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drm/bridge: implement generic DP HPD bridge
Several USB-C controllers implement a pretty simple DRM bridge which implements just the HPD notification operations. Add special helper for creating such simple bridges. Acked-by: Neil Armstrong <[email protected]> Signed-off-by: Dmitry Baryshkov <[email protected]> Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
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‎drivers/gpu/drm/bridge/Kconfig

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@@ -21,6 +21,14 @@ config DRM_AUX_BRIDGE
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Simple transparent bridge that is used by several non-DRM drivers to
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build bridges chain.
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config DRM_AUX_HPD_BRIDGE
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tristate
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depends on DRM_BRIDGE && OF
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select AUXILIARY_BUS
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help
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Simple bridge that terminates the bridge chain and provides HPD
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support.
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menu "Display Interface Bridges"
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depends on DRM && DRM_BRIDGE
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‎drivers/gpu/drm/bridge/Makefile

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@@ -1,5 +1,6 @@
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# SPDX-License-Identifier: GPL-2.0
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obj-$(CONFIG_DRM_AUX_BRIDGE) += aux-bridge.o
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obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += aux-hpd-bridge.o
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obj-$(CONFIG_DRM_CHIPONE_ICN6211) += chipone-icn6211.o
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obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
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obj-$(CONFIG_DRM_CROS_EC_ANX7688) += cros-ec-anx7688.o

