drivers/gpu/drm/drm_bridge_connector.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (C) 2019 Laurent Pinchart <laurent.pinchart@ideasonboard.com>
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>

 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_bridge_connector.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_device.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_probe_helper.h>

 /**
  * DOC: overview
  *
  * The DRM bridge connector helper object provides a DRM connector
  * implementation that wraps a chain of &struct drm_bridge. The connector
  * operations are fully implemented based on the operations of the bridges in
  * the chain, and don't require any intervention from the display controller
  * driver at runtime.
  *
  * To use the helper, display controller drivers create a bridge connector with
  * a call to drm_bridge_connector_init(). This associates the newly created
  * connector with the chain of bridges passed to the function and registers it
  * with the DRM device. At that point the connector becomes fully usable, no
  * further operation is needed.
  *
  * The DRM bridge connector operations are implemented based on the operations
  * provided by the bridges in the chain. Each connector operation is delegated
  * to the bridge closest to the connector (at the end of the chain) that
  * provides the relevant functionality.
  *
  * To make use of this helper, all bridges in the chain shall report bridge
  * operation flags (&drm_bridge->ops) and bridge output type
  * (&drm_bridge->type), as well as the DRM_BRIDGE_ATTACH_NO_CONNECTOR attach
  * flag (none of the bridges shall create a DRM connector directly).
  */

 /**
  * struct drm_bridge_connector - A connector backed by a chain of bridges
  */
 struct drm_bridge_connector {
 	/**
 	 * @base: The base DRM connector
 	 */
 	struct drm_connector base;
 	/**
 	 * @encoder:
 	 *
 	 * The encoder at the start of the bridges chain.
 	 */
 	struct drm_encoder *encoder;
 	/**
 	 * @bridge_edid:
 	 *
 	 * The last bridge in the chain (closest to the connector) that provides
 	 * EDID read support, if any (see &DRM_BRIDGE_OP_EDID).
 	 */
 	struct drm_bridge *bridge_edid;
 	/**
 	 * @bridge_hpd:
 	 *
 	 * The last bridge in the chain (closest to the connector) that provides
 	 * hot-plug detection notification, if any (see &DRM_BRIDGE_OP_HPD).
 	 */
 	struct drm_bridge *bridge_hpd;
 	/**
 	 * @bridge_detect:
 	 *
 	 * The last bridge in the chain (closest to the connector) that provides
 	 * connector detection, if any (see &DRM_BRIDGE_OP_DETECT).
 	 */
 	struct drm_bridge *bridge_detect;
 	/**
 	 * @bridge_modes:
 	 *
 	 * The last bridge in the chain (closest to the connector) that provides
 	 * connector modes detection, if any (see &DRM_BRIDGE_OP_MODES).
 	 */
 	struct drm_bridge *bridge_modes;
 };

 #define to_drm_bridge_connector(x) \
 	container_of(x, struct drm_bridge_connector, base)

 /* -----------------------------------------------------------------------------
  * Bridge Connector Hot-Plug Handling
  */

 static void drm_bridge_connector_hpd_notify(struct drm_connector *connector,
 					    enum drm_connector_status status)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 	struct drm_bridge *bridge;

 	/* Notify all bridges in the pipeline of hotplug events. */
 	drm_for_each_bridge_in_chain(bridge_connector->encoder, bridge) {
 		if (bridge->funcs->hpd_notify)
 			bridge->funcs->hpd_notify(bridge, status);
 	}
 }

 static void drm_bridge_connector_hpd_cb(void *cb_data,
 					enum drm_connector_status status)
 {
 	struct drm_bridge_connector *drm_bridge_connector = cb_data;
 	struct drm_connector *connector = &drm_bridge_connector->base;
 	struct drm_device *dev = connector->dev;
 	enum drm_connector_status old_status;

 	mutex_lock(&dev->mode_config.mutex);
 	old_status = connector->status;
 	connector->status = status;
 	mutex_unlock(&dev->mode_config.mutex);

 	if (old_status == status)
 		return;

 	drm_bridge_connector_hpd_notify(connector, status);

 	drm_kms_helper_hotplug_event(dev);
 }

 /**
  * drm_bridge_connector_enable_hpd - Enable hot-plug detection for the connector
  * @connector: The DRM bridge connector
  *
  * This function enables hot-plug detection for the given bridge connector.
  * This is typically used by display drivers in their resume handler.
  */
 void drm_bridge_connector_enable_hpd(struct drm_connector *connector)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 	struct drm_bridge *hpd = bridge_connector->bridge_hpd;

 	if (hpd)
 		drm_bridge_hpd_enable(hpd, drm_bridge_connector_hpd_cb,
 				      bridge_connector);
 }
 EXPORT_SYMBOL_GPL(drm_bridge_connector_enable_hpd);

