drivers/gpu/drm/drm_probe_helper.c - kernel/msm-4.9 - Gitiles

 /*
  * 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/export.h>
 #include <linux/moduleparam.h>

 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_edid.h>

 /**
  * DOC: output probing helper overview
  *
  * This library provides some helper code for output probing. It provides an
  * implementation of the core connector->fill_modes interface with
  * drm_helper_probe_single_connector_modes.
  *
  * It also provides support for polling connectors with a work item and for
  * generic hotplug interrupt handling where the driver doesn't or cannot keep
  * track of a per-connector hpd interrupt.
  *
  * This helper library can be used independently of the modeset helper library.
  * Drivers can also overwrite different parts e.g. use their own hotplug
  * handling code to avoid probing unrelated outputs.
  *
  * The probe helpers share the function table structures with other display
  * helper libraries. See struct &drm_connector_helper_funcs for the details.
  */

 static bool drm_kms_helper_poll = true;
 module_param_named(poll, drm_kms_helper_poll, bool, 0600);

 static enum drm_mode_status
 drm_mode_validate_flag(const struct drm_display_mode *mode,
 		       int flags)
 {
 	if ((mode->flags & DRM_MODE_FLAG_INTERLACE) &&
 	    !(flags & DRM_MODE_FLAG_INTERLACE))
 		return MODE_NO_INTERLACE;

 	if ((mode->flags & DRM_MODE_FLAG_DBLSCAN) &&
 	    !(flags & DRM_MODE_FLAG_DBLSCAN))
 		return MODE_NO_DBLESCAN;

 	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) &&
 	    !(flags & DRM_MODE_FLAG_3D_MASK))
 		return MODE_NO_STEREO;

 	return MODE_OK;
 }

 static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
 {
 	struct drm_cmdline_mode *cmdline_mode;
 	struct drm_display_mode *mode;

 	cmdline_mode = &connector->cmdline_mode;
 	if (!cmdline_mode->specified)
 		return 0;

 	/* Only add a GTF mode if we find no matching probed modes */
 	list_for_each_entry(mode, &connector->probed_modes, head) {
 		if (mode->hdisplay != cmdline_mode->xres ||
 		    mode->vdisplay != cmdline_mode->yres)
 			continue;

 		if (cmdline_mode->refresh_specified) {
 			/* The probed mode's vrefresh is set until later */
 			if (drm_mode_vrefresh(mode) != cmdline_mode->refresh)
 				continue;
 		}

 		return 0;
 	}

 	mode = drm_mode_create_from_cmdline_mode(connector->dev,
 						 cmdline_mode);
 	if (mode == NULL)
 		return 0;

 	drm_mode_probed_add(connector, mode);
 	return 1;
 }

 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
 /**
  * drm_kms_helper_poll_enable_locked - re-enable output polling.
  * @dev: drm_device
  *
  * This function re-enables the output polling work without
  * locking the mode_config mutex.
  *
  * This is like drm_kms_helper_poll_enable() however it is to be
  * called from a context where the mode_config mutex is locked
  * already.
  */
 void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
 {
 	bool poll = false;
 	struct drm_connector *connector;
 	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;

 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

 	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
 		return;

 	drm_for_each_connector(connector, dev) {
 		if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
 					 DRM_CONNECTOR_POLL_DISCONNECT))
 			poll = true;
 	}

 	if (dev->mode_config.delayed_event) {
 		/*
 		 * FIXME:
 		 *
 		 * Use short (1s) delay to handle the initial delayed event.
 		 * This delay should not be needed, but Optimus/nouveau will
 		 * fail in a mysterious way if the delayed event is handled as
 		 * soon as possible like it is done in
 		 * drm_helper_probe_single_connector_modes() in case the poll
 		 * was enabled before.
 		 */
 		poll = true;
 		delay = HZ;
 	}

 	if (poll)
 		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);

