/*
   * Copyright © 2014 Red Hat
   *
   * 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.
   */

  #include <linux/bitfield.h>

  #include <linux/delay.h>

  #include <linux/errno.h>

  #include <linux/i2c.h>
  #include <linux/init.h>
  #include <linux/kernel.h>

  #include <linux/random.h>

  #include <linux/sched.h>

  #include <linux/seq_file.h>

  #include <linux/iopoll.h>

  #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)

  #include <linux/stacktrace.h>

  #include <linux/sort.h>
  #include <linux/timekeeping.h>
  #include <linux/math64.h>
  #endif

  #include <drm/drm_atomic.h>
  #include <drm/drm_atomic_helper.h>

  #include <drm/drm_dp_mst_helper.h>
  #include <drm/drm_drv.h>

  #include <drm/drm_print.h>

  #include <drm/drm_probe_helper.h>

  #include "drm_crtc_helper_internal.h"

  #include "drm_dp_mst_topology_internal.h"

  /**
   * DOC: dp mst helper
   *
   * These functions contain parts of the DisplayPort 1.2a MultiStream Transport
   * protocol. The helpers contain a topology manager and bandwidth manager.
   * The helpers encapsulate the sending and received of sideband msgs.
   */

  struct drm_dp_pending_up_req {
  	struct drm_dp_sideband_msg_hdr hdr;
  	struct drm_dp_sideband_msg_req_body msg;
  	struct list_head next;
  };

  static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
  				  char *buf);

  static void drm_dp_mst_topology_put_port(struct drm_dp_mst_port *port);

  
  static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
  				     int id,
  				     struct drm_dp_payload *payload);

  static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
  				 struct drm_dp_mst_port *port,
  				 int offset, int size, u8 *bytes);

  static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
  				  struct drm_dp_mst_port *port,
  				  int offset, int size, u8 *bytes);

  static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
  				    struct drm_dp_mst_branch *mstb);

  
  static void
  drm_dp_send_clear_payload_id_table(struct drm_dp_mst_topology_mgr *mgr,
  				   struct drm_dp_mst_branch *mstb);

  static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
  					   struct drm_dp_mst_branch *mstb,
  					   struct drm_dp_mst_port *port);
  static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
  				 u8 *guid);

  static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port);
  static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_mst_port *port);

  static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr);

  #define DBG_PREFIX "[dp_mst]"

  #define DP_STR(x) [DP_ ## x] = #x
  
  static const char *drm_dp_mst_req_type_str(u8 req_type)
  {
  	static const char * const req_type_str[] = {
  		DP_STR(GET_MSG_TRANSACTION_VERSION),
  		DP_STR(LINK_ADDRESS),
  		DP_STR(CONNECTION_STATUS_NOTIFY),
  		DP_STR(ENUM_PATH_RESOURCES),
  		DP_STR(ALLOCATE_PAYLOAD),
  		DP_STR(QUERY_PAYLOAD),
  		DP_STR(RESOURCE_STATUS_NOTIFY),
  		DP_STR(CLEAR_PAYLOAD_ID_TABLE),
  		DP_STR(REMOTE_DPCD_READ),
  		DP_STR(REMOTE_DPCD_WRITE),
  		DP_STR(REMOTE_I2C_READ),
  		DP_STR(REMOTE_I2C_WRITE),
  		DP_STR(POWER_UP_PHY),
  		DP_STR(POWER_DOWN_PHY),
  		DP_STR(SINK_EVENT_NOTIFY),
  		DP_STR(QUERY_STREAM_ENC_STATUS),
  	};
  
  	if (req_type >= ARRAY_SIZE(req_type_str) ||
  	    !req_type_str[req_type])
  		return "unknown";
  
