1/*
2 * Copyright (c) 2006-2008 Intel Corporation
3 * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
4 *
5 * DRM core CRTC related functions
6 *
7 * Permission to use, copy, modify, distribute, and sell this software and its
8 * documentation for any purpose is hereby granted without fee, provided that
9 * the above copyright notice appear in all copies and that both that copyright
10 * notice and this permission notice appear in supporting documentation, and
11 * that the name of the copyright holders not be used in advertising or
12 * publicity pertaining to distribution of the software without specific,
13 * written prior permission. The copyright holders make no representations
14 * about the suitability of this software for any purpose. It is provided "as
15 * is" without express or implied warranty.
16 *
17 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
18 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
19 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
20 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
21 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
22 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
23 * OF THIS SOFTWARE.
24 *
25 * Authors:
26 * Keith Packard
27 * Eric Anholt <eric@anholt.net>
28 * Dave Airlie <airlied@linux.ie>
29 * Jesse Barnes <jesse.barnes@intel.com>
30 */
31
32#include <linux/export.h>
33#include <linux/moduleparam.h>
34
35#include <drm/drm_bridge.h>
36#include <drm/drm_client_event.h>
37#include <drm/drm_crtc.h>
38#include <drm/drm_edid.h>
39#include <drm/drm_fourcc.h>
40#include <drm/drm_managed.h>
41#include <drm/drm_modeset_helper_vtables.h>
42#include <drm/drm_print.h>
43#include <drm/drm_probe_helper.h>
44#include <drm/drm_sysfs.h>
45
46#include "drm_crtc_helper_internal.h"
47
48/**
49 * DOC: output probing helper overview
50 *
51 * This library provides some helper code for output probing. It provides an
52 * implementation of the core &drm_connector_funcs.fill_modes interface with
53 * drm_helper_probe_single_connector_modes().
54 *
55 * It also provides support for polling connectors with a work item and for
56 * generic hotplug interrupt handling where the driver doesn't or cannot keep
57 * track of a per-connector hpd interrupt.
58 *
59 * This helper library can be used independently of the modeset helper library.
60 * Drivers can also overwrite different parts e.g. use their own hotplug
61 * handling code to avoid probing unrelated outputs.
62 *
63 * The probe helpers share the function table structures with other display
64 * helper libraries. See &struct drm_connector_helper_funcs for the details.
65 */
66
67static bool drm_kms_helper_poll = true;
68module_param_named(poll, drm_kms_helper_poll, bool, 0600);
69
70static enum drm_mode_status
71drm_mode_validate_flag(const struct drm_display_mode *mode,
72 int flags)
73{
74 if ((mode->flags & DRM_MODE_FLAG_INTERLACE) &&
75 !(flags & DRM_MODE_FLAG_INTERLACE))
76 return MODE_NO_INTERLACE;
77
78 if ((mode->flags & DRM_MODE_FLAG_DBLSCAN) &&
79 !(flags & DRM_MODE_FLAG_DBLSCAN))
80 return MODE_NO_DBLESCAN;
81
82 if ((mode->flags & DRM_MODE_FLAG_3D_MASK) &&
83 !(flags & DRM_MODE_FLAG_3D_MASK))
84 return MODE_NO_STEREO;
85
86 return MODE_OK;
87}
88
89static int
90drm_mode_validate_pipeline(struct drm_display_mode *mode,
91 struct drm_connector *connector,
92 struct drm_modeset_acquire_ctx *ctx,
93 enum drm_mode_status *status)
94{
95 struct drm_device *dev = connector->dev;
96 struct drm_encoder *encoder;
97 int ret;
98
99 /* Step 1: Validate against connector */
100 ret = drm_connector_mode_valid(connector, mode, ctx, status);
101 if (ret || *status != MODE_OK)
102 return ret;
103
104 /* Step 2: Validate against encoders and crtcs */
105 drm_connector_for_each_possible_encoder(connector, encoder) {
106 struct drm_bridge *bridge;
107 struct drm_crtc *crtc;
108
109 *status = drm_encoder_mode_valid(encoder, mode);
110 if (*status != MODE_OK) {
111 /* No point in continuing for crtc check as this encoder
112 * will not accept the mode anyway. If all encoders
113 * reject the mode then, at exit, ret will not be
114 * MODE_OK. */
115 continue;
116 }
117
118 bridge = drm_bridge_chain_get_first_bridge(encoder);
119 *status = drm_bridge_chain_mode_valid(bridge,
120 info: &connector->display_info,
121 mode);
122 drm_bridge_put(bridge);
123 if (*status != MODE_OK) {
124 /* There is also no point in continuing for crtc check
125 * here. */
126 continue;
127 }
128
129 drm_for_each_crtc(crtc, dev) {
130 if (!drm_encoder_crtc_ok(encoder, crtc))
131 continue;
132
133 *status = drm_crtc_mode_valid(crtc, mode);
134 if (*status == MODE_OK) {
135 /* If we get to this point there is at least
136 * one combination of encoder+crtc that works
137 * for this mode. Lets return now. */
138 return 0;
139 }
140 }
141 }
142
143 return 0;
144}
145
146static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
147{
148 struct drm_cmdline_mode *cmdline_mode;
149 struct drm_display_mode *mode;
150
151 cmdline_mode = &connector->cmdline_mode;
152 if (!cmdline_mode->specified)
153 return 0;
154
155 /* Only add a GTF mode if we find no matching probed modes */
156 list_for_each_entry(mode, &connector->probed_modes, head) {
157 if (mode->hdisplay != cmdline_mode->xres ||
158 mode->vdisplay != cmdline_mode->yres)
159 continue;
160
161 if (cmdline_mode->refresh_specified) {
162 /* The probed mode's vrefresh is set until later */
