From: Hans Verkuil <hans.verk...@cisco.com>

This adds support for the DisplayPort CEC-Tunneling-over-AUX
feature that is part of the DisplayPort 1.3 standard.

Unfortunately, not all DisplayPort/USB-C to HDMI adapters with a
chip that has this capability actually hook up the CEC pin, so
even though a CEC device is created, it may not actually work.

Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
Reviewed-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
---
 drivers/gpu/drm/Kconfig         |  10 +
 drivers/gpu/drm/Makefile        |   1 +
 drivers/gpu/drm/drm_dp_cec.c    | 428 ++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_dp_helper.c |   1 +
 include/drm/drm_dp_helper.h     |  56 +++++
 5 files changed, 496 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_dp_cec.c

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 757825ac60df..4567b66e6434 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -121,6 +121,16 @@ config DRM_LOAD_EDID_FIRMWARE
          default case is N. Details and instructions how to build your own
          EDID data are given in Documentation/EDID/HOWTO.txt.
 
+config DRM_DP_CEC
+       bool "Enable DisplayPort CEC-Tunneling-over-AUX HDMI support"
+       select CEC_CORE
+       help
+         Choose this option if you want to enable HDMI CEC support for
+         DisplayPort/USB-C to HDMI adapters.
+
+         Note: not all adapters support this feature, and even for those
+         that do support this they often do not hook up the CEC pin.
+
 config DRM_TTM
        tristate
        depends on DRM && MMU
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 9d66657ea117..2917953076a5 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -41,6 +41,7 @@ drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
 drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
 drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
+drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
 
