include/drm/drm_dp_helper.h - maze/linux - Git at Google

 /*
  * Copyright © 2008 Keith Packard
  *
  * 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.
  */

 #ifndef _DRM_DP_HELPER_H_
 #define _DRM_DP_HELPER_H_

 #include <linux/types.h>
 #include <linux/i2c.h>
 #include <linux/delay.h>

 /*
  * Unless otherwise noted, all values are from the DP 1.1a spec.  Note that
  * DP and DPCD versions are independent.  Differences from 1.0 are not noted,
  * 1.0 devices basically don't exist in the wild.
  *
  * Abbreviations, in chronological order:
  *
  * eDP: Embedded DisplayPort version 1
  * DPI: DisplayPort Interoperability Guideline v1.1a
  * 1.2: DisplayPort 1.2
  *
  * 1.2 formally includes both eDP and DPI definitions.
  */

 #define DP_AUX_I2C_WRITE		0x0
 #define DP_AUX_I2C_READ			0x1
 #define DP_AUX_I2C_STATUS		0x2
 #define DP_AUX_I2C_MOT			0x4
 #define DP_AUX_NATIVE_WRITE		0x8
 #define DP_AUX_NATIVE_READ		0x9

 #define DP_AUX_NATIVE_REPLY_ACK		(0x0 << 0)
 #define DP_AUX_NATIVE_REPLY_NACK	(0x1 << 0)
 #define DP_AUX_NATIVE_REPLY_DEFER	(0x2 << 0)
 #define DP_AUX_NATIVE_REPLY_MASK	(0x3 << 0)

 #define DP_AUX_I2C_REPLY_ACK		(0x0 << 2)
 #define DP_AUX_I2C_REPLY_NACK		(0x1 << 2)
 #define DP_AUX_I2C_REPLY_DEFER		(0x2 << 2)
 #define DP_AUX_I2C_REPLY_MASK		(0x3 << 2)

 /* AUX CH addresses */
 /* DPCD */
 #define DP_DPCD_REV                         0x000

 #define DP_MAX_LINK_RATE                    0x001

 #define DP_MAX_LANE_COUNT                   0x002
 # define DP_MAX_LANE_COUNT_MASK		    0x1f
 # define DP_TPS3_SUPPORTED		    (1 << 6) /* 1.2 */
 # define DP_ENHANCED_FRAME_CAP		    (1 << 7)

 #define DP_MAX_DOWNSPREAD                   0x003
 # define DP_NO_AUX_HANDSHAKE_LINK_TRAINING  (1 << 6)

 #define DP_NORP                             0x004

 #define DP_DOWNSTREAMPORT_PRESENT           0x005
 # define DP_DWN_STRM_PORT_PRESENT           (1 << 0)
 # define DP_DWN_STRM_PORT_TYPE_MASK         0x06
 # define DP_DWN_STRM_PORT_TYPE_DP           (0 << 1)
 # define DP_DWN_STRM_PORT_TYPE_ANALOG       (1 << 1)
 # define DP_DWN_STRM_PORT_TYPE_TMDS         (2 << 1)
 # define DP_DWN_STRM_PORT_TYPE_OTHER        (3 << 1)
 # define DP_FORMAT_CONVERSION               (1 << 3)
 # define DP_DETAILED_CAP_INFO_AVAILABLE	    (1 << 4) /* DPI */

 #define DP_MAIN_LINK_CHANNEL_CODING         0x006

 #define DP_DOWN_STREAM_PORT_COUNT	    0x007
 # define DP_PORT_COUNT_MASK		    0x0f
 # define DP_MSA_TIMING_PAR_IGNORED	    (1 << 6) /* eDP */
 # define DP_OUI_SUPPORT			    (1 << 7)

 #define DP_I2C_SPEED_CAP		    0x00c    /* DPI */
 # define DP_I2C_SPEED_1K		    0x01
 # define DP_I2C_SPEED_5K		    0x02
 # define DP_I2C_SPEED_10K		    0x04
 # define DP_I2C_SPEED_100K		    0x08
 # define DP_I2C_SPEED_400K		    0x10
 # define DP_I2C_SPEED_1M		    0x20

 #define DP_EDP_CONFIGURATION_CAP            0x00d   /* XXX 1.2? */
 #define DP_TRAINING_AUX_RD_INTERVAL         0x00e   /* XXX 1.2? */

 /* Multiple stream transport */
 #define DP_MSTM_CAP			    0x021   /* 1.2 */
 # define DP_MST_CAP			    (1 << 0)

 #define DP_PSR_SUPPORT                      0x070   /* XXX 1.2? */
 # define DP_PSR_IS_SUPPORTED                1
 #define DP_PSR_CAPS                         0x071   /* XXX 1.2? */
 # define DP_PSR_NO_TRAIN_ON_EXIT            1
 # define DP_PSR_SETUP_TIME_330              (0 << 1)
 # define DP_PSR_SETUP_TIME_275              (1 << 1)
 # define DP_PSR_SETUP_TIME_220              (2 << 1)
 # define DP_PSR_SETUP_TIME_165              (3 << 1)
 # define DP_PSR_SETUP_TIME_110              (4 << 1)
 # define DP_PSR_SETUP_TIME_55               (5 << 1)
 # define DP_PSR_SETUP_TIME_0                (6 << 1)
 # define DP_PSR_SETUP_TIME_MASK             (7 << 1)
 # define DP_PSR_SETUP_TIME_SHIFT            1

 /*
  * 0x80-0x8f describe downstream port capabilities, but there are two layouts
  * based on whether DP_DETAILED_CAP_INFO_AVAILABLE was set.  If it was not,
  * each port's descriptor is one byte wide.  If it was set, each port's is
  * four bytes wide, starting with the one byte from the base info.  As of
  * DP interop v1.1a only VGA defines additional detail.
  */

