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+/*
+ * Copyright © 2006 Keith Packard
+ * Copyright © 2007-2008 Dave Airlie
+ * Copyright © 2007-2008 Intel Corporation
+ * Jesse Barnes <jesse.barnes@intel.com>
+ * Copyright © 2011-2013 Intel Corporation
+ * Copyright © 2015 Intel Corporation
+ * Daniel Vetter <daniel.vetter@ffwll.ch>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef __DRM_MODESET_HELPER_VTABLES_H__
+#define __DRM_MODESET_HELPER_VTABLES_H__
+
+#include <drm/drm_crtc.h>
+#include <drm/drm_encoder.h>
+
+/**
+ * DOC: overview
+ *
+ * The DRM mode setting helper functions are common code for drivers to use if
+ * they wish. Drivers are not forced to use this code in their
+ * implementations but it would be useful if the code they do use at least
+ * provides a consistent interface and operation to userspace. Therefore it is
+ * highly recommended to use the provided helpers as much as possible.
+ *
+ * Because there is only one pointer per modeset object to hold a vfunc table
+ * for helper libraries they are by necessity shared among the different
+ * helpers.
+ *
+ * To make this clear all the helper vtables are pulled together in this location here.
+ */
+
+enum mode_set_atomic;
+struct drm_writeback_connector;
+struct drm_writeback_job;
+
+/**
+ * struct drm_crtc_helper_funcs - helper operations for CRTCs
+ *
+ * These hooks are used by the legacy CRTC helpers, the transitional plane
+ * helpers and the new atomic modesetting helpers.
+ */
+struct drm_crtc_helper_funcs {
+ /**
+ * @dpms:
+ *
+ * Callback to control power levels on the CRTC. If the mode passed in
+ * is unsupported, the provider must use the next lowest power level.
+ * This is used by the legacy CRTC helpers to implement DPMS
+ * functionality in drm_helper_connector_dpms().
+ *
+ * This callback is also used to disable a CRTC by calling it with
+ * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
+ *
+ * This callback is used by the legacy CRTC helpers. Atomic helpers
+ * also support using this hook for enabling and disabling a CRTC to
+ * facilitate transitions to atomic, but it is deprecated. Instead
+ * @atomic_enable and @atomic_disable should be used.
+ */
+ void (*dpms)(struct drm_crtc *crtc, int mode);
+
+ /**
+ * @prepare:
+ *
+ * This callback should prepare the CRTC for a subsequent modeset, which
+ * in practice means the driver should disable the CRTC if it is
+ * running. Most drivers ended up implementing this by calling their
+ * @dpms hook with DRM_MODE_DPMS_OFF.
+ *
+ * This callback is used by the legacy CRTC helpers. Atomic helpers
+ * also support using this hook for disabling a CRTC to facilitate
+ * transitions to atomic, but it is deprecated. Instead @atomic_disable
+ * should be used.
+ */
+ void (*prepare)(struct drm_crtc *crtc);
+
+ /**
+ * @commit:
+ *
+ * This callback should commit the new mode on the CRTC after a modeset,
+ * which in practice means the driver should enable the CRTC. Most
+ * drivers ended up implementing this by calling their @dpms hook with
+ * DRM_MODE_DPMS_ON.
+ *
+ * This callback is used by the legacy CRTC helpers. Atomic helpers
+ * also support using this hook for enabling a CRTC to facilitate
+ * transitions to atomic, but it is deprecated. Instead @atomic_enable
+ * should be used.
+ */
+ void (*commit)(struct drm_crtc *crtc);
+
+ /**
+ * @mode_valid:
+ *
+ * This callback is used to check if a specific mode is valid in this
+ * crtc. This should be implemented if the crtc has some sort of
+ * restriction in the modes it can display. For example, a given crtc
+ * may be responsible to set a clock value. If the clock can not
+ * produce all the values for the available modes then this callback
+ * can be used to restrict the number of modes to only the ones that
+ * can be displayed.
+ *
+ * This hook is used by the probe helpers to filter the mode list in
+ * drm_helper_probe_single_connector_modes(), and it is used by the
+ * atomic helpers to validate modes supplied by userspace in
+ * drm_atomic_helper_check_modeset().
+ *
+ * This function is optional.
+ *
+ * NOTE:
+ *
+ * Since this function is both called from the check phase of an atomic
+ * commit, and the mode validation in the probe paths it is not allowed
+ * to look at anything else but the passed-in mode, and validate it
+ * against configuration-invariant hardward constraints. Any further
+ * limits which depend upon the configuration can only be checked in
+ * @mode_fixup or @atomic_check.
+ *
+ * RETURNS:
+ *
+ * drm_mode_status Enum
+ */
+ enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc,
+ const struct drm_display_mode *mode);
+
+ /**
+ * @mode_fixup:
+ *
+ * This callback is used to validate a mode. The parameter mode is the
+ * display mode that userspace requested, adjusted_mode is the mode the
+ * encoders need to be fed with. Note that this is the inverse semantics
+ * of the meaning for the &drm_encoder and &drm_bridge_funcs.mode_fixup
+ * vfunc. If the CRTC cannot support the requested conversion from mode
+ * to adjusted_mode it should reject the modeset. See also
+ * &drm_crtc_state.adjusted_mode for more details.
+ *
+ * This function is used by both legacy CRTC helpers and atomic helpers.
+ * With atomic helpers it is optional.
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of atomic modesets, which
+ * can be aborted for any reason (including on userspace's request to
+ * just check whether a configuration would be possible). Atomic drivers
+ * MUST NOT touch any persistent state (hardware or software) or data
+ * structures except the passed in adjusted_mode parameter.
+ *
+ * This is in contrast to the legacy CRTC helpers where this was
+ * allowed.
+ *
+ * Atomic drivers which need to inspect and adjust more state should
+ * instead use the @atomic_check callback, but note that they're not
+ * perfectly equivalent: @mode_valid is called from
+ * drm_atomic_helper_check_modeset(), but @atomic_check is called from
+ * drm_atomic_helper_check_planes(), because originally it was meant for
+ * plane update checks only.
+ *
+ * Also beware that userspace can request its own custom modes, neither
+ * core nor helpers filter modes to the list of probe modes reported by
+ * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
+ * that modes are filtered consistently put any CRTC constraints and
+ * limits checks into @mode_valid.
+ *
+ * RETURNS:
+ *
+ * True if an acceptable configuration is possible, false if the modeset
+ * operation should be rejected.
