text: /*
   * Copyright (c) 2006-2008 Intel Corporation
   * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
   *
   * DRM core CRTC related functions
   *
   * Permission to use, copy, modify, distribute, and sell this software and its
   * documentation for any purpose is hereby granted without fee, provided that
   * the above copyright notice appear in all copies and that both that copyright
   * notice and this permission notice appear in supporting documentation, and
   * that the name of the copyright holders not be used in advertising or
   * publicity pertaining to distribution of the software without specific,
   * written prior permission.  The copyright holders make no representations
   * about the suitability of this software for any purpose.  It is provided "as
   * is" without express or implied warranty.
   *
   * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
   * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
   * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
   * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
   * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   * OF THIS SOFTWARE.
   *
   * Authors:
   *      Keith Packard
   *	Eric Anholt <eric@anholt.net>
   *      Dave Airlie <airlied@linux.ie>
   *      Jesse Barnes <jesse.barnes@intel.com>
   */
  
  #include <linux/kernel.h>
  #include <linux/export.h>
  #include <linux/moduleparam.h>
  
  #include <drm/drmP.h>
  #include <drm/drm_atomic.h>
  #include <drm/drm_crtc.h>
  #include <drm/drm_encoder.h>
  #include <drm/drm_fourcc.h>
  #include <drm/drm_crtc_helper.h>
  #include <drm/drm_fb_helper.h>
  #include <drm/drm_plane_helper.h>
  #include <drm/drm_atomic_helper.h>
  #include <drm/drm_edid.h>
  
  /**
   * DOC: overview
   *
   * The CRTC modeset helper library provides a default set_config implementation
   * in drm_crtc_helper_set_config(). Plus a few other convenience functions using
   * the same callbacks which drivers can use to e.g. restore the modeset
   * configuration on resume with drm_helper_resume_force_mode().
   *
   * Note that this helper library doesn't track the current power state of CRTCs
   * and encoders. It can call callbacks like &drm_encoder_helper_funcs.dpms even
   * though the hardware is already in the desired state. This deficiency has been
   * fixed in the atomic helpers.
   *
   * The driver callbacks are mostly compatible with the atomic modeset helpers,
   * except for the handling of the primary plane: Atomic helpers require that the
   * primary plane is implemented as a real standalone plane and not directly tied
   * to the CRTC state. For easier transition this library provides functions to
   * implement the old semantics required by the CRTC helpers using the new plane
   * and atomic helper callbacks.
   *
   * Drivers are strongly urged to convert to the atomic helpers (by way of first
   * converting to the plane helpers). New drivers must not use these functions
   * but need to implement the atomic interface instead, potentially using the
   * atomic helpers for that.
   *
   * These legacy modeset helpers use the same function table structures as
   * all other modesetting helpers. See the documentation for struct
   * &drm_crtc_helper_funcs, &struct drm_encoder_helper_funcs and struct
   * &drm_connector_helper_funcs.
   */
  
  /**
   * drm_helper_encoder_in_use - check if a given encoder is in use
   * @encoder: encoder to check
   *
   * Checks whether @encoder is with the current mode setting output configuration
   * in use by any connector. This doesn't mean that it is actually enabled since
   * the DPMS state is tracked separately.
   *
   * Returns:
   * True if @encoder is used, false otherwise.
   */
  bool drm_helper_encoder_in_use(struct drm_encoder *encoder)
  {
  	struct drm_connector *connector;
  	struct drm_connector_list_iter conn_iter;
  	struct drm_device *dev = encoder->dev;
  
  	/*
  	 * We can expect this mutex to be locked if we are not panicking.
  	 * Locking is currently fubar in the panic handler.
  	 */
  	if (!oops_in_progress) {
  		WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
  		WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
  	}
  
  
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter) {
  		if (connector->encoder == encoder) {
  			drm_connector_list_iter_put(&conn_iter);
  			return true;
  		}
  	}
  	drm_connector_list_iter_put(&conn_iter);
  	return false;
  }
  EXPORT_SYMBOL(drm_helper_encoder_in_use);
  
  /**
   * drm_helper_crtc_in_use - check if a given CRTC is in a mode_config
   * @crtc: CRTC to check
   *
   * Checks whether @crtc is with the current mode setting output configuration
   * in use by any connector. This doesn't mean that it is actually enabled since
   * the DPMS state is tracked separately.
   *
   * Returns:
   * True if @crtc is used, false otherwise.
   */
  bool drm_helper_crtc_in_use(struct drm_crtc *crtc)
  {
  	struct drm_encoder *encoder;
  	struct drm_device *dev = crtc->dev;
  