 /**
  * drm_helper_probe_single_connector_modes - get complete set of display modes
  * @connector: connector to probe
  * @maxX: max width for modes
  * @maxY: max height for modes
  *
  * Based on the helper callbacks implemented by @connector in struct
  * &drm_connector_helper_funcs try to detect all valid modes.  Modes will first
  * be added to the connector's probed_modes list, then culled (based on validity
  * and the @maxX, @maxY parameters) and put into the normal modes list.
  *
  * Intended to be used as a generic implementation of the ->fill_modes()
  * @connector vfunc for drivers that use the CRTC helpers for output mode
  * filtering and detection.
  *
  * The basic procedure is as follows
  *
  * 1. All modes currently on the connector's modes list are marked as stale
  *
  * 2. New modes are added to the connector's probed_modes list with
  *    drm_mode_probed_add(). New modes start their life with status as OK.
  *    Modes are added from a single source using the following priority order.
  *
  *    - debugfs 'override_edid' (used for testing only)
  *    - firmware EDID (drm_load_edid_firmware())
  *    - connector helper ->get_modes() vfunc
  *    - if the connector status is connector_status_connected, standard
  *      VESA DMT modes up to 1024x768 are automatically added
  *      (drm_add_modes_noedid())
  *
  *    Finally modes specified via the kernel command line (video=...) are
  *    added in addition to what the earlier probes produced
  *    (drm_helper_probe_add_cmdline_mode()). These modes are generated
  *    using the VESA GTF/CVT formulas.
  *
  * 3. Modes are moved from the probed_modes list to the modes list. Potential
  *    duplicates are merged together (see drm_mode_connector_list_update()).
  *    After this step the probed_modes list will be empty again.
  *
  * 4. Any non-stale mode on the modes list then undergoes validation
  *
  *    - drm_mode_validate_basic() performs basic sanity checks
  *    - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
  *      (if specified)
  *    - drm_mode_validate_flag() checks the modes againt basic connector
  *      capabilites (interlace_allowed,doublescan_allowed,stereo_allowed)
  *    - the optional connector ->mode_valid() helper can perform driver and/or
  *      hardware specific checks
  *
  * 5. Any mode whose status is not OK is pruned from the connector's modes list,
  *    accompanied by a debug message indicating the reason for the mode's
  *    rejection (see drm_mode_prune_invalid()).
  *
  * Returns:
  * The number of modes found on @connector.
  */
 int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 					    uint32_t maxX, uint32_t maxY)
 {
 	struct drm_device *dev = connector->dev;
 	struct drm_display_mode *mode;
 	const struct drm_connector_helper_funcs *connector_funcs =
 		connector->helper_private;
 	int count = 0;
 	int mode_flags = 0;
 	bool verbose_prune = true;
 	enum drm_connector_status old_status;

 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
 			connector->name);
 	/* set all old modes to the stale state */
 	list_for_each_entry(mode, &connector->modes, head)
 		mode->status = MODE_STALE;

 	old_status = connector->status;

 	if (connector->force) {
 		if (connector->force == DRM_FORCE_ON ||
 		    connector->force == DRM_FORCE_ON_DIGITAL)
 			connector->status = connector_status_connected;
 		else
 			connector->status = connector_status_disconnected;
 		if (connector->funcs->force)
 			connector->funcs->force(connector);
 	} else {
 		connector->status = connector->funcs->detect(connector, true);
 	}

 	/*
 	 * Normally either the driver's hpd code or the poll loop should
 	 * pick up any changes and fire the hotplug event. But if
 	 * userspace sneaks in a probe, we might miss a change. Hence
 	 * check here, and if anything changed start the hotplug code.
 	 */
 	if (old_status != connector->status) {
 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
 			      connector->base.id,
 			      connector->name,
 			      drm_get_connector_status_name(old_status),
 			      drm_get_connector_status_name(connector->status));

 		/*
 		 * The hotplug event code might call into the fb
 		 * helpers, and so expects that we do not hold any
 		 * locks. Fire up the poll struct instead, it will
 		 * disable itself again.
 		 */
 		dev->mode_config.delayed_event = true;
 		if (dev->mode_config.poll_enabled)
 			schedule_delayed_work(&dev->mode_config.output_poll_work,
 					      0);
 	}

 	/* Re-enable polling in case the global poll config changed. */
 	if (drm_kms_helper_poll != dev->mode_config.poll_running)
 		drm_kms_helper_poll_enable_locked(dev);

 	dev->mode_config.poll_running = drm_kms_helper_poll;

 	if (connector->status == connector_status_disconnected) {
 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
 			connector->base.id, connector->name);
 		drm_mode_connector_update_edid_property(connector, NULL);
 		verbose_prune = false;
 		goto prune;
 	}

 	if (connector->override_edid) {
 		struct edid *edid = (struct edid *) connector->edid_blob_ptr->data;

 		count = drm_add_edid_modes(connector, edid);
 		drm_edid_to_eld(connector, edid);
 	} else {
 		count = drm_load_edid_firmware(connector);
 		if (count == 0)
 			count = (*connector_funcs->get_modes)(connector);
 	}

 	if (count == 0 && connector->status == connector_status_connected)
 		count = drm_add_modes_noedid(connector, 1024, 768);
 	count += drm_helper_probe_add_cmdline_mode(connector);
 	if (count == 0)
 		goto prune;

 	drm_mode_connector_list_update(connector);