+ */
+ bool (*mode_fixup)(struct drm_crtc *crtc,
+ const struct drm_display_mode *mode,
+ struct drm_display_mode *adjusted_mode);
+
+ /**
+ * @mode_set:
+ *
+ * This callback is used by the legacy CRTC helpers to set a new mode,
+ * position and framebuffer. Since it ties the primary plane to every
+ * mode change it is incompatible with universal plane support. And
+ * since it can't update other planes it's incompatible with atomic
+ * modeset support.
+ *
+ * This callback is only used by CRTC helpers and deprecated.
+ *
+ * RETURNS:
+ *
+ * 0 on success or a negative error code on failure.
+ */
+ int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
+ struct drm_display_mode *adjusted_mode, int x, int y,
+ struct drm_framebuffer *old_fb);
+
+ /**
+ * @mode_set_nofb:
+ *
+ * This callback is used to update the display mode of a CRTC without
+ * changing anything of the primary plane configuration. This fits the
+ * requirement of atomic and hence is used by the atomic helpers. It is
+ * also used by the transitional plane helpers to implement a
+ * @mode_set hook in drm_helper_crtc_mode_set().
+ *
+ * Note that the display pipe is completely off when this function is
+ * called. Atomic drivers which need hardware to be running before they
+ * program the new display mode (e.g. because they implement runtime PM)
+ * should not use this hook. This is because the helper library calls
+ * this hook only once per mode change and not every time the display
+ * pipeline is suspended using either DPMS or the new "ACTIVE" property.
+ * Which means register values set in this callback might get reset when
+ * the CRTC is suspended, but not restored. Such drivers should instead
+ * move all their CRTC setup into the @atomic_enable callback.
+ *
+ * This callback is optional.
+ */
+ void (*mode_set_nofb)(struct drm_crtc *crtc);
+
+ /**
+ * @mode_set_base:
+ *
+ * This callback is used by the legacy CRTC helpers to set a new
+ * framebuffer and scanout position. It is optional and used as an
+ * optimized fast-path instead of a full mode set operation with all the
+ * resulting flickering. If it is not present
+ * drm_crtc_helper_set_config() will fall back to a full modeset, using
+ * the @mode_set callback. Since it can't update other planes it's
+ * incompatible with atomic modeset support.
+ *
+ * This callback is only used by the CRTC helpers and deprecated.
+ *
+ * RETURNS:
+ *
+ * 0 on success or a negative error code on failure.
+ */
+ int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
+ struct drm_framebuffer *old_fb);
+
+ /**
+ * @mode_set_base_atomic:
+ *
+ * This callback is used by the fbdev helpers to set a new framebuffer
+ * and scanout without sleeping, i.e. from an atomic calling context. It
+ * is only used to implement kgdb support.
+ *
+ * This callback is optional and only needed for kgdb support in the fbdev
+ * helpers.
+ *
+ * RETURNS:
+ *
+ * 0 on success or a negative error code on failure.
+ */
+ int (*mode_set_base_atomic)(struct drm_crtc *crtc,
+ struct drm_framebuffer *fb, int x, int y,
+ enum mode_set_atomic);
+
+ /**
+ * @disable:
+ *
+ * This callback should be used to disable the CRTC. With the atomic
+ * drivers it is called after all encoders connected to this CRTC have
+ * been shut off already using their own
+ * &drm_encoder_helper_funcs.disable hook. If that sequence is too
+ * simple drivers can just add their own hooks and call it from this
+ * CRTC callback here by looping over all encoders connected to it using
+ * for_each_encoder_on_crtc().
+ *
+ * This hook is used both by legacy CRTC helpers and atomic helpers.
+ * Atomic drivers don't need to implement it if there's no need to
+ * disable anything at the CRTC level. To ensure that runtime PM
+ * handling (using either DPMS or the new "ACTIVE" property) works
+ * @disable must be the inverse of @atomic_enable for atomic drivers.
+ * Atomic drivers should consider to use @atomic_disable instead of
+ * this one.
+ *
+ * NOTE:
+ *
+ * With legacy CRTC helpers there's a big semantic difference between
+ * @disable and other hooks (like @prepare or @dpms) used to shut down a
+ * CRTC: @disable is only called when also logically disabling the
+ * display pipeline and needs to release any resources acquired in
+ * @mode_set (like shared PLLs, or again release pinned framebuffers).
+ *
+ * Therefore @disable must be the inverse of @mode_set plus @commit for
+ * drivers still using legacy CRTC helpers, which is different from the
+ * rules under atomic.
+ */
+ void (*disable)(struct drm_crtc *crtc);
+
+ /**
+ * @atomic_check:
+ *
+ * Drivers should check plane-update related CRTC constraints in this
+ * hook. They can also check mode related limitations but need to be
+ * aware of the calling order, since this hook is used by
+ * drm_atomic_helper_check_planes() whereas the preparations needed to
+ * check output routing and the display mode is done in
+ * drm_atomic_helper_check_modeset(). Therefore drivers that want to
+ * check output routing and display mode constraints in this callback
+ * must ensure that drm_atomic_helper_check_modeset() has been called
+ * beforehand. This is calling order used by the default helper
+ * implementation in drm_atomic_helper_check().
+ *
+ * When using drm_atomic_helper_check_planes() this hook is called
+ * after the &drm_plane_helper_funcs.atomic_check hook for planes, which
+ * allows drivers to assign shared resources requested by planes in this
+ * callback here. For more complicated dependencies the driver can call
+ * the provided check helpers multiple times until the computed state
+ * has a final configuration and everything has been checked.
+ *
+ * This function is also allowed to inspect any other object's state and
+ * can add more state objects to the atomic commit if needed. Care must
+ * be taken though to ensure that state check and compute functions for
+ * these added states are all called, and derived state in other objects
+ * all updated. Again the recommendation is to just call check helpers
+ * until a maximal configuration is reached.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of an atomic update. The
+ * driver is not allowed to change anything outside of the free-standing
+ * state objects passed-in or assembled in the overall &drm_atomic_state
+ * update tracking structure.
+ *
+ * Also beware that userspace can request its own custom modes, neither
+ * core nor helpers filter modes to the list of probe modes reported by
+ * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
+ * that modes are filtered consistently put any CRTC constraints and
+ * limits checks into @mode_valid.
+ *
+ * RETURNS:
+ *
+ * 0 on success, -EINVAL if the state or the transition can't be
+ * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
+ * attempt to obtain another state object ran into a &drm_modeset_lock
+ * deadlock.