  	return req_type_str[req_type];
  }
  
  #undef DP_STR
  #define DP_STR(x) [DP_NAK_ ## x] = #x
  
  static const char *drm_dp_mst_nak_reason_str(u8 nak_reason)
  {
  	static const char * const nak_reason_str[] = {
  		DP_STR(WRITE_FAILURE),
  		DP_STR(INVALID_READ),
  		DP_STR(CRC_FAILURE),
  		DP_STR(BAD_PARAM),
  		DP_STR(DEFER),
  		DP_STR(LINK_FAILURE),
  		DP_STR(NO_RESOURCES),
  		DP_STR(DPCD_FAIL),
  		DP_STR(I2C_NAK),
  		DP_STR(ALLOCATE_FAIL),
  	};
  
  	if (nak_reason >= ARRAY_SIZE(nak_reason_str) ||
  	    !nak_reason_str[nak_reason])
  		return "unknown";
  
  	return nak_reason_str[nak_reason];
  }
  
  #undef DP_STR

  #define DP_STR(x) [DRM_DP_SIDEBAND_TX_ ## x] = #x
  
  static const char *drm_dp_mst_sideband_tx_state_str(int state)
  {
  	static const char * const sideband_reason_str[] = {
  		DP_STR(QUEUED),
  		DP_STR(START_SEND),
  		DP_STR(SENT),
  		DP_STR(RX),
  		DP_STR(TIMEOUT),
  	};
  
  	if (state >= ARRAY_SIZE(sideband_reason_str) ||
  	    !sideband_reason_str[state])
  		return "unknown";
  
  	return sideband_reason_str[state];
  }
  
  static int
  drm_dp_mst_rad_to_str(const u8 rad[8], u8 lct, char *out, size_t len)
  {
  	int i;
  	u8 unpacked_rad[16];
  
  	for (i = 0; i < lct; i++) {
  		if (i % 2)
  			unpacked_rad[i] = rad[i / 2] >> 4;
  		else
  			unpacked_rad[i] = rad[i / 2] & BIT_MASK(4);
  	}
  
  	/* TODO: Eventually add something to printk so we can format the rad
  	 * like this: 1.2.3
  	 */
  	return snprintf(out, len, "%*phC", lct, unpacked_rad);
  }

  /* sideband msg handling */
  static u8 drm_dp_msg_header_crc4(const uint8_t *data, size_t num_nibbles)
  {
  	u8 bitmask = 0x80;
  	u8 bitshift = 7;
  	u8 array_index = 0;
  	int number_of_bits = num_nibbles * 4;
  	u8 remainder = 0;
  
  	while (number_of_bits != 0) {
  		number_of_bits--;
  		remainder <<= 1;
  		remainder |= (data[array_index] & bitmask) >> bitshift;
  		bitmask >>= 1;
  		bitshift--;
  		if (bitmask == 0) {
  			bitmask = 0x80;
  			bitshift = 7;
  			array_index++;
  		}
  		if ((remainder & 0x10) == 0x10)
  			remainder ^= 0x13;
  	}
  
  	number_of_bits = 4;
  	while (number_of_bits != 0) {
  		number_of_bits--;
  		remainder <<= 1;
  		if ((remainder & 0x10) != 0)
  			remainder ^= 0x13;
  	}
  
  	return remainder;
  }
  
  static u8 drm_dp_msg_data_crc4(const uint8_t *data, u8 number_of_bytes)
  {
  	u8 bitmask = 0x80;
  	u8 bitshift = 7;
  	u8 array_index = 0;
  	int number_of_bits = number_of_bytes * 8;
  	u16 remainder = 0;
  
  	while (number_of_bits != 0) {
  		number_of_bits--;
  		remainder <<= 1;
  		remainder |= (data[array_index] & bitmask) >> bitshift;
  		bitmask >>= 1;
  		bitshift--;
  		if (bitmask == 0) {
  			bitmask = 0x80;
  			bitshift = 7;
  			array_index++;
  		}
  		if ((remainder & 0x100) == 0x100)
  			remainder ^= 0xd5;
  	}
  
  	number_of_bits = 8;
  	while (number_of_bits != 0) {
  		number_of_bits--;
  		remainder <<= 1;
  		if ((remainder & 0x100) != 0)
  			remainder ^= 0xd5;
  	}
  