 /* offset 0 */
 #define DP_DOWNSTREAM_PORT_0		    0x80
 # define DP_DS_PORT_TYPE_MASK		    (7 << 0)
 # define DP_DS_PORT_TYPE_DP		    0
 # define DP_DS_PORT_TYPE_VGA		    1
 # define DP_DS_PORT_TYPE_DVI		    2
 # define DP_DS_PORT_TYPE_HDMI		    3
 # define DP_DS_PORT_TYPE_NON_EDID	    4
 # define DP_DS_PORT_HPD			    (1 << 3)
 /* offset 1 for VGA is maximum megapixels per second / 8 */
 /* offset 2 */
 # define DP_DS_VGA_MAX_BPC_MASK		    (3 << 0)
 # define DP_DS_VGA_8BPC			    0
 # define DP_DS_VGA_10BPC		    1
 # define DP_DS_VGA_12BPC		    2
 # define DP_DS_VGA_16BPC		    3

 /* link configuration */
 #define	DP_LINK_BW_SET		            0x100
 # define DP_LINK_BW_1_62		    0x06
 # define DP_LINK_BW_2_7			    0x0a
 # define DP_LINK_BW_5_4			    0x14    /* 1.2 */

 #define DP_LANE_COUNT_SET	            0x101
 # define DP_LANE_COUNT_MASK		    0x0f
 # define DP_LANE_COUNT_ENHANCED_FRAME_EN    (1 << 7)

 #define DP_TRAINING_PATTERN_SET	            0x102
 # define DP_TRAINING_PATTERN_DISABLE	    0
 # define DP_TRAINING_PATTERN_1		    1
 # define DP_TRAINING_PATTERN_2		    2
 # define DP_TRAINING_PATTERN_3		    3	    /* 1.2 */
 # define DP_TRAINING_PATTERN_MASK	    0x3

 # define DP_LINK_QUAL_PATTERN_DISABLE	    (0 << 2)
 # define DP_LINK_QUAL_PATTERN_D10_2	    (1 << 2)
 # define DP_LINK_QUAL_PATTERN_ERROR_RATE    (2 << 2)
 # define DP_LINK_QUAL_PATTERN_PRBS7	    (3 << 2)
 # define DP_LINK_QUAL_PATTERN_MASK	    (3 << 2)

 # define DP_RECOVERED_CLOCK_OUT_EN	    (1 << 4)
 # define DP_LINK_SCRAMBLING_DISABLE	    (1 << 5)

 # define DP_SYMBOL_ERROR_COUNT_BOTH	    (0 << 6)
 # define DP_SYMBOL_ERROR_COUNT_DISPARITY    (1 << 6)
 # define DP_SYMBOL_ERROR_COUNT_SYMBOL	    (2 << 6)
 # define DP_SYMBOL_ERROR_COUNT_MASK	    (3 << 6)

 #define DP_TRAINING_LANE0_SET		    0x103
 #define DP_TRAINING_LANE1_SET		    0x104
 #define DP_TRAINING_LANE2_SET		    0x105
 #define DP_TRAINING_LANE3_SET		    0x106

 # define DP_TRAIN_VOLTAGE_SWING_MASK	    0x3
 # define DP_TRAIN_VOLTAGE_SWING_SHIFT	    0
 # define DP_TRAIN_MAX_SWING_REACHED	    (1 << 2)
 # define DP_TRAIN_VOLTAGE_SWING_400	    (0 << 0)
 # define DP_TRAIN_VOLTAGE_SWING_600	    (1 << 0)
 # define DP_TRAIN_VOLTAGE_SWING_800	    (2 << 0)
 # define DP_TRAIN_VOLTAGE_SWING_1200	    (3 << 0)

 # define DP_TRAIN_PRE_EMPHASIS_MASK	    (3 << 3)
 # define DP_TRAIN_PRE_EMPHASIS_0	    (0 << 3)
 # define DP_TRAIN_PRE_EMPHASIS_3_5	    (1 << 3)
 # define DP_TRAIN_PRE_EMPHASIS_6	    (2 << 3)
 # define DP_TRAIN_PRE_EMPHASIS_9_5	    (3 << 3)

 # define DP_TRAIN_PRE_EMPHASIS_SHIFT	    3
 # define DP_TRAIN_MAX_PRE_EMPHASIS_REACHED  (1 << 5)

 #define DP_DOWNSPREAD_CTRL		    0x107
 # define DP_SPREAD_AMP_0_5		    (1 << 4)
 # define DP_MSA_TIMING_PAR_IGNORE_EN	    (1 << 7) /* eDP */

 #define DP_MAIN_LINK_CHANNEL_CODING_SET	    0x108
 # define DP_SET_ANSI_8B10B		    (1 << 0)

 #define DP_I2C_SPEED_CONTROL_STATUS	    0x109   /* DPI */
 /* bitmask as for DP_I2C_SPEED_CAP */

 #define DP_EDP_CONFIGURATION_SET            0x10a   /* XXX 1.2? */

 #define DP_MSTM_CTRL			    0x111   /* 1.2 */
 # define DP_MST_EN			    (1 << 0)
 # define DP_UP_REQ_EN			    (1 << 1)
 # define DP_UPSTREAM_IS_SRC		    (1 << 2)

 #define DP_PSR_EN_CFG			    0x170   /* XXX 1.2? */
 # define DP_PSR_ENABLE			    (1 << 0)
 # define DP_PSR_MAIN_LINK_ACTIVE	    (1 << 1)
 # define DP_PSR_CRC_VERIFICATION	    (1 << 2)
 # define DP_PSR_FRAME_CAPTURE		    (1 << 3)