+ */
+ int (*atomic_check)(struct drm_crtc *crtc,
+ struct drm_crtc_state *state);
+
+ /**
+ * @atomic_begin:
+ *
+ * Drivers should prepare for an atomic update of multiple planes on
+ * a CRTC in this hook. Depending upon hardware this might be vblank
+ * evasion, blocking updates by setting bits or doing preparatory work
+ * for e.g. manual update display.
+ *
+ * This hook is called before any plane commit functions are called.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_helper_commit_planes() for a discussion of
+ * the tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
+ void (*atomic_begin)(struct drm_crtc *crtc,
+ struct drm_crtc_state *old_crtc_state);
+ /**
+ * @atomic_flush:
+ *
+ * Drivers should finalize an atomic update of multiple planes on
+ * a CRTC in this hook. Depending upon hardware this might include
+ * checking that vblank evasion was successful, unblocking updates by
+ * setting bits or setting the GO bit to flush out all updates.
+ *
+ * Simple hardware or hardware with special requirements can commit and
+ * flush out all updates for all planes from this hook and forgo all the
+ * other commit hooks for plane updates.
+ *
+ * This hook is called after any plane commit functions are called.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_helper_commit_planes() for a discussion of
+ * the tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
+ void (*atomic_flush)(struct drm_crtc *crtc,
+ struct drm_crtc_state *old_crtc_state);
+
+ /**
+ * @atomic_enable:
+ *
+ * This callback should be used to enable the CRTC. With the atomic
+ * drivers it is called before all encoders connected to this CRTC are
+ * enabled through the encoder's own &drm_encoder_helper_funcs.enable
+ * hook. If that sequence is too simple drivers can just add their own
+ * hooks and call it from this CRTC callback here by looping over all
+ * encoders connected to it using for_each_encoder_on_crtc().
+ *
+ * This hook is used only by atomic helpers, for symmetry with
+ * @atomic_disable. Atomic drivers don't need to implement it if there's
+ * no need to enable anything at the CRTC level. To ensure that runtime
+ * PM handling (using either DPMS or the new "ACTIVE" property) works
+ * @atomic_enable must be the inverse of @atomic_disable for atomic
+ * drivers.
+ *
+ * Drivers can use the @old_crtc_state input parameter if the operations
+ * needed to enable the CRTC don't depend solely on the new state but
+ * also on the transition between the old state and the new state.
+ *
+ * This function is optional.
+ */
+ void (*atomic_enable)(struct drm_crtc *crtc,
+ struct drm_crtc_state *old_crtc_state);
+
+ /**
+ * @atomic_disable:
+ *
+ * This callback should be used to disable the CRTC. With the atomic
+ * drivers it is called after all encoders connected to this CRTC have
+ * been shut off already using their own
+ * &drm_encoder_helper_funcs.disable hook. If that sequence is too
+ * simple drivers can just add their own hooks and call it from this
+ * CRTC callback here by looping over all encoders connected to it using
+ * for_each_encoder_on_crtc().
+ *
+ * This hook is used only by atomic helpers. Atomic drivers don't
+ * need to implement it if there's no need to disable anything at the
+ * CRTC level.
+ *
+ * Comparing to @disable, this one provides the additional input
+ * parameter @old_crtc_state which could be used to access the old
+ * state. Atomic drivers should consider to use this one instead
+ * of @disable.
+ *
+ * This function is optional.
+ */
+ void (*atomic_disable)(struct drm_crtc *crtc,
+ struct drm_crtc_state *old_crtc_state);
+
+ /**
+ * @get_scanout_position:
+ *
+ * Called by vblank timestamping code.
+ *
+ * Returns the current display scanout position from a CRTC and an
+ * optional accurate ktime_get() timestamp of when the position was
+ * measured. Note that this is a helper callback which is only used
+ * if a driver uses drm_crtc_vblank_helper_get_vblank_timestamp()
+ * for the @drm_crtc_funcs.get_vblank_timestamp callback.
+ *
+ * Parameters:
+ *
+ * crtc:
+ * The CRTC.
+ * in_vblank_irq:
+ * True when called from drm_crtc_handle_vblank(). Some drivers
+ * need to apply some workarounds for gpu-specific vblank irq
+ * quirks if the flag is set.
+ * vpos:
+ * Target location for current vertical scanout position.
+ * hpos:
+ * Target location for current horizontal scanout position.
+ * stime:
+ * Target location for timestamp taken immediately before
+ * scanout position query. Can be NULL to skip timestamp.
+ * etime:
+ * Target location for timestamp taken immediately after
+ * scanout position query. Can be NULL to skip timestamp.
+ * mode:
+ * Current display timings.
+ *
+ * Returns vpos as a positive number while in active scanout area.
+ * Returns vpos as a negative number inside vblank, counting the number
+ * of scanlines to go until end of vblank, e.g., -1 means "one scanline
+ * until start of active scanout / end of vblank."
+ *
+ * Returns:
+ *
+ * True on success, false if a reliable scanout position counter could
+ * not be read out.
+ */
+ bool (*get_scanout_position)(struct drm_crtc *crtc,
+ bool in_vblank_irq, int *vpos, int *hpos,
+ ktime_t *stime, ktime_t *etime,
+ const struct drm_display_mode *mode);
+};
+
+/**
+ * drm_crtc_helper_add - sets the helper vtable for a crtc
+ * @crtc: DRM CRTC
+ * @funcs: helper vtable to set for @crtc
+ */
+static inline void drm_crtc_helper_add(struct drm_crtc *crtc,
+ const struct drm_crtc_helper_funcs *funcs)
+{
+ crtc->helper_private = funcs;
+}
+
+/**
+ * struct drm_encoder_helper_funcs - helper operations for encoders
+ *
+ * These hooks are used by the legacy CRTC helpers, the transitional plane
+ * helpers and the new atomic modesetting helpers.
+ */
+struct drm_encoder_helper_funcs {
+ /**
+ * @dpms:
+ *
+ * Callback to control power levels on the encoder. If the mode passed in
+ * is unsupported, the provider must use the next lowest power level.
+ * This is used by the legacy encoder helpers to implement DPMS
+ * functionality in drm_helper_connector_dpms().
+ *
+ * This callback is also used to disable an encoder by calling it with
+ * DRM_MODE_DPMS_OFF if the @disable hook isn't used.
+ *
+ * This callback is used by the legacy CRTC helpers. Atomic helpers
+ * also support using this hook for enabling and disabling an encoder to
+ * facilitate transitions to atomic, but it is deprecated. Instead
+ * @enable and @disable should be used.