  	return remainder & 0xff;
  }
  static inline u8 drm_dp_calc_sb_hdr_size(struct drm_dp_sideband_msg_hdr *hdr)
  {
  	u8 size = 3;

  	size += (hdr->lct / 2);
  	return size;
  }
  
  static void drm_dp_encode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
  					   u8 *buf, int *len)
  {
  	int idx = 0;
  	int i;
  	u8 crc4;

  	buf[idx++] = ((hdr->lct & 0xf) << 4) | (hdr->lcr & 0xf);
  	for (i = 0; i < (hdr->lct / 2); i++)
  		buf[idx++] = hdr->rad[i];
  	buf[idx++] = (hdr->broadcast << 7) | (hdr->path_msg << 6) |
  		(hdr->msg_len & 0x3f);
  	buf[idx++] = (hdr->somt << 7) | (hdr->eomt << 6) | (hdr->seqno << 4);
  
  	crc4 = drm_dp_msg_header_crc4(buf, (idx * 2) - 1);
  	buf[idx - 1] |= (crc4 & 0xf);
  
  	*len = idx;
  }
  
  static bool drm_dp_decode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
  					   u8 *buf, int buflen, u8 *hdrlen)
  {
  	u8 crc4;
  	u8 len;
  	int i;
  	u8 idx;

  	if (buf[0] == 0)
  		return false;
  	len = 3;
  	len += ((buf[0] & 0xf0) >> 4) / 2;
  	if (len > buflen)
  		return false;
  	crc4 = drm_dp_msg_header_crc4(buf, (len * 2) - 1);
  
  	if ((crc4 & 0xf) != (buf[len - 1] & 0xf)) {
  		DRM_DEBUG_KMS("crc4 mismatch 0x%x 0x%x
  ", crc4, buf[len - 1]);
  		return false;
  	}
  
  	hdr->lct = (buf[0] & 0xf0) >> 4;
  	hdr->lcr = (buf[0] & 0xf);
  	idx = 1;
  	for (i = 0; i < (hdr->lct / 2); i++)
  		hdr->rad[i] = buf[idx++];
  	hdr->broadcast = (buf[idx] >> 7) & 0x1;
  	hdr->path_msg = (buf[idx] >> 6) & 0x1;
  	hdr->msg_len = buf[idx] & 0x3f;
  	idx++;
  	hdr->somt = (buf[idx] >> 7) & 0x1;
  	hdr->eomt = (buf[idx] >> 6) & 0x1;
  	hdr->seqno = (buf[idx] >> 4) & 0x1;
  	idx++;
  	*hdrlen = idx;
  	return true;
  }

  void
  drm_dp_encode_sideband_req(const struct drm_dp_sideband_msg_req_body *req,
  			   struct drm_dp_sideband_msg_tx *raw)

  {
  	int idx = 0;
  	int i;
  	u8 *buf = raw->msg;

  	buf[idx++] = req->req_type & 0x7f;
  
  	switch (req->req_type) {
  	case DP_ENUM_PATH_RESOURCES:

  	case DP_POWER_DOWN_PHY:
  	case DP_POWER_UP_PHY:

