summaryrefslogtreecommitdiffstats
path: root/include/drm/drm_modeset_helper_vtables.h
diff options
context:
space:
mode:
Diffstat (limited to 'include/drm/drm_modeset_helper_vtables.h')
-rw-r--r--include/drm/drm_modeset_helper_vtables.h928
1 files changed, 928 insertions, 0 deletions
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
new file mode 100644
index 000000000000..a126a0d7aed4
--- /dev/null
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -0,0 +1,928 @@
+/*
+ * 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>
+
+/**
+ * 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_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
+ * @enable and @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 @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 @enable should
+ * be used.
+ */
+ void (*commit)(struct drm_crtc *crtc);
+
+ /**
+ * @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
+ * ->mode_fixup() functions. If the CRTC cannot support the requested
+ * conversion from mode to adjusted_mode it should reject the modeset.
+ *
+ * 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.
+ *
+ * Also beware that neither core nor helpers filter modes before
+ * passing them to the driver: While the list of modes that is
+ * advertised to userspace is filtered using the connector's
+ * ->mode_valid() callback, neither the core nor the helpers do any
+ * filtering on modes passed in from userspace when setting a mode. It
+ * is therefore possible for userspace to pass in a mode that was
+ * previously filtered out using ->mode_valid() or add a custom mode
+ * that wasn't probed from EDID or similar to begin with. Even though
+ * this is an advanced feature and rarely used nowadays, some users rely
+ * on being able to specify modes manually so drivers must be prepared
+ * to deal with it. Specifically this means that all drivers need not
+ * only validate modes in ->mode_valid() but also in ->mode_fixup() to
+ * make sure invalid modes passed in from userspace are rejected.
+ *
+ * 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 @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);
+
+ /**
+ * @load_lut:
+ *
+ * Load a LUT prepared with the @gamma_set functions from
+ * &drm_fb_helper_funcs.
+ *
+ * This callback is optional and is only used by the fbdev emulation
+ * helpers.
+ *
+ * FIXME:
+ *
+ * This callback is functionally redundant with the core gamma table
+ * support and simply exists because the fbdev hasn't yet been
+ * refactored to use the core gamma table interfaces.
+ */
+ void (*load_lut)(struct drm_crtc *crtc);
+
+ /**
+ * @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 ->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 @enable for atomic drivers.
+ *
+ * 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);
+
+ /**
+ * @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 ->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 @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
+ * @enable must be the inverse of @disable for atomic drivers.
+ */
+ void (*enable)(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() CRTCs' ->atomic_check()
+ * hooks are called after the ones for planes, which allows drivers to
+ * assign shared resources requested by planes in the CRTC 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&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_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_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_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);
+};
+
+/**
+ * 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_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.
+ *
+ * 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.
+ *
+ * Also beware that neither core nor helpers filter modes before
+ * passing them to the driver: While the list of modes that is
+ * advertised to userspace is filtered using the connector's
+ * ->mode_valid() callback, neither the core nor the helpers do any
+ * filtering on modes passed in from userspace when setting a mode. It
+ * is therefore possible for userspace to pass in a mode that was
+ * previously filtered out using ->mode_valid() or add a custom mode
+ * that wasn't probed from EDID or similar to begin with. Even though
+ * this is an advanced feature and rarely used nowadays, some users rely
+ * on being able to specify modes manually so drivers must be prepared
+ * to deal with it. Specifically this means that all drivers need not
+ * only validate modes in ->mode_valid() but also in ->mode_fixup() to
+ * make sure invalid modes passed in from userspace are rejected.
+ *
+ * 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.
+ */
+ void (*mode_set)(struct drm_encoder *encoder,
+ struct drm_display_mode *mode,
+ struct drm_display_mode *adjusted_mode);
+
+ /**
+ * @get_crtc:
+ *
+ * This callback is used by the legacy CRTC helpers to work around
+ * deficiencies in its own book-keeping.
+ *
+ * Do not use, use atomic helpers instead, which get the book keeping
+ * right.
+ *
+ * FIXME:
+ *
+ * Currently only nouveau is using this, and as soon as nouveau is
+ * atomic we can ditch this hook.
+ */
+ struct drm_crtc *(*get_crtc)(struct drm_encoder *encoder);
+
+ /**
+ * @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);
+
+ /**
+ * @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 the CRTC's own ->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.
+ *
+ * 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
+ * the CRTC's own ->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 used only by atomic helpers, for symmetry with @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.
+ *
+ * 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.
+ *
+ * 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 connector->probed_modes list. It should also update the
+ * EDID property by calling drm_mode_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 @display_info, @width_mm and @height_mm fields of the
+ * struct #drm_connector 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().
+ *
+ * Finally drivers that support audio probably want to update the ELD
+ * data, too, using drm_edid_to_eld().
+ *
+ * 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().
+ *
+ * RETURNS:
+ *
+ * The number of modes added by calling drm_mode_probed_add().
+ */
+ int (*get_modes)(struct drm_connector *connector);
+
+ /**
+ * @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().
+ *
+ * NOTE:
+ *
+ * This only filters the mode list supplied to userspace in the
+ * GETCONNECOTR IOCTL. Userspace is free to create modes of its own and
+ * ask the kernel to use them. It this case the atomic helpers or legacy
+ * CRTC helpers will not call this function. Drivers therefore must
+ * still fully validate any mode passed in in a modeset request.
+ *
+ * RETURNS:
+ *
+ * Either 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);
+ /**
+ * @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.
+ *
+ * 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() and either
+ * this or @best_encoder is required.
+ *
+ * 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);
+};
+
+/**
+ * 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
+ * it's 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 fence member 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.
+ *
+ * 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 atomic_commit hook in &drm_mode_config_funcs. 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,
+ const 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,
+ const 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&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 ->atomic_begin() and
+ * ->atomic_flush() of &drm_crtc_helper_funcs.
+ *
+ * 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_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 ->atomic_begin() and
+ * ->atomic_flush() of &drm_crtc_helper_funcs. 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
+ * ->disable() hook in &drm_crtc_helper_funcs.
+ *
+ * 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_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);
+};
+
+/**
+ * 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;
+}
+
+#endif