Re: [PATCHv7 1/3] drm: add support for DisplayPort CEC-Tunneling-over-AUX

On Thu, Jun 28, 2018 at 09:42:51AM +0200, Hans Verkuil wrote:

From: Hans Verkuil hans.verkuil@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.verkuil@cisco.com

drivers/gpu/drm/Kconfig | 10 + drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_dp_cec.c | 433 ++++++++++++++++++++++++++++++++ drivers/gpu/drm/drm_dp_helper.c | 1 + include/drm/drm_dp_helper.h | 56 +++++ 5 files changed, 501 insertions(+) create mode 100644 drivers/gpu/drm/drm_dp_cec.c

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 2a72d2feb76d..d5e217fd0c14 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -122,6 +122,16 @@ 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 ef9f3dab287f..270266cc6eca 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_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..1530ca685955 --- /dev/null +++ b/drivers/gpu/drm/drm_dp_cec.c @@ -0,0 +1,433 @@ +// 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 (hverkuil@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);
  

• if (!aux->cec.adap)

• return;
  

I guess this NULL check isn't particularly critical?

• 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);
  

... considering here we don't check for NULL.

Also the check in the work is unlocked so I could imagine some slight race conditions if set_edid()/unset_edid() get called in a particularly funky way. But I suppose we shouldn't really do that so it's probably fine. And the cec_unregister_adapter() is done with the lock held anyway so any bogus pointers can't reach it.

• 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) +{

• 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))
  

• goto unlock;
  

• mutex_unlock(&aux->cec.lock);
• cancel_delayed_work_sync(&aux->cec.unregister_work);
• mutex_lock(&aux->cec.lock);

Can't we just do the cancel_work_sync() at the very start of the function?

Either way this shouldn't deadlock anymore. For the series Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com

• if (aux->cec.adap) {

• /*
  

•  * 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 a7ba602a43a8..f4a06b54aa7d 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1087,6 +1087,7 @@ 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 c01564991a9f..d0a23db271dc 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -1078,6 +1078,25 @@ 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

@@ -1136,6 +1155,10 @@ 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, @@ -1258,4 +1281,37 @@ 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_ */

2.17.0