163 if (drm_mode_vrefresh(mode) != cmdline_mode->refresh)
164 continue;
165 }
166
167 /* Mark the matching mode as being preferred by the user */
168 mode->type |= DRM_MODE_TYPE_USERDEF;
169 return 0;
170 }
171
172 mode = drm_mode_create_from_cmdline_mode(dev: connector->dev,
173 cmd: cmdline_mode);
174 if (mode == NULL)
175 return 0;
176
177 drm_mode_probed_add(connector, mode);
178 return 1;
179}
180
181enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
182 const struct drm_display_mode *mode)
183{
184 const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
185
186 if (!crtc_funcs || !crtc_funcs->mode_valid)
187 return MODE_OK;
188
189 return crtc_funcs->mode_valid(crtc, mode);
190}
191
192enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
193 const struct drm_display_mode *mode)
194{
195 const struct drm_encoder_helper_funcs *encoder_funcs =
196 encoder->helper_private;
197
198 if (!encoder_funcs || !encoder_funcs->mode_valid)
199 return MODE_OK;
200
201 return encoder_funcs->mode_valid(encoder, mode);
202}
203
204int
205drm_connector_mode_valid(struct drm_connector *connector,
206 const struct drm_display_mode *mode,
207 struct drm_modeset_acquire_ctx *ctx,
208 enum drm_mode_status *status)
209{
210 const struct drm_connector_helper_funcs *connector_funcs =
211 connector->helper_private;
212 int ret = 0;
213
214 if (!connector_funcs)
215 *status = MODE_OK;
216 else if (connector_funcs->mode_valid_ctx)
217 ret = connector_funcs->mode_valid_ctx(connector, mode, ctx,
218 status);
219 else if (connector_funcs->mode_valid)
220 *status = connector_funcs->mode_valid(connector, mode);
221 else
222 *status = MODE_OK;
223
224 return ret;
225}
226
227static void drm_kms_helper_disable_hpd(struct drm_device *dev)
228{
229 struct drm_connector *connector;
230 struct drm_connector_list_iter conn_iter;
231
232 drm_connector_list_iter_begin(dev, iter: &conn_iter);
233 drm_for_each_connector_iter(connector, &conn_iter) {
234 const struct drm_connector_helper_funcs *funcs =
235 connector->helper_private;
236
237 if (funcs && funcs->disable_hpd)
238 funcs->disable_hpd(connector);
239 }
240 drm_connector_list_iter_end(iter: &conn_iter);
241}
242
243static bool drm_kms_helper_enable_hpd(struct drm_device *dev)
244{
245 bool poll = false;
246 struct drm_connector *connector;
247 struct drm_connector_list_iter conn_iter;
248
249 drm_connector_list_iter_begin(dev, iter: &conn_iter);
250 drm_for_each_connector_iter(connector, &conn_iter) {
251 const struct drm_connector_helper_funcs *funcs =
252 connector->helper_private;
253
254 if (funcs && funcs->enable_hpd)
255 funcs->enable_hpd(connector);
256
257 if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
258 DRM_CONNECTOR_POLL_DISCONNECT))
259 poll = true;
260 }
261 drm_connector_list_iter_end(iter: &conn_iter);
262
263 return poll;
264}
265
266#define DRM_OUTPUT_POLL_PERIOD (10*HZ)
267static void reschedule_output_poll_work(struct drm_device *dev)
268{
269 unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
270
271 if (dev->mode_config.delayed_event)
272 /*
273 * FIXME:
274 *
275 * Use short (1s) delay to handle the initial delayed event.
276 * This delay should not be needed, but Optimus/nouveau will
277 * fail in a mysterious way if the delayed event is handled as
278 * soon as possible like it is done in
279 * drm_helper_probe_single_connector_modes() in case the poll
280 * was enabled before.
281 */
282 delay = HZ;
283
284 schedule_delayed_work(dwork: &dev->mode_config.output_poll_work, delay);
285}
286
287/**
288 * drm_kms_helper_poll_enable - re-enable output polling.
289 * @dev: drm_device
290 *
291 * This function re-enables the output polling work, after it has been
292 * temporarily disabled using drm_kms_helper_poll_disable(), for example over
293 * suspend/resume.
294 *
295 * Drivers can call this helper from their device resume implementation. It is
296 * not an error to call this even when output polling isn't enabled.
297 *
298 * If device polling was never initialized before, this call will trigger a
299 * warning and return.
300 *
301 * Note that calls to enable and disable polling must be strictly ordered, which
302 * is automatically the case when they're only call from suspend/resume
303 * callbacks.
304 */
305void drm_kms_helper_poll_enable(struct drm_device *dev)
306{
307 if (drm_WARN_ON_ONCE(dev, !dev->mode_config.poll_enabled) ||
308 !drm_kms_helper_poll || dev->mode_config.poll_running)
309 return;
310
311 if (drm_kms_helper_enable_hpd(dev) ||
312 dev->mode_config.delayed_event)
313 reschedule_output_poll_work(dev);
314
315 dev->mode_config.poll_running = true;
316}
317EXPORT_SYMBOL(drm_kms_helper_poll_enable);
318
319/**
320 * drm_kms_helper_poll_reschedule - reschedule the output polling work
321 * @dev: drm_device
322 *
323 * This function reschedules the output polling work, after polling for a
324 * connector has been enabled.
325 *
326 * Drivers must call this helper after enabling polling for a connector by
327 * setting %DRM_CONNECTOR_POLL_CONNECT / %DRM_CONNECTOR_POLL_DISCONNECT flags
328 * in drm_connector::polled. Note that after disabling polling by clearing these
329 * flags for a connector will stop the output polling work automatically if
330 * the polling is disabled for all other connectors as well.
331 *
332 * The function can be called only after polling has been enabled by calling
333 * drm_kms_helper_poll_init() / drm_kms_helper_poll_enable().