  	/*
  	 * We can expect this mutex to be locked if we are not panicking.
  	 * Locking is currently fubar in the panic handler.
  	 */
  	if (!oops_in_progress)
  		WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
  
  	drm_for_each_encoder(encoder, dev)
  		if (encoder->crtc == crtc && drm_helper_encoder_in_use(encoder))
  			return true;
  	return false;
  }
  EXPORT_SYMBOL(drm_helper_crtc_in_use);
  
  static void
  drm_encoder_disable(struct drm_encoder *encoder)
  {
  	const struct drm_encoder_helper_funcs *encoder_funcs = encoder->helper_private;
  
  	if (!encoder_funcs)
  		return;
  
  	drm_bridge_disable(encoder->bridge);
  
  	if (encoder_funcs->disable)
  		(*encoder_funcs->disable)(encoder);
  	else if (encoder_funcs->dpms)
  		(*encoder_funcs->dpms)(encoder, DRM_MODE_DPMS_OFF);
  
  	drm_bridge_post_disable(encoder->bridge);
  }
  
  static void __drm_helper_disable_unused_functions(struct drm_device *dev)
  {
  	struct drm_encoder *encoder;
  	struct drm_crtc *crtc;
  
  	drm_warn_on_modeset_not_all_locked(dev);
  
  	drm_for_each_encoder(encoder, dev) {
  		if (!drm_helper_encoder_in_use(encoder)) {
  			drm_encoder_disable(encoder);
  			/* disconnect encoder from any connector */
  			encoder->crtc = NULL;
  		}
  	}
  
  	drm_for_each_crtc(crtc, dev) {
  		const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
  		crtc->enabled = drm_helper_crtc_in_use(crtc);
  		if (!crtc->enabled) {
  			if (crtc_funcs->disable)
  				(*crtc_funcs->disable)(crtc);
  			else
  				(*crtc_funcs->dpms)(crtc, DRM_MODE_DPMS_OFF);
  			crtc->primary->fb = NULL;
  		}
  	}
  }
  
  /**
   * drm_helper_disable_unused_functions - disable unused objects
   * @dev: DRM device
   *
   * This function walks through the entire mode setting configuration of @dev. It
   * will remove any CRTC links of unused encoders and encoder links of
   * disconnected connectors. Then it will disable all unused encoders and CRTCs
   * either by calling their disable callback if available or by calling their
   * dpms callback with DRM_MODE_DPMS_OFF.
   *
   * NOTE:
   *
   * This function is part of the legacy modeset helper library and will cause
   * major confusion with atomic drivers. This is because atomic helpers guarantee
   * to never call ->disable() hooks on a disabled function, or ->enable() hooks
   * on an enabled functions. drm_helper_disable_unused_functions() on the other
   * hand throws such guarantees into the wind and calls disable hooks
   * unconditionally on unused functions.
   */
  void drm_helper_disable_unused_functions(struct drm_device *dev)
  {
  	if (drm_core_check_feature(dev, DRIVER_ATOMIC))
  		DRM_ERROR("Called for atomic driver, this is not what you want.\n");
  
  	drm_modeset_lock_all(dev);
  	__drm_helper_disable_unused_functions(dev);
  	drm_modeset_unlock_all(dev);
  }
  EXPORT_SYMBOL(drm_helper_disable_unused_functions);
  
  /*
   * Check the CRTC we're going to map each output to vs. its current
   * CRTC.  If they don't match, we have to disable the output and the CRTC
   * since the driver will have to re-route things.
   */
  static void
  drm_crtc_prepare_encoders(struct drm_device *dev)
  {
  	const struct drm_encoder_helper_funcs *encoder_funcs;
  	struct drm_encoder *encoder;
  
  	drm_for_each_encoder(encoder, dev) {
  		encoder_funcs = encoder->helper_private;
  		if (!encoder_funcs)
  			continue;
  
  		/* Disable unused encoders */
  		if (encoder->crtc == NULL)
  			drm_encoder_disable(encoder);
  		/* Disable encoders whose CRTC is about to change */
  		if (encoder_funcs->get_crtc &&
  		    encoder->crtc != (*encoder_funcs->get_crtc)(encoder))
  			drm_encoder_disable(encoder);
  	}
  }
  
  /**
   * drm_crtc_helper_set_mode - internal helper to set a mode
   * @crtc: CRTC to program
   * @mode: mode to use
   * @x: horizontal offset into the surface
   * @y: vertical offset into the surface
   * @old_fb: old framebuffer, for cleanup
   *
   * Try to set @mode on @crtc.  Give @crtc and its associated connectors a chance
   * to fixup or reject the mode prior to trying to set it. This is an internal
   * helper that drivers could e.g. use to update properties that require the
   * entire output pipe to be disabled and re-enabled in a new configuration. For
   * example for changing whether audio is enabled on a hdmi link or for changing
   * panel fitter or dither attributes. It is also called by the
   * drm_crtc_helper_set_config() helper function to drive the mode setting
   * sequence.
   *
   * Returns:
   * True if the mode was set successfully, false otherwise.
   */
  bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
  			      struct drm_display_mode *mode,
  			      int x, int y,
  			      struct drm_framebuffer *old_fb)
  {
  	struct drm_device *dev = crtc->dev;
  	struct drm_display_mode *adjusted_mode, saved_mode, saved_hwmode;
  	const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
  	const struct drm_encoder_helper_funcs *encoder_funcs;
  	int saved_x, saved_y;
  	bool saved_enabled;
  	struct drm_encoder *encoder;
  	bool ret = true;
  