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 obj-$(CONFIG_DRM_DEBUG_MM_SELFTEST) += selftests/
diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
new file mode 100644
index 000000000000..ddb1c5adebb9
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_cec.c
@@ -0,0 +1,428 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DisplayPort CEC-Tunneling-over-AUX support
+ *
+ * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights 
reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <drm/drm_dp_helper.h>
+#include <media/cec.h>
+
+/*
+ * Unfortunately it turns out that we have a chicken-and-egg situation
+ * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters
+ * have a converter chip that supports CEC-Tunneling-over-AUX (usually the
+ * Parade PS176), but they do not wire up the CEC pin, thus making CEC
+ * useless.
+ *
+ * Sadly there is no way for this driver to know this. What happens is
+ * that a /dev/cecX device is created that is isolated and unable to see
+ * any of the other CEC devices. Quite literally the CEC wire is cut
+ * (or in this case, never connected in the first place).
+ *
+ * The reason so few adapters support this is that this tunneling protocol
+ * was never supported by any OS. So there was no easy way of testing it,
+ * and no incentive to correctly wire up the CEC pin.
+ *
+ * Hopefully by creating this driver it will be easier for vendors to
+ * finally fix their adapters and test the CEC functionality.
+ *
+ * I keep a list of known working adapters here:
+ *
+ * https://hverkuil.home.xs4all.nl/cec-status.txt
+ *
+ * Please mail me (hverk...@xs4all.nl) if you find an adapter that works
+ * and is not yet listed there.
+ *
+ * Note that the current implementation does not support CEC over an MST hub.
+ * As far as I can see there is no mechanism defined in the DisplayPort
+ * standard to transport CEC interrupts over an MST device. It might be
+ * possible to do this through polling, but I have not been able to get that
+ * to work.
+ */
+
+/**
+ * DOC: dp cec helpers
+ *
+ * These functions take care of supporting the CEC-Tunneling-over-AUX
+ * feature of DisplayPort-to-HDMI adapters.
+ */
+
+/*
+ * When the EDID is unset because the HPD went low, then the CEC DPCD registers
+ * typically can no longer be read (true for a DP-to-HDMI adapter since it is
+ * powered by the HPD). However, some displays toggle the HPD off and on for a
+ * short period for one reason or another, and that would cause the CEC adapter
+ * to be removed and added again, even though nothing else changed.
+ *
+ * This module parameter sets a delay in seconds before the CEC adapter is
+ * actually unregistered. Only if the HPD does not return within that time will
+ * the CEC adapter be unregistered.
+ *
+ * If it is set to a value >= NEVER_UNREG_DELAY, then the CEC adapter will 
never
+ * be unregistered for as long as the connector remains registered.
+ *
+ * If it is set to 0, then the CEC adapter will be unregistered immediately as
+ * soon as the HPD disappears.
+ *
+ * The default is one second to prevent short HPD glitches from unregistering
+ * the CEC adapter.
+ *
+ * Note that for integrated HDMI branch devices that support CEC the DPCD
+ * registers remain available even if the HPD goes low since it is not powered
+ * by the HPD. In that case the CEC adapter will never be unregistered during
+ * the life time of the connector. At least, this is the theory since I do not
+ * have hardware with an integrated HDMI branch device that supports CEC.
+ */
+#define NEVER_UNREG_DELAY 1000
+static unsigned int drm_dp_cec_unregister_delay = 1;
+module_param(drm_dp_cec_unregister_delay, uint, 0600);
+MODULE_PARM_DESC(drm_dp_cec_unregister_delay,
+                "CEC unregister delay in seconds, 0: no delay, >= 1000: never 
unregister");
+
+static int drm_dp_cec_adap_enable(struct cec_adapter *adap, bool enable)
+{
+       struct drm_dp_aux *aux = cec_get_drvdata(adap);
+       u32 val = enable ? DP_CEC_TUNNELING_ENABLE : 0;
+       ssize_t err = 0;
+
+       err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val);
+       return (enable && err < 0) ? err : 0;
+}
+
+static int drm_dp_cec_adap_log_addr(struct cec_adapter *adap, u8 addr)
+{
+       struct drm_dp_aux *aux = cec_get_drvdata(adap);
+       /* Bit 15 (logical address 15) should always be set */
+       u16 la_mask = 1 << CEC_LOG_ADDR_BROADCAST;
+       u8 mask[2];
+       ssize_t err;
+
+       if (addr != CEC_LOG_ADDR_INVALID)
+               la_mask |= adap->log_addrs.log_addr_mask | (1 << addr);
+       mask[0] = la_mask & 0xff;
+       mask[1] = la_mask >> 8;
+       err = drm_dp_dpcd_write(aux, DP_CEC_LOGICAL_ADDRESS_MASK, mask, 2);
+       return (addr != CEC_LOG_ADDR_INVALID && err < 0) ? err : 0;
+}
+
+static int drm_dp_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,
+                                   u32 signal_free_time, struct cec_msg *msg)
+{
+       struct drm_dp_aux *aux = cec_get_drvdata(adap);
+       unsigned int retries = min(5, attempts - 1);
+       ssize_t err;
+
+       err = drm_dp_dpcd_write(aux, DP_CEC_TX_MESSAGE_BUFFER,
+                               msg->msg, msg->len);
+       if (err < 0)
+               return err;
+
+       err = drm_dp_dpcd_writeb(aux, DP_CEC_TX_MESSAGE_INFO,
+                                (msg->len - 1) | (retries << 4) |
+                                DP_CEC_TX_MESSAGE_SEND);
+       return err < 0 ? err : 0;
+}
+