334 */
335void drm_kms_helper_poll_reschedule(struct drm_device *dev)
336{
337 if (dev->mode_config.poll_running)
338 reschedule_output_poll_work(dev);
339}
340EXPORT_SYMBOL(drm_kms_helper_poll_reschedule);
341
342static int detect_connector_status(struct drm_connector *connector,
343 struct drm_modeset_acquire_ctx *ctx,
344 bool force)
345{
346 const struct drm_connector_helper_funcs *funcs = connector->helper_private;
347
348 if (funcs->detect_ctx)
349 return funcs->detect_ctx(connector, ctx, force);
350 else if (connector->funcs->detect)
351 return connector->funcs->detect(connector, force);
352
353 return connector_status_connected;
354}
355
356static enum drm_connector_status
357drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
358{
359 struct drm_modeset_acquire_ctx ctx;
360 int ret;
361
362 drm_modeset_acquire_init(ctx: &ctx, flags: 0);
363
364retry:
365 ret = drm_modeset_lock(lock: &connector->dev->mode_config.connection_mutex, ctx: &ctx);
366 if (!ret)
367 ret = detect_connector_status(connector, ctx: &ctx, force);
368
369 if (ret == -EDEADLK) {
370 drm_modeset_backoff(ctx: &ctx);
371 goto retry;
372 }
373
374 if (WARN_ON(ret < 0))
375 ret = connector_status_unknown;
376
377 if (ret != connector->status)
378 connector->epoch_counter += 1;
379
380 drm_modeset_drop_locks(ctx: &ctx);
381 drm_modeset_acquire_fini(ctx: &ctx);
382
383 return ret;
384}
385
386/**
387 * drm_helper_probe_detect - probe connector status
388 * @connector: connector to probe
389 * @ctx: acquire_ctx, or NULL to let this function handle locking.
390 * @force: Whether destructive probe operations should be performed.
391 *
392 * This function calls the detect callbacks of the connector.
393 * This function returns &drm_connector_status, or
394 * if @ctx is set, it might also return -EDEADLK.
395 */
396int
397drm_helper_probe_detect(struct drm_connector *connector,
398 struct drm_modeset_acquire_ctx *ctx,
399 bool force)
400{
401 struct drm_device *dev = connector->dev;
402 int ret;
403
404 if (!ctx)
405 return drm_helper_probe_detect_ctx(connector, force);
406
407 ret = drm_modeset_lock(lock: &dev->mode_config.connection_mutex, ctx);
408 if (ret)
409 return ret;
410
411 ret = detect_connector_status(connector, ctx, force);
412
413 if (ret != connector->status)
414 connector->epoch_counter += 1;
415
416 return ret;
417}
418EXPORT_SYMBOL(drm_helper_probe_detect);
419
420static int drm_helper_probe_get_modes(struct drm_connector *connector)
421{
422 const struct drm_connector_helper_funcs *connector_funcs =
423 connector->helper_private;
424 int count;
425
426 count = connector_funcs->get_modes(connector);
427
428 /* The .get_modes() callback should not return negative values. */
429 if (count < 0) {
430 drm_err(connector->dev, ".get_modes() returned %pe\n",
431 ERR_PTR(count));
432 count = 0;
433 }
434
435 /*
436 * Fallback for when DDC probe failed in drm_get_edid() and thus skipped
437 * override/firmware EDID.
438 */
439 if (count == 0 && connector->status == connector_status_connected)
440 count = drm_edid_override_connector_update(connector);
441
442 return count;
443}
444
445static int __drm_helper_update_and_validate(struct drm_connector *connector,
446 uint32_t maxX, uint32_t maxY,
447 struct drm_modeset_acquire_ctx *ctx)
448{
449 struct drm_device *dev = connector->dev;
450 struct drm_display_mode *mode;
451 int mode_flags = 0;
452 int ret;
453
454 drm_connector_list_update(connector);
455
456 if (connector->interlace_allowed)
457 mode_flags |= DRM_MODE_FLAG_INTERLACE;
458 if (connector->doublescan_allowed)
459 mode_flags |= DRM_MODE_FLAG_DBLSCAN;
460 if (connector->stereo_allowed)
461 mode_flags |= DRM_MODE_FLAG_3D_MASK;
462
463 list_for_each_entry(mode, &connector->modes, head) {
464 if (mode->status != MODE_OK)
465 continue;
466
467 mode->status = drm_mode_validate_driver(dev, mode);
468 if (mode->status != MODE_OK)
469 continue;
470
471 mode->status = drm_mode_validate_size(mode, maxX, maxY);
472 if (mode->status != MODE_OK)
473 continue;
474
475 mode->status = drm_mode_validate_flag(mode, flags: mode_flags);
476 if (mode->status != MODE_OK)
477 continue;
478
479 mode->status = drm_mode_validate_ycbcr420(mode, connector);
480 if (mode->status != MODE_OK)
481 continue;
482
483 ret = drm_mode_validate_pipeline(mode, connector, ctx,
484 status: &mode->status);
485 if (ret) {
486 drm_dbg_kms(dev,
487 "drm_mode_validate_pipeline failed: %d\n",
488 ret);
489
490 if (drm_WARN_ON_ONCE(dev, ret != -EDEADLK))
491 mode->status = MODE_ERROR;
492 else
493 return -EDEADLK;
494 }
495 }
496
497 return 0;
498}
499
500/**
501 * drm_helper_probe_single_connector_modes - get complete set of display modes
502 * @connector: connector to probe
503 * @maxX: max width for modes
504 * @maxY: max height for modes
505 *
506 * Based on the helper callbacks implemented by @connector in struct
507 * &drm_connector_helper_funcs try to detect all valid modes. Modes will first
508 * be added to the connector's probed_modes list, then culled (based on validity
509 * and the @maxX, @maxY parameters) and put into the normal modes list.
510 *
511 * Intended to be used as a generic implementation of the
512 * &drm_connector_funcs.fill_modes() vfunc for drivers that use the CRTC helpers
513 * for output mode filtering and detection.
514 *
515 * The basic procedure is as follows
516 *
517 * 1. All modes currently on the connector's modes list are marked as stale
518 *
519 * 2. New modes are added to the connector's probed_modes list with
520 * drm_mode_probed_add(). New modes start their life with status as OK.
521 * Modes are added from a single source using the following priority order.
522 *
523 * - &drm_connector_helper_funcs.get_modes vfunc
524 * - if the connector status is connector_status_connected, standard
525 * VESA DMT modes up to 1024x768 are automatically added
526 * (drm_add_modes_noedid())
527 *
528 * Finally modes specified via the kernel command line (video=...) are
529 * added in addition to what the earlier probes produced
530 * (drm_helper_probe_add_cmdline_mode()). These modes are generated
531 * using the VESA GTF/CVT formulas.