+ */
+ void (*dpms)(struct drm_encoder *encoder, int mode);
+
+ /**
+ * @mode_valid:
+ *
+ * This callback is used to check if a specific mode is valid in this
+ * encoder. This should be implemented if the encoder has some sort
+ * of restriction in the modes it can display. For example, a given
+ * encoder may be responsible to set a clock value. If the clock can
+ * not produce all the values for the available modes then this callback
+ * can be used to restrict the number of modes to only the ones that
+ * can be displayed.
+ *
+ * This hook is used by the probe helpers to filter the mode list in
+ * drm_helper_probe_single_connector_modes(), and it is used by the
+ * atomic helpers to validate modes supplied by userspace in
+ * drm_atomic_helper_check_modeset().
+ *
+ * This function is optional.
+ *
+ * NOTE:
+ *
+ * Since this function is both called from the check phase of an atomic
+ * commit, and the mode validation in the probe paths it is not allowed
+ * to look at anything else but the passed-in mode, and validate it
+ * against configuration-invariant hardward constraints. Any further
+ * limits which depend upon the configuration can only be checked in
+ * @mode_fixup or @atomic_check.
+ *
+ * RETURNS:
+ *
+ * drm_mode_status Enum
+ */
+ enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc,
+ const struct drm_display_mode *mode);
+
+ /**
+ * @mode_fixup:
+ *
+ * This callback is used to validate and adjust a mode. The parameter
+ * mode is the display mode that should be fed to the next element in
+ * the display chain, either the final &drm_connector or a &drm_bridge.
+ * The parameter adjusted_mode is the input mode the encoder requires. It
+ * can be modified by this callback and does not need to match mode. See
+ * also &drm_crtc_state.adjusted_mode for more details.
+ *
+ * This function is used by both legacy CRTC helpers and atomic helpers.
+ * This hook is optional.
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of atomic modesets, which
+ * can be aborted for any reason (including on userspace's request to
+ * just check whether a configuration would be possible). Atomic drivers
+ * MUST NOT touch any persistent state (hardware or software) or data
+ * structures except the passed in adjusted_mode parameter.
+ *
+ * This is in contrast to the legacy CRTC helpers where this was
+ * allowed.
+ *
+ * Atomic drivers which need to inspect and adjust more state should
+ * instead use the @atomic_check callback. If @atomic_check is used,
+ * this hook isn't called since @atomic_check allows a strict superset
+ * of the functionality of @mode_fixup.
+ *
+ * Also beware that userspace can request its own custom modes, neither
+ * core nor helpers filter modes to the list of probe modes reported by
+ * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
+ * that modes are filtered consistently put any encoder constraints and
+ * limits checks into @mode_valid.
+ *
+ * RETURNS:
+ *
+ * True if an acceptable configuration is possible, false if the modeset
+ * operation should be rejected.
+ */
+ bool (*mode_fixup)(struct drm_encoder *encoder,
+ const struct drm_display_mode *mode,
+ struct drm_display_mode *adjusted_mode);
+
+ /**
+ * @prepare:
+ *
+ * This callback should prepare the encoder for a subsequent modeset,
+ * which in practice means the driver should disable the encoder if it
+ * is running. Most drivers ended up implementing this by calling their
+ * @dpms hook with DRM_MODE_DPMS_OFF.
+ *
+ * This callback is used by the legacy CRTC helpers. Atomic helpers
+ * also support using this hook for disabling an encoder to facilitate
+ * transitions to atomic, but it is deprecated. Instead @disable should
+ * be used.
+ */
+ void (*prepare)(struct drm_encoder *encoder);
+
+ /**
+ * @commit:
+ *
+ * This callback should commit the new mode on the encoder after a modeset,
+ * which in practice means the driver should enable the encoder. Most
+ * drivers ended up implementing this by calling their @dpms hook with
+ * DRM_MODE_DPMS_ON.
+ *
+ * This callback is used by the legacy CRTC helpers. Atomic helpers
+ * also support using this hook for enabling an encoder to facilitate
+ * transitions to atomic, but it is deprecated. Instead @enable should
+ * be used.
+ */
+ void (*commit)(struct drm_encoder *encoder);
+
+ /**
+ * @mode_set:
+ *
+ * This callback is used to update the display mode of an encoder.
+ *
+ * Note that the display pipe is completely off when this function is
+ * called. Drivers which need hardware to be running before they program
+ * the new display mode (because they implement runtime PM) should not
+ * use this hook, because the helper library calls it only once and not
+ * every time the display pipeline is suspend using either DPMS or the
+ * new "ACTIVE" property. Such drivers should instead move all their
+ * encoder setup into the @enable callback.
+ *
+ * This callback is used both by the legacy CRTC helpers and the atomic
+ * modeset helpers. It is optional in the atomic helpers.
+ *
+ * NOTE:
+ *
+ * If the driver uses the atomic modeset helpers and needs to inspect
+ * the connector state or connector display info during mode setting,
+ * @atomic_mode_set can be used instead.
+ */
+ void (*mode_set)(struct drm_encoder *encoder,
+ struct drm_display_mode *mode,
+ struct drm_display_mode *adjusted_mode);
+
+ /**
+ * @atomic_mode_set:
+ *
+ * This callback is used to update the display mode of an encoder.
+ *
+ * Note that the display pipe is completely off when this function is
+ * called. Drivers which need hardware to be running before they program
+ * the new display mode (because they implement runtime PM) should not
+ * use this hook, because the helper library calls it only once and not
+ * every time the display pipeline is suspended using either DPMS or the
+ * new "ACTIVE" property. Such drivers should instead move all their
+ * encoder setup into the @enable callback.
+ *
+ * This callback is used by the atomic modeset helpers in place of the
+ * @mode_set callback, if set by the driver. It is optional and should
+ * be used instead of @mode_set if the driver needs to inspect the
+ * connector state or display info, since there is no direct way to
+ * go from the encoder to the current connector.
+ */
+ void (*atomic_mode_set)(struct drm_encoder *encoder,
+ struct drm_crtc_state *crtc_state,
+ struct drm_connector_state *conn_state);
+
+ /**
+ * @detect:
+ *
+ * This callback can be used by drivers who want to do detection on the
+ * encoder object instead of in connector functions.
+ *
+ * It is not used by any helper and therefore has purely driver-specific
+ * semantics. New drivers shouldn't use this and instead just implement
+ * their own private callbacks.
+ *
+ * FIXME:
+ *
+ * This should just be converted into a pile of driver vfuncs.