+static int drm_dp_cec_adap_monitor_all_enable(struct cec_adapter *adap,
+                                             bool enable)
+{
+       struct drm_dp_aux *aux = cec_get_drvdata(adap);
+       ssize_t err;
+       u8 val;
+
+       if (!(adap->capabilities & CEC_CAP_MONITOR_ALL))
+               return 0;
+
+       err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CONTROL, &val);
+       if (err >= 0) {
+               if (enable)
+                       val |= DP_CEC_SNOOPING_ENABLE;
+               else
+                       val &= ~DP_CEC_SNOOPING_ENABLE;
+               err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val);
+       }
+       return (enable && err < 0) ? err : 0;
+}
+
+static void drm_dp_cec_adap_status(struct cec_adapter *adap,
+                                  struct seq_file *file)
+{
+       struct drm_dp_aux *aux = cec_get_drvdata(adap);
+       struct drm_dp_desc desc;
+       struct drm_dp_dpcd_ident *id = &desc.ident;
+
+       if (drm_dp_read_desc(aux, &desc, true))
+               return;
+       seq_printf(file, "OUI: %*pdH\n",
+                  (int)sizeof(id->oui), id->oui);
+       seq_printf(file, "ID: %*pE\n",
+                  (int)strnlen(id->device_id, sizeof(id->device_id)),
+                  id->device_id);
+       seq_printf(file, "HW Rev: %d.%d\n", id->hw_rev >> 4, id->hw_rev & 0xf);
+       /*
+        * Show this both in decimal and hex: at least one vendor
+        * always reports this in hex.
+        */
+       seq_printf(file, "FW/SW Rev: %d.%d (0x%02x.0x%02x)\n",
+                  id->sw_major_rev, id->sw_minor_rev,
+                  id->sw_major_rev, id->sw_minor_rev);
+}
+
+static const struct cec_adap_ops drm_dp_cec_adap_ops = {
+       .adap_enable = drm_dp_cec_adap_enable,
+       .adap_log_addr = drm_dp_cec_adap_log_addr,
+       .adap_transmit = drm_dp_cec_adap_transmit,
+       .adap_monitor_all_enable = drm_dp_cec_adap_monitor_all_enable,
+       .adap_status = drm_dp_cec_adap_status,
+};
+
+static int drm_dp_cec_received(struct drm_dp_aux *aux)
+{
+       struct cec_adapter *adap = aux->cec.adap;
+       struct cec_msg msg;
+       u8 rx_msg_info;
+       ssize_t err;
+
+       err = drm_dp_dpcd_readb(aux, DP_CEC_RX_MESSAGE_INFO, &rx_msg_info);
+       if (err < 0)
+               return err;
+
+       if (!(rx_msg_info & DP_CEC_RX_MESSAGE_ENDED))
+               return 0;
+
+       msg.len = (rx_msg_info & DP_CEC_RX_MESSAGE_LEN_MASK) + 1;
+       err = drm_dp_dpcd_read(aux, DP_CEC_RX_MESSAGE_BUFFER, msg.msg, msg.len);
+       if (err < 0)
+               return err;
+
+       cec_received_msg(adap, &msg);
+       return 0;
+}
+
+static void drm_dp_cec_handle_irq(struct drm_dp_aux *aux)
+{
+       struct cec_adapter *adap = aux->cec.adap;
+       u8 flags;
+
+       if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, &flags) < 0)
+               return;
+
+       if (flags & DP_CEC_RX_MESSAGE_INFO_VALID)
+               drm_dp_cec_received(aux);
+
+       if (flags & DP_CEC_TX_MESSAGE_SENT)
+               cec_transmit_attempt_done(adap, CEC_TX_STATUS_OK);
+       else if (flags & DP_CEC_TX_LINE_ERROR)
+               cec_transmit_attempt_done(adap, CEC_TX_STATUS_ERROR |
+                                               CEC_TX_STATUS_MAX_RETRIES);
+       else if (flags &
+                (DP_CEC_TX_ADDRESS_NACK_ERROR | DP_CEC_TX_DATA_NACK_ERROR))
+               cec_transmit_attempt_done(adap, CEC_TX_STATUS_NACK |
+                                               CEC_TX_STATUS_MAX_RETRIES);
+       drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, flags);
+}
+
+/**
+ * drm_dp_cec_irq() - handle CEC interrupt, if any
+ * @aux: DisplayPort AUX channel
+ *
+ * Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX
+ * is present, then it will check for a CEC_IRQ and handle it accordingly.
+ */
+void drm_dp_cec_irq(struct drm_dp_aux *aux)
+{
+       u8 cec_irq;
+       int ret;
+
+       mutex_lock(&aux->cec.lock);
+       if (!aux->cec.adap)
+               goto unlock;
+
+       ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,
+                               &cec_irq);
+       if (ret < 0 || !(cec_irq & DP_CEC_IRQ))
+               goto unlock;
+
+       drm_dp_cec_handle_irq(aux);
+       drm_dp_dpcd_writeb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, DP_CEC_IRQ);
+unlock:
+       mutex_unlock(&aux->cec.lock);
+}
+EXPORT_SYMBOL(drm_dp_cec_irq);
+
+static bool drm_dp_cec_cap(struct drm_dp_aux *aux, u8 *cec_cap)
+{
+       u8 cap = 0;
+
+       if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CAPABILITY, &cap) != 1 ||
+           !(cap & DP_CEC_TUNNELING_CAPABLE))
+               return false;
+       if (cec_cap)
+               *cec_cap = cap;
+       return true;
+}
+
+/*
+ * Called if the HPD was low for more than drm_dp_cec_unregister_delay
+ * seconds. This unregisters the CEC adapter.
+ */
+static void drm_dp_cec_unregister_work(struct work_struct *work)
+{
+       struct drm_dp_aux *aux = container_of(work, struct drm_dp_aux,
+                                             cec.unregister_work.work);
+
+       mutex_lock(&aux->cec.lock);
+       cec_unregister_adapter(aux->cec.adap);
+       aux->cec.adap = NULL;
+       mutex_unlock(&aux->cec.lock);
+}
+
+/*
+ * A new EDID is set. If there is no CEC adapter, then create one. If
+ * there was a CEC adapter, then check if the CEC adapter properties
+ * were unchanged and just update the CEC physical address. Otherwise