 #define DP_SINK_COUNT			    0x200
 /* prior to 1.2 bit 7 was reserved mbz */
 # define DP_GET_SINK_COUNT(x)		    ((((x) & 0x80) >> 1) | ((x) & 0x3f))
 # define DP_SINK_CP_READY		    (1 << 6)

 #define DP_DEVICE_SERVICE_IRQ_VECTOR	    0x201
 # define DP_REMOTE_CONTROL_COMMAND_PENDING  (1 << 0)
 # define DP_AUTOMATED_TEST_REQUEST	    (1 << 1)
 # define DP_CP_IRQ			    (1 << 2)
 # define DP_SINK_SPECIFIC_IRQ		    (1 << 6)

 #define DP_LANE0_1_STATUS		    0x202
 #define DP_LANE2_3_STATUS		    0x203
 # define DP_LANE_CR_DONE		    (1 << 0)
 # define DP_LANE_CHANNEL_EQ_DONE	    (1 << 1)
 # define DP_LANE_SYMBOL_LOCKED		    (1 << 2)

 #define DP_CHANNEL_EQ_BITS (DP_LANE_CR_DONE |		\
 			    DP_LANE_CHANNEL_EQ_DONE |	\
 			    DP_LANE_SYMBOL_LOCKED)

 #define DP_LANE_ALIGN_STATUS_UPDATED	    0x204

 #define DP_INTERLANE_ALIGN_DONE		    (1 << 0)
 #define DP_DOWNSTREAM_PORT_STATUS_CHANGED   (1 << 6)
 #define DP_LINK_STATUS_UPDATED		    (1 << 7)

 #define DP_SINK_STATUS			    0x205

 #define DP_RECEIVE_PORT_0_STATUS	    (1 << 0)
 #define DP_RECEIVE_PORT_1_STATUS	    (1 << 1)

 #define DP_ADJUST_REQUEST_LANE0_1	    0x206
 #define DP_ADJUST_REQUEST_LANE2_3	    0x207
 # define DP_ADJUST_VOLTAGE_SWING_LANE0_MASK  0x03
 # define DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT 0
 # define DP_ADJUST_PRE_EMPHASIS_LANE0_MASK   0x0c
 # define DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT  2
 # define DP_ADJUST_VOLTAGE_SWING_LANE1_MASK  0x30
 # define DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT 4
 # define DP_ADJUST_PRE_EMPHASIS_LANE1_MASK   0xc0
 # define DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT  6

 #define DP_TEST_REQUEST			    0x218
 # define DP_TEST_LINK_TRAINING		    (1 << 0)
 # define DP_TEST_LINK_VIDEO_PATTERN	    (1 << 1)
 # define DP_TEST_LINK_EDID_READ		    (1 << 2)
 # define DP_TEST_LINK_PHY_TEST_PATTERN	    (1 << 3) /* DPCD >= 1.1 */
 # define DP_TEST_LINK_FAUX_PATTERN	    (1 << 4) /* DPCD >= 1.2 */

 #define DP_TEST_LINK_RATE		    0x219
 # define DP_LINK_RATE_162		    (0x6)
 # define DP_LINK_RATE_27		    (0xa)

 #define DP_TEST_LANE_COUNT		    0x220

 #define DP_TEST_PATTERN			    0x221

 #define DP_TEST_CRC_R_CR		    0x240
 #define DP_TEST_CRC_G_Y			    0x242
 #define DP_TEST_CRC_B_CB		    0x244

 #define DP_TEST_SINK_MISC		    0x246
 #define DP_TEST_CRC_SUPPORTED		    (1 << 5)

 #define DP_TEST_RESPONSE		    0x260
 # define DP_TEST_ACK			    (1 << 0)
 # define DP_TEST_NAK			    (1 << 1)
 # define DP_TEST_EDID_CHECKSUM_WRITE	    (1 << 2)

 #define DP_TEST_SINK			    0x270
 #define DP_TEST_SINK_START	    (1 << 0)

 #define DP_SOURCE_OUI			    0x300
 #define DP_SINK_OUI			    0x400
 #define DP_BRANCH_OUI			    0x500

 #define DP_SET_POWER                        0x600
 # define DP_SET_POWER_D0                    0x1
 # define DP_SET_POWER_D3                    0x2
 # define DP_SET_POWER_MASK                  0x3

 #define DP_PSR_ERROR_STATUS                 0x2006  /* XXX 1.2? */
 # define DP_PSR_LINK_CRC_ERROR              (1 << 0)
 # define DP_PSR_RFB_STORAGE_ERROR           (1 << 1)

 #define DP_PSR_ESI                          0x2007  /* XXX 1.2? */
 # define DP_PSR_CAPS_CHANGE                 (1 << 0)

 #define DP_PSR_STATUS                       0x2008  /* XXX 1.2? */
 # define DP_PSR_SINK_INACTIVE               0
 # define DP_PSR_SINK_ACTIVE_SRC_SYNCED      1
 # define DP_PSR_SINK_ACTIVE_RFB             2
 # define DP_PSR_SINK_ACTIVE_SINK_SYNCED     3
 # define DP_PSR_SINK_ACTIVE_RESYNC          4
 # define DP_PSR_SINK_INTERNAL_ERROR         7
 # define DP_PSR_SINK_STATE_MASK             0x07

 #define MODE_I2C_START	1
 #define MODE_I2C_WRITE	2
 #define MODE_I2C_READ	4
 #define MODE_I2C_STOP	8

 /**
  * struct i2c_algo_dp_aux_data - driver interface structure for i2c over dp
  * 				 aux algorithm
  * @running: set by the algo indicating whether an i2c is ongoing or whether
  * 	     the i2c bus is quiescent
  * @address: i2c target address for the currently ongoing transfer
  * @aux_ch: driver callback to transfer a single byte of the i2c payload
  */
 struct i2c_algo_dp_aux_data {
 	bool running;
 	u16 address;
 	int (*aux_ch) (struct i2c_adapter *adapter,
 		       int mode, uint8_t write_byte,
 		       uint8_t *read_byte);
 };

 int
 i2c_dp_aux_add_bus(struct i2c_adapter *adapter);