  	drm_warn_on_modeset_not_all_locked(dev);
  
  	saved_enabled = crtc->enabled;
  	crtc->enabled = drm_helper_crtc_in_use(crtc);
  	if (!crtc->enabled)
  		return true;
  
  	adjusted_mode = drm_mode_duplicate(dev, mode);
  	if (!adjusted_mode) {
  		crtc->enabled = saved_enabled;
  		return false;
  	}
  
  	saved_mode = crtc->mode;
  	saved_hwmode = crtc->hwmode;
  	saved_x = crtc->x;
  	saved_y = crtc->y;
  
  	/* Update crtc values up front so the driver can rely on them for mode
  	 * setting.
  	 */
  	crtc->mode = *mode;
  	crtc->x = x;
  	crtc->y = y;
  
  	/* Pass our mode to the connectors and the CRTC to give them a chance to
  	 * adjust it according to limitations or connector properties, and also
  	 * a chance to reject the mode entirely.
  	 */
  	drm_for_each_encoder(encoder, dev) {
  
  		if (encoder->crtc != crtc)
  			continue;
  
  		encoder_funcs = encoder->helper_private;
  		if (!encoder_funcs)
  			continue;
  
  		ret = drm_bridge_mode_fixup(encoder->bridge,
  			mode, adjusted_mode);
  		if (!ret) {
  			DRM_DEBUG_KMS("Bridge fixup failed\n");
  			goto done;
  		}
  
  		encoder_funcs = encoder->helper_private;
  		if (encoder_funcs->mode_fixup) {
  			if (!(ret = encoder_funcs->mode_fixup(encoder, mode,
  							      adjusted_mode))) {
  				DRM_DEBUG_KMS("Encoder fixup failed\n");
  				goto done;
  			}
  		}
  	}
  
  	if (crtc_funcs->mode_fixup) {
  		if (!(ret = crtc_funcs->mode_fixup(crtc, mode,
  						adjusted_mode))) {
  			DRM_DEBUG_KMS("CRTC fixup failed\n");
  			goto done;
  		}
  	}
  	DRM_DEBUG_KMS("[CRTC:%d:%s]\n", crtc->base.id, crtc->name);
  
  	crtc->hwmode = *adjusted_mode;
  
  	/* Prepare the encoders and CRTCs before setting the mode. */
  	drm_for_each_encoder(encoder, dev) {
  
  		if (encoder->crtc != crtc)
  			continue;
  
  		encoder_funcs = encoder->helper_private;
  		if (!encoder_funcs)
  			continue;
  
  		drm_bridge_disable(encoder->bridge);
  
  		/* Disable the encoders as the first thing we do. */
  		if (encoder_funcs->prepare)
  			encoder_funcs->prepare(encoder);
  
  		drm_bridge_post_disable(encoder->bridge);
  	}
  
  	drm_crtc_prepare_encoders(dev);
  
  	crtc_funcs->prepare(crtc);
  
  	/* Set up the DPLL and any encoders state that needs to adjust or depend
  	 * on the DPLL.
  	 */
  	ret = !crtc_funcs->mode_set(crtc, mode, adjusted_mode, x, y, old_fb);
  	if (!ret)
  	    goto done;
  
  	drm_for_each_encoder(encoder, dev) {
  
  		if (encoder->crtc != crtc)
  			continue;
  
  		encoder_funcs = encoder->helper_private;
  		if (!encoder_funcs)
  			continue;
  
  		DRM_DEBUG_KMS("[ENCODER:%d:%s] set [MODE:%d:%s]\n",
  			encoder->base.id, encoder->name,
  			mode->base.id, mode->name);
  		if (encoder_funcs->mode_set)
  			encoder_funcs->mode_set(encoder, mode, adjusted_mode);
  
  		drm_bridge_mode_set(encoder->bridge, mode, adjusted_mode);
  	}
  
  	/* Now enable the clocks, plane, pipe, and connectors that we set up. */
  	crtc_funcs->commit(crtc);
  
  	drm_for_each_encoder(encoder, dev) {
  
  		if (encoder->crtc != crtc)
  			continue;
  
  		encoder_funcs = encoder->helper_private;
  		if (!encoder_funcs)
  			continue;
  
  		drm_bridge_pre_enable(encoder->bridge);
  
  		if (encoder_funcs->commit)
  			encoder_funcs->commit(encoder);
  
  		drm_bridge_enable(encoder->bridge);
  	}
  
  	/* Calculate and store various constants which
  	 * are later needed by vblank and swap-completion
  	 * timestamping. They are derived from true hwmode.
  	 */
  	drm_calc_timestamping_constants(crtc, &crtc->hwmode);
  