+ * unregister the old CEC adapter and create a new one.
+ */
+void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid)
+{
+       u32 cec_caps = CEC_CAP_DEFAULTS | CEC_CAP_NEEDS_HPD;
+       unsigned int num_las = 1;
+       u8 cap;
+
+#ifndef CONFIG_MEDIA_CEC_RC
+       /*
+        * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by
+        * cec_allocate_adapter() if CONFIG_MEDIA_CEC_RC is undefined.
+        *
+        * Do this here as well to ensure the tests against cec_caps are
+        * correct.
+        */
+       cec_caps &= ~CEC_CAP_RC;
+#endif
+       cancel_delayed_work_sync(&aux->cec.unregister_work);
+
+       mutex_lock(&aux->cec.lock);
+       if (!drm_dp_cec_cap(aux, &cap)) {
+               /* CEC is not supported, unregister any existing adapter */
+               cec_unregister_adapter(aux->cec.adap);
+               aux->cec.adap = NULL;
+               goto unlock;
+       }
+
+       if (cap & DP_CEC_SNOOPING_CAPABLE)
+               cec_caps |= CEC_CAP_MONITOR_ALL;
+       if (cap & DP_CEC_MULTIPLE_LA_CAPABLE)
+               num_las = CEC_MAX_LOG_ADDRS;
+
+       if (aux->cec.adap) {
+               if (aux->cec.adap->capabilities == cec_caps &&
+                   aux->cec.adap->available_log_addrs == num_las) {
+                       /* Unchanged, so just set the phys addr */
+                       cec_s_phys_addr_from_edid(aux->cec.adap, edid);
+                       goto unlock;
+               }
+               /*
+                * The capabilities changed, so unregister the old
+                * adapter first.
+                */
+               cec_unregister_adapter(aux->cec.adap);
+       }
+
+       /* Create a new adapter */
+       aux->cec.adap = cec_allocate_adapter(&drm_dp_cec_adap_ops,
+                                            aux, aux->cec.name, cec_caps,
+                                            num_las);
+       if (IS_ERR(aux->cec.adap)) {
+               aux->cec.adap = NULL;
+               goto unlock;
+       }
+       if (cec_register_adapter(aux->cec.adap, aux->cec.parent)) {
+               cec_delete_adapter(aux->cec.adap);
+               aux->cec.adap = NULL;
+       } else {
+               /*
+                * Update the phys addr for the new CEC adapter. When called
+                * from drm_dp_cec_register_connector() edid == NULL, so in
+                * that case the phys addr is just invalidated.
+                */
+               cec_s_phys_addr_from_edid(aux->cec.adap, edid);
+       }
+unlock:
+       mutex_unlock(&aux->cec.lock);
+}
+EXPORT_SYMBOL(drm_dp_cec_set_edid);
+
+/*
+ * The EDID disappeared (likely because of the HPD going down).
+ */
+void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)
+{
+       cancel_delayed_work_sync(&aux->cec.unregister_work);
+
+       mutex_lock(&aux->cec.lock);
+       if (!aux->cec.adap)
+               goto unlock;
+
+       cec_phys_addr_invalidate(aux->cec.adap);
+       /*
+        * We're done if we want to keep the CEC device
+        * (drm_dp_cec_unregister_delay is >= NEVER_UNREG_DELAY) or if the
+        * DPCD still indicates the CEC capability (expected for an integrated
+        * HDMI branch device).
+        */
+       if (drm_dp_cec_unregister_delay < NEVER_UNREG_DELAY &&
+           !drm_dp_cec_cap(aux, NULL)) {
+               /*
+                * Unregister the CEC adapter after drm_dp_cec_unregister_delay
+                * seconds. This to debounce short HPD off-and-on cycles from
+                * displays.
+                */
+               schedule_delayed_work(&aux->cec.unregister_work,
+                                     drm_dp_cec_unregister_delay * HZ);
+       }
+unlock:
+       mutex_unlock(&aux->cec.lock);
+}
+EXPORT_SYMBOL(drm_dp_cec_unset_edid);
+
+/**
+ * drm_dp_cec_register_connector() - register a new connector
+ * @aux: DisplayPort AUX channel
+ * @name: name of the CEC device
+ * @parent: parent device
+ *
+ * A new connector was registered with associated CEC adapter name and
+ * CEC adapter parent device. After registering the name and parent
+ * drm_dp_cec_set_edid() is called to check if the connector supports
+ * CEC and to register a CEC adapter if that is the case.
+ */
+void drm_dp_cec_register_connector(struct drm_dp_aux *aux, const char *name,
+                                  struct device *parent)
+{
+       WARN_ON(aux->cec.adap);
+       aux->cec.name = name;
+       aux->cec.parent = parent;
+       INIT_DELAYED_WORK(&aux->cec.unregister_work,
+                         drm_dp_cec_unregister_work);
+
+       drm_dp_cec_set_edid(aux, NULL);
+}
+EXPORT_SYMBOL(drm_dp_cec_register_connector);
+
+/**
+ * drm_dp_cec_unregister_connector() - unregister the CEC adapter, if any
+ * @aux: DisplayPort AUX channel
+ */
+void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux)
+{
+       if (!aux->cec.adap)
+               return;
+       cancel_delayed_work_sync(&aux->cec.unregister_work);
+       cec_unregister_adapter(aux->cec.adap);
+       aux->cec.adap = NULL;
+}
+EXPORT_SYMBOL(drm_dp_cec_unregister_connector);
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index ffe14ec3e7f2..ce0c0264a492 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1073,6 +1073,7 @@ static void drm_dp_aux_crc_work(struct work_struct *work)
 void drm_dp_aux_init(struct drm_dp_aux *aux)
 {
        mutex_init(&aux->hw_mutex);
+       mutex_init(&aux->cec.lock);
        INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work);
 
