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TOMOYO Linux Cross Reference
Linux/include/drm/drm_modeset_helper_vtables.h

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  1 /*
  2  * Copyright © 2006 Keith Packard
  3  * Copyright © 2007-2008 Dave Airlie
  4  * Copyright © 2007-2008 Intel Corporation
  5  *   Jesse Barnes <jesse.barnes@intel.com>
  6  * Copyright © 2011-2013 Intel Corporation
  7  * Copyright © 2015 Intel Corporation
  8  *   Daniel Vetter <daniel.vetter@ffwll.ch>
  9  *
 10  * Permission is hereby granted, free of charge, to any person obtaining a
 11  * copy of this software and associated documentation files (the "Software"),
 12  * to deal in the Software without restriction, including without limitation
 13  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 14  * and/or sell copies of the Software, and to permit persons to whom the
 15  * Software is furnished to do so, subject to the following conditions:
 16  *
 17  * The above copyright notice and this permission notice shall be included in
 18  * all copies or substantial portions of the Software.
 19  *
 20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 22  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 23  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 24  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 25  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 26  * OTHER DEALINGS IN THE SOFTWARE.
 27  */
 28 
 29 #ifndef __DRM_MODESET_HELPER_VTABLES_H__
 30 #define __DRM_MODESET_HELPER_VTABLES_H__
 31 
 32 #include <drm/drm_crtc.h>
 33 #include <drm/drm_encoder.h>
 34 
 35 /**
 36  * DOC: overview
 37  *
 38  * The DRM mode setting helper functions are common code for drivers to use if
 39  * they wish.  Drivers are not forced to use this code in their
 40  * implementations but it would be useful if the code they do use at least
 41  * provides a consistent interface and operation to userspace. Therefore it is
 42  * highly recommended to use the provided helpers as much as possible.
 43  *
 44  * Because there is only one pointer per modeset object to hold a vfunc table
 45  * for helper libraries they are by necessity shared among the different
 46  * helpers.
 47  *
 48  * To make this clear all the helper vtables are pulled together in this location here.
 49  */
 50 
 51 enum mode_set_atomic;
 52 struct drm_writeback_connector;
 53 struct drm_writeback_job;
 54 
 55 /**
 56  * struct drm_crtc_helper_funcs - helper operations for CRTCs
 57  *
 58  * These hooks are used by the legacy CRTC helpers, the transitional plane
 59  * helpers and the new atomic modesetting helpers.
 60  */
 61 struct drm_crtc_helper_funcs {
 62         /**
 63          * @dpms:
 64          *
 65          * Callback to control power levels on the CRTC.  If the mode passed in
 66          * is unsupported, the provider must use the next lowest power level.
 67          * This is used by the legacy CRTC helpers to implement DPMS
 68          * functionality in drm_helper_connector_dpms().
 69          *
 70          * This callback is also used to disable a CRTC by calling it with
 71          * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
 72          *
 73          * This callback is used by the legacy CRTC helpers.  Atomic helpers
 74          * also support using this hook for enabling and disabling a CRTC to
 75          * facilitate transitions to atomic, but it is deprecated. Instead
 76          * @atomic_enable and @atomic_disable should be used.
 77          */
 78         void (*dpms)(struct drm_crtc *crtc, int mode);
 79 
 80         /**
 81          * @prepare:
 82          *
 83          * This callback should prepare the CRTC for a subsequent modeset, which
 84          * in practice means the driver should disable the CRTC if it is
 85          * running. Most drivers ended up implementing this by calling their
 86          * @dpms hook with DRM_MODE_DPMS_OFF.
 87          *
 88          * This callback is used by the legacy CRTC helpers.  Atomic helpers
 89          * also support using this hook for disabling a CRTC to facilitate
 90          * transitions to atomic, but it is deprecated. Instead @atomic_disable
 91          * should be used.
 92          */
 93         void (*prepare)(struct drm_crtc *crtc);
 94 
 95         /**
 96          * @commit:
 97          *
 98          * This callback should commit the new mode on the CRTC after a modeset,
 99          * which in practice means the driver should enable the CRTC.  Most
100          * drivers ended up implementing this by calling their @dpms hook with
101          * DRM_MODE_DPMS_ON.
102          *
103          * This callback is used by the legacy CRTC helpers.  Atomic helpers
104          * also support using this hook for enabling a CRTC to facilitate
105          * transitions to atomic, but it is deprecated. Instead @atomic_enable
106          * should be used.
107          */
108         void (*commit)(struct drm_crtc *crtc);
109 
110         /**
111          * @mode_valid:
112          *
113          * This callback is used to check if a specific mode is valid in this
114          * crtc. This should be implemented if the crtc has some sort of
115          * restriction in the modes it can display. For example, a given crtc
116          * may be responsible to set a clock value. If the clock can not
117          * produce all the values for the available modes then this callback
118          * can be used to restrict the number of modes to only the ones that
119          * can be displayed.
120          *
121          * This hook is used by the probe helpers to filter the mode list in
122          * drm_helper_probe_single_connector_modes(), and it is used by the
123          * atomic helpers to validate modes supplied by userspace in
124          * drm_atomic_helper_check_modeset().
125          *
126          * This function is optional.
127          *
128          * NOTE:
129          *
130          * Since this function is both called from the check phase of an atomic
131          * commit, and the mode validation in the probe paths it is not allowed
132          * to look at anything else but the passed-in mode, and validate it
133          * against configuration-invariant hardward constraints. Any further
134          * limits which depend upon the configuration can only be checked in
135          * @mode_fixup or @atomic_check.
136          *
137          * RETURNS:
138          *
139          * drm_mode_status Enum
140          */
141         enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc,
142                                            const struct drm_display_mode *mode);
143 
144         /**
145          * @mode_fixup:
146          *
147          * This callback is used to validate a mode. The parameter mode is the
148          * display mode that userspace requested, adjusted_mode is the mode the
149          * encoders need to be fed with. Note that this is the inverse semantics
150          * of the meaning for the &drm_encoder and &drm_bridge_funcs.mode_fixup
151          * vfunc. If the CRTC cannot support the requested conversion from mode
152          * to adjusted_mode it should reject the modeset. See also
153          * &drm_crtc_state.adjusted_mode for more details.
154          *
155          * This function is used by both legacy CRTC helpers and atomic helpers.
156          * With atomic helpers it is optional.
157          *
158          * NOTE:
159          *
160          * This function is called in the check phase of atomic modesets, which
161          * can be aborted for any reason (including on userspace's request to
162          * just check whether a configuration would be possible). Atomic drivers
163          * MUST NOT touch any persistent state (hardware or software) or data
164          * structures except the passed in adjusted_mode parameter.
165          *
166          * This is in contrast to the legacy CRTC helpers where this was
167          * allowed.
168          *
169          * Atomic drivers which need to inspect and adjust more state should
170          * instead use the @atomic_check callback, but note that they're not
171          * perfectly equivalent: @mode_valid is called from
172          * drm_atomic_helper_check_modeset(), but @atomic_check is called from
173          * drm_atomic_helper_check_planes(), because originally it was meant for
174          * plane update checks only.