  	/* FIXME: add subpixel order */
  done:
  	drm_mode_destroy(dev, adjusted_mode);
  	if (!ret) {
  		crtc->enabled = saved_enabled;
  		crtc->mode = saved_mode;
  		crtc->hwmode = saved_hwmode;
  		crtc->x = saved_x;
  		crtc->y = saved_y;
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL(drm_crtc_helper_set_mode);
  
  static void
  drm_crtc_helper_disable(struct drm_crtc *crtc)
  {
  	struct drm_device *dev = crtc->dev;
  	struct drm_connector *connector;
  	struct drm_encoder *encoder;
  
  	/* Decouple all encoders and their attached connectors from this crtc */
  	drm_for_each_encoder(encoder, dev) {
  		struct drm_connector_list_iter conn_iter;
  
  		if (encoder->crtc != crtc)
  			continue;
  
  		drm_connector_list_iter_get(dev, &conn_iter);
  		drm_for_each_connector_iter(connector, &conn_iter) {
  			if (connector->encoder != encoder)
  				continue;
  
  			connector->encoder = NULL;
  
  			/*
  			 * drm_helper_disable_unused_functions() ought to be
  			 * doing this, but since we've decoupled the encoder
  			 * from the connector above, the required connection
  			 * between them is henceforth no longer available.
  			 */
  			connector->dpms = DRM_MODE_DPMS_OFF;
  
  			/* we keep a reference while the encoder is bound */
  			drm_connector_unreference(connector);
  		}
  		drm_connector_list_iter_put(&conn_iter);
  	}
  
  	__drm_helper_disable_unused_functions(dev);
  }
  
  /**
   * drm_crtc_helper_set_config - set a new config from userspace
   * @set: mode set configuration
   *
   * The drm_crtc_helper_set_config() helper function implements the of
   * &drm_crtc_funcs.set_config callback for drivers using the legacy CRTC
   * helpers.
   *
   * It first tries to locate the best encoder for each connector by calling the
   * connector @drm_connector_helper_funcs.best_encoder helper operation.
   *
   * After locating the appropriate encoders, the helper function will call the
   * mode_fixup encoder and CRTC helper operations to adjust the requested mode,
   * or reject it completely in which case an error will be returned to the
   * application. If the new configuration after mode adjustment is identical to
   * the current configuration the helper function will return without performing
   * any other operation.
   *
   * If the adjusted mode is identical to the current mode but changes to the
   * frame buffer need to be applied, the drm_crtc_helper_set_config() function
   * will call the CRTC &drm_crtc_helper_funcs.mode_set_base helper operation.
   *
   * If the adjusted mode differs from the current mode, or if the
   * ->mode_set_base() helper operation is not provided, the helper function
   * performs a full mode set sequence by calling the ->prepare(), ->mode_set()
   * and ->commit() CRTC and encoder helper operations, in that order.
   * Alternatively it can also use the dpms and disable helper operations. For
   * details see &struct drm_crtc_helper_funcs and struct
   * &drm_encoder_helper_funcs.
   *
   * This function is deprecated.  New drivers must implement atomic modeset
   * support, for which this function is unsuitable. Instead drivers should use
   * drm_atomic_helper_set_config().
   *
   * Returns:
   * Returns 0 on success, negative errno numbers on failure.
   */
  int drm_crtc_helper_set_config(struct drm_mode_set *set)
  {
  	struct drm_device *dev;
  	struct drm_crtc **save_encoder_crtcs, *new_crtc;
  	struct drm_encoder **save_connector_encoders, *new_encoder, *encoder;
  	bool mode_changed = false; /* if true do a full mode set */
  	bool fb_changed = false; /* if true and !mode_changed just do a flip */
  	struct drm_connector *connector;
  	struct drm_connector_list_iter conn_iter;
  	int count = 0, ro, fail = 0;
  	const struct drm_crtc_helper_funcs *crtc_funcs;
  	struct drm_mode_set save_set;
  	int ret;
  	int i;
  
  	DRM_DEBUG_KMS("\n");
  
  	BUG_ON(!set);
  	BUG_ON(!set->crtc);
  	BUG_ON(!set->crtc->helper_private);
  
  	/* Enforce sane interface api - has been abused by the fb helper. */
  	BUG_ON(!set->mode && set->fb);
  	BUG_ON(set->fb && set->num_connectors == 0);
  
  	crtc_funcs = set->crtc->helper_private;
  
  	if (!set->mode)
  		set->fb = NULL;
  
  	if (set->fb) {
  		DRM_DEBUG_KMS("[CRTC:%d:%s] [FB:%d] #connectors=%d (x y) (%i %i)\n",
  			      set->crtc->base.id, set->crtc->name,
  			      set->fb->base.id,
  			      (int)set->num_connectors, set->x, set->y);
  	} else {
  		DRM_DEBUG_KMS("[CRTC:%d:%s] [NOFB]\n",
  			      set->crtc->base.id, set->crtc->name);
  		drm_crtc_helper_disable(set->crtc);
  		return 0;
  	}
  
  	dev = set->crtc->dev;
  
  	drm_warn_on_modeset_not_all_locked(dev);
  