 /**
  * drm_bridge_connector_disable_hpd - Disable hot-plug detection for the
  * connector
  * @connector: The DRM bridge connector
  *
  * This function disables hot-plug detection for the given bridge connector.
  * This is typically used by display drivers in their suspend handler.
  */
 void drm_bridge_connector_disable_hpd(struct drm_connector *connector)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 	struct drm_bridge *hpd = bridge_connector->bridge_hpd;

 	if (hpd)
 		drm_bridge_hpd_disable(hpd);
 }
 EXPORT_SYMBOL_GPL(drm_bridge_connector_disable_hpd);

 /* -----------------------------------------------------------------------------
  * Bridge Connector Functions
  */

 static enum drm_connector_status
 drm_bridge_connector_detect(struct drm_connector *connector, bool force)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 	struct drm_bridge *detect = bridge_connector->bridge_detect;
 	enum drm_connector_status status;

 	if (detect) {
 		status = detect->funcs->detect(detect);

 		drm_bridge_connector_hpd_notify(connector, status);
 	} else {
 		switch (connector->connector_type) {
 		case DRM_MODE_CONNECTOR_DPI:
 		case DRM_MODE_CONNECTOR_LVDS:
 		case DRM_MODE_CONNECTOR_DSI:
 		case DRM_MODE_CONNECTOR_eDP:
 			status = connector_status_connected;
 			break;
 		default:
 			status = connector_status_unknown;
 			break;
 		}
 	}

 	return status;
 }

 static void drm_bridge_connector_destroy(struct drm_connector *connector)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);

 	if (bridge_connector->bridge_hpd) {
 		struct drm_bridge *hpd = bridge_connector->bridge_hpd;

 		drm_bridge_hpd_disable(hpd);
 	}

 	drm_connector_unregister(connector);
 	drm_connector_cleanup(connector);

 	kfree(bridge_connector);
 }

 static void drm_bridge_connector_debugfs_init(struct drm_connector *connector,
 					      struct dentry *root)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 	struct drm_encoder *encoder = bridge_connector->encoder;
 	struct drm_bridge *bridge;

 	list_for_each_entry(bridge, &encoder->bridge_chain, chain_node) {
 		if (bridge->funcs->debugfs_init)
 			bridge->funcs->debugfs_init(bridge, root);
 	}
 }

 static const struct drm_connector_funcs drm_bridge_connector_funcs = {
 	.reset = drm_atomic_helper_connector_reset,
 	.detect = drm_bridge_connector_detect,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.destroy = drm_bridge_connector_destroy,
 	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 	.debugfs_init = drm_bridge_connector_debugfs_init,
 };

 /* -----------------------------------------------------------------------------
  * Bridge Connector Helper Functions
  */

 static int drm_bridge_connector_get_modes_edid(struct drm_connector *connector,
 					       struct drm_bridge *bridge)
 {
 	enum drm_connector_status status;
 	struct edid *edid;
 	int n;

 	status = drm_bridge_connector_detect(connector, false);
 	if (status != connector_status_connected)
 		goto no_edid;

 	edid = bridge->funcs->get_edid(bridge, connector);
 	if (!drm_edid_is_valid(edid)) {
 		kfree(edid);
 		goto no_edid;
 	}

 	drm_connector_update_edid_property(connector, edid);
 	n = drm_add_edid_modes(connector, edid);

 	kfree(edid);
 	return n;

 no_edid:
 	drm_connector_update_edid_property(connector, NULL);
 	return 0;
 }

 static int drm_bridge_connector_get_modes(struct drm_connector *connector)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 	struct drm_bridge *bridge;

 	/*
 	 * If display exposes EDID, then we parse that in the normal way to
 	 * build table of supported modes.
 	 */
 	bridge = bridge_connector->bridge_edid;
 	if (bridge)
 		return drm_bridge_connector_get_modes_edid(connector, bridge);