532 *
533 * 3. Modes are moved from the probed_modes list to the modes list. Potential
534 * duplicates are merged together (see drm_connector_list_update()).
535 * After this step the probed_modes list will be empty again.
536 *
537 * 4. Any non-stale mode on the modes list then undergoes validation
538 *
539 * - drm_mode_validate_basic() performs basic sanity checks
540 * - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
541 * (if specified)
542 * - drm_mode_validate_flag() checks the modes against basic connector
543 * capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
544 * - the optional &drm_connector_helper_funcs.mode_valid or
545 * &drm_connector_helper_funcs.mode_valid_ctx helpers can perform driver
546 * and/or sink specific checks
547 * - the optional &drm_crtc_helper_funcs.mode_valid,
548 * &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
549 * helpers can perform driver and/or source specific checks which are also
550 * enforced by the modeset/atomic helpers
551 *
552 * 5. Any mode whose status is not OK is pruned from the connector's modes list,
553 * accompanied by a debug message indicating the reason for the mode's
554 * rejection (see drm_mode_prune_invalid()).
555 *
556 * Returns:
557 * The number of modes found on @connector.
558 */
559int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
560 uint32_t maxX, uint32_t maxY)
561{
562 struct drm_device *dev = connector->dev;
563 struct drm_display_mode *mode;
564 int count = 0, ret;
565 enum drm_connector_status old_status;
566 struct drm_modeset_acquire_ctx ctx;
567
568 WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
569
570 drm_modeset_acquire_init(ctx: &ctx, flags: 0);
571
572 drm_dbg_kms(dev, "[CONNECTOR:%d:%s]\n", connector->base.id,
573 connector->name);
574
575retry:
576 ret = drm_modeset_lock(lock: &dev->mode_config.connection_mutex, ctx: &ctx);
577 if (ret == -EDEADLK) {
578 drm_modeset_backoff(ctx: &ctx);
579 goto retry;
580 } else
581 WARN_ON(ret < 0);
582
583 /* set all old modes to the stale state */
584 list_for_each_entry(mode, &connector->modes, head)
585 mode->status = MODE_STALE;
586
587 old_status = connector->status;
588
589 if (connector->force) {
590 if (connector->force == DRM_FORCE_ON ||
591 connector->force == DRM_FORCE_ON_DIGITAL)
592 connector->status = connector_status_connected;
593 else
594 connector->status = connector_status_disconnected;
595 if (connector->funcs->force)
596 connector->funcs->force(connector);
597 } else {
598 ret = drm_helper_probe_detect(connector, &ctx, true);
599
600 if (ret == -EDEADLK) {
601 drm_modeset_backoff(ctx: &ctx);
602 goto retry;
603 } else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
604 ret = connector_status_unknown;
605
606 connector->status = ret;
607 }
608
609 /*
610 * Normally either the driver's hpd code or the poll loop should
611 * pick up any changes and fire the hotplug event. But if
612 * userspace sneaks in a probe, we might miss a change. Hence
613 * check here, and if anything changed start the hotplug code.
614 */
615 if (old_status != connector->status) {
616 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] status updated from %s to %s\n",
617 connector->base.id, connector->name,
618 drm_get_connector_status_name(old_status),
619 drm_get_connector_status_name(connector->status));
620
621 /*
622 * The hotplug event code might call into the fb
623 * helpers, and so expects that we do not hold any
624 * locks. Fire up the poll struct instead, it will
625 * disable itself again.
626 */
627 dev->mode_config.delayed_event = true;
628 if (dev->mode_config.poll_enabled)
629 mod_delayed_work(wq: system_wq,
630 dwork: &dev->mode_config.output_poll_work,
631 delay: 0);
632 }
633
634 /*
635 * Re-enable polling in case the global poll config changed but polling
636 * is still initialized.
637 */
638 if (dev->mode_config.poll_enabled)
639 drm_kms_helper_poll_enable(dev);
640
641 if (connector->status == connector_status_disconnected) {
642 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] disconnected\n",
643 connector->base.id, connector->name);
644 drm_connector_update_edid_property(connector, NULL);
645 drm_mode_prune_invalid(dev, mode_list: &connector->modes, verbose: false);
646 goto exit;
647 }
648
649 count = drm_helper_probe_get_modes(connector);
650
651 if (count == 0 && (connector->status == connector_status_connected ||
652 connector->status == connector_status_unknown)) {
653 count = drm_add_modes_noedid(connector, hdisplay: 1024, vdisplay: 768);
654
655 /*
656 * Section 4.2.2.6 (EDID Corruption Detection) of the DP 1.4a
657 * Link CTS specifies that 640x480 (the official "failsafe"
658 * mode) needs to be the default if there's no EDID.
659 */
660 if (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort)
661 drm_set_preferred_mode(connector, hpref: 640, vpref: 480);
662 }
663 count += drm_helper_probe_add_cmdline_mode(connector);
664 if (count != 0) {
665 ret = __drm_helper_update_and_validate(connector, maxX, maxY, ctx: &ctx);
666 if (ret == -EDEADLK) {
667 drm_modeset_backoff(ctx: &ctx);
668 goto retry;
669 }
670 }
671
672 drm_mode_prune_invalid(dev, mode_list: &connector->modes, verbose: true);
673
674 /*
675 * Displayport spec section 5.2.1.2 ("Video Timing Format") says that
676 * all detachable sinks shall support 640x480 @60Hz as a fail safe
677 * mode. If all modes were pruned, perhaps because they need more
678 * lanes or a higher pixel clock than available, at least try to add
679 * in 640x480.