  	/*
  	 * Allocate space for the backup of all (non-pointer) encoder and
  	 * connector data.
  	 */
  	save_encoder_crtcs = kzalloc(dev->mode_config.num_encoder *
  				sizeof(struct drm_crtc *), GFP_KERNEL);
  	if (!save_encoder_crtcs)
  		return -ENOMEM;
  
  	save_connector_encoders = kzalloc(dev->mode_config.num_connector *
  				sizeof(struct drm_encoder *), GFP_KERNEL);
  	if (!save_connector_encoders) {
  		kfree(save_encoder_crtcs);
  		return -ENOMEM;
  	}
  
  	/*
  	 * Copy data. Note that driver private data is not affected.
  	 * Should anything bad happen only the expected state is
  	 * restored, not the drivers personal bookkeeping.
  	 */
  	count = 0;
  	drm_for_each_encoder(encoder, dev) {
  		save_encoder_crtcs[count++] = encoder->crtc;
  	}
  
  	count = 0;
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter)
  		save_connector_encoders[count++] = connector->encoder;
  	drm_connector_list_iter_put(&conn_iter);
  
  	save_set.crtc = set->crtc;
  	save_set.mode = &set->crtc->mode;
  	save_set.x = set->crtc->x;
  	save_set.y = set->crtc->y;
  	save_set.fb = set->crtc->primary->fb;
  
  	/* We should be able to check here if the fb has the same properties
  	 * and then just flip_or_move it */
  	if (set->crtc->primary->fb != set->fb) {
  		/* If we have no fb then treat it as a full mode set */
  		if (set->crtc->primary->fb == NULL) {
  			DRM_DEBUG_KMS("crtc has no fb, full mode set\n");
  			mode_changed = true;
  		} else if (set->fb->format != set->crtc->primary->fb->format) {
  			mode_changed = true;
  		} else
  			fb_changed = true;
  	}
  
  	if (set->x != set->crtc->x || set->y != set->crtc->y)
  		fb_changed = true;
  
  	if (!drm_mode_equal(set->mode, &set->crtc->mode)) {
  		DRM_DEBUG_KMS("modes are different, full mode set\n");
  		drm_mode_debug_printmodeline(&set->crtc->mode);
  		drm_mode_debug_printmodeline(set->mode);
  		mode_changed = true;
  	}
  
  	/* take a reference on all unbound connectors in set, reuse the
  	 * already taken reference for bound connectors
  	 */
  	for (ro = 0; ro < set->num_connectors; ro++) {
  		if (set->connectors[ro]->encoder)
  			continue;
  		drm_connector_reference(set->connectors[ro]);
  	}
  
  	/* a) traverse passed in connector list and get encoders for them */
  	count = 0;
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter) {
  		const struct drm_connector_helper_funcs *connector_funcs =
  			connector->helper_private;
  		new_encoder = connector->encoder;
  		for (ro = 0; ro < set->num_connectors; ro++) {
  			if (set->connectors[ro] == connector) {
  				new_encoder = connector_funcs->best_encoder(connector);
  				/* if we can't get an encoder for a connector
  				   we are setting now - then fail */
  				if (new_encoder == NULL)
  					/* don't break so fail path works correct */
  					fail = 1;
  
  				if (connector->dpms != DRM_MODE_DPMS_ON) {
  					DRM_DEBUG_KMS("connector dpms not on, full mode switch\n");
  					mode_changed = true;
  				}
  
  				break;
  			}
  		}
  
  		if (new_encoder != connector->encoder) {
  			DRM_DEBUG_KMS("encoder changed, full mode switch\n");
  			mode_changed = true;
  			/* If the encoder is reused for another connector, then
  			 * the appropriate crtc will be set later.
  			 */
  			if (connector->encoder)
  				connector->encoder->crtc = NULL;
  			connector->encoder = new_encoder;
  		}
  	}
  	drm_connector_list_iter_put(&conn_iter);
  
  	if (fail) {
  		ret = -EINVAL;
  		goto fail;
  	}
  
  	count = 0;
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter) {
  		if (!connector->encoder)
  			continue;
  
  		if (connector->encoder->crtc == set->crtc)
  			new_crtc = NULL;
  		else
  			new_crtc = connector->encoder->crtc;
  
  		for (ro = 0; ro < set->num_connectors; ro++) {
  			if (set->connectors[ro] == connector)
  				new_crtc = set->crtc;
  		}
  