+ * Currently radeon, amdgpu and nouveau are using it.
+ */
+ enum drm_connector_status (*detect)(struct drm_encoder *encoder,
+ struct drm_connector *connector);
+
+ /**
+ * @atomic_disable:
+ *
+ * This callback should be used to disable the encoder. With the atomic
+ * drivers it is called before this encoder's CRTC has been shut off
+ * using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
+ * sequence is too simple drivers can just add their own driver private
+ * encoder hooks and call them from CRTC's callback by looping over all
+ * encoders connected to it using for_each_encoder_on_crtc().
+ *
+ * This callback is a variant of @disable that provides the atomic state
+ * to the driver. If @atomic_disable is implemented, @disable is not
+ * called by the helpers.
+ *
+ * This hook is only used by atomic helpers. Atomic drivers don't need
+ * to implement it if there's no need to disable anything at the encoder
+ * level. To ensure that runtime PM handling (using either DPMS or the
+ * new "ACTIVE" property) works @atomic_disable must be the inverse of
+ * @atomic_enable.
+ */
+ void (*atomic_disable)(struct drm_encoder *encoder,
+ struct drm_atomic_state *state);
+
+ /**
+ * @atomic_enable:
+ *
+ * This callback should be used to enable the encoder. It is called
+ * after this encoder's CRTC has been enabled using their own
+ * &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
+ * too simple drivers can just add their own driver private encoder
+ * hooks and call them from CRTC's callback by looping over all encoders
+ * connected to it using for_each_encoder_on_crtc().
+ *
+ * This callback is a variant of @enable that provides the atomic state
+ * to the driver. If @atomic_enable is implemented, @enable is not
+ * called by the helpers.
+ *
+ * This hook is only used by atomic helpers, it is the opposite of
+ * @atomic_disable. Atomic drivers don't need to implement it if there's
+ * no need to enable anything at the encoder level. To ensure that
+ * runtime PM handling works @atomic_enable must be the inverse of
+ * @atomic_disable.
+ */
+ void (*atomic_enable)(struct drm_encoder *encoder,
+ struct drm_atomic_state *state);
+
+ /**
+ * @disable:
+ *
+ * This callback should be used to disable the encoder. With the atomic
+ * drivers it is called before this encoder's CRTC has been shut off
+ * using their own &drm_crtc_helper_funcs.disable hook. If that
+ * sequence is too simple drivers can just add their own driver private
+ * encoder hooks and call them from CRTC's callback by looping over all
+ * encoders connected to it using for_each_encoder_on_crtc().
+ *
+ * This hook is used both by legacy CRTC helpers and atomic helpers.
+ * Atomic drivers don't need to implement it if there's no need to
+ * disable anything at the encoder level. To ensure that runtime PM
+ * handling (using either DPMS or the new "ACTIVE" property) works
+ * @disable must be the inverse of @enable for atomic drivers.
+ *
+ * For atomic drivers also consider @atomic_disable and save yourself
+ * from having to read the NOTE below!
+ *
+ * NOTE:
+ *
+ * With legacy CRTC helpers there's a big semantic difference between
+ * @disable and other hooks (like @prepare or @dpms) used to shut down a
+ * encoder: @disable is only called when also logically disabling the
+ * display pipeline and needs to release any resources acquired in
+ * @mode_set (like shared PLLs, or again release pinned framebuffers).
+ *
+ * Therefore @disable must be the inverse of @mode_set plus @commit for
+ * drivers still using legacy CRTC helpers, which is different from the
+ * rules under atomic.
+ */
+ void (*disable)(struct drm_encoder *encoder);
+
+ /**
+ * @enable:
+ *
+ * This callback should be used to enable the encoder. With the atomic
+ * drivers it is called after this encoder's CRTC has been enabled using
+ * their own &drm_crtc_helper_funcs.enable hook. If that sequence is
+ * too simple drivers can just add their own driver private encoder
+ * hooks and call them from CRTC's callback by looping over all encoders
+ * connected to it using for_each_encoder_on_crtc().
+ *
+ * This hook is only used by atomic helpers, it is the opposite of
+ * @disable. Atomic drivers don't need to implement it if there's no
+ * need to enable anything at the encoder level. To ensure that
+ * runtime PM handling (using either DPMS or the new "ACTIVE" property)
+ * works @enable must be the inverse of @disable for atomic drivers.
+ */
+ void (*enable)(struct drm_encoder *encoder);
+
+ /**
+ * @atomic_check:
+ *
+ * This callback is used to validate encoder state for atomic drivers.
+ * Since the encoder is the object connecting the CRTC and connector it
+ * gets passed both states, to be able to validate interactions and
+ * update the CRTC to match what the encoder needs for the requested
+ * connector.
+ *
+ * Since this provides a strict superset of the functionality of
+ * @mode_fixup (the requested and adjusted modes are both available
+ * through the passed in &struct drm_crtc_state) @mode_fixup is not
+ * called when @atomic_check is implemented.
+ *
+ * This function is used by the atomic helpers, but it is optional.
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of an atomic update. The
+ * driver is not allowed to change anything outside of the free-standing
+ * state objects passed-in or assembled in the overall &drm_atomic_state
+ * update tracking structure.
+ *
+ * Also beware that userspace can request its own custom modes, neither
+ * core nor helpers filter modes to the list of probe modes reported by
+ * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
+ * that modes are filtered consistently put any encoder constraints and
+ * limits checks into @mode_valid.
+ *
+ * RETURNS:
+ *
+ * 0 on success, -EINVAL if the state or the transition can't be
+ * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
+ * attempt to obtain another state object ran into a &drm_modeset_lock
+ * deadlock.
+ */
+ int (*atomic_check)(struct drm_encoder *encoder,
+ struct drm_crtc_state *crtc_state,
+ struct drm_connector_state *conn_state);
+};
+
+/**
+ * drm_encoder_helper_add - sets the helper vtable for an encoder
+ * @encoder: DRM encoder
+ * @funcs: helper vtable to set for @encoder
+ */
+static inline void drm_encoder_helper_add(struct drm_encoder *encoder,
+ const struct drm_encoder_helper_funcs *funcs)
+{
+ encoder->helper_private = funcs;
+}
+
+/**
+ * struct drm_connector_helper_funcs - helper operations for connectors
+ *
+ * These functions are used by the atomic and legacy modeset helpers and by the
+ * probe helpers.