  		buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
  		idx++;
  		break;
  	case DP_ALLOCATE_PAYLOAD:
  		buf[idx] = (req->u.allocate_payload.port_number & 0xf) << 4 |
  			(req->u.allocate_payload.number_sdp_streams & 0xf);
  		idx++;
  		buf[idx] = (req->u.allocate_payload.vcpi & 0x7f);
  		idx++;
  		buf[idx] = (req->u.allocate_payload.pbn >> 8);
  		idx++;
  		buf[idx] = (req->u.allocate_payload.pbn & 0xff);
  		idx++;
  		for (i = 0; i < req->u.allocate_payload.number_sdp_streams / 2; i++) {
  			buf[idx] = ((req->u.allocate_payload.sdp_stream_sink[i * 2] & 0xf) << 4) |
  				(req->u.allocate_payload.sdp_stream_sink[i * 2 + 1] & 0xf);
  			idx++;
  		}
  		if (req->u.allocate_payload.number_sdp_streams & 1) {
  			i = req->u.allocate_payload.number_sdp_streams - 1;
  			buf[idx] = (req->u.allocate_payload.sdp_stream_sink[i] & 0xf) << 4;
  			idx++;
  		}
  		break;
  	case DP_QUERY_PAYLOAD:
  		buf[idx] = (req->u.query_payload.port_number & 0xf) << 4;
  		idx++;
  		buf[idx] = (req->u.query_payload.vcpi & 0x7f);
  		idx++;
  		break;
  	case DP_REMOTE_DPCD_READ:
  		buf[idx] = (req->u.dpcd_read.port_number & 0xf) << 4;
  		buf[idx] |= ((req->u.dpcd_read.dpcd_address & 0xf0000) >> 16) & 0xf;
  		idx++;
  		buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff00) >> 8;
  		idx++;
  		buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff);
  		idx++;
  		buf[idx] = (req->u.dpcd_read.num_bytes);
  		idx++;
  		break;
  
  	case DP_REMOTE_DPCD_WRITE:
  		buf[idx] = (req->u.dpcd_write.port_number & 0xf) << 4;
  		buf[idx] |= ((req->u.dpcd_write.dpcd_address & 0xf0000) >> 16) & 0xf;
  		idx++;
  		buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff00) >> 8;
  		idx++;
  		buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff);
  		idx++;
  		buf[idx] = (req->u.dpcd_write.num_bytes);
  		idx++;
  		memcpy(&buf[idx], req->u.dpcd_write.bytes, req->u.dpcd_write.num_bytes);
  		idx += req->u.dpcd_write.num_bytes;
  		break;
  	case DP_REMOTE_I2C_READ:
  		buf[idx] = (req->u.i2c_read.port_number & 0xf) << 4;
  		buf[idx] |= (req->u.i2c_read.num_transactions & 0x3);
  		idx++;
  		for (i = 0; i < (req->u.i2c_read.num_transactions & 0x3); i++) {
  			buf[idx] = req->u.i2c_read.transactions[i].i2c_dev_id & 0x7f;
  			idx++;
  			buf[idx] = req->u.i2c_read.transactions[i].num_bytes;
  			idx++;
  			memcpy(&buf[idx], req->u.i2c_read.transactions[i].bytes, req->u.i2c_read.transactions[i].num_bytes);
  			idx += req->u.i2c_read.transactions[i].num_bytes;

  			buf[idx] = (req->u.i2c_read.transactions[i].no_stop_bit & 0x1) << 4;

  			buf[idx] |= (req->u.i2c_read.transactions[i].i2c_transaction_delay & 0xf);
  			idx++;
  		}
  		buf[idx] = (req->u.i2c_read.read_i2c_device_id) & 0x7f;
  		idx++;
  		buf[idx] = (req->u.i2c_read.num_bytes_read);
  		idx++;
  		break;
  
  	case DP_REMOTE_I2C_WRITE:
  		buf[idx] = (req->u.i2c_write.port_number & 0xf) << 4;
  		idx++;
  		buf[idx] = (req->u.i2c_write.write_i2c_device_id) & 0x7f;
  		idx++;
  		buf[idx] = (req->u.i2c_write.num_bytes);
  		idx++;
  		memcpy(&buf[idx], req->u.i2c_write.bytes, req->u.i2c_write.num_bytes);
  		idx += req->u.i2c_write.num_bytes;
  		break;

  	case DP_QUERY_STREAM_ENC_STATUS: {
  		const struct drm_dp_query_stream_enc_status *msg;
  
  		msg = &req->u.enc_status;
  		buf[idx] = msg->stream_id;
  		idx++;
  		memcpy(&buf[idx], msg->client_id, sizeof(msg->client_id));
  		idx += sizeof(msg->client_id);
  		buf[idx] = 0;
  		buf[idx] |= FIELD_PREP(GENMASK(1, 0), msg->stream_event);
  		buf[idx] |= msg->valid_stream_event ? BIT(2) : 0;
  		buf[idx] |= FIELD_PREP(GENMASK(4, 3), msg->stream_behavior);
  		buf[idx] |= msg->valid_stream_behavior ? BIT(5) : 0;
  		idx++;
  		}
  		break;