  		/* Make sure the new CRTC will work with the encoder */
  		if (new_crtc &&
  		    !drm_encoder_crtc_ok(connector->encoder, new_crtc)) {
  			ret = -EINVAL;
  			drm_connector_list_iter_put(&conn_iter);
  			goto fail;
  		}
  		if (new_crtc != connector->encoder->crtc) {
  			DRM_DEBUG_KMS("crtc changed, full mode switch\n");
  			mode_changed = true;
  			connector->encoder->crtc = new_crtc;
  		}
  		if (new_crtc) {
  			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] to [CRTC:%d:%s]\n",
  				      connector->base.id, connector->name,
  				      new_crtc->base.id, new_crtc->name);
  		} else {
  			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] to [NOCRTC]\n",
  				      connector->base.id, connector->name);
  		}
  	}
  	drm_connector_list_iter_put(&conn_iter);
  
  	/* mode_set_base is not a required function */
  	if (fb_changed && !crtc_funcs->mode_set_base)
  		mode_changed = true;
  
  	if (mode_changed) {
  		if (drm_helper_crtc_in_use(set->crtc)) {
  			DRM_DEBUG_KMS("attempting to set mode from"
  					" userspace\n");
  			drm_mode_debug_printmodeline(set->mode);
  			set->crtc->primary->fb = set->fb;
  			if (!drm_crtc_helper_set_mode(set->crtc, set->mode,
  						      set->x, set->y,
  						      save_set.fb)) {
  				DRM_ERROR("failed to set mode on [CRTC:%d:%s]\n",
  					  set->crtc->base.id, set->crtc->name);
  				set->crtc->primary->fb = save_set.fb;
  				ret = -EINVAL;
  				goto fail;
  			}
  			DRM_DEBUG_KMS("Setting connector DPMS state to on\n");
  			for (i = 0; i < set->num_connectors; i++) {
  				DRM_DEBUG_KMS("\t[CONNECTOR:%d:%s] set DPMS on\n", set->connectors[i]->base.id,
  					      set->connectors[i]->name);
  				set->connectors[i]->funcs->dpms(set->connectors[i], DRM_MODE_DPMS_ON);
  			}
  		}
  		__drm_helper_disable_unused_functions(dev);
  	} else if (fb_changed) {
  		set->crtc->x = set->x;
  		set->crtc->y = set->y;
  		set->crtc->primary->fb = set->fb;
  		ret = crtc_funcs->mode_set_base(set->crtc,
  						set->x, set->y, save_set.fb);
  		if (ret != 0) {
  			set->crtc->x = save_set.x;
  			set->crtc->y = save_set.y;
  			set->crtc->primary->fb = save_set.fb;
  			goto fail;
  		}
  	}
  
  	kfree(save_connector_encoders);
  	kfree(save_encoder_crtcs);
  	return 0;
  
  fail:
  	/* Restore all previous data. */
  	count = 0;
  	drm_for_each_encoder(encoder, dev) {
  		encoder->crtc = save_encoder_crtcs[count++];
  	}
  
  	count = 0;
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter)
  		connector->encoder = save_connector_encoders[count++];
  	drm_connector_list_iter_put(&conn_iter);
  
  	/* after fail drop reference on all unbound connectors in set, let
  	 * bound connectors keep their reference
  	 */
  	for (ro = 0; ro < set->num_connectors; ro++) {
  		if (set->connectors[ro]->encoder)
  			continue;
  		drm_connector_unreference(set->connectors[ro]);
  	}
  
  	/* Try to restore the config */
  	if (mode_changed &&
  	    !drm_crtc_helper_set_mode(save_set.crtc, save_set.mode, save_set.x,
  				      save_set.y, save_set.fb))
  		DRM_ERROR("failed to restore config after modeset failure\n");
  
  	kfree(save_connector_encoders);
  	kfree(save_encoder_crtcs);
  	return ret;
  }
  EXPORT_SYMBOL(drm_crtc_helper_set_config);
  
  static int drm_helper_choose_encoder_dpms(struct drm_encoder *encoder)
  {
  	int dpms = DRM_MODE_DPMS_OFF;
  	struct drm_connector *connector;
  	struct drm_connector_list_iter conn_iter;
  	struct drm_device *dev = encoder->dev;
  
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter)
  		if (connector->encoder == encoder)
  			if (connector->dpms < dpms)
  				dpms = connector->dpms;
  	drm_connector_list_iter_put(&conn_iter);
  
  	return dpms;
  }
  
  /* Helper which handles bridge ordering around encoder dpms */
  static void drm_helper_encoder_dpms(struct drm_encoder *encoder, int mode)
  {
  	struct drm_bridge *bridge = encoder->bridge;
  	const struct drm_encoder_helper_funcs *encoder_funcs;
  
  	encoder_funcs = encoder->helper_private;
  	if (!encoder_funcs)
  		return;
  
  	if (mode == DRM_MODE_DPMS_ON)
  		drm_bridge_pre_enable(bridge);
  	else
  		drm_bridge_disable(bridge);
  
  	if (encoder_funcs->dpms)
  		encoder_funcs->dpms(encoder, mode);
  
  	if (mode == DRM_MODE_DPMS_ON)
  		drm_bridge_enable(bridge);
  	else
  		drm_bridge_post_disable(bridge);
  }
  