 #define DP_LINK_STATUS_SIZE	   6
 bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
 			  int lane_count);
 bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
 			      int lane_count);
 u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
 				     int lane);
 u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
 					  int lane);

 #define DP_RECEIVER_CAP_SIZE		0xf
 #define EDP_PSR_RECEIVER_CAP_SIZE	2

 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
 void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]);

 u8 drm_dp_link_rate_to_bw_code(int link_rate);
 int drm_dp_bw_code_to_link_rate(u8 link_bw);

 struct edp_sdp_header {
 	u8 HB0; /* Secondary Data Packet ID */
 	u8 HB1; /* Secondary Data Packet Type */
 	u8 HB2; /* 7:5 reserved, 4:0 revision number */
 	u8 HB3; /* 7:5 reserved, 4:0 number of valid data bytes */
 } __packed;

 #define EDP_SDP_HEADER_REVISION_MASK		0x1F
 #define EDP_SDP_HEADER_VALID_PAYLOAD_BYTES	0x1F

 struct edp_vsc_psr {
 	struct edp_sdp_header sdp_header;
 	u8 DB0; /* Stereo Interface */
 	u8 DB1; /* 0 - PSR State; 1 - Update RFB; 2 - CRC Valid */
 	u8 DB2; /* CRC value bits 7:0 of the R or Cr component */
 	u8 DB3; /* CRC value bits 15:8 of the R or Cr component */
 	u8 DB4; /* CRC value bits 7:0 of the G or Y component */
 	u8 DB5; /* CRC value bits 15:8 of the G or Y component */
 	u8 DB6; /* CRC value bits 7:0 of the B or Cb component */
 	u8 DB7; /* CRC value bits 15:8 of the B or Cb component */
 	u8 DB8_31[24]; /* Reserved */
 } __packed;

 #define EDP_VSC_PSR_STATE_ACTIVE	(1<<0)
 #define EDP_VSC_PSR_UPDATE_RFB		(1<<1)
 #define EDP_VSC_PSR_CRC_VALUES_VALID	(1<<2)

 static inline int
 drm_dp_max_link_rate(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 {
 	return drm_dp_bw_code_to_link_rate(dpcd[DP_MAX_LINK_RATE]);
 }

 static inline u8
 drm_dp_max_lane_count(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 {
 	return dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK;
 }

 static inline bool
 drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 {
 	return dpcd[DP_DPCD_REV] >= 0x11 &&
 		(dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);
 }

 /*
  * DisplayPort AUX channel
  */

 /**
  * struct drm_dp_aux_msg - DisplayPort AUX channel transaction
  * @address: address of the (first) register to access
  * @request: contains the type of transaction (see DP_AUX_* macros)
  * @reply: upon completion, contains the reply type of the transaction
  * @buffer: pointer to a transmission or reception buffer
  * @size: size of @buffer
  */
 struct drm_dp_aux_msg {
 	unsigned int address;
 	u8 request;
 	u8 reply;
 	void *buffer;
 	size_t size;
 };

 /**
  * struct drm_dp_aux - DisplayPort AUX channel
  * @ddc: I2C adapter that can be used for I2C-over-AUX communication
  * @dev: pointer to struct device that is the parent for this AUX channel
  * @transfer: transfers a message representing a single AUX transaction
  *
  * The .dev field should be set to a pointer to the device that implements
  * the AUX channel.
  *
  * Drivers provide a hardware-specific implementation of how transactions
  * are executed via the .transfer() function. A pointer to a drm_dp_aux_msg
  * structure describing the transaction is passed into this function. Upon
  * success, the implementation should return the number of payload bytes
  * that were transferred, or a negative error-code on failure. Helpers
  * propagate errors from the .transfer() function, with the exception of
  * the -EBUSY error, which causes a transaction to be retried. On a short,
  * helpers will return -EPROTO to make it simpler to check for failure.
  *
  * An AUX channel can also be used to transport I2C messages to a sink. A
  * typical application of that is to access an EDID that's present in the
  * sink device. The .transfer() function can also be used to execute such
  * transactions. The drm_dp_aux_register_i2c_bus() function registers an
  * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers
  * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.
  */
 struct drm_dp_aux {
 	struct i2c_adapter ddc;
 	struct device *dev;

 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
 };

 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
 			 void *buffer, size_t size);
 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
 			  void *buffer, size_t size);

 /**
  * drm_dp_dpcd_readb() - read a single byte from the DPCD
  * @aux: DisplayPort AUX channel
  * @offset: address of the register to read
  * @valuep: location where the value of the register will be stored
  *
  * Returns the number of bytes transferred (1) on success, or a negative
  * error code on failure.
  */
 static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,
 					unsigned int offset, u8 *valuep)
 {
 	return drm_dp_dpcd_read(aux, offset, valuep, 1);
 }

 /**
  * drm_dp_dpcd_writeb() - write a single byte to the DPCD
  * @aux: DisplayPort AUX channel
  * @offset: address of the register to write
  * @value: value to write to the register
  *
  * Returns the number of bytes transferred (1) on success, or a negative
  * error code on failure.
  */
 static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
 					 unsigned int offset, u8 value)
 {
 	return drm_dp_dpcd_write(aux, offset, &value, 1);
 }

 int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
 				 u8 status[DP_LINK_STATUS_SIZE]);

 /*
  * DisplayPort link
  */
 #define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)

 struct drm_dp_link {
 	unsigned char revision;
 	unsigned int rate;
 	unsigned int num_lanes;
 	unsigned long capabilities;
 };