175          *
176          * Also beware that userspace can request its own custom modes, neither
177          * core nor helpers filter modes to the list of probe modes reported by
178          * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
179          * that modes are filtered consistently put any CRTC constraints and
180          * limits checks into @mode_valid.
181          *
182          * RETURNS:
183          *
184          * True if an acceptable configuration is possible, false if the modeset
185          * operation should be rejected.
186          */
187         bool (*mode_fixup)(struct drm_crtc *crtc,
188                            const struct drm_display_mode *mode,
189                            struct drm_display_mode *adjusted_mode);
190 
191         /**
192          * @mode_set:
193          *
194          * This callback is used by the legacy CRTC helpers to set a new mode,
195          * position and framebuffer. Since it ties the primary plane to every
196          * mode change it is incompatible with universal plane support. And
197          * since it can't update other planes it's incompatible with atomic
198          * modeset support.
199          *
200          * This callback is only used by CRTC helpers and deprecated.
201          *
202          * RETURNS:
203          *
204          * 0 on success or a negative error code on failure.
205          */
206         int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
207                         struct drm_display_mode *adjusted_mode, int x, int y,
208                         struct drm_framebuffer *old_fb);
209 
210         /**
211          * @mode_set_nofb:
212          *
213          * This callback is used to update the display mode of a CRTC without
214          * changing anything of the primary plane configuration. This fits the
215          * requirement of atomic and hence is used by the atomic helpers. It is
216          * also used by the transitional plane helpers to implement a
217          * @mode_set hook in drm_helper_crtc_mode_set().
218          *
219          * Note that the display pipe is completely off when this function is
220          * called. Atomic drivers which need hardware to be running before they
221          * program the new display mode (e.g. because they implement runtime PM)
222          * should not use this hook. This is because the helper library calls
223          * this hook only once per mode change and not every time the display
224          * pipeline is suspended using either DPMS or the new "ACTIVE" property.
225          * Which means register values set in this callback might get reset when
226          * the CRTC is suspended, but not restored.  Such drivers should instead
227          * move all their CRTC setup into the @atomic_enable callback.
228          *
229          * This callback is optional.
230          */
231         void (*mode_set_nofb)(struct drm_crtc *crtc);
232 
233         /**
234          * @mode_set_base:
235          *
236          * This callback is used by the legacy CRTC helpers to set a new
237          * framebuffer and scanout position. It is optional and used as an
238          * optimized fast-path instead of a full mode set operation with all the
239          * resulting flickering. If it is not present
240          * drm_crtc_helper_set_config() will fall back to a full modeset, using
241          * the @mode_set callback. Since it can't update other planes it's
242          * incompatible with atomic modeset support.
243          *
244          * This callback is only used by the CRTC helpers and deprecated.
245          *
246          * RETURNS:
247          *
248          * 0 on success or a negative error code on failure.
249          */
250         int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
251                              struct drm_framebuffer *old_fb);
252 
253         /**
254          * @mode_set_base_atomic:
255          *
256          * This callback is used by the fbdev helpers to set a new framebuffer
257          * and scanout without sleeping, i.e. from an atomic calling context. It
258          * is only used to implement kgdb support.
259          *
260          * This callback is optional and only needed for kgdb support in the fbdev
261          * helpers.
262          *
263          * RETURNS:
264          *
265          * 0 on success or a negative error code on failure.
266          */
267         int (*mode_set_base_atomic)(struct drm_crtc *crtc,
268                                     struct drm_framebuffer *fb, int x, int y,
269                                     enum mode_set_atomic);
270 
271         /**
272          * @disable:
273          *
274          * This callback should be used to disable the CRTC. With the atomic
275          * drivers it is called after all encoders connected to this CRTC have
276          * been shut off already using their own
277          * &drm_encoder_helper_funcs.disable hook. If that sequence is too
278          * simple drivers can just add their own hooks and call it from this
279          * CRTC callback here by looping over all encoders connected to it using
280          * for_each_encoder_on_crtc().
281          *
282          * This hook is used both by legacy CRTC helpers and atomic helpers.
283          * Atomic drivers don't need to implement it if there's no need to
284          * disable anything at the CRTC level. To ensure that runtime PM
285          * handling (using either DPMS or the new "ACTIVE" property) works
286          * @disable must be the inverse of @atomic_enable for atomic drivers.
287          * Atomic drivers should consider to use @atomic_disable instead of
288          * this one.
289          *
290          * NOTE:
291          *
292          * With legacy CRTC helpers there's a big semantic difference between
293          * @disable and other hooks (like @prepare or @dpms) used to shut down a
294          * CRTC: @disable is only called when also logically disabling the
295          * display pipeline and needs to release any resources acquired in
296          * @mode_set (like shared PLLs, or again release pinned framebuffers).
297          *
298          * Therefore @disable must be the inverse of @mode_set plus @commit for
299          * drivers still using legacy CRTC helpers, which is different from the
300          * rules under atomic.
301          */
302         void (*disable)(struct drm_crtc *crtc);
303 
304         /**
305          * @atomic_check:
306          *
307          * Drivers should check plane-update related CRTC constraints in this
308          * hook. They can also check mode related limitations but need to be
309          * aware of the calling order, since this hook is used by
310          * drm_atomic_helper_check_planes() whereas the preparations needed to
311          * check output routing and the display mode is done in
312          * drm_atomic_helper_check_modeset(). Therefore drivers that want to
313          * check output routing and display mode constraints in this callback
314          * must ensure that drm_atomic_helper_check_modeset() has been called
315          * beforehand. This is calling order used by the default helper
316          * implementation in drm_atomic_helper_check().
317          *
318          * When using drm_atomic_helper_check_planes() this hook is called
319          * after the &drm_plane_helper_funcs.atomic_check hook for planes, which
320          * allows drivers to assign shared resources requested by planes in this
321          * callback here. For more complicated dependencies the driver can call
322          * the provided check helpers multiple times until the computed state
323          * has a final configuration and everything has been checked.
324          *
325          * This function is also allowed to inspect any other object's state and
326          * can add more state objects to the atomic commit if needed. Care must
327          * be taken though to ensure that state check and compute functions for
328          * these added states are all called, and derived state in other objects
329          * all updated. Again the recommendation is to just call check helpers
330          * until a maximal configuration is reached.
331          *
332          * This callback is used by the atomic modeset helpers and by the
333          * transitional plane helpers, but it is optional.
334          *
335          * NOTE:
336          *
337          * This function is called in the check phase of an atomic update. The
338          * driver is not allowed to change anything outside of the free-standing
339          * state objects passed-in or assembled in the overall &drm_atomic_state
340          * update tracking structure.
341          *
342          * Also beware that userspace can request its own custom modes, neither
343          * core nor helpers filter modes to the list of probe modes reported by
344          * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
345          * that modes are filtered consistently put any CRTC constraints and
346          * limits checks into @mode_valid.
347          *
348          * RETURNS:
349          *
350          * 0 on success, -EINVAL if the state or the transition can't be
351          * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
352          * attempt to obtain another state object ran into a &drm_modeset_lock
353          * deadlock.