+ */
+struct drm_connector_helper_funcs {
+ /**
+ * @get_modes:
+ *
+ * This function should fill in all modes currently valid for the sink
+ * into the &drm_connector.probed_modes list. It should also update the
+ * EDID property by calling drm_connector_update_edid_property().
+ *
+ * The usual way to implement this is to cache the EDID retrieved in the
+ * probe callback somewhere in the driver-private connector structure.
+ * In this function drivers then parse the modes in the EDID and add
+ * them by calling drm_add_edid_modes(). But connectors that driver a
+ * fixed panel can also manually add specific modes using
+ * drm_mode_probed_add(). Drivers which manually add modes should also
+ * make sure that the &drm_connector.display_info,
+ * &drm_connector.width_mm and &drm_connector.height_mm fields are
+ * filled in.
+ *
+ * Virtual drivers that just want some standard VESA mode with a given
+ * resolution can call drm_add_modes_noedid(), and mark the preferred
+ * one using drm_set_preferred_mode().
+ *
+ * This function is only called after the @detect hook has indicated
+ * that a sink is connected and when the EDID isn't overridden through
+ * sysfs or the kernel commandline.
+ *
+ * This callback is used by the probe helpers in e.g.
+ * drm_helper_probe_single_connector_modes().
+ *
+ * To avoid races with concurrent connector state updates, the helper
+ * libraries always call this with the &drm_mode_config.connection_mutex
+ * held. Because of this it's safe to inspect &drm_connector->state.
+ *
+ * RETURNS:
+ *
+ * The number of modes added by calling drm_mode_probed_add().
+ */
+ int (*get_modes)(struct drm_connector *connector);
+
+ /**
+ * @detect_ctx:
+ *
+ * Check to see if anything is attached to the connector. The parameter
+ * force is set to false whilst polling, true when checking the
+ * connector due to a user request. force can be used by the driver to
+ * avoid expensive, destructive operations during automated probing.
+ *
+ * This callback is optional, if not implemented the connector will be
+ * considered as always being attached.
+ *
+ * This is the atomic version of &drm_connector_funcs.detect.
+ *
+ * To avoid races against concurrent connector state updates, the
+ * helper libraries always call this with ctx set to a valid context,
+ * and &drm_mode_config.connection_mutex will always be locked with
+ * the ctx parameter set to this ctx. This allows taking additional
+ * locks as required.
+ *
+ * RETURNS:
+ *
+ * &drm_connector_status indicating the connector's status,
+ * or the error code returned by drm_modeset_lock(), -EDEADLK.
+ */
+ int (*detect_ctx)(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force);
+
+ /**
+ * @mode_valid:
+ *
+ * Callback to validate a mode for a connector, irrespective of the
+ * specific display configuration.
+ *
+ * This callback is used by the probe helpers to filter the mode list
+ * (which is usually derived from the EDID data block from the sink).
+ * See e.g. drm_helper_probe_single_connector_modes().
+ *
+ * This function is optional.
+ *
+ * NOTE:
+ *
+ * This only filters the mode list supplied to userspace in the
+ * GETCONNECTOR IOCTL. Compared to &drm_encoder_helper_funcs.mode_valid,
+ * &drm_crtc_helper_funcs.mode_valid and &drm_bridge_funcs.mode_valid,
+ * which are also called by the atomic helpers from
+ * drm_atomic_helper_check_modeset(). This allows userspace to force and
+ * ignore sink constraint (like the pixel clock limits in the screen's
+ * EDID), which is useful for e.g. testing, or working around a broken
+ * EDID. Any source hardware constraint (which always need to be
+ * enforced) therefore should be checked in one of the above callbacks,
+ * and not this one here.
+ *
+ * To avoid races with concurrent connector state updates, the helper
+ * libraries always call this with the &drm_mode_config.connection_mutex
+ * held. Because of this it's safe to inspect &drm_connector->state.
+ *
+ * RETURNS:
+ *
+ * Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum
+ * drm_mode_status.
+ */
+ enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
+ struct drm_display_mode *mode);
+
+ /**
+ * @mode_valid_ctx:
+ *
+ * Callback to validate a mode for a connector, irrespective of the
+ * specific display configuration.
+ *
+ * This callback is used by the probe helpers to filter the mode list
+ * (which is usually derived from the EDID data block from the sink).
+ * See e.g. drm_helper_probe_single_connector_modes().
+ *
+ * This function is optional, and is the atomic version of
+ * &drm_connector_helper_funcs.mode_valid.
+ *
+ * To allow for accessing the atomic state of modesetting objects, the
+ * helper libraries always call this with ctx set to a valid context,
+ * and &drm_mode_config.connection_mutex will always be locked with
+ * the ctx parameter set to @ctx. This allows for taking additional
+ * locks as required.
+ *
+ * Even though additional locks may be acquired, this callback is
+ * still expected not to take any constraints into account which would
+ * be influenced by the currently set display state - such constraints
+ * should be handled in the driver's atomic check. For example, if a
+ * connector shares display bandwidth with other connectors then it
+ * would be ok to validate the minimum bandwidth requirement of a mode
+ * against the maximum possible bandwidth of the connector. But it
+ * wouldn't be ok to take the current bandwidth usage of other
+ * connectors into account, as this would change depending on the
+ * display state.
+ *
+ * Returns:
+ * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
+ * the &enum drm_mode_status value to @status, or a negative error
+ * code otherwise.
+ *
+ */
+ int (*mode_valid_ctx)(struct drm_connector *connector,
+ struct drm_display_mode *mode,
+ struct drm_modeset_acquire_ctx *ctx,
+ enum drm_mode_status *status);
+
+ /**
+ * @best_encoder:
+ *
+ * This function should select the best encoder for the given connector.
+ *
+ * This function is used by both the atomic helpers (in the
+ * drm_atomic_helper_check_modeset() function) and in the legacy CRTC
+ * helpers.
+ *
+ * NOTE:
+ *
+ * In atomic drivers this function is called in the check phase of an
+ * atomic update. The driver is not allowed to change or inspect
+ * anything outside of arguments passed-in. Atomic drivers which need to
+ * inspect dynamic configuration state should instead use
+ * @atomic_best_encoder.
+ *
+ * You can leave this function to NULL if the connector is only
+ * attached to a single encoder. In this case, the core will call
+ * drm_connector_get_single_encoder() for you.
+ *
+ * RETURNS:
+ *
+ * Encoder that should be used for the given connector and connector
+ * state, or NULL if no suitable encoder exists. Note that the helpers
+ * will ensure that encoders aren't used twice, drivers should not check
+ * for this.