 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);

 int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);
 void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);

 #endif /* _DRM_DP_HELPER_H_ */
	/*
	* Copyright © 2008 Keith Packard
	*
	* 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.
	*/

	#ifndef _DRM_DP_HELPER_H_
	#define _DRM_DP_HELPER_H_

	#include <linux/types.h>
	#include <linux/i2c.h>
	#include <linux/delay.h>

	/*
	* Unless otherwise noted, all values are from the DP 1.1a spec. Note that
	* DP and DPCD versions are independent. Differences from 1.0 are not noted,
	* 1.0 devices basically don't exist in the wild.
	*
	* Abbreviations, in chronological order:
	*
	* eDP: Embedded DisplayPort version 1
	* DPI: DisplayPort Interoperability Guideline v1.1a
	* 1.2: DisplayPort 1.2
	*
	* 1.2 formally includes both eDP and DPI definitions.
	*/

	#define DP_AUX_I2C_WRITE 0x0
	#define DP_AUX_I2C_READ 0x1
	#define DP_AUX_I2C_STATUS 0x2
	#define DP_AUX_I2C_MOT 0x4
	#define DP_AUX_NATIVE_WRITE 0x8
	#define DP_AUX_NATIVE_READ 0x9

	#define DP_AUX_NATIVE_REPLY_ACK (0x0 << 0)
	#define DP_AUX_NATIVE_REPLY_NACK (0x1 << 0)
	#define DP_AUX_NATIVE_REPLY_DEFER (0x2 << 0)
	#define DP_AUX_NATIVE_REPLY_MASK (0x3 << 0)

	#define DP_AUX_I2C_REPLY_ACK (0x0 << 2)
	#define DP_AUX_I2C_REPLY_NACK (0x1 << 2)
	#define DP_AUX_I2C_REPLY_DEFER (0x2 << 2)
	#define DP_AUX_I2C_REPLY_MASK (0x3 << 2)

	/* AUX CH addresses */
	/* DPCD */
	#define DP_DPCD_REV 0x000

	#define DP_MAX_LINK_RATE 0x001

	#define DP_MAX_LANE_COUNT 0x002
	# define DP_MAX_LANE_COUNT_MASK 0x1f
	# define DP_TPS3_SUPPORTED (1 << 6) /* 1.2 */
	# define DP_ENHANCED_FRAME_CAP (1 << 7)

	#define DP_MAX_DOWNSPREAD 0x003
	# define DP_NO_AUX_HANDSHAKE_LINK_TRAINING (1 << 6)

	#define DP_NORP 0x004

	#define DP_DOWNSTREAMPORT_PRESENT 0x005
	# define DP_DWN_STRM_PORT_PRESENT (1 << 0)
	# define DP_DWN_STRM_PORT_TYPE_MASK 0x06
	# define DP_DWN_STRM_PORT_TYPE_DP (0 << 1)
	# define DP_DWN_STRM_PORT_TYPE_ANALOG (1 << 1)
	# define DP_DWN_STRM_PORT_TYPE_TMDS (2 << 1)
	# define DP_DWN_STRM_PORT_TYPE_OTHER (3 << 1)
	# define DP_FORMAT_CONVERSION (1 << 3)
	# define DP_DETAILED_CAP_INFO_AVAILABLE (1 << 4) /* DPI */

	#define DP_MAIN_LINK_CHANNEL_CODING 0x006

	#define DP_DOWN_STREAM_PORT_COUNT 0x007
	# define DP_PORT_COUNT_MASK 0x0f
	# define DP_MSA_TIMING_PAR_IGNORED (1 << 6) /* eDP */
	# define DP_OUI_SUPPORT (1 << 7)

	#define DP_I2C_SPEED_CAP 0x00c /* DPI */
	# define DP_I2C_SPEED_1K 0x01
	# define DP_I2C_SPEED_5K 0x02
	# define DP_I2C_SPEED_10K 0x04
	# define DP_I2C_SPEED_100K 0x08
	# define DP_I2C_SPEED_400K 0x10
	# define DP_I2C_SPEED_1M 0x20

	#define DP_EDP_CONFIGURATION_CAP 0x00d /* XXX 1.2? */
	#define DP_TRAINING_AUX_RD_INTERVAL 0x00e /* XXX 1.2? */

	/* Multiple stream transport */
	#define DP_MSTM_CAP 0x021 /* 1.2 */
	# define DP_MST_CAP (1 << 0)

	#define DP_PSR_SUPPORT 0x070 /* XXX 1.2? */
	# define DP_PSR_IS_SUPPORTED 1
	#define DP_PSR_CAPS 0x071 /* XXX 1.2? */
	# define DP_PSR_NO_TRAIN_ON_EXIT 1
	# define DP_PSR_SETUP_TIME_330 (0 << 1)
	# define DP_PSR_SETUP_TIME_275 (1 << 1)
	# define DP_PSR_SETUP_TIME_220 (2 << 1)
	# define DP_PSR_SETUP_TIME_165 (3 << 1)
	# define DP_PSR_SETUP_TIME_110 (4 << 1)
	# define DP_PSR_SETUP_TIME_55 (5 << 1)
	# define DP_PSR_SETUP_TIME_0 (6 << 1)
	# define DP_PSR_SETUP_TIME_MASK (7 << 1)
	# define DP_PSR_SETUP_TIME_SHIFT 1

	/*
	* 0x80-0x8f describe downstream port capabilities, but there are two layouts
	* based on whether DP_DETAILED_CAP_INFO_AVAILABLE was set. If it was not,
	* each port's descriptor is one byte wide. If it was set, each port's is
	* four bytes wide, starting with the one byte from the base info. As of
	* DP interop v1.1a only VGA defines additional detail.
	*/