354          */
355         int (*atomic_check)(struct drm_crtc *crtc,
356                             struct drm_crtc_state *state);
357 
358         /**
359          * @atomic_begin:
360          *
361          * Drivers should prepare for an atomic update of multiple planes on
362          * a CRTC in this hook. Depending upon hardware this might be vblank
363          * evasion, blocking updates by setting bits or doing preparatory work
364          * for e.g. manual update display.
365          *
366          * This hook is called before any plane commit functions are called.
367          *
368          * Note that the power state of the display pipe when this function is
369          * called depends upon the exact helpers and calling sequence the driver
370          * has picked. See drm_atomic_helper_commit_planes() for a discussion of
371          * the tradeoffs and variants of plane commit helpers.
372          *
373          * This callback is used by the atomic modeset helpers and by the
374          * transitional plane helpers, but it is optional.
375          */
376         void (*atomic_begin)(struct drm_crtc *crtc,
377                              struct drm_crtc_state *old_crtc_state);
378         /**
379          * @atomic_flush:
380          *
381          * Drivers should finalize an atomic update of multiple planes on
382          * a CRTC in this hook. Depending upon hardware this might include
383          * checking that vblank evasion was successful, unblocking updates by
384          * setting bits or setting the GO bit to flush out all updates.
385          *
386          * Simple hardware or hardware with special requirements can commit and
387          * flush out all updates for all planes from this hook and forgo all the
388          * other commit hooks for plane updates.
389          *
390          * This hook is called after any plane commit functions are called.
391          *
392          * Note that the power state of the display pipe when this function is
393          * called depends upon the exact helpers and calling sequence the driver
394          * has picked. See drm_atomic_helper_commit_planes() for a discussion of
395          * the tradeoffs and variants of plane commit helpers.
396          *
397          * This callback is used by the atomic modeset helpers and by the
398          * transitional plane helpers, but it is optional.
399          */
400         void (*atomic_flush)(struct drm_crtc *crtc,
401                              struct drm_crtc_state *old_crtc_state);
402 
403         /**
404          * @atomic_enable:
405          *
406          * This callback should be used to enable the CRTC. With the atomic
407          * drivers it is called before all encoders connected to this CRTC are
408          * enabled through the encoder's own &drm_encoder_helper_funcs.enable
409          * hook.  If that sequence is too simple drivers can just add their own
410          * hooks and call it from this CRTC callback here by looping over all
411          * encoders connected to it using for_each_encoder_on_crtc().
412          *
413          * This hook is used only by atomic helpers, for symmetry with
414          * @atomic_disable. Atomic drivers don't need to implement it if there's
415          * no need to enable anything at the CRTC level. To ensure that runtime
416          * PM handling (using either DPMS or the new "ACTIVE" property) works
417          * @atomic_enable must be the inverse of @atomic_disable for atomic
418          * drivers.
419          *
420          * Drivers can use the @old_crtc_state input parameter if the operations
421          * needed to enable the CRTC don't depend solely on the new state but
422          * also on the transition between the old state and the new state.
423          *
424          * This function is optional.
425          */
426         void (*atomic_enable)(struct drm_crtc *crtc,
427                               struct drm_crtc_state *old_crtc_state);
428 
429         /**
430          * @atomic_disable:
431          *
432          * This callback should be used to disable the CRTC. With the atomic
433          * drivers it is called after all encoders connected to this CRTC have
434          * been shut off already using their own
435          * &drm_encoder_helper_funcs.disable hook. If that sequence is too
436          * simple drivers can just add their own hooks and call it from this
437          * CRTC callback here by looping over all encoders connected to it using
438          * for_each_encoder_on_crtc().
439          *
440          * This hook is used only by atomic helpers. Atomic drivers don't
441          * need to implement it if there's no need to disable anything at the
442          * CRTC level.
443          *
444          * Comparing to @disable, this one provides the additional input
445          * parameter @old_crtc_state which could be used to access the old
446          * state. Atomic drivers should consider to use this one instead
447          * of @disable.
448          *
449          * This function is optional.
450          */
451         void (*atomic_disable)(struct drm_crtc *crtc,
452                                struct drm_crtc_state *old_crtc_state);
453 
454         /**
455          * @get_scanout_position:
456          *
457          * Called by vblank timestamping code.
458          *
459          * Returns the current display scanout position from a CRTC and an
460          * optional accurate ktime_get() timestamp of when the position was
461          * measured. Note that this is a helper callback which is only used
462          * if a driver uses drm_crtc_vblank_helper_get_vblank_timestamp()
463          * for the @drm_crtc_funcs.get_vblank_timestamp callback.
464          *
465          * Parameters:
466          *
467          * crtc:
468          *     The CRTC.
469          * in_vblank_irq:
470          *     True when called from drm_crtc_handle_vblank(). Some drivers
471          *     need to apply some workarounds for gpu-specific vblank irq
472          *     quirks if the flag is set.
473          * vpos:
474          *     Target location for current vertical scanout position.
475          * hpos:
476          *     Target location for current horizontal scanout position.
477          * stime:
478          *     Target location for timestamp taken immediately before
479          *     scanout position query. Can be NULL to skip timestamp.
480          * etime:
481          *     Target location for timestamp taken immediately after
482          *     scanout position query. Can be NULL to skip timestamp.
483          * mode:
484          *     Current display timings.
485          *
486          * Returns vpos as a positive number while in active scanout area.
487          * Returns vpos as a negative number inside vblank, counting the number
488          * of scanlines to go until end of vblank, e.g., -1 means "one scanline
489          * until start of active scanout / end of vblank."
490          *
491          * Returns:
492          *
493          * True on success, false if a reliable scanout position counter could
494          * not be read out.
495          */
496         bool (*get_scanout_position)(struct drm_crtc *crtc,
497                                      bool in_vblank_irq, int *vpos, int *hpos,
498                                      ktime_t *stime, ktime_t *etime,
499                                      const struct drm_display_mode *mode);
500 };
501 
502 /**
503  * drm_crtc_helper_add - sets the helper vtable for a crtc
504  * @crtc: DRM CRTC
505  * @funcs: helper vtable to set for @crtc
506  */
507 static inline void drm_crtc_helper_add(struct drm_crtc *crtc,
508                                        const struct drm_crtc_helper_funcs *funcs)
509 {
510         crtc->helper_private = funcs;
511 }
512 
513 /**
514  * struct drm_encoder_helper_funcs - helper operations for encoders
515  *
516  * These hooks are used by the legacy CRTC helpers, the transitional plane
517  * helpers and the new atomic modesetting helpers.
518  */
519 struct drm_encoder_helper_funcs {
520         /**
521          * @dpms:
522          *
523          * Callback to control power levels on the encoder.  If the mode passed in
524          * is unsupported, the provider must use the next lowest power level.
525          * This is used by the legacy encoder helpers to implement DPMS
526          * functionality in drm_helper_connector_dpms().