+ */
+ struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
+
+ /**
+ * @atomic_best_encoder:
+ *
+ * This is the atomic version of @best_encoder for atomic drivers which
+ * need to select the best encoder depending upon the desired
+ * configuration and can't select it statically.
+ *
+ * This function is used by drm_atomic_helper_check_modeset().
+ * If it is not implemented, the core will fallback to @best_encoder
+ * (or drm_connector_get_single_encoder() if @best_encoder is NULL).
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of an atomic update. The
+ * driver is not allowed to change anything outside of the free-standing
+ * state objects passed-in or assembled in the overall &drm_atomic_state
+ * update tracking structure.
+ *
+ * RETURNS:
+ *
+ * Encoder that should be used for the given connector and connector
+ * state, or NULL if no suitable encoder exists. Note that the helpers
+ * will ensure that encoders aren't used twice, drivers should not check
+ * for this.
+ */
+ struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
+ struct drm_connector_state *connector_state);
+
+ /**
+ * @atomic_check:
+ *
+ * This hook is used to validate connector state. This function is
+ * called from &drm_atomic_helper_check_modeset, and is called when
+ * a connector property is set, or a modeset on the crtc is forced.
+ *
+ * Because &drm_atomic_helper_check_modeset may be called multiple times,
+ * this function should handle being called multiple times as well.
+ *
+ * This function is also allowed to inspect any other object's state and
+ * can add more state objects to the atomic commit if needed. Care must
+ * be taken though to ensure that state check and compute functions for
+ * these added states are all called, and derived state in other objects
+ * all updated. Again the recommendation is to just call check helpers
+ * until a maximal configuration is reached.
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of an atomic update. The
+ * driver is not allowed to change anything outside of the free-standing
+ * state objects passed-in or assembled in the overall &drm_atomic_state
+ * update tracking structure.
+ *
+ * RETURNS:
+ *
+ * 0 on success, -EINVAL if the state or the transition can't be
+ * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
+ * attempt to obtain another state object ran into a &drm_modeset_lock
+ * deadlock.
+ */
+ int (*atomic_check)(struct drm_connector *connector,
+ struct drm_atomic_state *state);
+
+ /**
+ * @atomic_commit:
+ *
+ * This hook is to be used by drivers implementing writeback connectors
+ * that need a point when to commit the writeback job to the hardware.
+ * The writeback_job to commit is available in
+ * &drm_connector_state.writeback_job.
+ *
+ * This hook is optional.
+ *
+ * This callback is used by the atomic modeset helpers.
+ */
+ void (*atomic_commit)(struct drm_connector *connector,
+ struct drm_connector_state *state);
+
+ /**
+ * @prepare_writeback_job:
+ *
+ * As writeback jobs contain a framebuffer, drivers may need to
+ * prepare and clean them up the same way they can prepare and
+ * clean up framebuffers for planes. This optional connector operation
+ * is used to support the preparation of writeback jobs. The job
+ * prepare operation is called from drm_atomic_helper_prepare_planes()
+ * for struct &drm_writeback_connector connectors only.
+ *
+ * This operation is optional.
+ *
+ * This callback is used by the atomic modeset helpers.
+ */
+ int (*prepare_writeback_job)(struct drm_writeback_connector *connector,
+ struct drm_writeback_job *job);
+ /**
+ * @cleanup_writeback_job:
+ *
+ * This optional connector operation is used to support the
+ * cleanup of writeback jobs. The job cleanup operation is called
+ * from the existing drm_writeback_cleanup_job() function, invoked
+ * both when destroying the job as part of an aborted commit, or when
+ * the job completes.
+ *
+ * This operation is optional.
+ *
+ * This callback is used by the atomic modeset helpers.
+ */
+ void (*cleanup_writeback_job)(struct drm_writeback_connector *connector,
+ struct drm_writeback_job *job);
+};
+
+/**
+ * drm_connector_helper_add - sets the helper vtable for a connector
+ * @connector: DRM connector
+ * @funcs: helper vtable to set for @connector
+ */
+static inline void drm_connector_helper_add(struct drm_connector *connector,
+ const struct drm_connector_helper_funcs *funcs)
+{
+ connector->helper_private = funcs;
+}
+
+/**
+ * struct drm_plane_helper_funcs - helper operations for planes
+ *
+ * These functions are used by the atomic helpers and by the transitional plane
+ * helpers.
+ */
+struct drm_plane_helper_funcs {
+ /**
+ * @prepare_fb:
+ *
+ * This hook is to prepare a framebuffer for scanout by e.g. pinning
+ * its backing storage or relocating it into a contiguous block of
+ * VRAM. Other possible preparatory work includes flushing caches.
+ *
+ * This function must not block for outstanding rendering, since it is
+ * called in the context of the atomic IOCTL even for async commits to
+ * be able to return any errors to userspace. Instead the recommended
+ * way is to fill out the &drm_plane_state.fence of the passed-in
+ * &drm_plane_state. If the driver doesn't support native fences then
+ * equivalent functionality should be implemented through private
+ * members in the plane structure.
+ *
+ * Drivers which always have their buffers pinned should use
+ * drm_gem_fb_prepare_fb() for this hook.
+ *
+ * The helpers will call @cleanup_fb with matching arguments for every
+ * successful call to this hook.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ *
+ * RETURNS:
+ *
+ * 0 on success or one of the following negative error codes allowed by
+ * the &drm_mode_config_funcs.atomic_commit vfunc. When using helpers
+ * this callback is the only one which can fail an atomic commit,
+ * everything else must complete successfully.
+ */
+ int (*prepare_fb)(struct drm_plane *plane,
+ struct drm_plane_state *new_state);
+ /**
+ * @cleanup_fb:
+ *
+ * This hook is called to clean up any resources allocated for the given
+ * framebuffer and plane configuration in @prepare_fb.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
+ void (*cleanup_fb)(struct drm_plane *plane,
+ struct drm_plane_state *old_state);
+
+ /**
+ * @atomic_check:
+ *
+ * Drivers should check plane specific constraints in this hook.
+ *
+ * When using drm_atomic_helper_check_planes() plane's @atomic_check
+ * hooks are called before the ones for CRTCs, which allows drivers to
+ * request shared resources that the CRTC controls here. For more
+ * complicated dependencies the driver can call the provided check helpers
+ * multiple times until the computed state has a final configuration and
+ * everything has been checked.