	/* offset 0 */
	#define DP_DOWNSTREAM_PORT_0 0x80
	# define DP_DS_PORT_TYPE_MASK (7 << 0)
	# define DP_DS_PORT_TYPE_DP 0
	# define DP_DS_PORT_TYPE_VGA 1
	# define DP_DS_PORT_TYPE_DVI 2
	# define DP_DS_PORT_TYPE_HDMI 3
	# define DP_DS_PORT_TYPE_NON_EDID 4
	# define DP_DS_PORT_HPD (1 << 3)
	/* offset 1 for VGA is maximum megapixels per second / 8 */
	/* offset 2 */
	# define DP_DS_VGA_MAX_BPC_MASK (3 << 0)
	# define DP_DS_VGA_8BPC 0
	# define DP_DS_VGA_10BPC 1
	# define DP_DS_VGA_12BPC 2
	# define DP_DS_VGA_16BPC 3

	/* link configuration */
	#define DP_LINK_BW_SET 0x100
	# define DP_LINK_BW_1_62 0x06
	# define DP_LINK_BW_2_7 0x0a
	# define DP_LINK_BW_5_4 0x14 /* 1.2 */

	#define DP_LANE_COUNT_SET 0x101
	# define DP_LANE_COUNT_MASK 0x0f
	# define DP_LANE_COUNT_ENHANCED_FRAME_EN (1 << 7)

	#define DP_TRAINING_PATTERN_SET 0x102
	# define DP_TRAINING_PATTERN_DISABLE 0
	# define DP_TRAINING_PATTERN_1 1
	# define DP_TRAINING_PATTERN_2 2
	# define DP_TRAINING_PATTERN_3 3 /* 1.2 */
	# define DP_TRAINING_PATTERN_MASK 0x3

	# define DP_LINK_QUAL_PATTERN_DISABLE (0 << 2)
	# define DP_LINK_QUAL_PATTERN_D10_2 (1 << 2)
	# define DP_LINK_QUAL_PATTERN_ERROR_RATE (2 << 2)
	# define DP_LINK_QUAL_PATTERN_PRBS7 (3 << 2)
	# define DP_LINK_QUAL_PATTERN_MASK (3 << 2)

	# define DP_RECOVERED_CLOCK_OUT_EN (1 << 4)
	# define DP_LINK_SCRAMBLING_DISABLE (1 << 5)

	# define DP_SYMBOL_ERROR_COUNT_BOTH (0 << 6)
	# define DP_SYMBOL_ERROR_COUNT_DISPARITY (1 << 6)
	# define DP_SYMBOL_ERROR_COUNT_SYMBOL (2 << 6)
	# define DP_SYMBOL_ERROR_COUNT_MASK (3 << 6)

	#define DP_TRAINING_LANE0_SET 0x103
	#define DP_TRAINING_LANE1_SET 0x104
	#define DP_TRAINING_LANE2_SET 0x105
	#define DP_TRAINING_LANE3_SET 0x106

	# define DP_TRAIN_VOLTAGE_SWING_MASK 0x3
	# define DP_TRAIN_VOLTAGE_SWING_SHIFT 0
	# define DP_TRAIN_MAX_SWING_REACHED (1 << 2)
	# define DP_TRAIN_VOLTAGE_SWING_400 (0 << 0)
	# define DP_TRAIN_VOLTAGE_SWING_600 (1 << 0)
	# define DP_TRAIN_VOLTAGE_SWING_800 (2 << 0)
	# define DP_TRAIN_VOLTAGE_SWING_1200 (3 << 0)

	# define DP_TRAIN_PRE_EMPHASIS_MASK (3 << 3)
	# define DP_TRAIN_PRE_EMPHASIS_0 (0 << 3)
	# define DP_TRAIN_PRE_EMPHASIS_3_5 (1 << 3)
	# define DP_TRAIN_PRE_EMPHASIS_6 (2 << 3)
	# define DP_TRAIN_PRE_EMPHASIS_9_5 (3 << 3)

	# define DP_TRAIN_PRE_EMPHASIS_SHIFT 3
	# define DP_TRAIN_MAX_PRE_EMPHASIS_REACHED (1 << 5)

	#define DP_DOWNSPREAD_CTRL 0x107
	# define DP_SPREAD_AMP_0_5 (1 << 4)
	# define DP_MSA_TIMING_PAR_IGNORE_EN (1 << 7) /* eDP */

	#define DP_MAIN_LINK_CHANNEL_CODING_SET 0x108
	# define DP_SET_ANSI_8B10B (1 << 0)

	#define DP_I2C_SPEED_CONTROL_STATUS 0x109 /* DPI */
	/* bitmask as for DP_I2C_SPEED_CAP */

	#define DP_EDP_CONFIGURATION_SET 0x10a /* XXX 1.2? */

	#define DP_MSTM_CTRL 0x111 /* 1.2 */
	# define DP_MST_EN (1 << 0)
	# define DP_UP_REQ_EN (1 << 1)
	# define DP_UPSTREAM_IS_SRC (1 << 2)

	#define DP_PSR_EN_CFG 0x170 /* XXX 1.2? */
	# define DP_PSR_ENABLE (1 << 0)
	# define DP_PSR_MAIN_LINK_ACTIVE (1 << 1)
	# define DP_PSR_CRC_VERIFICATION (1 << 2)
	# define DP_PSR_FRAME_CAPTURE (1 << 3)

	#define DP_SINK_COUNT 0x200
	/* prior to 1.2 bit 7 was reserved mbz */
	# define DP_GET_SINK_COUNT(x) ((((x) & 0x80) >> 1) \| ((x) & 0x3f))
	# define DP_SINK_CP_READY (1 << 6)