527          *
528          * This callback is also used to disable an encoder by calling it with
529          * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
530          *
531          * This callback is used by the legacy CRTC helpers.  Atomic helpers
532          * also support using this hook for enabling and disabling an encoder to
533          * facilitate transitions to atomic, but it is deprecated. Instead
534          * @enable and @disable should be used.
535          */
536         void (*dpms)(struct drm_encoder *encoder, int mode);
537 
538         /**
539          * @mode_valid:
540          *
541          * This callback is used to check if a specific mode is valid in this
542          * encoder. This should be implemented if the encoder has some sort
543          * of restriction in the modes it can display. For example, a given
544          * encoder may be responsible to set a clock value. If the clock can
545          * not produce all the values for the available modes then this callback
546          * can be used to restrict the number of modes to only the ones that
547          * can be displayed.
548          *
549          * This hook is used by the probe helpers to filter the mode list in
550          * drm_helper_probe_single_connector_modes(), and it is used by the
551          * atomic helpers to validate modes supplied by userspace in
552          * drm_atomic_helper_check_modeset().
553          *
554          * This function is optional.
555          *
556          * NOTE:
557          *
558          * Since this function is both called from the check phase of an atomic
559          * commit, and the mode validation in the probe paths it is not allowed
560          * to look at anything else but the passed-in mode, and validate it
561          * against configuration-invariant hardward constraints. Any further
562          * limits which depend upon the configuration can only be checked in
563          * @mode_fixup or @atomic_check.
564          *
565          * RETURNS:
566          *
567          * drm_mode_status Enum
568          */
569         enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc,
570                                            const struct drm_display_mode *mode);
571 
572         /**
573          * @mode_fixup:
574          *
575          * This callback is used to validate and adjust a mode. The parameter
576          * mode is the display mode that should be fed to the next element in
577          * the display chain, either the final &drm_connector or a &drm_bridge.
578          * The parameter adjusted_mode is the input mode the encoder requires. It
579          * can be modified by this callback and does not need to match mode. See
580          * also &drm_crtc_state.adjusted_mode for more details.
581          *
582          * This function is used by both legacy CRTC helpers and atomic helpers.
583          * This hook is optional.
584          *
585          * NOTE:
586          *
587          * This function is called in the check phase of atomic modesets, which
588          * can be aborted for any reason (including on userspace's request to
589          * just check whether a configuration would be possible). Atomic drivers
590          * MUST NOT touch any persistent state (hardware or software) or data
591          * structures except the passed in adjusted_mode parameter.
592          *
593          * This is in contrast to the legacy CRTC helpers where this was
594          * allowed.
595          *
596          * Atomic drivers which need to inspect and adjust more state should
597          * instead use the @atomic_check callback. If @atomic_check is used,
598          * this hook isn't called since @atomic_check allows a strict superset
599          * of the functionality of @mode_fixup.
600          *
601          * Also beware that userspace can request its own custom modes, neither
602          * core nor helpers filter modes to the list of probe modes reported by
603          * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
604          * that modes are filtered consistently put any encoder constraints and
605          * limits checks into @mode_valid.
606          *
607          * RETURNS:
608          *
609          * True if an acceptable configuration is possible, false if the modeset
610          * operation should be rejected.
611          */
612         bool (*mode_fixup)(struct drm_encoder *encoder,
613                            const struct drm_display_mode *mode,
614                            struct drm_display_mode *adjusted_mode);
615 
616         /**
617          * @prepare:
618          *
619          * This callback should prepare the encoder for a subsequent modeset,
620          * which in practice means the driver should disable the encoder if it
621          * is running. Most drivers ended up implementing this by calling their
622          * @dpms hook with DRM_MODE_DPMS_OFF.
623          *
624          * This callback is used by the legacy CRTC helpers.  Atomic helpers
625          * also support using this hook for disabling an encoder to facilitate
626          * transitions to atomic, but it is deprecated. Instead @disable should
627          * be used.
628          */
629         void (*prepare)(struct drm_encoder *encoder);
630 
631         /**
632          * @commit:
633          *
634          * This callback should commit the new mode on the encoder after a modeset,
635          * which in practice means the driver should enable the encoder.  Most
636          * drivers ended up implementing this by calling their @dpms hook with
637          * DRM_MODE_DPMS_ON.
638          *
639          * This callback is used by the legacy CRTC helpers.  Atomic helpers
640          * also support using this hook for enabling an encoder to facilitate
641          * transitions to atomic, but it is deprecated. Instead @enable should
642          * be used.
643          */
644         void (*commit)(struct drm_encoder *encoder);
645 
646         /**
647          * @mode_set:
648          *
649          * This callback is used to update the display mode of an encoder.
650          *
651          * Note that the display pipe is completely off when this function is
652          * called. Drivers which need hardware to be running before they program
653          * the new display mode (because they implement runtime PM) should not
654          * use this hook, because the helper library calls it only once and not
655          * every time the display pipeline is suspend using either DPMS or the
656          * new "ACTIVE" property. Such drivers should instead move all their
657          * encoder setup into the @enable callback.
658          *
659          * This callback is used both by the legacy CRTC helpers and the atomic
660          * modeset helpers. It is optional in the atomic helpers.
661          *
662          * NOTE:
663          *
664          * If the driver uses the atomic modeset helpers and needs to inspect
665          * the connector state or connector display info during mode setting,
666          * @atomic_mode_set can be used instead.
667          */
668         void (*mode_set)(struct drm_encoder *encoder,
669                          struct drm_display_mode *mode,
670                          struct drm_display_mode *adjusted_mode);
671 
672         /**
673          * @atomic_mode_set:
674          *
675          * This callback is used to update the display mode of an encoder.
676          *
677          * Note that the display pipe is completely off when this function is
678          * called. Drivers which need hardware to be running before they program
679          * the new display mode (because they implement runtime PM) should not
680          * use this hook, because the helper library calls it only once and not
681          * every time the display pipeline is suspended using either DPMS or the
682          * new "ACTIVE" property. Such drivers should instead move all their
683          * encoder setup into the @enable callback.
684          *
685          * This callback is used by the atomic modeset helpers in place of the
686          * @mode_set callback, if set by the driver. It is optional and should
687          * be used instead of @mode_set if the driver needs to inspect the
688          * connector state or display info, since there is no direct way to
689          * go from the encoder to the current connector.
690          */
691         void (*atomic_mode_set)(struct drm_encoder *encoder,
692                                 struct drm_crtc_state *crtc_state,
693                                 struct drm_connector_state *conn_state);
694 
695         /**
696          * @detect:
697          *
698          * This callback can be used by drivers who want to do detection on the
699          * encoder object instead of in connector functions.
700          *
701          * It is not used by any helper and therefore has purely driver-specific
702          * semantics. New drivers shouldn't use this and instead just implement
703          * their own private callbacks.
704          *
705          * FIXME:
706          *
707          * This should just be converted into a pile of driver vfuncs.
708          * Currently radeon, amdgpu and nouveau are using it.