  	}
  	raw->cur_len = idx;
  }

  EXPORT_SYMBOL_FOR_TESTS_ONLY(drm_dp_encode_sideband_req);
  
  /* Decode a sideband request we've encoded, mainly used for debugging */
  int
  drm_dp_decode_sideband_req(const struct drm_dp_sideband_msg_tx *raw,
  			   struct drm_dp_sideband_msg_req_body *req)
  {
  	const u8 *buf = raw->msg;
  	int i, idx = 0;
  
  	req->req_type = buf[idx++] & 0x7f;
  	switch (req->req_type) {
  	case DP_ENUM_PATH_RESOURCES:
  	case DP_POWER_DOWN_PHY:
  	case DP_POWER_UP_PHY:
  		req->u.port_num.port_number = (buf[idx] >> 4) & 0xf;
  		break;
  	case DP_ALLOCATE_PAYLOAD:
  		{
  			struct drm_dp_allocate_payload *a =
  				&req->u.allocate_payload;
  
  			a->number_sdp_streams = buf[idx] & 0xf;
  			a->port_number = (buf[idx] >> 4) & 0xf;
  
  			WARN_ON(buf[++idx] & 0x80);
  			a->vcpi = buf[idx] & 0x7f;
  
  			a->pbn = buf[++idx] << 8;
  			a->pbn |= buf[++idx];
  
  			idx++;
  			for (i = 0; i < a->number_sdp_streams; i++) {
  				a->sdp_stream_sink[i] =
  					(buf[idx + (i / 2)] >> ((i % 2) ? 0 : 4)) & 0xf;
  			}
  		}
  		break;
  	case DP_QUERY_PAYLOAD:
  		req->u.query_payload.port_number = (buf[idx] >> 4) & 0xf;
  		WARN_ON(buf[++idx] & 0x80);
  		req->u.query_payload.vcpi = buf[idx] & 0x7f;
  		break;
  	case DP_REMOTE_DPCD_READ:
  		{
  			struct drm_dp_remote_dpcd_read *r = &req->u.dpcd_read;
  
  			r->port_number = (buf[idx] >> 4) & 0xf;
  
  			r->dpcd_address = (buf[idx] << 16) & 0xf0000;
  			r->dpcd_address |= (buf[++idx] << 8) & 0xff00;
  			r->dpcd_address |= buf[++idx] & 0xff;
  
  			r->num_bytes = buf[++idx];
  		}
  		break;
  	case DP_REMOTE_DPCD_WRITE:
  		{
  			struct drm_dp_remote_dpcd_write *w =
  				&req->u.dpcd_write;
  
  			w->port_number = (buf[idx] >> 4) & 0xf;
  
  			w->dpcd_address = (buf[idx] << 16) & 0xf0000;
  			w->dpcd_address |= (buf[++idx] << 8) & 0xff00;
  			w->dpcd_address |= buf[++idx] & 0xff;
  
  			w->num_bytes = buf[++idx];
  
  			w->bytes = kmemdup(&buf[++idx], w->num_bytes,
  					   GFP_KERNEL);
  			if (!w->bytes)
  				return -ENOMEM;
  		}
  		break;
  	case DP_REMOTE_I2C_READ:
  		{
  			struct drm_dp_remote_i2c_read *r = &req->u.i2c_read;
  			struct drm_dp_remote_i2c_read_tx *tx;
  			bool failed = false;
  