 	/*
 	 * Otherwise if the display pipeline reports modes (e.g. with a fixed
 	 * resolution panel or an analog TV output), query it.
 	 */
 	bridge = bridge_connector->bridge_modes;
 	if (bridge)
 		return bridge->funcs->get_modes(bridge, connector);

 	/*
 	 * We can't retrieve modes, which can happen for instance for a DVI or
 	 * VGA output with the DDC bus unconnected. The KMS core will add the
 	 * default modes.
 	 */
 	return 0;
 }

 static const struct drm_connector_helper_funcs drm_bridge_connector_helper_funcs = {
 	.get_modes = drm_bridge_connector_get_modes,
 	/* No need for .mode_valid(), the bridges are checked by the core. */
 };

 /* -----------------------------------------------------------------------------
  * Bridge Connector Initialisation
  */

 /**
  * drm_bridge_connector_init - Initialise a connector for a chain of bridges
  * @drm: the DRM device
  * @encoder: the encoder where the bridge chain starts
  *
  * Allocate, initialise and register a &drm_bridge_connector with the @drm
  * device. The connector is associated with a chain of bridges that starts at
  * the @encoder. All bridges in the chain shall report bridge operation flags
  * (&drm_bridge->ops) and bridge output type (&drm_bridge->type), and none of
  * them may create a DRM connector directly.
  *
  * Returns a pointer to the new connector on success, or a negative error
  * pointer otherwise.
  */
 struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 						struct drm_encoder *encoder)
 {
 	struct drm_bridge_connector *bridge_connector;
 	struct drm_connector *connector;
 	struct i2c_adapter *ddc = NULL;
 	struct drm_bridge *bridge, *panel_bridge = NULL;
 	int connector_type;

 	bridge_connector = kzalloc(sizeof(*bridge_connector), GFP_KERNEL);
 	if (!bridge_connector)
 		return ERR_PTR(-ENOMEM);

 	bridge_connector->encoder = encoder;

 	/*
 	 * TODO: Handle doublescan_allowed, stereo_allowed and
 	 * ycbcr_420_allowed.
 	 */
 	connector = &bridge_connector->base;
 	connector->interlace_allowed = true;

 	/*
 	 * Initialise connector status handling. First locate the furthest
 	 * bridges in the pipeline that support HPD and output detection. Then
 	 * initialise the connector polling mode, using HPD if available and
 	 * falling back to polling if supported. If neither HPD nor output
 	 * detection are available, we don't support hotplug detection at all.
 	 */
 	connector_type = DRM_MODE_CONNECTOR_Unknown;
 	drm_for_each_bridge_in_chain(encoder, bridge) {
 		if (!bridge->interlace_allowed)
 			connector->interlace_allowed = false;

 		if (bridge->ops & DRM_BRIDGE_OP_EDID)
 			bridge_connector->bridge_edid = bridge;
 		if (bridge->ops & DRM_BRIDGE_OP_HPD)
 			bridge_connector->bridge_hpd = bridge;
 		if (bridge->ops & DRM_BRIDGE_OP_DETECT)
 			bridge_connector->bridge_detect = bridge;
 		if (bridge->ops & DRM_BRIDGE_OP_MODES)
 			bridge_connector->bridge_modes = bridge;

 		if (!drm_bridge_get_next_bridge(bridge))
 			connector_type = bridge->type;

 		if (bridge->ddc)
 			ddc = bridge->ddc;

 		if (drm_bridge_is_panel(bridge))
 			panel_bridge = bridge;
 	}

 	if (connector_type == DRM_MODE_CONNECTOR_Unknown) {
 		kfree(bridge_connector);
 		return ERR_PTR(-EINVAL);
 	}

 	drm_connector_init_with_ddc(drm, connector, &drm_bridge_connector_funcs,
 				    connector_type, ddc);
 	drm_connector_helper_add(connector, &drm_bridge_connector_helper_funcs);

 	if (bridge_connector->bridge_hpd) {
 		connector->polled = DRM_CONNECTOR_POLL_HPD;
 		drm_bridge_connector_enable_hpd(connector);
 	}
 	else if (bridge_connector->bridge_detect)
 		connector->polled = DRM_CONNECTOR_POLL_CONNECT
 				  | DRM_CONNECTOR_POLL_DISCONNECT;

 	if (panel_bridge)
 		drm_panel_bridge_set_orientation(connector, panel_bridge);

 	return connector;
 }
 EXPORT_SYMBOL_GPL(drm_bridge_connector_init);
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (C) 2019 Laurent Pinchart <laurent.pinchart@ideasonboard.com>
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/slab.h>