709          */
710         enum drm_connector_status (*detect)(struct drm_encoder *encoder,
711                                             struct drm_connector *connector);
712 
713         /**
714          * @atomic_disable:
715          *
716          * This callback should be used to disable the encoder. With the atomic
717          * drivers it is called before this encoder's CRTC has been shut off
718          * using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
719          * sequence is too simple drivers can just add their own driver private
720          * encoder hooks and call them from CRTC's callback by looping over all
721          * encoders connected to it using for_each_encoder_on_crtc().
722          *
723          * This callback is a variant of @disable that provides the atomic state
724          * to the driver. If @atomic_disable is implemented, @disable is not
725          * called by the helpers.
726          *
727          * This hook is only used by atomic helpers. Atomic drivers don't need
728          * to implement it if there's no need to disable anything at the encoder
729          * level. To ensure that runtime PM handling (using either DPMS or the
730          * new "ACTIVE" property) works @atomic_disable must be the inverse of
731          * @atomic_enable.
732          */
733         void (*atomic_disable)(struct drm_encoder *encoder,
734                                struct drm_atomic_state *state);
735 
736         /**
737          * @atomic_enable:
738          *
739          * This callback should be used to enable the encoder. It is called
740          * after this encoder's CRTC has been enabled using their own
741          * &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
742          * too simple drivers can just add their own driver private encoder
743          * hooks and call them from CRTC's callback by looping over all encoders
744          * connected to it using for_each_encoder_on_crtc().
745          *
746          * This callback is a variant of @enable that provides the atomic state
747          * to the driver. If @atomic_enable is implemented, @enable is not
748          * called by the helpers.
749          *
750          * This hook is only used by atomic helpers, it is the opposite of
751          * @atomic_disable. Atomic drivers don't need to implement it if there's
752          * no need to enable anything at the encoder level. To ensure that
753          * runtime PM handling works @atomic_enable must be the inverse of
754          * @atomic_disable.
755          */
756         void (*atomic_enable)(struct drm_encoder *encoder,
757                               struct drm_atomic_state *state);
758 
759         /**
760          * @disable:
761          *
762          * This callback should be used to disable the encoder. With the atomic
763          * drivers it is called before this encoder's CRTC has been shut off
764          * using their own &drm_crtc_helper_funcs.disable hook.  If that
765          * sequence is too simple drivers can just add their own driver private
766          * encoder hooks and call them from CRTC's callback by looping over all
767          * encoders connected to it using for_each_encoder_on_crtc().
768          *
769          * This hook is used both by legacy CRTC helpers and atomic helpers.
770          * Atomic drivers don't need to implement it if there's no need to
771          * disable anything at the encoder level. To ensure that runtime PM
772          * handling (using either DPMS or the new "ACTIVE" property) works
773          * @disable must be the inverse of @enable for atomic drivers.
774          *
775          * For atomic drivers also consider @atomic_disable and save yourself
776          * from having to read the NOTE below!
777          *
778          * NOTE:
779          *
780          * With legacy CRTC helpers there's a big semantic difference between
781          * @disable and other hooks (like @prepare or @dpms) used to shut down a
782          * encoder: @disable is only called when also logically disabling the
783          * display pipeline and needs to release any resources acquired in
784          * @mode_set (like shared PLLs, or again release pinned framebuffers).
785          *
786          * Therefore @disable must be the inverse of @mode_set plus @commit for
787          * drivers still using legacy CRTC helpers, which is different from the
788          * rules under atomic.
789          */
790         void (*disable)(struct drm_encoder *encoder);
791 
792         /**
793          * @enable:
794          *
795          * This callback should be used to enable the encoder. With the atomic
796          * drivers it is called after this encoder's CRTC has been enabled using
797          * their own &drm_crtc_helper_funcs.enable hook.  If that sequence is
798          * too simple drivers can just add their own driver private encoder
799          * hooks and call them from CRTC's callback by looping over all encoders
800          * connected to it using for_each_encoder_on_crtc().
801          *
802          * This hook is only used by atomic helpers, it is the opposite of
803          * @disable. Atomic drivers don't need to implement it if there's no
804          * need to enable anything at the encoder level. To ensure that
805          * runtime PM handling (using either DPMS or the new "ACTIVE" property)
806          * works @enable must be the inverse of @disable for atomic drivers.
807          */
808         void (*enable)(struct drm_encoder *encoder);
809 
810         /**
811          * @atomic_check:
812          *
813          * This callback is used to validate encoder state for atomic drivers.
814          * Since the encoder is the object connecting the CRTC and connector it
815          * gets passed both states, to be able to validate interactions and
816          * update the CRTC to match what the encoder needs for the requested
817          * connector.
818          *
819          * Since this provides a strict superset of the functionality of
820          * @mode_fixup (the requested and adjusted modes are both available
821          * through the passed in &struct drm_crtc_state) @mode_fixup is not
822          * called when @atomic_check is implemented.
823          *
824          * This function is used by the atomic helpers, but it is optional.
825          *
826          * NOTE:
827          *
828          * This function is called in the check phase of an atomic update. The
829          * driver is not allowed to change anything outside of the free-standing
830          * state objects passed-in or assembled in the overall &drm_atomic_state
831          * update tracking structure.
832          *
833          * Also beware that userspace can request its own custom modes, neither
834          * core nor helpers filter modes to the list of probe modes reported by
835          * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
836          * that modes are filtered consistently put any encoder constraints and
837          * limits checks into @mode_valid.
838          *
839          * RETURNS:
840          *
841          * 0 on success, -EINVAL if the state or the transition can't be
842          * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
843          * attempt to obtain another state object ran into a &drm_modeset_lock
844          * deadlock.
845          */
846         int (*atomic_check)(struct drm_encoder *encoder,
847                             struct drm_crtc_state *crtc_state,
848                             struct drm_connector_state *conn_state);
849 };
850 
851 /**
852  * drm_encoder_helper_add - sets the helper vtable for an encoder
853  * @encoder: DRM encoder
854  * @funcs: helper vtable to set for @encoder
855  */
856 static inline void drm_encoder_helper_add(struct drm_encoder *encoder,
857                                           const struct drm_encoder_helper_funcs *funcs)
858 {
859         encoder->helper_private = funcs;
860 }
861 
862 /**
863  * struct drm_connector_helper_funcs - helper operations for connectors
864  *
865  * These functions are used by the atomic and legacy modeset helpers and by the
866  * probe helpers.
867  */
868 struct drm_connector_helper_funcs {
869         /**
870          * @get_modes:
871          *
872          * This function should fill in all modes currently valid for the sink
873          * into the &drm_connector.probed_modes list. It should also update the
874          * EDID property by calling drm_connector_update_edid_property().
875          *
876          * The usual way to implement this is to cache the EDID retrieved in the
877          * probe callback somewhere in the driver-private connector structure.
878          * In this function drivers then parse the modes in the EDID and add
879          * them by calling drm_add_edid_modes(). But connectors that driver a
880          * fixed panel can also manually add specific modes using
881          * drm_mode_probed_add(). Drivers which manually add modes should also
882          * make sure that the &drm_connector.display_info,
883          * &drm_connector.width_mm and &drm_connector.height_mm fields are
884          * filled in.