  static int drm_helper_choose_crtc_dpms(struct drm_crtc *crtc)
  {
  	int dpms = DRM_MODE_DPMS_OFF;
  	struct drm_connector *connector;
  	struct drm_connector_list_iter conn_iter;
  	struct drm_device *dev = crtc->dev;
  
  	drm_connector_list_iter_get(dev, &conn_iter);
  	drm_for_each_connector_iter(connector, &conn_iter)
  		if (connector->encoder && connector->encoder->crtc == crtc)
  			if (connector->dpms < dpms)
  				dpms = connector->dpms;
  	drm_connector_list_iter_put(&conn_iter);
  
  	return dpms;
  }
  
  /**
   * drm_helper_connector_dpms() - connector dpms helper implementation
   * @connector: affected connector
   * @mode: DPMS mode
   *
   * The drm_helper_connector_dpms() helper function implements the
   * &drm_connector_funcs.dpms callback for drivers using the legacy CRTC
   * helpers.
   *
   * This is the main helper function provided by the CRTC helper framework for
   * implementing the DPMS connector attribute. It computes the new desired DPMS
   * state for all encoders and CRTCs in the output mesh and calls the
   * &drm_crtc_helper_funcs.dpms and &drm_encoder_helper_funcs.dpms callbacks
   * provided by the driver.
   *
   * This function is deprecated.  New drivers must implement atomic modeset
   * support, for which this function is unsuitable. Instead drivers should use
   * drm_atomic_helper_connector_dpms().
   *
   * Returns:
   * Always returns 0.
   */
  int drm_helper_connector_dpms(struct drm_connector *connector, int mode)
  {
  	struct drm_encoder *encoder = connector->encoder;
  	struct drm_crtc *crtc = encoder ? encoder->crtc : NULL;
  	int old_dpms, encoder_dpms = DRM_MODE_DPMS_OFF;
  
  	if (mode == connector->dpms)
  		return 0;
  
  	old_dpms = connector->dpms;
  	connector->dpms = mode;
  
  	if (encoder)
  		encoder_dpms = drm_helper_choose_encoder_dpms(encoder);
  
  	/* from off to on, do crtc then encoder */
  	if (mode < old_dpms) {
  		if (crtc) {
  			const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
  			if (crtc_funcs->dpms)
  				(*crtc_funcs->dpms) (crtc,
  						     drm_helper_choose_crtc_dpms(crtc));
  		}
  		if (encoder)
  			drm_helper_encoder_dpms(encoder, encoder_dpms);
  	}
  
  	/* from on to off, do encoder then crtc */
  	if (mode > old_dpms) {
  		if (encoder)
  			drm_helper_encoder_dpms(encoder, encoder_dpms);
  		if (crtc) {
  			const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
  			if (crtc_funcs->dpms)
  				(*crtc_funcs->dpms) (crtc,
  						     drm_helper_choose_crtc_dpms(crtc));
  		}
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL(drm_helper_connector_dpms);
  
  /**
   * drm_helper_resume_force_mode - force-restore mode setting configuration
   * @dev: drm_device which should be restored
   *
   * Drivers which use the mode setting helpers can use this function to
   * force-restore the mode setting configuration e.g. on resume or when something
   * else might have trampled over the hw state (like some overzealous old BIOSen
   * tended to do).
   *
   * This helper doesn't provide a error return value since restoring the old
   * config should never fail due to resource allocation issues since the driver
   * has successfully set the restored configuration already. Hence this should
   * boil down to the equivalent of a few dpms on calls, which also don't provide
   * an error code.
   *
   * Drivers where simply restoring an old configuration again might fail (e.g.
   * due to slight differences in allocating shared resources when the
   * configuration is restored in a different order than when userspace set it up)
   * need to use their own restore logic.
   *
   * This function is deprecated. New drivers should implement atomic mode-
   * setting and use the atomic suspend/resume helpers.
   *
   * See also:
   * drm_atomic_helper_suspend(), drm_atomic_helper_resume()
   */
  void drm_helper_resume_force_mode(struct drm_device *dev)
  {
  	struct drm_crtc *crtc;
  	struct drm_encoder *encoder;
  	const struct drm_crtc_helper_funcs *crtc_funcs;
  	int encoder_dpms;
  	bool ret;
  
  	drm_modeset_lock_all(dev);
  	drm_for_each_crtc(crtc, dev) {
  
  		if (!crtc->enabled)
  			continue;
  
  		ret = drm_crtc_helper_set_mode(crtc, &crtc->mode,
  					       crtc->x, crtc->y, crtc->primary->fb);
  
  		/* Restoring the old config should never fail! */
  		if (ret == false)
  			DRM_ERROR("failed to set mode on crtc %p\n", crtc);
  