 	if (connector->interlace_allowed)
 		mode_flags |= DRM_MODE_FLAG_INTERLACE;
 	if (connector->doublescan_allowed)
 		mode_flags |= DRM_MODE_FLAG_DBLSCAN;
 	if (connector->stereo_allowed)
 		mode_flags |= DRM_MODE_FLAG_3D_MASK;

 	list_for_each_entry(mode, &connector->modes, head) {
 		if (mode->status == MODE_OK)
 			mode->status = drm_mode_validate_basic(mode);

 		if (mode->status == MODE_OK)
 			mode->status = drm_mode_validate_size(mode, maxX, maxY);

 		if (mode->status == MODE_OK)
 			mode->status = drm_mode_validate_flag(mode, mode_flags);

 		if (mode->status == MODE_OK && connector_funcs->mode_valid)
 			mode->status = connector_funcs->mode_valid(connector,
 								   mode);
 	}

 prune:
 	drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);

 	if (list_empty(&connector->modes))
 		return 0;

 	list_for_each_entry(mode, &connector->modes, head)
 		mode->vrefresh = drm_mode_vrefresh(mode);

 	drm_mode_sort(&connector->modes);

 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] probed modes :\n", connector->base.id,
 			connector->name);
 	list_for_each_entry(mode, &connector->modes, head) {
 		drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
 		drm_mode_debug_printmodeline(mode);
 	}

 	return count;
 }
 EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);

 /**
  * drm_kms_helper_hotplug_event - fire off KMS hotplug events
  * @dev: drm_device whose connector state changed
  *
  * This function fires off the uevent for userspace and also calls the
  * output_poll_changed function, which is most commonly used to inform the fbdev
  * emulation code and allow it to update the fbcon output configuration.
  *
  * Drivers should call this from their hotplug handling code when a change is
  * detected. Note that this function does not do any output detection of its
  * own, like drm_helper_hpd_irq_event() does - this is assumed to be done by the
  * driver already.
  *
  * This function must be called from process context with no mode
  * setting locks held.
  */
 void drm_kms_helper_hotplug_event(struct drm_device *dev)
 {
 	/* send a uevent + call fbdev */
 	drm_sysfs_hotplug_event(dev);
 	if (dev->mode_config.funcs->output_poll_changed)
 		dev->mode_config.funcs->output_poll_changed(dev);
 }
 EXPORT_SYMBOL(drm_kms_helper_hotplug_event);

 static void output_poll_execute(struct work_struct *work)
 {
 	struct delayed_work *delayed_work = to_delayed_work(work);
 	struct drm_device *dev = container_of(delayed_work, struct drm_device, mode_config.output_poll_work);
 	struct drm_connector *connector;
 	enum drm_connector_status old_status;
 	bool repoll = false, changed;

 	/* Pick up any changes detected by the probe functions. */
 	changed = dev->mode_config.delayed_event;
 	dev->mode_config.delayed_event = false;

 	if (!drm_kms_helper_poll)
 		goto out;

 	mutex_lock(&dev->mode_config.mutex);
 	drm_for_each_connector(connector, dev) {

 		/* Ignore forced connectors. */
 		if (connector->force)
 			continue;

 		/* Ignore HPD capable connectors and connectors where we don't
 		 * want any hotplug detection at all for polling. */
 		if (!connector->polled || connector->polled == DRM_CONNECTOR_POLL_HPD)
 			continue;

 		old_status = connector->status;
 		/* if we are connected and don't want to poll for disconnect
 		   skip it */
 		if (old_status == connector_status_connected &&
 		    !(connector->polled & DRM_CONNECTOR_POLL_DISCONNECT))
 			continue;

 		repoll = true;

 		connector->status = connector->funcs->detect(connector, false);
 		if (old_status != connector->status) {
 			const char *old, *new;

 			/*
 			 * The poll work sets force=false when calling detect so
 			 * that drivers can avoid to do disruptive tests (e.g.
 			 * when load detect cycles could cause flickering on
 			 * other, running displays). This bears the risk that we
 			 * flip-flop between unknown here in the poll work and
 			 * the real state when userspace forces a full detect
 			 * call after receiving a hotplug event due to this
 			 * change.
 			 *
 			 * Hence clamp an unknown detect status to the old
 			 * value.
 			 */
 			if (connector->status == connector_status_unknown) {
 				connector->status = old_status;
 				continue;
 			}

 			old = drm_get_connector_status_name(old_status);
 			new = drm_get_connector_status_name(connector->status);