680 */
681 if (list_empty(head: &connector->modes) &&
682 connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
683 count = drm_add_modes_noedid(connector, hdisplay: 640, vdisplay: 480);
684 ret = __drm_helper_update_and_validate(connector, maxX, maxY, ctx: &ctx);
685 if (ret == -EDEADLK) {
686 drm_modeset_backoff(ctx: &ctx);
687 goto retry;
688 }
689 drm_mode_prune_invalid(dev, mode_list: &connector->modes, verbose: true);
690 }
691
692exit:
693 drm_modeset_drop_locks(ctx: &ctx);
694 drm_modeset_acquire_fini(ctx: &ctx);
695
696 if (list_empty(head: &connector->modes))
697 return 0;
698
699 drm_mode_sort(mode_list: &connector->modes);
700
701 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] probed modes:\n",
702 connector->base.id, connector->name);
703
704 list_for_each_entry(mode, &connector->modes, head) {
705 drm_mode_set_crtcinfo(p: mode, CRTC_INTERLACE_HALVE_V);
706 drm_dbg_kms(dev, "Probed mode: " DRM_MODE_FMT "\n",
707 DRM_MODE_ARG(mode));
708 }
709
710 return count;
711}
712EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);
713
714/**
715 * drm_kms_helper_hotplug_event - fire off KMS hotplug events
716 * @dev: drm_device whose connector state changed
717 *
718 * This function fires off the uevent for userspace and also calls the
719 * client hotplug function, which is most commonly used to inform the fbdev
720 * emulation code and allow it to update the fbcon output configuration.
721 *
722 * Drivers should call this from their hotplug handling code when a change is
723 * detected. Note that this function does not do any output detection of its
724 * own, like drm_helper_hpd_irq_event() does - this is assumed to be done by the
725 * driver already.
726 *
727 * This function must be called from process context with no mode
728 * setting locks held.
729 *
730 * If only a single connector has changed, consider calling
731 * drm_kms_helper_connector_hotplug_event() instead.
732 */
733void drm_kms_helper_hotplug_event(struct drm_device *dev)
734{
735 drm_sysfs_hotplug_event(dev);
736 drm_client_dev_hotplug(dev);
737}
738EXPORT_SYMBOL(drm_kms_helper_hotplug_event);
739
740/**
741 * drm_kms_helper_connector_hotplug_event - fire off a KMS connector hotplug event
742 * @connector: drm_connector which has changed
743 *
744 * This is the same as drm_kms_helper_hotplug_event(), except it fires a more
745 * fine-grained uevent for a single connector.
746 */
747void drm_kms_helper_connector_hotplug_event(struct drm_connector *connector)
748{
749 struct drm_device *dev = connector->dev;
750
751 drm_sysfs_connector_hotplug_event(connector);
752 drm_client_dev_hotplug(dev);
753}
754EXPORT_SYMBOL(drm_kms_helper_connector_hotplug_event);
755
756static void output_poll_execute(struct work_struct *work)
757{
758 struct delayed_work *delayed_work = to_delayed_work(work);
759 struct drm_device *dev = container_of(delayed_work, struct drm_device, mode_config.output_poll_work);
760 struct drm_connector *connector;
761 struct drm_connector_list_iter conn_iter;
762 enum drm_connector_status old_status;
763 bool repoll = false, changed;
764 u64 old_epoch_counter;
765
766 if (!dev->mode_config.poll_enabled)
767 return;
768
769 /* Pick up any changes detected by the probe functions. */
770 changed = dev->mode_config.delayed_event;
771 dev->mode_config.delayed_event = false;
772
773 if (!drm_kms_helper_poll) {
774 if (dev->mode_config.poll_running) {
775 drm_kms_helper_disable_hpd(dev);
776 dev->mode_config.poll_running = false;
777 }
778 goto out;
779 }
780
781 if (!mutex_trylock(&dev->mode_config.mutex)) {
782 repoll = true;
783 goto out;
784 }
785
786 drm_connector_list_iter_begin(dev, iter: &conn_iter);
787 drm_for_each_connector_iter(connector, &conn_iter) {
788 /* Ignore forced connectors. */
789 if (connector->force)
790 continue;
791
792 /* Ignore HPD capable connectors and connectors where we don't
793 * want any hotplug detection at all for polling. */
794 if (!connector->polled || connector->polled == DRM_CONNECTOR_POLL_HPD)
795 continue;
796
797 old_status = connector->status;
798 /* if we are connected and don't want to poll for disconnect
799 skip it */
800 if (old_status == connector_status_connected &&
801 !(connector->polled & DRM_CONNECTOR_POLL_DISCONNECT))
802 continue;
803
804 repoll = true;
805
806 old_epoch_counter = connector->epoch_counter;
807 connector->status = drm_helper_probe_detect(connector, NULL, false);
808 if (old_epoch_counter != connector->epoch_counter) {
809 const char *old, *new;
810
811 /*
812 * The poll work sets force=false when calling detect so
813 * that drivers can avoid to do disruptive tests (e.g.
814 * when load detect cycles could cause flickering on
815 * other, running displays). This bears the risk that we
816 * flip-flop between unknown here in the poll work and
817 * the real state when userspace forces a full detect
818 * call after receiving a hotplug event due to this
819 * change.
820 *
821 * Hence clamp an unknown detect status to the old
822 * value.
823 */
824 if (connector->status == connector_status_unknown) {
825 connector->status = old_status;
826 continue;
827 }
828
829 old = drm_get_connector_status_name(status: old_status);
830 new = drm_get_connector_status_name(status: connector->status);
831
832 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] status updated from %s to %s\n",
833 connector->base.id, connector->name,
834 old, new);
835 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] epoch counter %llu -> %llu\n",
836 connector->base.id, connector->name,
837 old_epoch_counter, connector->epoch_counter);
838
839 changed = true;
840 }
841 }
842 drm_connector_list_iter_end(iter: &conn_iter);
843
844 mutex_unlock(lock: &dev->mode_config.mutex);
845
846out:
847 if (changed)
848 drm_kms_helper_hotplug_event(dev);
849
850 if (repoll)
851 schedule_delayed_work(dwork: delayed_work, DRM_OUTPUT_POLL_PERIOD);
852}
853
854/**
855 * drm_kms_helper_is_poll_worker - is %current task an output poll worker?
856 *
857 * Determine if %current task is an output poll worker. This can be used
858 * to select distinct code paths for output polling versus other contexts.