  		/* Turn off outputs that were already powered off */
  		if (drm_helper_choose_crtc_dpms(crtc)) {
  			drm_for_each_encoder(encoder, dev) {
  
  				if(encoder->crtc != crtc)
  					continue;
  
  				encoder_dpms = drm_helper_choose_encoder_dpms(
  							encoder);
  
  				drm_helper_encoder_dpms(encoder, encoder_dpms);
  			}
  
  			crtc_funcs = crtc->helper_private;
  			if (crtc_funcs->dpms)
  				(*crtc_funcs->dpms) (crtc,
  						     drm_helper_choose_crtc_dpms(crtc));
  		}
  	}
  
  	/* disable the unused connectors while restoring the modesetting */
  	__drm_helper_disable_unused_functions(dev);
  	drm_modeset_unlock_all(dev);
  }
  EXPORT_SYMBOL(drm_helper_resume_force_mode);
  
  /**
   * drm_helper_crtc_mode_set - mode_set implementation for atomic plane helpers
   * @crtc: DRM CRTC
   * @mode: DRM display mode which userspace requested
   * @adjusted_mode: DRM display mode adjusted by ->mode_fixup callbacks
   * @x: x offset of the CRTC scanout area on the underlying framebuffer
   * @y: y offset of the CRTC scanout area on the underlying framebuffer
   * @old_fb: previous framebuffer
   *
   * This function implements a callback useable as the ->mode_set callback
   * required by the CRTC helpers. Besides the atomic plane helper functions for
   * the primary plane the driver must also provide the ->mode_set_nofb callback
   * to set up the CRTC.
   *
   * This is a transitional helper useful for converting drivers to the atomic
   * interfaces.
   */
  int drm_helper_crtc_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)
  {
  	struct drm_crtc_state *crtc_state;
  	const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
  	int ret;
  
  	if (crtc->funcs->atomic_duplicate_state)
  		crtc_state = crtc->funcs->atomic_duplicate_state(crtc);
  	else {
  		if (!crtc->state)
  			drm_atomic_helper_crtc_reset(crtc);
  
  		crtc_state = drm_atomic_helper_crtc_duplicate_state(crtc);
  	}
  
  	if (!crtc_state)
  		return -ENOMEM;
  
  	crtc_state->planes_changed = true;
  	crtc_state->mode_changed = true;
  	ret = drm_atomic_set_mode_for_crtc(crtc_state, mode);
  	if (ret)
  		goto out;
  	drm_mode_copy(&crtc_state->adjusted_mode, adjusted_mode);
  
  	if (crtc_funcs->atomic_check) {
  		ret = crtc_funcs->atomic_check(crtc, crtc_state);
  		if (ret)
  			goto out;
  	}
  
  	swap(crtc->state, crtc_state);
  
  	crtc_funcs->mode_set_nofb(crtc);
  
  	ret = drm_helper_crtc_mode_set_base(crtc, x, y, old_fb);
  
  out:
  	if (crtc_state) {
  		if (crtc->funcs->atomic_destroy_state)
  			crtc->funcs->atomic_destroy_state(crtc, crtc_state);
  		else
  			drm_atomic_helper_crtc_destroy_state(crtc, crtc_state);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL(drm_helper_crtc_mode_set);
  
  /**
   * drm_helper_crtc_mode_set_base - mode_set_base implementation for atomic plane helpers
   * @crtc: DRM CRTC
   * @x: x offset of the CRTC scanout area on the underlying framebuffer
   * @y: y offset of the CRTC scanout area on the underlying framebuffer
   * @old_fb: previous framebuffer
   *
   * This function implements a callback useable as the ->mode_set_base used
   * required by the CRTC helpers. The driver must provide the atomic plane helper
   * functions for the primary plane.
   *
   * This is a transitional helper useful for converting drivers to the atomic
   * interfaces.
   */
  int drm_helper_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
  				  struct drm_framebuffer *old_fb)
  {
  	struct drm_plane_state *plane_state;
  	struct drm_plane *plane = crtc->primary;
  
  	if (plane->funcs->atomic_duplicate_state)
  		plane_state = plane->funcs->atomic_duplicate_state(plane);
  	else {
  		if (!plane->state)
  			drm_atomic_helper_plane_reset(plane);
  
  		plane_state = drm_atomic_helper_plane_duplicate_state(plane);
  	}
  	if (!plane_state)
  		return -ENOMEM;
  	plane_state->plane = plane;
  
  	plane_state->crtc = crtc;
  	drm_atomic_set_fb_for_plane(plane_state, crtc->primary->fb);
  	plane_state->crtc_x = 0;
  	plane_state->crtc_y = 0;
  	plane_state->crtc_h = crtc->mode.vdisplay;
  	plane_state->crtc_w = crtc->mode.hdisplay;
  	plane_state->src_x = x << 16;
  	plane_state->src_y = y << 16;
  	plane_state->src_h = crtc->mode.vdisplay << 16;
  	plane_state->src_w = crtc->mode.hdisplay << 16;
  
  	return drm_plane_helper_commit(plane, plane_state, old_fb);
  }
  EXPORT_SYMBOL(drm_helper_crtc_mode_set_base);
  