 			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] "
 				      "status updated from %s to %s\n",
 				      connector->base.id,
 				      connector->name,
 				      old, new);

 			changed = true;
 		}
 	}

 	mutex_unlock(&dev->mode_config.mutex);

 out:
 	if (changed)
 		drm_kms_helper_hotplug_event(dev);

 	if (repoll)
 		schedule_delayed_work(delayed_work, DRM_OUTPUT_POLL_PERIOD);
 }

 /**
  * drm_kms_helper_is_poll_worker - is %current task an output poll worker?
  *
  * Determine if %current task is an output poll worker.  This can be used
  * to select distinct code paths for output polling versus other contexts.
  *
  * One use case is to avoid a deadlock between the output poll worker and
  * the autosuspend worker wherein the latter waits for polling to finish
  * upon calling drm_kms_helper_poll_disable(), while the former waits for
  * runtime suspend to finish upon calling pm_runtime_get_sync() in a
  * connector ->detect hook.
  */
 bool drm_kms_helper_is_poll_worker(void)
 {
 	struct work_struct *work = current_work();

 	return work && work->func == output_poll_execute;
 }
 EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);

 /**
  * drm_kms_helper_poll_disable - disable output polling
  * @dev: drm_device
  *
  * This function disables the output polling work.
  *
  * Drivers can call this helper from their device suspend implementation. It is
  * not an error to call this even when output polling isn't enabled or arlready
  * disabled.
  */
 void drm_kms_helper_poll_disable(struct drm_device *dev)
 {
 	if (!dev->mode_config.poll_enabled)
 		return;
 	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_disable);

 /**
  * drm_kms_helper_poll_enable - re-enable output polling.
  * @dev: drm_device
  *
  * This function re-enables the output polling work.
  *
  * Drivers can call this helper from their device resume implementation. It is
  * an error to call this when the output polling support has not yet been set
  * up.
  */
 void drm_kms_helper_poll_enable(struct drm_device *dev)
 {
 	mutex_lock(&dev->mode_config.mutex);
 	drm_kms_helper_poll_enable_locked(dev);
 	mutex_unlock(&dev->mode_config.mutex);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_enable);

 /**
  * drm_kms_helper_poll_init - initialize and enable output polling
  * @dev: drm_device
  *
  * This function intializes and then also enables output polling support for
  * @dev. Drivers which do not have reliable hotplug support in hardware can use
  * this helper infrastructure to regularly poll such connectors for changes in
  * their connection state.
  *
  * Drivers can control which connectors are polled by setting the
  * DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On
  * connectors where probing live outputs can result in visual distortion drivers
  * should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this.
  * Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are
  * completely ignored by the polling logic.
  *
  * Note that a connector can be both polled and probed from the hotplug handler,
  * in case the hotplug interrupt is known to be unreliable.
  */
 void drm_kms_helper_poll_init(struct drm_device *dev)
 {
 	INIT_DELAYED_WORK(&dev->mode_config.output_poll_work, output_poll_execute);
 	dev->mode_config.poll_enabled = true;

 	drm_kms_helper_poll_enable(dev);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_init);

 /**
  * drm_kms_helper_poll_fini - disable output polling and clean it up
  * @dev: drm_device
  */
 void drm_kms_helper_poll_fini(struct drm_device *dev)
 {
 	drm_kms_helper_poll_disable(dev);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_fini);

 /**
  * drm_helper_hpd_irq_event - hotplug processing
  * @dev: drm_device
  *
  * Drivers can use this helper function to run a detect cycle on all connectors
  * which have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All
  * other connectors are ignored, which is useful to avoid reprobing fixed
  * panels.
  *
  * This helper function is useful for drivers which can't or don't track hotplug
  * interrupts for each connector.
  *
  * Drivers which support hotplug interrupts for each connector individually and
  * which have a more fine-grained detect logic should bypass this code and
  * directly call drm_kms_helper_hotplug_event() in case the connector state
  * changed.
  *
  * This function must be called from process context with no mode
  * setting locks held.
  *
  * Note that a connector can be both polled and probed from the hotplug handler,
  * in case the hotplug interrupt is known to be unreliable.
  */
 bool drm_helper_hpd_irq_event(struct drm_device *dev)
 {
 	struct drm_connector *connector;
 	enum drm_connector_status old_status;
 	bool changed = false;

 	if (!dev->mode_config.poll_enabled)
 		return false;

 	mutex_lock(&dev->mode_config.mutex);
 	drm_for_each_connector(connector, dev) {

 		/* Only handle HPD capable connectors. */
 		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
 			continue;

 		old_status = connector->status;

 		connector->status = connector->funcs->detect(connector, false);
 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
 			      connector->base.id,
 			      connector->name,
 			      drm_get_connector_status_name(old_status),
 			      drm_get_connector_status_name(connector->status));
 		if (old_status != connector->status)
 			changed = true;
 	}

 	mutex_unlock(&dev->mode_config.mutex);

 	if (changed)
 		drm_kms_helper_hotplug_event(dev);

 	return changed;
 }
 EXPORT_SYMBOL(drm_helper_hpd_irq_event);
	/*
	* 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/export.h>
	#include <linux/moduleparam.h>

