
		if (old_status == connector_status_connected &&
		    !(connector->polled & DRM_CONNECTOR_POLL_DISCONNECT))
			continue;

		repoll = true;

		connector->status = drm_helper_probe_detect(connector, NULL, false);
		if (old_status != connector->status) {
			const char *old, *new;

			/*
			 * The poll work sets force=false when calling detect so
			 * that drivers can avoid to do disruptive tests (e.g.
			 * when load detect cycles could cause flickering on
			 * other, running displays). This bears the risk that we
			 * flip-flop between unknown here in the poll work and
			 * the real state when userspace forces a full detect
			 * call after receiving a hotplug event due to this
			 * change.
			 *
			 * Hence clamp an unknown detect status to the old
			 * value.
			 */
			if (connector->status == connector_status_unknown) {
				connector->status = old_status;
				continue;
			}

			old = drm_get_connector_status_name(old_status);
			new = drm_get_connector_status_name(connector->status);

			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] "
				      "status updated from %s to %s\n",
				      connector->base.id,
				      connector->name,
				      old, new);

			changed = true;
		}
	}
	drm_connector_list_iter_end(&conn_iter);

	mutex_unlock(&dev->mode_config.mutex);

out:
	if (changed)
		drm_kms_helper_hotplug_event(dev);

	if (repoll)
		schedule_delayed_work(delayed_work, DRM_OUTPUT_POLL_PERIOD);
}

/**
 * drm_kms_helper_is_poll_worker - is %current task an output poll worker?
 *
 * Determine if %current task is an output poll worker.  This can be used
 * to select distinct code paths for output polling versus other contexts.
 *
 * One use case is to avoid a deadlock between the output poll worker and
 * the autosuspend worker wherein the latter waits for polling to finish
 * upon calling drm_kms_helper_poll_disable(), while the former waits for
 * runtime suspend to finish upon calling pm_runtime_get_sync() in a
 * connector ->detect hook.
 */
bool drm_kms_helper_is_poll_worker(void)
{
	struct work_struct *work = current_work();

	return work && work->func == output_poll_execute;
}
EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);

/**
 * drm_kms_helper_poll_disable - disable output polling
 * @dev: drm_device
 *
 * This function disables the output polling work.
 *
 * Drivers can call this helper from their device suspend implementation. It is
 * not an error to call this even when output polling isn't enabled or already
 * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
 *
 * Note that calls to enable and disable polling must be strictly ordered, which
 * is automatically the case when they're only call from suspend/resume
 * callbacks.
 */
void drm_kms_helper_poll_disable(struct drm_device *dev)
{
	if (!dev->mode_config.poll_enabled)
		return;
	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
}
EXPORT_SYMBOL(drm_kms_helper_poll_disable);

/**
 * drm_kms_helper_poll_init - initialize and enable output polling
 * @dev: drm_device
 *
 * This function intializes and then also enables output polling support for
 * @dev. Drivers which do not have reliable hotplug support in hardware can use
 * this helper infrastructure to regularly poll such connectors for changes in
 * their connection state.
 *
 * Drivers can control which connectors are polled by setting the
 * DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On
 * connectors where probing live outputs can result in visual distortion drivers
 * should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this.
 * Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are
 * completely ignored by the polling logic.
 *
 * Note that a connector can be both polled and probed from the hotplug handler,
 * in case the hotplug interrupt is known to be unreliable.
 */
void drm_kms_helper_poll_init(struct drm_device *dev)
{
	INIT_DELAYED_WORK(&dev->mode_config.output_poll_work, output_poll_execute);
	dev->mode_config.poll_enabled = true;

	drm_kms_helper_poll_enable(dev);
}
EXPORT_SYMBOL(drm_kms_helper_poll_init);

/**
 * drm_kms_helper_poll_fini - disable output polling and clean it up
 * @dev: drm_device
 */
void drm_kms_helper_poll_fini(struct drm_device *dev)
{
	drm_kms_helper_poll_disable(dev);
}
EXPORT_SYMBOL(drm_kms_helper_poll_fini);

/**
 * drm_helper_hpd_irq_event - hotplug processing
 * @dev: drm_device
 *
 * Drivers can use this helper function to run a detect cycle on all connectors
 * which have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All
 * other connectors are ignored, which is useful to avoid reprobing fixed
 * panels.
 *
 * This helper function is useful for drivers which can't or don't track hotplug
 * interrupts for each connector.
 *
 * Drivers which support hotplug interrupts for each connector individually and
 * which have a more fine-grained detect logic should bypass this code and
 * directly call drm_kms_helper_hotplug_event() in case the connector state
 * changed.
 *
 * This function must be called from process context with no mode
 * setting locks held.
 *
 * Note that a connector can be both polled and probed from the hotplug handler,
 * in case the hotplug interrupt is known to be unreliable.
 */
bool drm_helper_hpd_irq_event(struct drm_device *dev)
{
	struct drm_connector *connector;
	struct drm_connector_list_iter conn_iter;
	enum drm_connector_status old_status;
	bool changed = false;

	if (!dev->mode_config.poll_enabled)
		return false;

	mutex_lock(&dev->mode_config.mutex);
	drm_connector_list_iter_begin(dev, &conn_iter);
	drm_for_each_connector_iter(connector, &conn_iter) {
		/* Only handle HPD capable connectors. */
		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
			continue;

		old_status = connector->status;

		connector->status = drm_helper_probe_detect(connector, NULL, false);
		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
			      connector->base.id,
			      connector->name,
			      drm_get_connector_status_name(old_status),
			      drm_get_connector_status_name(connector->status));
		if (old_status != connector->status)
			changed = true;
	}
	drm_connector_list_iter_end(&conn_iter);
	mutex_unlock(&dev->mode_config.mutex);

	if (changed)
		drm_kms_helper_hotplug_event(dev);

	return changed;
}
EXPORT_SYMBOL(drm_helper_hpd_irq_event);