859 *
860 * One use case is to avoid a deadlock between the output poll worker and
861 * the autosuspend worker wherein the latter waits for polling to finish
862 * upon calling drm_kms_helper_poll_disable(), while the former waits for
863 * runtime suspend to finish upon calling pm_runtime_get_sync() in a
864 * connector ->detect hook.
865 */
866bool drm_kms_helper_is_poll_worker(void)
867{
868 struct work_struct *work = current_work();
869
870 return work && work->func == output_poll_execute;
871}
872EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
873
874/**
875 * drm_kms_helper_poll_disable - disable output polling
876 * @dev: drm_device
877 *
878 * This function disables the output polling work.
879 *
880 * Drivers can call this helper from their device suspend implementation. It is
881 * not an error to call this even when output polling isn't enabled or already
882 * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
883 *
884 * If however, the polling was never initialized, this call will trigger a
885 * warning and return.
886 *
887 * Note that calls to enable and disable polling must be strictly ordered, which
888 * is automatically the case when they're only call from suspend/resume
889 * callbacks.
890 */
891void drm_kms_helper_poll_disable(struct drm_device *dev)
892{
893 if (drm_WARN_ON(dev, !dev->mode_config.poll_enabled))
894 return;
895
896 if (dev->mode_config.poll_running)
897 drm_kms_helper_disable_hpd(dev);
898
899 cancel_delayed_work_sync(dwork: &dev->mode_config.output_poll_work);
900
901 dev->mode_config.poll_running = false;
902}
903EXPORT_SYMBOL(drm_kms_helper_poll_disable);
904
905/**
906 * drm_kms_helper_poll_init - initialize and enable output polling
907 * @dev: drm_device
908 *
909 * This function initializes and then also enables output polling support for
910 * @dev. Drivers which do not have reliable hotplug support in hardware can use
911 * this helper infrastructure to regularly poll such connectors for changes in
912 * their connection state.
913 *
914 * Drivers can control which connectors are polled by setting the
915 * DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On
916 * connectors where probing live outputs can result in visual distortion drivers
917 * should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this.
918 * Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are
919 * completely ignored by the polling logic.
920 *
921 * Note that a connector can be both polled and probed from the hotplug handler,
922 * in case the hotplug interrupt is known to be unreliable.
923 */
924void drm_kms_helper_poll_init(struct drm_device *dev)
925{
926 INIT_DELAYED_WORK(&dev->mode_config.output_poll_work, output_poll_execute);
927 dev->mode_config.poll_enabled = true;
928
929 drm_kms_helper_poll_enable(dev);
930}
931EXPORT_SYMBOL(drm_kms_helper_poll_init);
932
933/**
934 * drm_kms_helper_poll_fini - disable output polling and clean it up
935 * @dev: drm_device
936 */
937void drm_kms_helper_poll_fini(struct drm_device *dev)
938{
939 if (!dev->mode_config.poll_enabled)
940 return;
941
942 drm_kms_helper_poll_disable(dev);
943
944 dev->mode_config.poll_enabled = false;
945}
946EXPORT_SYMBOL(drm_kms_helper_poll_fini);
947
948static void drm_kms_helper_poll_init_release(struct drm_device *dev, void *res)
949{
950 drm_kms_helper_poll_fini(dev);
951}
952
953/**
954 * drmm_kms_helper_poll_init - initialize and enable output polling
955 * @dev: drm_device
956 *
957 * This function initializes and then also enables output polling support for
958 * @dev similar to drm_kms_helper_poll_init(). Polling will automatically be
959 * cleaned up when the DRM device goes away.
960 *
961 * See drm_kms_helper_poll_init() for more information.
962 */
963void drmm_kms_helper_poll_init(struct drm_device *dev)
964{
965 int ret;
966
967 drm_kms_helper_poll_init(dev);
968
969 ret = drmm_add_action_or_reset(dev, drm_kms_helper_poll_init_release, dev);
970 if (ret)
971 drm_warn(dev, "Connector status will not be updated, error %d\n", ret);
972}
973EXPORT_SYMBOL(drmm_kms_helper_poll_init);
974
975static bool check_connector_changed(struct drm_connector *connector)
976{
977 struct drm_device *dev = connector->dev;
978 enum drm_connector_status old_status;
979 u64 old_epoch_counter;
980
981 /* Only handle HPD capable connectors. */
982 drm_WARN_ON(dev, !(connector->polled & DRM_CONNECTOR_POLL_HPD));
983
984 drm_WARN_ON(dev, !mutex_is_locked(&dev->mode_config.mutex));
985
986 old_status = connector->status;
987 old_epoch_counter = connector->epoch_counter;
988 connector->status = drm_helper_probe_detect(connector, NULL, false);
989
990 if (old_epoch_counter == connector->epoch_counter) {
991 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Same epoch counter %llu\n",
992 connector->base.id,
993 connector->name,
994 connector->epoch_counter);
995
996 return false;
997 }
998
999 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] status updated from %s to %s\n",
1000 connector->base.id,
1001 connector->name,
1002 drm_get_connector_status_name(old_status),
1003 drm_get_connector_status_name(connector->status));
1004
1005 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Changed epoch counter %llu => %llu\n",
1006 connector->base.id,
1007 connector->name,
1008 old_epoch_counter,
1009 connector->epoch_counter);
1010
1011 return true;
1012}
1013
1014/**
1015 * drm_connector_helper_hpd_irq_event - hotplug processing
1016 * @connector: drm_connector
1017 *
1018 * Drivers can use this helper function to run a detect cycle on a connector
1019 * which has the DRM_CONNECTOR_POLL_HPD flag set in its &polled member.
1020 *
1021 * This helper function is useful for drivers which can track hotplug
1022 * interrupts for a single connector. Drivers that want to send a
1023 * hotplug event for all connectors or can't track hotplug interrupts
1024 * per connector need to use drm_helper_hpd_irq_event().
1025 *
1026 * This function must be called from process context with no mode
1027 * setting locks held.
1028 *
1029 * Note that a connector can be both polled and probed from the hotplug
1030 * handler, in case the hotplug interrupt is known to be unreliable.