	#include <drm/drmP.h>
	#include <drm/drm_crtc.h>
	#include <drm/drm_fourcc.h>
	#include <drm/drm_crtc_helper.h>
	#include <drm/drm_fb_helper.h>
	#include <drm/drm_edid.h>

	/**
	* DOC: output probing helper overview
	*
	* This library provides some helper code for output probing. It provides an
	* implementation of the core connector->fill_modes interface with
	* drm_helper_probe_single_connector_modes.
	*
	* It also provides support for polling connectors with a work item and for
	* generic hotplug interrupt handling where the driver doesn't or cannot keep
	* track of a per-connector hpd interrupt.
	*
	* This helper library can be used independently of the modeset helper library.
	* Drivers can also overwrite different parts e.g. use their own hotplug
	* handling code to avoid probing unrelated outputs.
	*
	* The probe helpers share the function table structures with other display
	* helper libraries. See struct &drm_connector_helper_funcs for the details.
	*/

	static bool drm_kms_helper_poll = true;
	module_param_named(poll, drm_kms_helper_poll, bool, 0600);

	static enum drm_mode_status
	drm_mode_validate_flag(const struct drm_display_mode *mode,
	int flags)
	{
	if ((mode->flags & DRM_MODE_FLAG_INTERLACE) &&
	!(flags & DRM_MODE_FLAG_INTERLACE))
	return MODE_NO_INTERLACE;

	if ((mode->flags & DRM_MODE_FLAG_DBLSCAN) &&
	!(flags & DRM_MODE_FLAG_DBLSCAN))
	return MODE_NO_DBLESCAN;

	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) &&
	!(flags & DRM_MODE_FLAG_3D_MASK))
	return MODE_NO_STEREO;

	return MODE_OK;
	}

	static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
	{
	struct drm_cmdline_mode *cmdline_mode;
	struct drm_display_mode *mode;

	cmdline_mode = &connector->cmdline_mode;
	if (!cmdline_mode->specified)
	return 0;

	/* Only add a GTF mode if we find no matching probed modes */
	list_for_each_entry(mode, &connector->probed_modes, head) {
	if (mode->hdisplay != cmdline_mode->xres \|\|
	mode->vdisplay != cmdline_mode->yres)
	continue;

	if (cmdline_mode->refresh_specified) {
	/* The probed mode's vrefresh is set until later */
	if (drm_mode_vrefresh(mode) != cmdline_mode->refresh)
	continue;
	}

	return 0;
	}

	mode = drm_mode_create_from_cmdline_mode(connector->dev,
	cmdline_mode);
	if (mode == NULL)
	return 0;

	drm_mode_probed_add(connector, mode);
	return 1;
	}

	#define DRM_OUTPUT_POLL_PERIOD (10*HZ)
	/**
	* drm_kms_helper_poll_enable_locked - re-enable output polling.
	* @dev: drm_device
	*
	* This function re-enables the output polling work without
	* locking the mode_config mutex.
	*
	* This is like drm_kms_helper_poll_enable() however it is to be
	* called from a context where the mode_config mutex is locked
	* already.
	*/
	void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
	{
	bool poll = false;
	struct drm_connector *connector;
	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;

	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

	if (!dev->mode_config.poll_enabled \|\| !drm_kms_helper_poll)
	return;

	drm_for_each_connector(connector, dev) {
	if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT \|
	DRM_CONNECTOR_POLL_DISCONNECT))
	poll = true;
	}

	if (dev->mode_config.delayed_event) {
	/*
	* FIXME:
	*
	* Use short (1s) delay to handle the initial delayed event.
	* This delay should not be needed, but Optimus/nouveau will
	* fail in a mysterious way if the delayed event is handled as
	* soon as possible like it is done in
	* drm_helper_probe_single_connector_modes() in case the poll
	* was enabled before.
	*/
	poll = true;
	delay = HZ;
	}

	if (poll)
	schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
	}
	EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);