  			r->num_transactions = buf[idx] & 0x3;
  			r->port_number = (buf[idx] >> 4) & 0xf;
  			for (i = 0; i < r->num_transactions; i++) {
  				tx = &r->transactions[i];
  
  				tx->i2c_dev_id = buf[++idx] & 0x7f;
  				tx->num_bytes = buf[++idx];
  				tx->bytes = kmemdup(&buf[++idx],
  						    tx->num_bytes,
  						    GFP_KERNEL);
  				if (!tx->bytes) {
  					failed = true;
  					break;
  				}
  				idx += tx->num_bytes;
  				tx->no_stop_bit = (buf[idx] >> 5) & 0x1;
  				tx->i2c_transaction_delay = buf[idx] & 0xf;
  			}
  
  			if (failed) {

  				for (i = 0; i < r->num_transactions; i++) {
  					tx = &r->transactions[i];

  					kfree(tx->bytes);

  				}

  				return -ENOMEM;
  			}
  
  			r->read_i2c_device_id = buf[++idx] & 0x7f;
  			r->num_bytes_read = buf[++idx];
  		}
  		break;
  	case DP_REMOTE_I2C_WRITE:
  		{
  			struct drm_dp_remote_i2c_write *w = &req->u.i2c_write;
  
  			w->port_number = (buf[idx] >> 4) & 0xf;
  			w->write_i2c_device_id = buf[++idx] & 0x7f;
  			w->num_bytes = buf[++idx];
  			w->bytes = kmemdup(&buf[++idx], w->num_bytes,
  					   GFP_KERNEL);
  			if (!w->bytes)
  				return -ENOMEM;
  		}
  		break;

  	case DP_QUERY_STREAM_ENC_STATUS:
  		req->u.enc_status.stream_id = buf[idx++];
  		for (i = 0; i < sizeof(req->u.enc_status.client_id); i++)
  			req->u.enc_status.client_id[i] = buf[idx++];
  
  		req->u.enc_status.stream_event = FIELD_GET(GENMASK(1, 0),
  							   buf[idx]);
  		req->u.enc_status.valid_stream_event = FIELD_GET(BIT(2),
  								 buf[idx]);
  		req->u.enc_status.stream_behavior = FIELD_GET(GENMASK(4, 3),
  							      buf[idx]);
  		req->u.enc_status.valid_stream_behavior = FIELD_GET(BIT(5),
  								    buf[idx]);
  		break;

  	}
  
  	return 0;
  }
  EXPORT_SYMBOL_FOR_TESTS_ONLY(drm_dp_decode_sideband_req);
  
  void
  drm_dp_dump_sideband_msg_req_body(const struct drm_dp_sideband_msg_req_body *req,
  				  int indent, struct drm_printer *printer)
  {
  	int i;
  
  #define P(f, ...) drm_printf_indent(printer, indent, f, ##__VA_ARGS__)
  	if (req->req_type == DP_LINK_ADDRESS) {
  		/* No contents to print */
  		P("type=%s
  ", drm_dp_mst_req_type_str(req->req_type));
  		return;
  	}
  
  	P("type=%s contents:
  ", drm_dp_mst_req_type_str(req->req_type));
  	indent++;
  