‎drivers/gpu/drm/bridge/aux-hpd-bridge.c

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// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (C) 2023 Linaro Ltd.
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*
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* Author: Dmitry Baryshkov <[email protected]>
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*/
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#include <linux/auxiliary_bus.h>
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#include <linux/module.h>
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#include <linux/of_device.h>
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#include <drm/drm_bridge.h>
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#include <drm/bridge/aux-bridge.h>
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static DEFINE_IDA(drm_aux_hpd_bridge_ida);
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struct drm_aux_hpd_bridge_data {
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struct drm_bridge bridge;
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struct device *dev;
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};
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static void drm_aux_hpd_bridge_release(struct device *dev)
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{
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struct auxiliary_device *adev = to_auxiliary_dev(dev);
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ida_free(&drm_aux_hpd_bridge_ida, adev->id);
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of_node_put(adev->dev.platform_data);
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kfree(adev);
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}
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static void drm_aux_hpd_bridge_unregister_adev(void *_adev)
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{
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struct auxiliary_device *adev = _adev;
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auxiliary_device_delete(adev);
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auxiliary_device_uninit(adev);
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}
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/**
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* drm_dp_hpd_bridge_register - Create a simple HPD DisplayPort bridge
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* @parent: device instance providing this bridge
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* @np: device node pointer corresponding to this bridge instance
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*
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* Creates a simple DRM bridge with the type set to
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* DRM_MODE_CONNECTOR_DisplayPort, which terminates the bridge chain and is
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* able to send the HPD events.
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*
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* Return: device instance that will handle created bridge or an error code
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* encoded into the pointer.
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*/
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struct device *drm_dp_hpd_bridge_register(struct device *parent,
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struct device_node *np)
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{
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struct auxiliary_device *adev;
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int ret;
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adev = kzalloc(sizeof(*adev), GFP_KERNEL);
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if (!adev)
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return ERR_PTR(-ENOMEM);
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ret = ida_alloc(&drm_aux_hpd_bridge_ida, GFP_KERNEL);
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if (ret < 0) {
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kfree(adev);
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return ERR_PTR(ret);
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}
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adev->id = ret;
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adev->name = "dp_hpd_bridge";
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adev->dev.parent = parent;
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adev->dev.of_node = parent->of_node;
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adev->dev.release = drm_aux_hpd_bridge_release;
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adev->dev.platform_data = np;
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ret = auxiliary_device_init(adev);
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if (ret) {
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ida_free(&drm_aux_hpd_bridge_ida, adev->id);
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kfree(adev);
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return ERR_PTR(ret);
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}
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ret = auxiliary_device_add(adev);
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if (ret) {
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auxiliary_device_uninit(adev);
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return ERR_PTR(ret);
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}
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ret = devm_add_action_or_reset(parent, drm_aux_hpd_bridge_unregister_adev, adev);
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if (ret)
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return ERR_PTR(ret);
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return &adev->dev;
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}
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EXPORT_SYMBOL_GPL(drm_dp_hpd_bridge_register);
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/**
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* drm_aux_hpd_bridge_notify - notify hot plug detection events
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* @dev: device created for the HPD bridge
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* @status: output connection status
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*
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* A wrapper around drm_bridge_hpd_notify() that is used to report hot plug
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* detection events for bridges created via drm_dp_hpd_bridge_register().
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*
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* This function shall be called in a context that can sleep.
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*/
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void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
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{
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struct auxiliary_device *adev = to_auxiliary_dev(dev);
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struct drm_aux_hpd_bridge_data *data = auxiliary_get_drvdata(adev);
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if (!data)
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return;
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drm_bridge_hpd_notify(&data->bridge, status);
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}
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EXPORT_SYMBOL_GPL(drm_aux_hpd_bridge_notify);
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static int drm_aux_hpd_bridge_attach(struct drm_bridge *bridge,
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enum drm_bridge_attach_flags flags)
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{
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return flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR ? 0 : -EINVAL;
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}
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static const struct drm_bridge_funcs drm_aux_hpd_bridge_funcs = {
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.attach = drm_aux_hpd_bridge_attach,
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};
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static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
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const struct auxiliary_device_id *id)
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{
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struct drm_aux_hpd_bridge_data *data;
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data = devm_kzalloc(&auxdev->dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->dev = &auxdev->dev;
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data->bridge.funcs = &drm_aux_hpd_bridge_funcs;
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data->bridge.of_node = dev_get_platdata(data->dev);
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data->bridge.ops = DRM_BRIDGE_OP_HPD;
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data->bridge.type = id->driver_data;
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auxiliary_set_drvdata(auxdev, data);
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return devm_drm_bridge_add(data->dev, &data->bridge);
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}
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static const struct auxiliary_device_id drm_aux_hpd_bridge_table[] = {
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{ .name = KBUILD_MODNAME ".dp_hpd_bridge", .driver_data = DRM_MODE_CONNECTOR_DisplayPort, },
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{},
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};
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MODULE_DEVICE_TABLE(auxiliary, drm_aux_hpd_bridge_table);
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static struct auxiliary_driver drm_aux_hpd_bridge_drv = {
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.name = "aux_hpd_bridge",
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.id_table = drm_aux_hpd_bridge_table,
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.probe = drm_aux_hpd_bridge_probe,
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};
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module_auxiliary_driver(drm_aux_hpd_bridge_drv);
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MODULE_AUTHOR("Dmitry Baryshkov <[email protected]>");
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MODULE_DESCRIPTION("DRM HPD bridge");
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MODULE_LICENSE("GPL");

‎include/drm/bridge/aux-bridge.h

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@@ -7,6 +7,8 @@
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#ifndef DRM_AUX_BRIDGE_H
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#define DRM_AUX_BRIDGE_H
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#include <drm/drm_connector.h>
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#if IS_ENABLED(CONFIG_DRM_AUX_BRIDGE)
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int drm_aux_bridge_register(struct device *parent);
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#else
@@ -16,4 +18,20 @@ static inline int drm_aux_bridge_register(struct device *parent)
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}
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#endif
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#if IS_ENABLED(CONFIG_DRM_AUX_HPD_BRIDGE)
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struct device *drm_dp_hpd_bridge_register(struct device *parent,
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struct device_node *np);
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void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status);
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#else
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static inline struct device *drm_dp_hpd_bridge_register(struct device *parent,
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struct device_node *np)
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{
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return 0;
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}
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static inline void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
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{
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}
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#endif
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#endif

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