	/**
	* drm_helper_probe_single_connector_modes - get complete set of display modes
	* @connector: connector to probe
	* @maxX: max width for modes
	* @maxY: max height for modes
	*
	* Based on the helper callbacks implemented by @connector in struct
	* &drm_connector_helper_funcs try to detect all valid modes. Modes will first
	* be added to the connector's probed_modes list, then culled (based on validity
	* and the @maxX, @maxY parameters) and put into the normal modes list.
	*
	* Intended to be used as a generic implementation of the ->fill_modes()
	* @connector vfunc for drivers that use the CRTC helpers for output mode
	* filtering and detection.
	*
	* The basic procedure is as follows
	*
	* 1. All modes currently on the connector's modes list are marked as stale
	*
	* 2. New modes are added to the connector's probed_modes list with
	* drm_mode_probed_add(). New modes start their life with status as OK.
	* Modes are added from a single source using the following priority order.
	*
	* - debugfs 'override_edid' (used for testing only)
	* - firmware EDID (drm_load_edid_firmware())
	* - connector helper ->get_modes() vfunc
	* - if the connector status is connector_status_connected, standard
	* VESA DMT modes up to 1024x768 are automatically added
	* (drm_add_modes_noedid())
	*
	* Finally modes specified via the kernel command line (video=...) are
	* added in addition to what the earlier probes produced
	* (drm_helper_probe_add_cmdline_mode()). These modes are generated
	* using the VESA GTF/CVT formulas.
	*
	* 3. Modes are moved from the probed_modes list to the modes list. Potential
	* duplicates are merged together (see drm_mode_connector_list_update()).
	* After this step the probed_modes list will be empty again.
	*
	* 4. Any non-stale mode on the modes list then undergoes validation
	*
	* - drm_mode_validate_basic() performs basic sanity checks
	* - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
	* (if specified)
	* - drm_mode_validate_flag() checks the modes againt basic connector
	* capabilites (interlace_allowed,doublescan_allowed,stereo_allowed)
	* - the optional connector ->mode_valid() helper can perform driver and/or
	* hardware specific checks
	*
	* 5. Any mode whose status is not OK is pruned from the connector's modes list,
	* accompanied by a debug message indicating the reason for the mode's
	* rejection (see drm_mode_prune_invalid()).
	*
	* Returns:
	* The number of modes found on @connector.
	*/
	int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
	uint32_t maxX, uint32_t maxY)
	{
	struct drm_device *dev = connector->dev;
	struct drm_display_mode *mode;
	const struct drm_connector_helper_funcs *connector_funcs =
	connector->helper_private;
	int count = 0;
	int mode_flags = 0;
	bool verbose_prune = true;
	enum drm_connector_status old_status;

	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
	connector->name);
	/* set all old modes to the stale state */
	list_for_each_entry(mode, &connector->modes, head)
	mode->status = MODE_STALE;

	old_status = connector->status;

	if (connector->force) {
	if (connector->force == DRM_FORCE_ON \|\|
	connector->force == DRM_FORCE_ON_DIGITAL)
	connector->status = connector_status_connected;
	else
	connector->status = connector_status_disconnected;
	if (connector->funcs->force)
	connector->funcs->force(connector);
	} else {
	connector->status = connector->funcs->detect(connector, true);
	}

	/*
	* Normally either the driver's hpd code or the poll loop should
	* pick up any changes and fire the hotplug event. But if
	* userspace sneaks in a probe, we might miss a change. Hence
	* check here, and if anything changed start the hotplug code.
	*/
	if (old_status != connector->status) {
	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
	connector->base.id,
	connector->name,
	drm_get_connector_status_name(old_status),
	drm_get_connector_status_name(connector->status));

	/*
	* The hotplug event code might call into the fb
	* helpers, and so expects that we do not hold any
	* locks. Fire up the poll struct instead, it will
	* disable itself again.
	*/
	dev->mode_config.delayed_event = true;
	if (dev->mode_config.poll_enabled)
	schedule_delayed_work(&dev->mode_config.output_poll_work,
	0);
	}

	/* Re-enable polling in case the global poll config changed. */
	if (drm_kms_helper_poll != dev->mode_config.poll_running)
	drm_kms_helper_poll_enable_locked(dev);

	dev->mode_config.poll_running = drm_kms_helper_poll;

	if (connector->status == connector_status_disconnected) {
	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
	connector->base.id, connector->name);
	drm_mode_connector_update_edid_property(connector, NULL);
	verbose_prune = false;
	goto prune;
	}

	if (connector->override_edid) {
	struct edid edid = (struct edid ) connector->edid_blob_ptr->data;

	count = drm_add_edid_modes(connector, edid);
	drm_edid_to_eld(connector, edid);
	} else {
	count = drm_load_edid_firmware(connector);
	if (count == 0)
	count = (*connector_funcs->get_modes)(connector);
	}

	if (count == 0 && connector->status == connector_status_connected)
	count = drm_add_modes_noedid(connector, 1024, 768);
	count += drm_helper_probe_add_cmdline_mode(connector);
	if (count == 0)
	goto prune;

	drm_mode_connector_list_update(connector);