+ *
+ * This function is also allowed to inspect any other object's state and
+ * can add more state objects to the atomic commit if needed. Care must
+ * be taken though to ensure that state check and compute functions for
+ * these added states are all called, and derived state in other objects
+ * all updated. Again the recommendation is to just call check helpers
+ * until a maximal configuration is reached.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ *
+ * NOTE:
+ *
+ * This function is called in the check phase of an atomic update. The
+ * driver is not allowed to change anything outside of the free-standing
+ * state objects passed-in or assembled in the overall &drm_atomic_state
+ * update tracking structure.
+ *
+ * RETURNS:
+ *
+ * 0 on success, -EINVAL if the state or the transition can't be
+ * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
+ * attempt to obtain another state object ran into a &drm_modeset_lock
+ * deadlock.
+ */
+ int (*atomic_check)(struct drm_plane *plane,
+ struct drm_plane_state *state);
+
+ /**
+ * @atomic_update:
+ *
+ * Drivers should use this function to update the plane state. This
+ * hook is called in-between the &drm_crtc_helper_funcs.atomic_begin and
+ * drm_crtc_helper_funcs.atomic_flush callbacks.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_helper_commit_planes() for a discussion of
+ * the tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
+ void (*atomic_update)(struct drm_plane *plane,
+ struct drm_plane_state *old_state);
+ /**
+ * @atomic_disable:
+ *
+ * Drivers should use this function to unconditionally disable a plane.
+ * This hook is called in-between the
+ * &drm_crtc_helper_funcs.atomic_begin and
+ * drm_crtc_helper_funcs.atomic_flush callbacks. It is an alternative to
+ * @atomic_update, which will be called for disabling planes, too, if
+ * the @atomic_disable hook isn't implemented.
+ *
+ * This hook is also useful to disable planes in preparation of a modeset,
+ * by calling drm_atomic_helper_disable_planes_on_crtc() from the
+ * &drm_crtc_helper_funcs.disable hook.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_helper_commit_planes() for a discussion of
+ * the tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
+ void (*atomic_disable)(struct drm_plane *plane,
+ struct drm_plane_state *old_state);
+
+ /**
+ * @atomic_async_check:
+ *
+ * Drivers should set this function pointer to check if the plane state
+ * can be updated in a async fashion. Here async means "not vblank
+ * synchronized".
+ *
+ * This hook is called by drm_atomic_async_check() to establish if a
+ * given update can be committed asynchronously, that is, if it can
+ * jump ahead of the state currently queued for update.
+ *
+ * RETURNS:
+ *
+ * Return 0 on success and any error returned indicates that the update
+ * can not be applied in asynchronous manner.
+ */
+ int (*atomic_async_check)(struct drm_plane *plane,
+ struct drm_plane_state *state);
+
+ /**
+ * @atomic_async_update:
+ *
+ * Drivers should set this function pointer to perform asynchronous
+ * updates of planes, that is, jump ahead of the currently queued
+ * state and update the plane. Here async means "not vblank
+ * synchronized".
+ *
+ * This hook is called by drm_atomic_helper_async_commit().
+ *
+ * An async update will happen on legacy cursor updates. An async
+ * update won't happen if there is an outstanding commit modifying
+ * the same plane.
+ *
+ * Note that unlike &drm_plane_helper_funcs.atomic_update this hook
+ * takes the new &drm_plane_state as parameter. When doing async_update
+ * drivers shouldn't replace the &drm_plane_state but update the
+ * current one with the new plane configurations in the new
+ * plane_state.
+ *
+ * Drivers should also swap the framebuffers between current plane
+ * state (&drm_plane.state) and new_state.
+ * This is required since cleanup for async commits is performed on
+ * the new state, rather than old state like for traditional commits.
+ * Since we want to give up the reference on the current (old) fb
+ * instead of our brand new one, swap them in the driver during the
+ * async commit.
+ *
+ * FIXME:
+ * - It only works for single plane updates
+ * - Async Pageflips are not supported yet
+ * - Some hw might still scan out the old buffer until the next
+ * vblank, however we let go of the fb references as soon as
+ * we run this hook. For now drivers must implement their own workers
+ * for deferring if needed, until a common solution is created.
+ */
+ void (*atomic_async_update)(struct drm_plane *plane,
+ struct drm_plane_state *new_state);
+};
+
+/**
+ * drm_plane_helper_add - sets the helper vtable for a plane
+ * @plane: DRM plane
+ * @funcs: helper vtable to set for @plane
+ */
+static inline void drm_plane_helper_add(struct drm_plane *plane,
+ const struct drm_plane_helper_funcs *funcs)
+{
+ plane->helper_private = funcs;
+}
+
+/**
+ * struct drm_mode_config_helper_funcs - global modeset helper operations
+ *
+ * These helper functions are used by the atomic helpers.
+ */
+struct drm_mode_config_helper_funcs {
+ /**
+ * @atomic_commit_tail:
+ *
+ * This hook is used by the default atomic_commit() hook implemented in
+ * drm_atomic_helper_commit() together with the nonblocking commit
+ * helpers (see drm_atomic_helper_setup_commit() for a starting point)
+ * to implement blocking and nonblocking commits easily. It is not used
+ * by the atomic helpers
+ *
+ * This function is called when the new atomic state has already been
+ * swapped into the various state pointers. The passed in state
+ * therefore contains copies of the old/previous state. This hook should
+ * commit the new state into hardware. Note that the helpers have
+ * already waited for preceeding atomic commits and fences, but drivers
+ * can add more waiting calls at the start of their implementation, e.g.
+ * to wait for driver-internal request for implicit syncing, before
+ * starting to commit the update to the hardware.
+ *
+ * After the atomic update is committed to the hardware this hook needs
+ * to call drm_atomic_helper_commit_hw_done(). Then wait for the upate
+ * to be executed by the hardware, for example using
+ * drm_atomic_helper_wait_for_vblanks() or
+ * drm_atomic_helper_wait_for_flip_done(), and then clean up the old
+ * framebuffers using drm_atomic_helper_cleanup_planes().
+ *
+ * When disabling a CRTC this hook _must_ stall for the commit to
+ * complete. Vblank waits don't work on disabled CRTC, hence the core
+ * can't take care of this. And it also can't rely on the vblank event,
+ * since that can be signalled already when the screen shows black,
+ * which can happen much earlier than the last hardware access needed to
+ * shut off the display pipeline completely.
+ *
+ * This hook is optional, the default implementation is
+ * drm_atomic_helper_commit_tail().
+ */
+ void (*atomic_commit_tail)(struct drm_atomic_state *state);
+};
+
+#endif