885          *
886          * Virtual drivers that just want some standard VESA mode with a given
887          * resolution can call drm_add_modes_noedid(), and mark the preferred
888          * one using drm_set_preferred_mode().
889          *
890          * This function is only called after the @detect hook has indicated
891          * that a sink is connected and when the EDID isn't overridden through
892          * sysfs or the kernel commandline.
893          *
894          * This callback is used by the probe helpers in e.g.
895          * drm_helper_probe_single_connector_modes().
896          *
897          * To avoid races with concurrent connector state updates, the helper
898          * libraries always call this with the &drm_mode_config.connection_mutex
899          * held. Because of this it's safe to inspect &drm_connector->state.
900          *
901          * RETURNS:
902          *
903          * The number of modes added by calling drm_mode_probed_add().
904          */
905         int (*get_modes)(struct drm_connector *connector);
906 
907         /**
908          * @detect_ctx:
909          *
910          * Check to see if anything is attached to the connector. The parameter
911          * force is set to false whilst polling, true when checking the
912          * connector due to a user request. force can be used by the driver to
913          * avoid expensive, destructive operations during automated probing.
914          *
915          * This callback is optional, if not implemented the connector will be
916          * considered as always being attached.
917          *
918          * This is the atomic version of &drm_connector_funcs.detect.
919          *
920          * To avoid races against concurrent connector state updates, the
921          * helper libraries always call this with ctx set to a valid context,
922          * and &drm_mode_config.connection_mutex will always be locked with
923          * the ctx parameter set to this ctx. This allows taking additional
924          * locks as required.
925          *
926          * RETURNS:
927          *
928          * &drm_connector_status indicating the connector's status,
929          * or the error code returned by drm_modeset_lock(), -EDEADLK.
930          */
931         int (*detect_ctx)(struct drm_connector *connector,
932                           struct drm_modeset_acquire_ctx *ctx,
933                           bool force);
934 
935         /**
936          * @mode_valid:
937          *
938          * Callback to validate a mode for a connector, irrespective of the
939          * specific display configuration.
940          *
941          * This callback is used by the probe helpers to filter the mode list
942          * (which is usually derived from the EDID data block from the sink).
943          * See e.g. drm_helper_probe_single_connector_modes().
944          *
945          * This function is optional.
946          *
947          * NOTE:
948          *
949          * This only filters the mode list supplied to userspace in the
950          * GETCONNECTOR IOCTL. Compared to &drm_encoder_helper_funcs.mode_valid,
951          * &drm_crtc_helper_funcs.mode_valid and &drm_bridge_funcs.mode_valid,
952          * which are also called by the atomic helpers from
953          * drm_atomic_helper_check_modeset(). This allows userspace to force and
954          * ignore sink constraint (like the pixel clock limits in the screen's
955          * EDID), which is useful for e.g. testing, or working around a broken
956          * EDID. Any source hardware constraint (which always need to be
957          * enforced) therefore should be checked in one of the above callbacks,
958          * and not this one here.
959          *
960          * To avoid races with concurrent connector state updates, the helper
961          * libraries always call this with the &drm_mode_config.connection_mutex
962          * held. Because of this it's safe to inspect &drm_connector->state.
963          *
964          * RETURNS:
965          *
966          * Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum
967          * drm_mode_status.
968          */
969         enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
970                                            struct drm_display_mode *mode);
971 
972         /**
973          * @mode_valid_ctx:
974          *
975          * Callback to validate a mode for a connector, irrespective of the
976          * specific display configuration.
977          *
978          * This callback is used by the probe helpers to filter the mode list
979          * (which is usually derived from the EDID data block from the sink).
980          * See e.g. drm_helper_probe_single_connector_modes().
981          *
982          * This function is optional, and is the atomic version of
983          * &drm_connector_helper_funcs.mode_valid.
984          *
985          * To allow for accessing the atomic state of modesetting objects, the
986          * helper libraries always call this with ctx set to a valid context,
987          * and &drm_mode_config.connection_mutex will always be locked with
988          * the ctx parameter set to @ctx. This allows for taking additional
989          * locks as required.
990          *
991          * Even though additional locks may be acquired, this callback is
992          * still expected not to take any constraints into account which would
993          * be influenced by the currently set display state - such constraints
994          * should be handled in the driver's atomic check. For example, if a
995          * connector shares display bandwidth with other connectors then it
996          * would be ok to validate the minimum bandwidth requirement of a mode
997          * against the maximum possible bandwidth of the connector. But it
998          * wouldn't be ok to take the current bandwidth usage of other
999          * connectors into account, as this would change depending on the
1000          * display state.
1001          *
1002          * Returns:
1003          * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
1004          * the &enum drm_mode_status value to @status, or a negative error
1005          * code otherwise.
1006          *
1007          */
1008         int (*mode_valid_ctx)(struct drm_connector *connector,
1009                               struct drm_display_mode *mode,
1010                               struct drm_modeset_acquire_ctx *ctx,
1011                               enum drm_mode_status *status);
1012 
1013         /**
1014          * @best_encoder:
1015          *
1016          * This function should select the best encoder for the given connector.
1017          *
1018          * This function is used by both the atomic helpers (in the
1019          * drm_atomic_helper_check_modeset() function) and in the legacy CRTC
1020          * helpers.
1021          *
1022          * NOTE:
1023          *
1024          * In atomic drivers this function is called in the check phase of an
1025          * atomic update. The driver is not allowed to change or inspect
1026          * anything outside of arguments passed-in. Atomic drivers which need to
1027          * inspect dynamic configuration state should instead use
1028          * @atomic_best_encoder.
1029          *
1030          * You can leave this function to NULL if the connector is only
1031          * attached to a single encoder. In this case, the core will call
1032          * drm_connector_get_single_encoder() for you.
1033          *
1034          * RETURNS:
1035          *
1036          * Encoder that should be used for the given connector and connector
1037          * state, or NULL if no suitable encoder exists. Note that the helpers
1038          * will ensure that encoders aren't used twice, drivers should not check
1039          * for this.
1040          */
1041         struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
1042 
1043         /**
1044          * @atomic_best_encoder:
1045          *
1046          * This is the atomic version of @best_encoder for atomic drivers which
1047          * need to select the best encoder depending upon the desired
1048          * configuration and can't select it statically.
1049          *
1050          * This function is used by drm_atomic_helper_check_modeset().
1051          * If it is not implemented, the core will fallback to @best_encoder
1052          * (or drm_connector_get_single_encoder() if @best_encoder is NULL).
1053          *
1054          * NOTE:
1055          *
1056          * This function is called in the check phase of an atomic update. The
1057          * driver is not allowed to change anything outside of the free-standing
1058          * state objects passed-in or assembled in the overall &drm_atomic_state
1059          * update tracking structure.
1060          *
1061          * RETURNS:
1062          *
1063          * Encoder that should be used for the given connector and connector
1064          * state, or NULL if no suitable encoder exists. Note that the helpers
1065          * will ensure that encoders aren't used twice, drivers should not check
1066          * for this.
