/*
 * 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
 * MST: Multistream Transport - part of DP 1.2a
 *
 * 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_FAUX_CAP                         0x020   /* 1.2 */
# define DP_FAUX_CAP_1                      (1 << 0)

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

#define DP_GUID                             0x030   /* 1.2 */

#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_LEVEL_0 (0 << 0)
# define DP_TRAIN_VOLTAGE_SWING_LEVEL_1 (1 << 0)
# define DP_TRAIN_VOLTAGE_SWING_LEVEL_2 (2 << 0)
# define DP_TRAIN_VOLTAGE_SWING_LEVEL_3 (3 << 0)

# define DP_TRAIN_PRE_EMPHASIS_MASK         (3 << 3)
# define DP_TRAIN_PRE_EMPH_LEVEL_0              (0 << 3)
# define DP_TRAIN_PRE_EMPH_LEVEL_1              (1 << 3)
# define DP_TRAIN_PRE_EMPH_LEVEL_2              (2 << 3)
# define DP_TRAIN_PRE_EMPH_LEVEL_3              (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_ADAPTER_CTRL                     0x1a0
# define DP_ADAPTER_CTRL_FORCE_LOAD_SENSE   (1 << 0)

#define DP_BRANCH_DEVICE_CTRL               0x1a1
# define DP_BRANCH_DEVICE_IRQ_HPD           (1 << 0)

#define DP_PAYLOAD_ALLOCATE_SET             0x1c0
#define DP_PAYLOAD_ALLOCATE_START_TIME_SLOT 0x1c1
#define DP_PAYLOAD_ALLOCATE_TIME_SLOT_COUNT 0x1c2

#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_MCCS_IRQ                        (1 << 3)
# define DP_DOWN_REP_MSG_RDY                (1 << 4) /* 1.2 MST */
# define DP_UP_REQ_MSG_RDY                  (1 << 5) /* 1.2 MST */
# 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_COUNT_MASK                 0x7

#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_EDID_CHECKSUM               0x261

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

#define DP_PAYLOAD_TABLE_UPDATE_STATUS      0x2c0   /* 1.2 MST */
# define DP_PAYLOAD_TABLE_UPDATED           (1 << 0)
# define DP_PAYLOAD_ACT_HANDLED             (1 << 1)

#define DP_VC_PAYLOAD_ID_SLOT_1             0x2c1   /* 1.2 MST */
/* up to ID_SLOT_63 at 0x2ff */

#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_SIDEBAND_MSG_DOWN_REQ_BASE       0x1000   /* 1.2 MST */
#define DP_SIDEBAND_MSG_UP_REP_BASE         0x1200   /* 1.2 MST */
#define DP_SIDEBAND_MSG_DOWN_REP_BASE       0x1400   /* 1.2 MST */
#define DP_SIDEBAND_MSG_UP_REQ_BASE         0x1600   /* 1.2 MST */

#define DP_SINK_COUNT_ESI                   0x2002   /* 1.2 */
/* 0-5 sink count */
# define DP_SINK_COUNT_CP_READY             (1 << 6)

#define DP_DEVICE_SERVICE_IRQ_VECTOR_ESI0   0x2003   /* 1.2 */

#define DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1   0x2004   /* 1.2 */

#define DP_LINK_SERVICE_IRQ_VECTOR_ESI0     0x2005   /* 1.2 */

#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

/* DP 1.2 Sideband message defines */
/* peer device type - DP 1.2a Table 2-92 */
#define DP_PEER_DEVICE_NONE             0x0
#define DP_PEER_DEVICE_SOURCE_OR_SST    0x1
#define DP_PEER_DEVICE_MST_BRANCHING    0x2
#define DP_PEER_DEVICE_SST_SINK         0x3
#define DP_PEER_DEVICE_DP_LEGACY_CONV   0x4

/* DP 1.2 MST sideband request names DP 1.2a Table 2-80 */
#define DP_LINK_ADDRESS                 0x01
#define DP_CONNECTION_STATUS_NOTIFY     0x02
#define DP_ENUM_PATH_RESOURCES          0x10
#define DP_ALLOCATE_PAYLOAD             0x11
#define DP_QUERY_PAYLOAD                0x12
#define DP_RESOURCE_STATUS_NOTIFY       0x13
#define DP_CLEAR_PAYLOAD_ID_TABLE       0x14
#define DP_REMOTE_DPCD_READ             0x20
#define DP_REMOTE_DPCD_WRITE            0x21
#define DP_REMOTE_I2C_READ              0x22
#define DP_REMOTE_I2C_WRITE             0x23
#define DP_POWER_UP_PHY                 0x24
#define DP_POWER_DOWN_PHY               0x25
#define DP_SINK_EVENT_NOTIFY            0x30
#define DP_QUERY_STREAM_ENC_STATUS      0x38

/* DP 1.2 MST sideband nak reasons - table 2.84 */
#define DP_NAK_WRITE_FAILURE            0x01
#define DP_NAK_INVALID_READ             0x02
#define DP_NAK_CRC_FAILURE              0x03
#define DP_NAK_BAD_PARAM                0x04
#define DP_NAK_DEFER                    0x05
#define DP_NAK_LINK_FAILURE             0x06
#define DP_NAK_NO_RESOURCES             0x07
#define DP_NAK_DPCD_FAIL                0x08
#define DP_NAK_I2C_NAK                  0x09
#define DP_NAK_ALLOCATE_FAIL            0x0a

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

#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
 * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
 * @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
 * @hw_mutex: internal mutex used for locking transfers
 * @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.
 *
 * The .name field may be used to specify the name of the I2C adapter. If set to
 * NULL, dev_name() of .dev will be used.
 *
 * 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.
 *
 * Note that the aux helper code assumes that the .transfer() function
 * only modifies the reply field of the drm_dp_aux_msg structure.  The
 * retry logic and i2c helpers assume this is the case.
 */
struct drm_dp_aux {
        const char *name;
        struct i2c_adapter ddc;
        struct device *dev;
        struct mutex hw_mutex;
        ssize_t (*transfer)(struct drm_dp_aux *aux,
                            struct drm_dp_aux_msg *msg);
        unsigned i2c_nack_count, i2c_defer_count;
};

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_power_down(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(struct drm_dp_aux *aux);
void drm_dp_aux_unregister(struct drm_dp_aux *aux);

#endif /* _DRM_DP_HELPER_H_ */