1031 *
1032 * Returns:
1033 * A boolean indicating whether the connector status changed or not
1034 */
1035bool drm_connector_helper_hpd_irq_event(struct drm_connector *connector)
1036{
1037 struct drm_device *dev = connector->dev;
1038 bool changed;
1039
1040 mutex_lock(&dev->mode_config.mutex);
1041 changed = check_connector_changed(connector);
1042 mutex_unlock(lock: &dev->mode_config.mutex);
1043
1044 if (changed) {
1045 drm_kms_helper_connector_hotplug_event(connector);
1046 drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Sent hotplug event\n",
1047 connector->base.id,
1048 connector->name);
1049 }
1050
1051 return changed;
1052}
1053EXPORT_SYMBOL(drm_connector_helper_hpd_irq_event);
1054
1055/**
1056 * drm_helper_hpd_irq_event - hotplug processing
1057 * @dev: drm_device
1058 *
1059 * Drivers can use this helper function to run a detect cycle on all connectors
1060 * which have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All
1061 * other connectors are ignored, which is useful to avoid reprobing fixed
1062 * panels.
1063 *
1064 * This helper function is useful for drivers which can't or don't track hotplug
1065 * interrupts for each connector.
1066 *
1067 * Drivers which support hotplug interrupts for each connector individually and
1068 * which have a more fine-grained detect logic can use
1069 * drm_connector_helper_hpd_irq_event(). Alternatively, they should bypass this
1070 * code and directly call drm_kms_helper_hotplug_event() in case the connector
1071 * state changed.
1072 *
1073 * This function must be called from process context with no mode
1074 * setting locks held.
1075 *
1076 * Note that a connector can be both polled and probed from the hotplug handler,
1077 * in case the hotplug interrupt is known to be unreliable.
1078 *
1079 * Returns:
1080 * A boolean indicating whether the connector status changed or not
1081 */
1082bool drm_helper_hpd_irq_event(struct drm_device *dev)
1083{
1084 struct drm_connector *connector, *first_changed_connector = NULL;
1085 struct drm_connector_list_iter conn_iter;
1086 int changed = 0;
1087
1088 if (!dev->mode_config.poll_enabled)
1089 return false;
1090
1091 mutex_lock(&dev->mode_config.mutex);
1092 drm_connector_list_iter_begin(dev, iter: &conn_iter);
1093 drm_for_each_connector_iter(connector, &conn_iter) {
1094 /* Only handle HPD capable connectors. */
1095 if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
1096 continue;
1097
1098 if (check_connector_changed(connector)) {
1099 if (!first_changed_connector) {
1100 drm_connector_get(connector);
1101 first_changed_connector = connector;
1102 }
1103
1104 changed++;
1105 }
1106 }
1107 drm_connector_list_iter_end(iter: &conn_iter);
1108 mutex_unlock(lock: &dev->mode_config.mutex);
1109
1110 if (changed == 1)
1111 drm_kms_helper_connector_hotplug_event(first_changed_connector);
1112 else if (changed > 0)
1113 drm_kms_helper_hotplug_event(dev);
1114
1115 if (first_changed_connector)
1116 drm_connector_put(connector: first_changed_connector);
1117
1118 return changed;
1119}
1120EXPORT_SYMBOL(drm_helper_hpd_irq_event);
1121
1122/**
1123 * drm_crtc_helper_mode_valid_fixed - Validates a display mode
1124 * @crtc: the crtc
1125 * @mode: the mode to validate
1126 * @fixed_mode: the display hardware's mode
1127 *
1128 * Returns:
1129 * MODE_OK on success, or another mode-status code otherwise.
1130 */
1131enum drm_mode_status drm_crtc_helper_mode_valid_fixed(struct drm_crtc *crtc,
1132 const struct drm_display_mode *mode,
1133 const struct drm_display_mode *fixed_mode)
1134{
1135 if (mode->hdisplay != fixed_mode->hdisplay && mode->vdisplay != fixed_mode->vdisplay)
1136 return MODE_ONE_SIZE;
1137 else if (mode->hdisplay != fixed_mode->hdisplay)
1138 return MODE_ONE_WIDTH;
1139 else if (mode->vdisplay != fixed_mode->vdisplay)
1140 return MODE_ONE_HEIGHT;
1141
1142 return MODE_OK;
1143}
1144EXPORT_SYMBOL(drm_crtc_helper_mode_valid_fixed);
1145
1146/**
1147 * drm_connector_helper_get_modes_fixed - Duplicates a display mode for a connector
1148 * @connector: the connector
1149 * @fixed_mode: the display hardware's mode
1150 *
1151 * This function duplicates a display modes for a connector. Drivers for hardware
1152 * that only supports a single fixed mode can use this function in their connector's
1153 * get_modes helper.
1154 *
1155 * Returns:
1156 * The number of created modes.
1157 */
1158int drm_connector_helper_get_modes_fixed(struct drm_connector *connector,
1159 const struct drm_display_mode *fixed_mode)
1160{
1161 struct drm_device *dev = connector->dev;
1162 struct drm_display_mode *mode;
1163
1164 mode = drm_mode_duplicate(dev, mode: fixed_mode);
1165 if (!mode) {
1166 drm_err(dev, "Failed to duplicate mode " DRM_MODE_FMT "\n",
1167 DRM_MODE_ARG(fixed_mode));
1168 return 0;
1169 }
1170
1171 if (mode->name[0] == '\0')
1172 drm_mode_set_name(mode);
1173
1174 mode->type |= DRM_MODE_TYPE_PREFERRED;
1175 drm_mode_probed_add(connector, mode);
1176
1177 if (mode->width_mm)
1178 connector->display_info.width_mm = mode->width_mm;
1179 if (mode->height_mm)
1180 connector->display_info.height_mm = mode->height_mm;
1181
1182 return 1;
1183}
1184EXPORT_SYMBOL(drm_connector_helper_get_modes_fixed);
1185
1186/**
1187 * drm_connector_helper_get_modes - Read EDID and update connector.
1188 * @connector: The connector
1189 *
1190 * Read the EDID using drm_edid_read() (which requires that connector->ddc is
1191 * set), and update the connector using the EDID.