	if (connector->interlace_allowed)
	mode_flags \|= DRM_MODE_FLAG_INTERLACE;
	if (connector->doublescan_allowed)
	mode_flags \|= DRM_MODE_FLAG_DBLSCAN;
	if (connector->stereo_allowed)
	mode_flags \|= DRM_MODE_FLAG_3D_MASK;

	list_for_each_entry(mode, &connector->modes, head) {
	if (mode->status == MODE_OK)
	mode->status = drm_mode_validate_basic(mode);

	if (mode->status == MODE_OK)
	mode->status = drm_mode_validate_size(mode, maxX, maxY);

	if (mode->status == MODE_OK)
	mode->status = drm_mode_validate_flag(mode, mode_flags);

	if (mode->status == MODE_OK && connector_funcs->mode_valid)
	mode->status = connector_funcs->mode_valid(connector,
	mode);
	}

	prune:
	drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);

	if (list_empty(&connector->modes))
	return 0;

	list_for_each_entry(mode, &connector->modes, head)
	mode->vrefresh = drm_mode_vrefresh(mode);

	drm_mode_sort(&connector->modes);

	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] probed modes :\n", connector->base.id,
	connector->name);
	list_for_each_entry(mode, &connector->modes, head) {
	drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
	drm_mode_debug_printmodeline(mode);
	}

	return count;
	}
	EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);

	/**
	* drm_kms_helper_hotplug_event - fire off KMS hotplug events
	* @dev: drm_device whose connector state changed
	*
	* This function fires off the uevent for userspace and also calls the
	* output_poll_changed function, which is most commonly used to inform the fbdev
	* emulation code and allow it to update the fbcon output configuration.
	*
	* Drivers should call this from their hotplug handling code when a change is
	* detected. Note that this function does not do any output detection of its
	* own, like drm_helper_hpd_irq_event() does - this is assumed to be done by the
	* driver already.
	*
	* This function must be called from process context with no mode
	* setting locks held.
	*/
	void drm_kms_helper_hotplug_event(struct drm_device *dev)
	{
	/* send a uevent + call fbdev */
	drm_sysfs_hotplug_event(dev);
	if (dev->mode_config.funcs->output_poll_changed)
	dev->mode_config.funcs->output_poll_changed(dev);
	}
	EXPORT_SYMBOL(drm_kms_helper_hotplug_event);

	static void output_poll_execute(struct work_struct *work)
	{
	struct delayed_work *delayed_work = to_delayed_work(work);
	struct drm_device *dev = container_of(delayed_work, struct drm_device, mode_config.output_poll_work);
	struct drm_connector *connector;
	enum drm_connector_status old_status;
	bool repoll = false, changed;

	/* Pick up any changes detected by the probe functions. */
	changed = dev->mode_config.delayed_event;
	dev->mode_config.delayed_event = false;

	if (!drm_kms_helper_poll)
	goto out;

	mutex_lock(&dev->mode_config.mutex);
	drm_for_each_connector(connector, dev) {

	/* Ignore forced connectors. */
	if (connector->force)
	continue;

	/* Ignore HPD capable connectors and connectors where we don't
	* want any hotplug detection at all for polling. */
	if (!connector->polled \|\| connector->polled == DRM_CONNECTOR_POLL_HPD)
	continue;

	old_status = connector->status;
	/* if we are connected and don't want to poll for disconnect
	skip it */
	if (old_status == connector_status_connected &&
	!(connector->polled & DRM_CONNECTOR_POLL_DISCONNECT))
	continue;

	repoll = true;

	connector->status = connector->funcs->detect(connector, false);
	if (old_status != connector->status) {
	const char old, new;

	/*
	* The poll work sets force=false when calling detect so
	* that drivers can avoid to do disruptive tests (e.g.
	* when load detect cycles could cause flickering on
	* other, running displays). This bears the risk that we
	* flip-flop between unknown here in the poll work and
	* the real state when userspace forces a full detect
	* call after receiving a hotplug event due to this
	* change.
	*
	* Hence clamp an unknown detect status to the old
	* value.
	*/
	if (connector->status == connector_status_unknown) {
	connector->status = old_status;
	continue;
	}

	old = drm_get_connector_status_name(old_status);
	new = drm_get_connector_status_name(connector->status);

	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] "
	"status updated from %s to %s\n",
	connector->base.id,
	connector->name,
	old, new);

	changed = true;
	}
	}

	mutex_unlock(&dev->mode_config.mutex);

	out:
	if (changed)
	drm_kms_helper_hotplug_event(dev);

	if (repoll)
	schedule_delayed_work(delayed_work, DRM_OUTPUT_POLL_PERIOD);
	}

	/**
	* drm_kms_helper_is_poll_worker - is %current task an output poll worker?
	*
	* Determine if %current task is an output poll worker. This can be used
	* to select distinct code paths for output polling versus other contexts.
	*
	* One use case is to avoid a deadlock between the output poll worker and
	* the autosuspend worker wherein the latter waits for polling to finish
	* upon calling drm_kms_helper_poll_disable(), while the former waits for
	* runtime suspend to finish upon calling pm_runtime_get_sync() in a
	* connector ->detect hook.
	*/
	bool drm_kms_helper_is_poll_worker(void)
	{
	struct work_struct *work = current_work();

	return work && work->func == output_poll_execute;
	}
	EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);