	#include <drm/drm_atomic_state_helper.h>
	#include <drm/drm_bridge.h>
	#include <drm/drm_bridge_connector.h>
	#include <drm/drm_connector.h>
	#include <drm/drm_device.h>
	#include <drm/drm_edid.h>
	#include <drm/drm_modeset_helper_vtables.h>
	#include <drm/drm_probe_helper.h>

	/**
	* DOC: overview
	*
	* The DRM bridge connector helper object provides a DRM connector
	* implementation that wraps a chain of &struct drm_bridge. The connector
	* operations are fully implemented based on the operations of the bridges in
	* the chain, and don't require any intervention from the display controller
	* driver at runtime.
	*
	* To use the helper, display controller drivers create a bridge connector with
	* a call to drm_bridge_connector_init(). This associates the newly created
	* connector with the chain of bridges passed to the function and registers it
	* with the DRM device. At that point the connector becomes fully usable, no
	* further operation is needed.
	*
	* The DRM bridge connector operations are implemented based on the operations
	* provided by the bridges in the chain. Each connector operation is delegated
	* to the bridge closest to the connector (at the end of the chain) that
	* provides the relevant functionality.
	*
	* To make use of this helper, all bridges in the chain shall report bridge
	* operation flags (&drm_bridge->ops) and bridge output type
	* (&drm_bridge->type), as well as the DRM_BRIDGE_ATTACH_NO_CONNECTOR attach
	* flag (none of the bridges shall create a DRM connector directly).
	*/

	/**
	* struct drm_bridge_connector - A connector backed by a chain of bridges
	*/
	struct drm_bridge_connector {
	/**
	* @base: The base DRM connector
	*/
	struct drm_connector base;
	/**
	* @encoder:
	*
	* The encoder at the start of the bridges chain.
	*/
	struct drm_encoder *encoder;
	/**
	* @bridge_edid:
	*
	* The last bridge in the chain (closest to the connector) that provides
	* EDID read support, if any (see &DRM_BRIDGE_OP_EDID).
	*/
	struct drm_bridge *bridge_edid;
	/**
	* @bridge_hpd:
	*
	* The last bridge in the chain (closest to the connector) that provides
	* hot-plug detection notification, if any (see &DRM_BRIDGE_OP_HPD).
	*/
	struct drm_bridge *bridge_hpd;
	/**
	* @bridge_detect:
	*
	* The last bridge in the chain (closest to the connector) that provides
	* connector detection, if any (see &DRM_BRIDGE_OP_DETECT).
	*/
	struct drm_bridge *bridge_detect;
	/**
	* @bridge_modes:
	*
	* The last bridge in the chain (closest to the connector) that provides
	* connector modes detection, if any (see &DRM_BRIDGE_OP_MODES).
	*/
	struct drm_bridge *bridge_modes;
	};

	#define to_drm_bridge_connector(x) \
	container_of(x, struct drm_bridge_connector, base)

	/* -----------------------------------------------------------------------------
	* Bridge Connector Hot-Plug Handling
	*/

	static void drm_bridge_connector_hpd_notify(struct drm_connector *connector,
	enum drm_connector_status status)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);
	struct drm_bridge *bridge;

	/* Notify all bridges in the pipeline of hotplug events. */
	drm_for_each_bridge_in_chain(bridge_connector->encoder, bridge) {
	if (bridge->funcs->hpd_notify)
	bridge->funcs->hpd_notify(bridge, status);
	}
	}

	static void drm_bridge_connector_hpd_cb(void *cb_data,
	enum drm_connector_status status)
	{
	struct drm_bridge_connector *drm_bridge_connector = cb_data;
	struct drm_connector *connector = &drm_bridge_connector->base;
	struct drm_device *dev = connector->dev;
	enum drm_connector_status old_status;

	mutex_lock(&dev->mode_config.mutex);
	old_status = connector->status;
	connector->status = status;
	mutex_unlock(&dev->mode_config.mutex);

	if (old_status == status)
	return;

	drm_bridge_connector_hpd_notify(connector, status);

	drm_kms_helper_hotplug_event(dev);
	}

	/**
	* drm_bridge_connector_enable_hpd - Enable hot-plug detection for the connector
	* @connector: The DRM bridge connector
	*
	* This function enables hot-plug detection for the given bridge connector.
	* This is typically used by display drivers in their resume handler.
	*/
	void drm_bridge_connector_enable_hpd(struct drm_connector *connector)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);
	struct drm_bridge *hpd = bridge_connector->bridge_hpd;

	if (hpd)
	drm_bridge_hpd_enable(hpd, drm_bridge_connector_hpd_cb,
	bridge_connector);
	}
	EXPORT_SYMBOL_GPL(drm_bridge_connector_enable_hpd);