	#define DP_DEVICE_SERVICE_IRQ_VECTOR 0x201
	# define DP_REMOTE_CONTROL_COMMAND_PENDING (1 << 0)
	# define DP_AUTOMATED_TEST_REQUEST (1 << 1)
	# define DP_CP_IRQ (1 << 2)
	# define DP_SINK_SPECIFIC_IRQ (1 << 6)

	#define DP_LANE0_1_STATUS 0x202
	#define DP_LANE2_3_STATUS 0x203
	# define DP_LANE_CR_DONE (1 << 0)
	# define DP_LANE_CHANNEL_EQ_DONE (1 << 1)
	# define DP_LANE_SYMBOL_LOCKED (1 << 2)

	#define DP_CHANNEL_EQ_BITS (DP_LANE_CR_DONE \| \
	DP_LANE_CHANNEL_EQ_DONE \| \
	DP_LANE_SYMBOL_LOCKED)

	#define DP_LANE_ALIGN_STATUS_UPDATED 0x204

	#define DP_INTERLANE_ALIGN_DONE (1 << 0)
	#define DP_DOWNSTREAM_PORT_STATUS_CHANGED (1 << 6)
	#define DP_LINK_STATUS_UPDATED (1 << 7)

	#define DP_SINK_STATUS 0x205

	#define DP_RECEIVE_PORT_0_STATUS (1 << 0)
	#define DP_RECEIVE_PORT_1_STATUS (1 << 1)

	#define DP_ADJUST_REQUEST_LANE0_1 0x206
	#define DP_ADJUST_REQUEST_LANE2_3 0x207
	# define DP_ADJUST_VOLTAGE_SWING_LANE0_MASK 0x03
	# define DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT 0
	# define DP_ADJUST_PRE_EMPHASIS_LANE0_MASK 0x0c
	# define DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT 2
	# define DP_ADJUST_VOLTAGE_SWING_LANE1_MASK 0x30
	# define DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT 4
	# define DP_ADJUST_PRE_EMPHASIS_LANE1_MASK 0xc0
	# define DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT 6

	#define DP_TEST_REQUEST 0x218
	# define DP_TEST_LINK_TRAINING (1 << 0)
	# define DP_TEST_LINK_VIDEO_PATTERN (1 << 1)
	# define DP_TEST_LINK_EDID_READ (1 << 2)
	# define DP_TEST_LINK_PHY_TEST_PATTERN (1 << 3) /* DPCD >= 1.1 */
	# define DP_TEST_LINK_FAUX_PATTERN (1 << 4) /* DPCD >= 1.2 */

	#define DP_TEST_LINK_RATE 0x219
	# define DP_LINK_RATE_162 (0x6)
	# define DP_LINK_RATE_27 (0xa)

	#define DP_TEST_LANE_COUNT 0x220

	#define DP_TEST_PATTERN 0x221

	#define DP_TEST_CRC_R_CR 0x240
	#define DP_TEST_CRC_G_Y 0x242
	#define DP_TEST_CRC_B_CB 0x244

	#define DP_TEST_SINK_MISC 0x246
	#define DP_TEST_CRC_SUPPORTED (1 << 5)

	#define DP_TEST_RESPONSE 0x260
	# define DP_TEST_ACK (1 << 0)
	# define DP_TEST_NAK (1 << 1)
	# define DP_TEST_EDID_CHECKSUM_WRITE (1 << 2)

	#define DP_TEST_SINK 0x270
	#define DP_TEST_SINK_START (1 << 0)

	#define DP_SOURCE_OUI 0x300
	#define DP_SINK_OUI 0x400
	#define DP_BRANCH_OUI 0x500

	#define DP_SET_POWER 0x600
	# define DP_SET_POWER_D0 0x1
	# define DP_SET_POWER_D3 0x2
	# define DP_SET_POWER_MASK 0x3

	#define DP_PSR_ERROR_STATUS 0x2006 /* XXX 1.2? */
	# define DP_PSR_LINK_CRC_ERROR (1 << 0)
	# define DP_PSR_RFB_STORAGE_ERROR (1 << 1)

	#define DP_PSR_ESI 0x2007 /* XXX 1.2? */
	# define DP_PSR_CAPS_CHANGE (1 << 0)

	#define DP_PSR_STATUS 0x2008 /* XXX 1.2? */
	# define DP_PSR_SINK_INACTIVE 0
	# define DP_PSR_SINK_ACTIVE_SRC_SYNCED 1
	# define DP_PSR_SINK_ACTIVE_RFB 2
	# define DP_PSR_SINK_ACTIVE_SINK_SYNCED 3
	# define DP_PSR_SINK_ACTIVE_RESYNC 4
	# define DP_PSR_SINK_INTERNAL_ERROR 7
	# define DP_PSR_SINK_STATE_MASK 0x07

	#define MODE_I2C_START 1
	#define MODE_I2C_WRITE 2
	#define MODE_I2C_READ 4
	#define MODE_I2C_STOP 8

	/**
	* struct i2c_algo_dp_aux_data - driver interface structure for i2c over dp
	* aux algorithm
	* @running: set by the algo indicating whether an i2c is ongoing or whether
	* the i2c bus is quiescent
	* @address: i2c target address for the currently ongoing transfer
	* @aux_ch: driver callback to transfer a single byte of the i2c payload
	*/
	struct i2c_algo_dp_aux_data {
	bool running;
	u16 address;
	int (aux_ch) (struct i2c_adapter adapter,
	int mode, uint8_t write_byte,
	uint8_t *read_byte);
	};

	int
	i2c_dp_aux_add_bus(struct i2c_adapter *adapter);


	#define DP_LINK_STATUS_SIZE 6
	bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
	int lane_count);
	bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
	int lane_count);
	u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
	int lane);
	u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
	int lane);