	/**
	* drm_kms_helper_poll_disable - disable output polling
	* @dev: drm_device
	*
	* This function disables the output polling work.
	*
	* Drivers can call this helper from their device suspend implementation. It is
	* not an error to call this even when output polling isn't enabled or arlready
	* disabled.
	*/
	void drm_kms_helper_poll_disable(struct drm_device *dev)
	{
	if (!dev->mode_config.poll_enabled)
	return;
	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
	}
	EXPORT_SYMBOL(drm_kms_helper_poll_disable);

	/**
	* drm_kms_helper_poll_enable - re-enable output polling.
	* @dev: drm_device
	*
	* This function re-enables the output polling work.
	*
	* Drivers can call this helper from their device resume implementation. It is
	* an error to call this when the output polling support has not yet been set
	* up.
	*/
	void drm_kms_helper_poll_enable(struct drm_device *dev)
	{
	mutex_lock(&dev->mode_config.mutex);
	drm_kms_helper_poll_enable_locked(dev);
	mutex_unlock(&dev->mode_config.mutex);
	}
	EXPORT_SYMBOL(drm_kms_helper_poll_enable);

	/**
	* drm_kms_helper_poll_init - initialize and enable output polling
	* @dev: drm_device
	*
	* This function intializes and then also enables output polling support for
	* @dev. Drivers which do not have reliable hotplug support in hardware can use
	* this helper infrastructure to regularly poll such connectors for changes in
	* their connection state.
	*
	* Drivers can control which connectors are polled by setting the
	* DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On
	* connectors where probing live outputs can result in visual distortion drivers
	* should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this.
	* Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are
	* completely ignored by the polling logic.
	*
	* Note that a connector can be both polled and probed from the hotplug handler,
	* in case the hotplug interrupt is known to be unreliable.
	*/
	void drm_kms_helper_poll_init(struct drm_device *dev)
	{
	INIT_DELAYED_WORK(&dev->mode_config.output_poll_work, output_poll_execute);
	dev->mode_config.poll_enabled = true;

	drm_kms_helper_poll_enable(dev);
	}
	EXPORT_SYMBOL(drm_kms_helper_poll_init);

	/**
	* drm_kms_helper_poll_fini - disable output polling and clean it up
	* @dev: drm_device
	*/
	void drm_kms_helper_poll_fini(struct drm_device *dev)
	{
	drm_kms_helper_poll_disable(dev);
	}
	EXPORT_SYMBOL(drm_kms_helper_poll_fini);

	/**
	* drm_helper_hpd_irq_event - hotplug processing
	* @dev: drm_device
	*
	* Drivers can use this helper function to run a detect cycle on all connectors
	* which have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All
	* other connectors are ignored, which is useful to avoid reprobing fixed
	* panels.
	*
	* This helper function is useful for drivers which can't or don't track hotplug
	* interrupts for each connector.
	*
	* Drivers which support hotplug interrupts for each connector individually and
	* which have a more fine-grained detect logic should bypass this code and
	* directly call drm_kms_helper_hotplug_event() in case the connector state
	* changed.
	*
	* This function must be called from process context with no mode
	* setting locks held.
	*
	* Note that a connector can be both polled and probed from the hotplug handler,
	* in case the hotplug interrupt is known to be unreliable.
	*/
	bool drm_helper_hpd_irq_event(struct drm_device *dev)
	{
	struct drm_connector *connector;
	enum drm_connector_status old_status;
	bool changed = false;

	if (!dev->mode_config.poll_enabled)
	return false;

	mutex_lock(&dev->mode_config.mutex);
	drm_for_each_connector(connector, dev) {

	/* Only handle HPD capable connectors. */
	if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
	continue;

	old_status = connector->status;

	connector->status = connector->funcs->detect(connector, false);
	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
	connector->base.id,
	connector->name,
	drm_get_connector_status_name(old_status),
	drm_get_connector_status_name(connector->status));
	if (old_status != connector->status)
	changed = true;
	}

	mutex_unlock(&dev->mode_config.mutex);

	if (changed)
	drm_kms_helper_hotplug_event(dev);

	return changed;
	}
	EXPORT_SYMBOL(drm_helper_hpd_irq_event);