1067          */
1068         struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
1069                                                    struct drm_connector_state *connector_state);
1070 
1071         /**
1072          * @atomic_check:
1073          *
1074          * This hook is used to validate connector state. This function is
1075          * called from &drm_atomic_helper_check_modeset, and is called when
1076          * a connector property is set, or a modeset on the crtc is forced.
1077          *
1078          * Because &drm_atomic_helper_check_modeset may be called multiple times,
1079          * this function should handle being called multiple times as well.
1080          *
1081          * This function is also allowed to inspect any other object's state and
1082          * can add more state objects to the atomic commit if needed. Care must
1083          * be taken though to ensure that state check and compute functions for
1084          * these added states are all called, and derived state in other objects
1085          * all updated. Again the recommendation is to just call check helpers
1086          * until a maximal configuration is reached.
1087          *
1088          * NOTE:
1089          *
1090          * This function is called in the check phase of an atomic update. The
1091          * driver is not allowed to change anything outside of the free-standing
1092          * state objects passed-in or assembled in the overall &drm_atomic_state
1093          * update tracking structure.
1094          *
1095          * RETURNS:
1096          *
1097          * 0 on success, -EINVAL if the state or the transition can't be
1098          * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
1099          * attempt to obtain another state object ran into a &drm_modeset_lock
1100          * deadlock.
1101          */
1102         int (*atomic_check)(struct drm_connector *connector,
1103                             struct drm_atomic_state *state);
1104 
1105         /**
1106          * @atomic_commit:
1107          *
1108          * This hook is to be used by drivers implementing writeback connectors
1109          * that need a point when to commit the writeback job to the hardware.
1110          * The writeback_job to commit is available in
1111          * &drm_connector_state.writeback_job.
1112          *
1113          * This hook is optional.
1114          *
1115          * This callback is used by the atomic modeset helpers.
1116          */
1117         void (*atomic_commit)(struct drm_connector *connector,
1118                               struct drm_connector_state *state);
1119 
1120         /**
1121          * @prepare_writeback_job:
1122          *
1123          * As writeback jobs contain a framebuffer, drivers may need to
1124          * prepare and clean them up the same way they can prepare and
1125          * clean up framebuffers for planes. This optional connector operation
1126          * is used to support the preparation of writeback jobs. The job
1127          * prepare operation is called from drm_atomic_helper_prepare_planes()
1128          * for struct &drm_writeback_connector connectors only.
1129          *
1130          * This operation is optional.
1131          *
1132          * This callback is used by the atomic modeset helpers.
1133          */
1134         int (*prepare_writeback_job)(struct drm_writeback_connector *connector,
1135                                      struct drm_writeback_job *job);
1136         /**
1137          * @cleanup_writeback_job:
1138          *
1139          * This optional connector operation is used to support the
1140          * cleanup of writeback jobs. The job cleanup operation is called
1141          * from the existing drm_writeback_cleanup_job() function, invoked
1142          * both when destroying the job as part of an aborted commit, or when
1143          * the job completes.
1144          *
1145          * This operation is optional.
1146          *
1147          * This callback is used by the atomic modeset helpers.
1148          */
1149         void (*cleanup_writeback_job)(struct drm_writeback_connector *connector,
1150                                       struct drm_writeback_job *job);
1151 };
1152 
1153 /**
1154  * drm_connector_helper_add - sets the helper vtable for a connector
1155  * @connector: DRM connector
1156  * @funcs: helper vtable to set for @connector
1157  */
1158 static inline void drm_connector_helper_add(struct drm_connector *connector,
1159                                             const struct drm_connector_helper_funcs *funcs)
1160 {
1161         connector->helper_private = funcs;
1162 }
1163 
1164 /**
1165  * struct drm_plane_helper_funcs - helper operations for planes
1166  *
1167  * These functions are used by the atomic helpers and by the transitional plane
1168  * helpers.
1169  */
1170 struct drm_plane_helper_funcs {
1171         /**
1172          * @prepare_fb:
1173          *
1174          * This hook is to prepare a framebuffer for scanout by e.g. pinning
1175          * its backing storage or relocating it into a contiguous block of
1176          * VRAM. Other possible preparatory work includes flushing caches.
1177          *
1178          * This function must not block for outstanding rendering, since it is
1179          * called in the context of the atomic IOCTL even for async commits to
1180          * be able to return any errors to userspace. Instead the recommended
1181          * way is to fill out the &drm_plane_state.fence of the passed-in
1182          * &drm_plane_state. If the driver doesn't support native fences then
1183          * equivalent functionality should be implemented through private
1184          * members in the plane structure.
1185          *
1186          * Drivers which always have their buffers pinned should use
1187          * drm_gem_fb_prepare_fb() for this hook.
1188          *
1189          * The helpers will call @cleanup_fb with matching arguments for every
1190          * successful call to this hook.
1191          *
1192          * This callback is used by the atomic modeset helpers and by the
1193          * transitional plane helpers, but it is optional.
1194          *
1195          * RETURNS:
1196          *
1197          * 0 on success or one of the following negative error codes allowed by
1198          * the &drm_mode_config_funcs.atomic_commit vfunc. When using helpers
1199          * this callback is the only one which can fail an atomic commit,
1200          * everything else must complete successfully.
1201          */
1202         int (*prepare_fb)(struct drm_plane *plane,
1203                           struct drm_plane_state *new_state);
1204         /**
1205          * @cleanup_fb:
1206          *
1207          * This hook is called to clean up any resources allocated for the given
1208          * framebuffer and plane configuration in @prepare_fb.
1209          *
1210          * This callback is used by the atomic modeset helpers and by the
1211          * transitional plane helpers, but it is optional.
1212          */
1213         void (*cleanup_fb)(struct drm_plane *plane,
1214                            struct drm_plane_state *old_state);
1215 
1216         /**
1217          * @atomic_check:
1218          *
1219          * Drivers should check plane specific constraints in this hook.
1220          *
1221          * When using drm_atomic_helper_check_planes() plane's @atomic_check
1222          * hooks are called before the ones for CRTCs, which allows drivers to
1223          * request shared resources that the CRTC controls here. For more
1224          * complicated dependencies the driver can call the provided check helpers
1225          * multiple times until the computed state has a final configuration and
1226          * everything has been checked.
1227          *
1228          * This function is also allowed to inspect any other object's state and
1229          * can add more state objects to the atomic commit if needed. Care must
1230          * be taken though to ensure that state check and compute functions for
1231          * these added states are all called, and derived state in other objects
1232          * all updated. Again the recommendation is to just call check helpers
1233          * until a maximal configuration is reached.
1234          *
1235          * This callback is used by the atomic modeset helpers and by the
1236          * transitional plane helpers, but it is optional.
1237          *
1238          * NOTE:
1239          *
1240          * This function is called in the check phase of an atomic update. The
1241          * driver is not allowed to change anything outside of the free-standing
1242          * state objects passed-in or assembled in the overall &drm_atomic_state
1243          * update tracking structure.
1244          *
1245          * RETURNS:
1246          *
1247          * 0 on success, -EINVAL if the state or the transition can't be
1248          * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
1249          * attempt to obtain another state object ran into a &drm_modeset_lock
1250          * deadlock.