	#define DP_RECEIVER_CAP_SIZE 0xf
	#define EDP_PSR_RECEIVER_CAP_SIZE 2

	void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
	void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]);

	u8 drm_dp_link_rate_to_bw_code(int link_rate);
	int drm_dp_bw_code_to_link_rate(u8 link_bw);

	struct edp_sdp_header {
	u8 HB0; /* Secondary Data Packet ID */
	u8 HB1; /* Secondary Data Packet Type */
	u8 HB2; /* 7:5 reserved, 4:0 revision number */
	u8 HB3; /* 7:5 reserved, 4:0 number of valid data bytes */
	} __packed;

	#define EDP_SDP_HEADER_REVISION_MASK 0x1F
	#define EDP_SDP_HEADER_VALID_PAYLOAD_BYTES 0x1F

	struct edp_vsc_psr {
	struct edp_sdp_header sdp_header;
	u8 DB0; /* Stereo Interface */
	u8 DB1; /* 0 - PSR State; 1 - Update RFB; 2 - CRC Valid */
	u8 DB2; /* CRC value bits 7:0 of the R or Cr component */
	u8 DB3; /* CRC value bits 15:8 of the R or Cr component */
	u8 DB4; /* CRC value bits 7:0 of the G or Y component */
	u8 DB5; /* CRC value bits 15:8 of the G or Y component */
	u8 DB6; /* CRC value bits 7:0 of the B or Cb component */
	u8 DB7; /* CRC value bits 15:8 of the B or Cb component */
	u8 DB8_31[24]; /* Reserved */
	} __packed;

	#define EDP_VSC_PSR_STATE_ACTIVE (1<<0)
	#define EDP_VSC_PSR_UPDATE_RFB (1<<1)
	#define EDP_VSC_PSR_CRC_VALUES_VALID (1<<2)

	static inline int
	drm_dp_max_link_rate(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
	{
	return drm_dp_bw_code_to_link_rate(dpcd[DP_MAX_LINK_RATE]);
	}

	static inline u8
	drm_dp_max_lane_count(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
	{
	return dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK;
	}

	static inline bool
	drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
	{
	return dpcd[DP_DPCD_REV] >= 0x11 &&
	(dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);
	}

	/*
	* DisplayPort AUX channel
	*/

	/**
	* struct drm_dp_aux_msg - DisplayPort AUX channel transaction
	* @address: address of the (first) register to access
	* @request: contains the type of transaction (see DP_AUX_* macros)
	* @reply: upon completion, contains the reply type of the transaction
	* @buffer: pointer to a transmission or reception buffer
	* @size: size of @buffer
	*/
	struct drm_dp_aux_msg {
	unsigned int address;
	u8 request;
	u8 reply;
	void *buffer;
	size_t size;
	};

	/**
	* struct drm_dp_aux - DisplayPort AUX channel
	* @ddc: I2C adapter that can be used for I2C-over-AUX communication
	* @dev: pointer to struct device that is the parent for this AUX channel
	* @transfer: transfers a message representing a single AUX transaction
	*
	* The .dev field should be set to a pointer to the device that implements
	* the AUX channel.
	*
	* Drivers provide a hardware-specific implementation of how transactions
	* are executed via the .transfer() function. A pointer to a drm_dp_aux_msg
	* structure describing the transaction is passed into this function. Upon
	* success, the implementation should return the number of payload bytes
	* that were transferred, or a negative error-code on failure. Helpers
	* propagate errors from the .transfer() function, with the exception of
	* the -EBUSY error, which causes a transaction to be retried. On a short,
	* helpers will return -EPROTO to make it simpler to check for failure.
	*
	* An AUX channel can also be used to transport I2C messages to a sink. A
	* typical application of that is to access an EDID that's present in the
	* sink device. The .transfer() function can also be used to execute such
	* transactions. The drm_dp_aux_register_i2c_bus() function registers an
	* I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers
	* should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.
	*/
	struct drm_dp_aux {
	struct i2c_adapter ddc;
	struct device *dev;

	ssize_t (transfer)(struct drm_dp_aux aux,
	struct drm_dp_aux_msg *msg);
	};

	ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
	void *buffer, size_t size);
	ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
	void *buffer, size_t size);

	/**
	* drm_dp_dpcd_readb() - read a single byte from the DPCD
	* @aux: DisplayPort AUX channel
	* @offset: address of the register to read
	* @valuep: location where the value of the register will be stored
	*
	* Returns the number of bytes transferred (1) on success, or a negative
	* error code on failure.
	*/
	static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,
	unsigned int offset, u8 *valuep)
	{
	return drm_dp_dpcd_read(aux, offset, valuep, 1);
	}

	/**
	* drm_dp_dpcd_writeb() - write a single byte to the DPCD
	* @aux: DisplayPort AUX channel
	* @offset: address of the register to write
	* @value: value to write to the register
	*
	* Returns the number of bytes transferred (1) on success, or a negative
	* error code on failure.
	*/
	static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
	unsigned int offset, u8 value)
	{
	return drm_dp_dpcd_write(aux, offset, &value, 1);
	}

	int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
	u8 status[DP_LINK_STATUS_SIZE]);

	/*
	* DisplayPort link
	*/
	#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)

	struct drm_dp_link {
	unsigned char revision;
	unsigned int rate;
	unsigned int num_lanes;
	unsigned long capabilities;
	};

	int drm_dp_link_probe(struct drm_dp_aux aux, struct drm_dp_link link);
	int drm_dp_link_power_up(struct drm_dp_aux aux, struct drm_dp_link link);
	int drm_dp_link_configure(struct drm_dp_aux aux, struct drm_dp_link link);

	int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);
	void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);

	#endif /* _DRM_DP_HELPER_H_ */