  	switch (req->req_type) {
  	case DP_ENUM_PATH_RESOURCES:
  	case DP_POWER_DOWN_PHY:
  	case DP_POWER_UP_PHY:
  		P("port=%d
  ", req->u.port_num.port_number);
  		break;
  	case DP_ALLOCATE_PAYLOAD:
  		P("port=%d vcpi=%d pbn=%d sdp_streams=%d %*ph
  ",
  		  req->u.allocate_payload.port_number,
  		  req->u.allocate_payload.vcpi, req->u.allocate_payload.pbn,
  		  req->u.allocate_payload.number_sdp_streams,
  		  req->u.allocate_payload.number_sdp_streams,
  		  req->u.allocate_payload.sdp_stream_sink);
  		break;
  	case DP_QUERY_PAYLOAD:
  		P("port=%d vcpi=%d
  ",
  		  req->u.query_payload.port_number,
  		  req->u.query_payload.vcpi);
  		break;
  	case DP_REMOTE_DPCD_READ:
  		P("port=%d dpcd_addr=%05x len=%d
  ",
  		  req->u.dpcd_read.port_number, req->u.dpcd_read.dpcd_address,
  		  req->u.dpcd_read.num_bytes);
  		break;
  	case DP_REMOTE_DPCD_WRITE:
  		P("port=%d addr=%05x len=%d: %*ph
  ",
  		  req->u.dpcd_write.port_number,
  		  req->u.dpcd_write.dpcd_address,
  		  req->u.dpcd_write.num_bytes, req->u.dpcd_write.num_bytes,
  		  req->u.dpcd_write.bytes);
  		break;
  	case DP_REMOTE_I2C_READ:
  		P("port=%d num_tx=%d id=%d size=%d:
  ",
  		  req->u.i2c_read.port_number,
  		  req->u.i2c_read.num_transactions,
  		  req->u.i2c_read.read_i2c_device_id,
  		  req->u.i2c_read.num_bytes_read);
  
  		indent++;
  		for (i = 0; i < req->u.i2c_read.num_transactions; i++) {
  			const struct drm_dp_remote_i2c_read_tx *rtx =
  				&req->u.i2c_read.transactions[i];
  
  			P("%d: id=%03d size=%03d no_stop_bit=%d tx_delay=%03d: %*ph
  ",
  			  i, rtx->i2c_dev_id, rtx->num_bytes,
  			  rtx->no_stop_bit, rtx->i2c_transaction_delay,
  			  rtx->num_bytes, rtx->bytes);
  		}
  		break;
  	case DP_REMOTE_I2C_WRITE:
  		P("port=%d id=%d size=%d: %*ph
  ",
  		  req->u.i2c_write.port_number,
  		  req->u.i2c_write.write_i2c_device_id,
  		  req->u.i2c_write.num_bytes, req->u.i2c_write.num_bytes,
  		  req->u.i2c_write.bytes);
  		break;

  	case DP_QUERY_STREAM_ENC_STATUS:
  		P("stream_id=%u client_id=%*ph stream_event=%x "
  		  "valid_event=%d stream_behavior=%x valid_behavior=%d",
  		  req->u.enc_status.stream_id,
  		  (int)ARRAY_SIZE(req->u.enc_status.client_id),
  		  req->u.enc_status.client_id, req->u.enc_status.stream_event,
  		  req->u.enc_status.valid_stream_event,
  		  req->u.enc_status.stream_behavior,
  		  req->u.enc_status.valid_stream_behavior);
  		break;

  	default:
  		P("???
  ");
  		break;
  	}
  #undef P
  }
  EXPORT_SYMBOL_FOR_TESTS_ONLY(drm_dp_dump_sideband_msg_req_body);
  
  static inline void
  drm_dp_mst_dump_sideband_msg_tx(struct drm_printer *p,
  				const struct drm_dp_sideband_msg_tx *txmsg)
  {
  	struct drm_dp_sideband_msg_req_body req;
  	char buf[64];
  	int ret;
  	int i;
  
  	drm_dp_mst_rad_to_str(txmsg->dst->rad, txmsg->dst->lct, buf,
  			      sizeof(buf));
  	drm_printf(p, "txmsg cur_offset=%x cur_len=%x seqno=%x state=%s path_msg=%d dst=%s
  ",
  		   txmsg->cur_offset, txmsg->cur_len, txmsg->seqno,
  		   drm_dp_mst_sideband_tx_state_str(txmsg->state),
  		   txmsg->path_msg, buf);
  
  	ret = drm_dp_decode_sideband_req(txmsg, &req);
  	if (ret) {
  		drm_printf(p, "<failed to decode sideband req: %d>
  ", ret);
  		return;
  	}
  	drm_dp_dump_sideband_msg_req_body(&req, 1, p);
  