	/**
	* drm_bridge_connector_disable_hpd - Disable hot-plug detection for the
	* connector
	* @connector: The DRM bridge connector
	*
	* This function disables hot-plug detection for the given bridge connector.
	* This is typically used by display drivers in their suspend handler.
	*/
	void drm_bridge_connector_disable_hpd(struct drm_connector *connector)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);
	struct drm_bridge *hpd = bridge_connector->bridge_hpd;

	if (hpd)
	drm_bridge_hpd_disable(hpd);
	}
	EXPORT_SYMBOL_GPL(drm_bridge_connector_disable_hpd);

	/* -----------------------------------------------------------------------------
	* Bridge Connector Functions
	*/

	static enum drm_connector_status
	drm_bridge_connector_detect(struct drm_connector *connector, bool force)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);
	struct drm_bridge *detect = bridge_connector->bridge_detect;
	enum drm_connector_status status;

	if (detect) {
	status = detect->funcs->detect(detect);

	drm_bridge_connector_hpd_notify(connector, status);
	} else {
	switch (connector->connector_type) {
	case DRM_MODE_CONNECTOR_DPI:
	case DRM_MODE_CONNECTOR_LVDS:
	case DRM_MODE_CONNECTOR_DSI:
	case DRM_MODE_CONNECTOR_eDP:
	status = connector_status_connected;
	break;
	default:
	status = connector_status_unknown;
	break;
	}
	}

	return status;
	}

	static void drm_bridge_connector_destroy(struct drm_connector *connector)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);

	if (bridge_connector->bridge_hpd) {
	struct drm_bridge *hpd = bridge_connector->bridge_hpd;

	drm_bridge_hpd_disable(hpd);
	}

	drm_connector_unregister(connector);
	drm_connector_cleanup(connector);

	kfree(bridge_connector);
	}

	static void drm_bridge_connector_debugfs_init(struct drm_connector *connector,
	struct dentry *root)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);
	struct drm_encoder *encoder = bridge_connector->encoder;
	struct drm_bridge *bridge;

	list_for_each_entry(bridge, &encoder->bridge_chain, chain_node) {
	if (bridge->funcs->debugfs_init)
	bridge->funcs->debugfs_init(bridge, root);
	}
	}

	static const struct drm_connector_funcs drm_bridge_connector_funcs = {
	.reset = drm_atomic_helper_connector_reset,
	.detect = drm_bridge_connector_detect,
	.fill_modes = drm_helper_probe_single_connector_modes,
	.destroy = drm_bridge_connector_destroy,
	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
	.debugfs_init = drm_bridge_connector_debugfs_init,
	};

	/* -----------------------------------------------------------------------------
	* Bridge Connector Helper Functions
	*/

	static int drm_bridge_connector_get_modes_edid(struct drm_connector *connector,
	struct drm_bridge *bridge)
	{
	enum drm_connector_status status;
	struct edid *edid;
	int n;

	status = drm_bridge_connector_detect(connector, false);
	if (status != connector_status_connected)
	goto no_edid;

	edid = bridge->funcs->get_edid(bridge, connector);
	if (!drm_edid_is_valid(edid)) {
	kfree(edid);
	goto no_edid;
	}

	drm_connector_update_edid_property(connector, edid);
	n = drm_add_edid_modes(connector, edid);

	kfree(edid);
	return n;

	no_edid:
	drm_connector_update_edid_property(connector, NULL);
	return 0;
	}

	static int drm_bridge_connector_get_modes(struct drm_connector *connector)
	{
	struct drm_bridge_connector *bridge_connector =
	to_drm_bridge_connector(connector);
	struct drm_bridge *bridge;

	/*
	* If display exposes EDID, then we parse that in the normal way to
	* build table of supported modes.
	*/
	bridge = bridge_connector->bridge_edid;
	if (bridge)
	return drm_bridge_connector_get_modes_edid(connector, bridge);