        aux->ddc.algo = &drm_dp_i2c_algo;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 91c9bcd4196f..10fc9467c3a8 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1072,6 +1072,25 @@ struct drm_dp_aux_msg {
        size_t size;
 };
 
+struct cec_adapter;
+struct edid;
+
+/**
+ * struct drm_dp_aux_cec - DisplayPort CEC-Tunneling-over-AUX
+ * @lock: mutex protecting this struct
+ * @adap: the CEC adapter for CEC-Tunneling-over-AUX support.
+ * @name: name of the CEC adapter
+ * @parent: parent device of the CEC adapter
+ * @unregister_work: unregister the CEC adapter
+ */
+struct drm_dp_aux_cec {
+       struct mutex lock;
+       struct cec_adapter *adap;
+       const char *name;
+       struct device *parent;
+       struct delayed_work unregister_work;
+};
+
 /**
  * struct drm_dp_aux - DisplayPort AUX channel
  * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
@@ -1130,6 +1149,10 @@ struct drm_dp_aux {
         * @i2c_defer_count: Counts I2C DEFERs, used for DP validation.
         */
        unsigned i2c_defer_count;
+       /**
+        * @cec: struct containing fields used for CEC-Tunneling-over-AUX.
+        */
+       struct drm_dp_aux_cec cec;
 };
 
 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
@@ -1252,4 +1275,37 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, enum 
drm_dp_quirk quirk)
        return desc->quirks & BIT(quirk);
 }
 
+#ifdef CONFIG_DRM_DP_CEC
+void drm_dp_cec_irq(struct drm_dp_aux *aux);
+void drm_dp_cec_register_connector(struct drm_dp_aux *aux, const char *name,
+                                  struct device *parent);
+void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux);
+void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid);
+void drm_dp_cec_unset_edid(struct drm_dp_aux *aux);
+#else
+static inline void drm_dp_cec_irq(struct drm_dp_aux *aux)
+{
+}
+
+static inline void drm_dp_cec_register_connector(struct drm_dp_aux *aux,
+                                                const char *name,
+                                                struct device *parent)
+{
+}
+
+static inline void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux)
+{
+}
+
+static inline void drm_dp_cec_set_edid(struct drm_dp_aux *aux,
+                                      const struct edid *edid)
+{
+}
+
+static inline void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)
+{
+}
+
+#endif
+
 #endif /* _DRM_DP_HELPER_H_ */
-- 
2.18.0

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