1192 *
1193 * This can be used as the "default" connector helper .get_modes() hook if the
1194 * driver does not need any special processing. This is sets the example what
1195 * custom .get_modes() hooks should do regarding EDID read and connector update.
1196 *
1197 * Returns: Number of modes.
1198 */
1199int drm_connector_helper_get_modes(struct drm_connector *connector)
1200{
1201 const struct drm_edid *drm_edid;
1202 int count;
1203
1204 drm_edid = drm_edid_read(connector);
1205
1206 /*
1207 * Unconditionally update the connector. If the EDID was read
1208 * successfully, fill in the connector information derived from the
1209 * EDID. Otherwise, if the EDID is NULL, clear the connector
1210 * information.
1211 */
1212 drm_edid_connector_update(connector, edid: drm_edid);
1213
1214 count = drm_edid_connector_add_modes(connector);
1215
1216 drm_edid_free(drm_edid);
1217
1218 return count;
1219}
1220EXPORT_SYMBOL(drm_connector_helper_get_modes);
1221
1222/**
1223 * drm_connector_helper_tv_get_modes - Fills the modes availables to a TV connector
1224 * @connector: The connector
1225 *
1226 * Fills the available modes for a TV connector based on the supported
1227 * TV modes, and the default mode expressed by the kernel command line.
1228 *
1229 * This can be used as the default TV connector helper .get_modes() hook
1230 * if the driver does not need any special processing.
1231 *
1232 * Returns:
1233 * The number of modes added to the connector.
1234 */
1235int drm_connector_helper_tv_get_modes(struct drm_connector *connector)
1236{
1237 struct drm_device *dev = connector->dev;
1238 struct drm_property *tv_mode_property =
1239 dev->mode_config.tv_mode_property;
1240 struct drm_cmdline_mode *cmdline = &connector->cmdline_mode;
1241 unsigned int ntsc_modes = BIT(DRM_MODE_TV_MODE_NTSC) |
1242 BIT(DRM_MODE_TV_MODE_NTSC_443) |
1243 BIT(DRM_MODE_TV_MODE_NTSC_J) |
1244 BIT(DRM_MODE_TV_MODE_PAL_M);
1245 unsigned int pal_modes = BIT(DRM_MODE_TV_MODE_PAL) |
1246 BIT(DRM_MODE_TV_MODE_PAL_N) |
1247 BIT(DRM_MODE_TV_MODE_SECAM);
1248 unsigned int tv_modes[2] = { UINT_MAX, UINT_MAX };
1249 unsigned int i, supported_tv_modes = 0;
1250
1251 if (!tv_mode_property)
1252 return 0;
1253
1254 for (i = 0; i < tv_mode_property->num_values; i++)
1255 supported_tv_modes |= BIT(tv_mode_property->values[i]);
1256
1257 if (((supported_tv_modes & ntsc_modes) &&
1258 (supported_tv_modes & pal_modes)) ||
1259 (supported_tv_modes & BIT(DRM_MODE_TV_MODE_MONOCHROME))) {
1260 uint64_t default_mode;
1261
1262 if (drm_object_property_get_default_value(obj: &connector->base,
1263 property: tv_mode_property,
1264 val: &default_mode))
1265 return 0;
1266
1267 if (cmdline->tv_mode_specified)
1268 default_mode = cmdline->tv_mode;
1269
1270 if (BIT(default_mode) & ntsc_modes) {
1271 tv_modes[0] = DRM_MODE_TV_MODE_NTSC;
1272 tv_modes[1] = DRM_MODE_TV_MODE_PAL;
1273 } else {
1274 tv_modes[0] = DRM_MODE_TV_MODE_PAL;
1275 tv_modes[1] = DRM_MODE_TV_MODE_NTSC;
1276 }
1277 } else if (supported_tv_modes & ntsc_modes) {
1278 tv_modes[0] = DRM_MODE_TV_MODE_NTSC;
1279 } else if (supported_tv_modes & pal_modes) {
1280 tv_modes[0] = DRM_MODE_TV_MODE_PAL;
1281 } else {
1282 return 0;
1283 }
1284
1285 for (i = 0; i < ARRAY_SIZE(tv_modes); i++) {
1286 struct drm_display_mode *mode;
1287
1288 if (tv_modes[i] == DRM_MODE_TV_MODE_NTSC)
1289 mode = drm_mode_analog_ntsc_480i(dev);
1290 else if (tv_modes[i] == DRM_MODE_TV_MODE_PAL)
1291 mode = drm_mode_analog_pal_576i(dev);
1292 else
1293 break;
1294 if (!mode)
1295 return i;
1296 if (!i)
1297 mode->type |= DRM_MODE_TYPE_PREFERRED;
1298 drm_mode_probed_add(connector, mode);
1299 }
1300
1301 return i;
1302}
1303EXPORT_SYMBOL(drm_connector_helper_tv_get_modes);
1304
1305/**
1306 * drm_connector_helper_detect_from_ddc - Read EDID and detect connector status.
1307 * @connector: The connector
1308 * @ctx: Acquire context
1309 * @force: Perform screen-destructive operations, if necessary
1310 *
1311 * Detects the connector status by reading the EDID using drm_probe_ddc(),
1312 * which requires connector->ddc to be set. Returns connector_status_connected
1313 * on success or connector_status_disconnected on failure.
1314 *
1315 * Returns:
1316 * The connector status as defined by enum drm_connector_status.
1317 */
1318int drm_connector_helper_detect_from_ddc(struct drm_connector *connector,
1319 struct drm_modeset_acquire_ctx *ctx,
1320 bool force)
1321{
1322 struct i2c_adapter *ddc = connector->ddc;
1323
1324 if (!ddc)
1325 return connector_status_unknown;
1326
1327 if (drm_probe_ddc(adapter: ddc))
1328 return connector_status_connected;
1329
1330 return connector_status_disconnected;
1331}
1332EXPORT_SYMBOL(drm_connector_helper_detect_from_ddc);
1333

source code of linux/drivers/gpu/drm/drm_probe_helper.c