1251          */
1252         int (*atomic_check)(struct drm_plane *plane,
1253                             struct drm_plane_state *state);
1254 
1255         /**
1256          * @atomic_update:
1257          *
1258          * Drivers should use this function to update the plane state.  This
1259          * hook is called in-between the &drm_crtc_helper_funcs.atomic_begin and
1260          * drm_crtc_helper_funcs.atomic_flush callbacks.
1261          *
1262          * Note that the power state of the display pipe when this function is
1263          * called depends upon the exact helpers and calling sequence the driver
1264          * has picked. See drm_atomic_helper_commit_planes() for a discussion of
1265          * the tradeoffs and variants of plane commit helpers.
1266          *
1267          * This callback is used by the atomic modeset helpers and by the
1268          * transitional plane helpers, but it is optional.
1269          */
1270         void (*atomic_update)(struct drm_plane *plane,
1271                               struct drm_plane_state *old_state);
1272         /**
1273          * @atomic_disable:
1274          *
1275          * Drivers should use this function to unconditionally disable a plane.
1276          * This hook is called in-between the
1277          * &drm_crtc_helper_funcs.atomic_begin and
1278          * drm_crtc_helper_funcs.atomic_flush callbacks. It is an alternative to
1279          * @atomic_update, which will be called for disabling planes, too, if
1280          * the @atomic_disable hook isn't implemented.
1281          *
1282          * This hook is also useful to disable planes in preparation of a modeset,
1283          * by calling drm_atomic_helper_disable_planes_on_crtc() from the
1284          * &drm_crtc_helper_funcs.disable hook.
1285          *
1286          * Note that the power state of the display pipe when this function is
1287          * called depends upon the exact helpers and calling sequence the driver
1288          * has picked. See drm_atomic_helper_commit_planes() for a discussion of
1289          * the tradeoffs and variants of plane commit helpers.
1290          *
1291          * This callback is used by the atomic modeset helpers and by the
1292          * transitional plane helpers, but it is optional.
1293          */
1294         void (*atomic_disable)(struct drm_plane *plane,
1295                                struct drm_plane_state *old_state);
1296 
1297         /**
1298          * @atomic_async_check:
1299          *
1300          * Drivers should set this function pointer to check if the plane state
1301          * can be updated in a async fashion. Here async means "not vblank
1302          * synchronized".
1303          *
1304          * This hook is called by drm_atomic_async_check() to establish if a
1305          * given update can be committed asynchronously, that is, if it can
1306          * jump ahead of the state currently queued for update.
1307          *
1308          * RETURNS:
1309          *
1310          * Return 0 on success and any error returned indicates that the update
1311          * can not be applied in asynchronous manner.
1312          */
1313         int (*atomic_async_check)(struct drm_plane *plane,
1314                                   struct drm_plane_state *state);
1315 
1316         /**
1317          * @atomic_async_update:
1318          *
1319          * Drivers should set this function pointer to perform asynchronous
1320          * updates of planes, that is, jump ahead of the currently queued
1321          * state and update the plane. Here async means "not vblank
1322          * synchronized".
1323          *
1324          * This hook is called by drm_atomic_helper_async_commit().
1325          *
1326          * An async update will happen on legacy cursor updates. An async
1327          * update won't happen if there is an outstanding commit modifying
1328          * the same plane.
1329          *
1330          * Note that unlike &drm_plane_helper_funcs.atomic_update this hook
1331          * takes the new &drm_plane_state as parameter. When doing async_update
1332          * drivers shouldn't replace the &drm_plane_state but update the
1333          * current one with the new plane configurations in the new
1334          * plane_state.
1335          *
1336          * Drivers should also swap the framebuffers between current plane
1337          * state (&drm_plane.state) and new_state.
1338          * This is required since cleanup for async commits is performed on
1339          * the new state, rather than old state like for traditional commits.
1340          * Since we want to give up the reference on the current (old) fb
1341          * instead of our brand new one, swap them in the driver during the
1342          * async commit.
1343          *
1344          * FIXME:
1345          *  - It only works for single plane updates
1346          *  - Async Pageflips are not supported yet
1347          *  - Some hw might still scan out the old buffer until the next
1348          *    vblank, however we let go of the fb references as soon as
1349          *    we run this hook. For now drivers must implement their own workers
1350          *    for deferring if needed, until a common solution is created.
1351          */
1352         void (*atomic_async_update)(struct drm_plane *plane,
1353                                     struct drm_plane_state *new_state);
1354 };
1355 
1356 /**
1357  * drm_plane_helper_add - sets the helper vtable for a plane
1358  * @plane: DRM plane
1359  * @funcs: helper vtable to set for @plane
1360  */
1361 static inline void drm_plane_helper_add(struct drm_plane *plane,
1362                                         const struct drm_plane_helper_funcs *funcs)
1363 {
1364         plane->helper_private = funcs;
1365 }
1366 
1367 /**
1368  * struct drm_mode_config_helper_funcs - global modeset helper operations
1369  *
1370  * These helper functions are used by the atomic helpers.
1371  */
1372 struct drm_mode_config_helper_funcs {
1373         /**
1374          * @atomic_commit_tail:
1375          *
1376          * This hook is used by the default atomic_commit() hook implemented in
1377          * drm_atomic_helper_commit() together with the nonblocking commit
1378          * helpers (see drm_atomic_helper_setup_commit() for a starting point)
1379          * to implement blocking and nonblocking commits easily. It is not used
1380          * by the atomic helpers
1381          *
1382          * This function is called when the new atomic state has already been
1383          * swapped into the various state pointers. The passed in state
1384          * therefore contains copies of the old/previous state. This hook should
1385          * commit the new state into hardware. Note that the helpers have
1386          * already waited for preceeding atomic commits and fences, but drivers
1387          * can add more waiting calls at the start of their implementation, e.g.
1388          * to wait for driver-internal request for implicit syncing, before
1389          * starting to commit the update to the hardware.
1390          *
1391          * After the atomic update is committed to the hardware this hook needs
1392          * to call drm_atomic_helper_commit_hw_done(). Then wait for the upate
1393          * to be executed by the hardware, for example using
1394          * drm_atomic_helper_wait_for_vblanks() or
1395          * drm_atomic_helper_wait_for_flip_done(), and then clean up the old
1396          * framebuffers using drm_atomic_helper_cleanup_planes().
1397          *
1398          * When disabling a CRTC this hook _must_ stall for the commit to
1399          * complete. Vblank waits don't work on disabled CRTC, hence the core
1400          * can't take care of this. And it also can't rely on the vblank event,
1401          * since that can be signalled already when the screen shows black,
1402          * which can happen much earlier than the last hardware access needed to
1403          * shut off the display pipeline completely.
1404          *
1405          * This hook is optional, the default implementation is
1406          * drm_atomic_helper_commit_tail().
1407          */
1408         void (*atomic_commit_tail)(struct drm_atomic_state *state);
1409 };
1410 
1411 #endif
1412 

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