	/*
	* Otherwise if the display pipeline reports modes (e.g. with a fixed
	* resolution panel or an analog TV output), query it.
	*/
	bridge = bridge_connector->bridge_modes;
	if (bridge)
	return bridge->funcs->get_modes(bridge, connector);

	/*
	* We can't retrieve modes, which can happen for instance for a DVI or
	* VGA output with the DDC bus unconnected. The KMS core will add the
	* default modes.
	*/
	return 0;
	}

	static const struct drm_connector_helper_funcs drm_bridge_connector_helper_funcs = {
	.get_modes = drm_bridge_connector_get_modes,
	/* No need for .mode_valid(), the bridges are checked by the core. */
	};

	/* -----------------------------------------------------------------------------
	* Bridge Connector Initialisation
	*/

	/**
	* drm_bridge_connector_init - Initialise a connector for a chain of bridges
	* @drm: the DRM device
	* @encoder: the encoder where the bridge chain starts
	*
	* Allocate, initialise and register a &drm_bridge_connector with the @drm
	* device. The connector is associated with a chain of bridges that starts at
	* the @encoder. All bridges in the chain shall report bridge operation flags
	* (&drm_bridge->ops) and bridge output type (&drm_bridge->type), and none of
	* them may create a DRM connector directly.
	*
	* Returns a pointer to the new connector on success, or a negative error
	* pointer otherwise.
	*/
	struct drm_connector drm_bridge_connector_init(struct drm_device drm,
	struct drm_encoder *encoder)
	{
	struct drm_bridge_connector *bridge_connector;
	struct drm_connector *connector;
	struct i2c_adapter *ddc = NULL;
	struct drm_bridge bridge, panel_bridge = NULL;
	int connector_type;

	bridge_connector = kzalloc(sizeof(*bridge_connector), GFP_KERNEL);
	if (!bridge_connector)
	return ERR_PTR(-ENOMEM);

	bridge_connector->encoder = encoder;

	/*
	* TODO: Handle doublescan_allowed, stereo_allowed and
	* ycbcr_420_allowed.
	*/
	connector = &bridge_connector->base;
	connector->interlace_allowed = true;

	/*
	* Initialise connector status handling. First locate the furthest
	* bridges in the pipeline that support HPD and output detection. Then
	* initialise the connector polling mode, using HPD if available and
	* falling back to polling if supported. If neither HPD nor output
	* detection are available, we don't support hotplug detection at all.
	*/
	connector_type = DRM_MODE_CONNECTOR_Unknown;
	drm_for_each_bridge_in_chain(encoder, bridge) {
	if (!bridge->interlace_allowed)
	connector->interlace_allowed = false;

	if (bridge->ops & DRM_BRIDGE_OP_EDID)
	bridge_connector->bridge_edid = bridge;
	if (bridge->ops & DRM_BRIDGE_OP_HPD)
	bridge_connector->bridge_hpd = bridge;
	if (bridge->ops & DRM_BRIDGE_OP_DETECT)
	bridge_connector->bridge_detect = bridge;
	if (bridge->ops & DRM_BRIDGE_OP_MODES)
	bridge_connector->bridge_modes = bridge;

	if (!drm_bridge_get_next_bridge(bridge))
	connector_type = bridge->type;

	if (bridge->ddc)
	ddc = bridge->ddc;

	if (drm_bridge_is_panel(bridge))
	panel_bridge = bridge;
	}

	if (connector_type == DRM_MODE_CONNECTOR_Unknown) {
	kfree(bridge_connector);
	return ERR_PTR(-EINVAL);
	}

	drm_connector_init_with_ddc(drm, connector, &drm_bridge_connector_funcs,
	connector_type, ddc);
	drm_connector_helper_add(connector, &drm_bridge_connector_helper_funcs);

	if (bridge_connector->bridge_hpd) {
	connector->polled = DRM_CONNECTOR_POLL_HPD;
	drm_bridge_connector_enable_hpd(connector);
	}
	else if (bridge_connector->bridge_detect)
	connector->polled = DRM_CONNECTOR_POLL_CONNECT
	\| DRM_CONNECTOR_POLL_DISCONNECT;

	if (panel_bridge)
	drm_panel_bridge_set_orientation(connector, panel_bridge);

	return connector;
	}
	EXPORT_SYMBOL_GPL(drm_bridge_connector_init);