  	switch (req.req_type) {
  	case DP_REMOTE_DPCD_WRITE:
  		kfree(req.u.dpcd_write.bytes);
  		break;
  	case DP_REMOTE_I2C_READ:
  		for (i = 0; i < req.u.i2c_read.num_transactions; i++)
  			kfree(req.u.i2c_read.transactions[i].bytes);
  		break;
  	case DP_REMOTE_I2C_WRITE:
  		kfree(req.u.i2c_write.bytes);
  		break;
  	}
  }

  
  static void drm_dp_crc_sideband_chunk_req(u8 *msg, u8 len)
  {
  	u8 crc4;

  	crc4 = drm_dp_msg_data_crc4(msg, len);
  	msg[len] = crc4;
  }
  
  static void drm_dp_encode_sideband_reply(struct drm_dp_sideband_msg_reply_body *rep,
  					 struct drm_dp_sideband_msg_tx *raw)
  {
  	int idx = 0;
  	u8 *buf = raw->msg;
  
  	buf[idx++] = (rep->reply_type & 0x1) << 7 | (rep->req_type & 0x7f);
  
  	raw->cur_len = idx;
  }

  static int drm_dp_sideband_msg_set_header(struct drm_dp_sideband_msg_rx *msg,
  					  struct drm_dp_sideband_msg_hdr *hdr,
  					  u8 hdrlen)

  {

  	/*
  	 * ignore out-of-order messages or messages that are part of a
  	 * failed transaction
  	 */
  	if (!hdr->somt && !msg->have_somt)
  		return false;

  	/* get length contained in this portion */
  	msg->curchunk_idx = 0;
  	msg->curchunk_len = hdr->msg_len;
  	msg->curchunk_hdrlen = hdrlen;

  	/* we have already gotten an somt - don't bother parsing */
  	if (hdr->somt && msg->have_somt)
  		return false;

  	if (hdr->somt) {
  		memcpy(&msg->initial_hdr, hdr,
  		       sizeof(struct drm_dp_sideband_msg_hdr));
  		msg->have_somt = true;
  	}
  	if (hdr->eomt)
  		msg->have_eomt = true;

  	return true;
  }

  /* this adds a chunk of msg to the builder to get the final msg */
  static bool drm_dp_sideband_append_payload(struct drm_dp_sideband_msg_rx *msg,
  					   u8 *replybuf, u8 replybuflen)
  {
  	u8 crc4;

  	memcpy(&msg->chunk[msg->curchunk_idx], replybuf, replybuflen);
  	msg->curchunk_idx += replybuflen;

  
  	if (msg->curchunk_idx >= msg->curchunk_len) {
  		/* do CRC */
  		crc4 = drm_dp_msg_data_crc4(msg->chunk, msg->curchunk_len - 1);

  		if (crc4 != msg->chunk[msg->curchunk_len - 1])
  			print_hex_dump(KERN_DEBUG, "wrong crc",
  				       DUMP_PREFIX_NONE, 16, 1,
  				       msg->chunk,  msg->curchunk_len, false);

  		/* copy chunk into bigger msg */
  		memcpy(&msg->msg[msg->curlen], msg->chunk, msg->curchunk_len - 1);
  		msg->curlen += msg->curchunk_len - 1;
  	}
  	return true;
  }
  
  static bool drm_dp_sideband_parse_link_address(struct drm_dp_sideband_msg_rx *raw,
  					       struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;
  	int i;

  	memcpy(repmsg->u.link_addr.guid, &raw->msg[idx], 16);
  	idx += 16;
  	repmsg->u.link_addr.nports = raw->msg[idx] & 0xf;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	for (i = 0; i < repmsg->u.link_addr.nports; i++) {
  		if (raw->msg[idx] & 0x80)
  			repmsg->u.link_addr.ports[i].input_port = 1;
  
  		repmsg->u.link_addr.ports[i].peer_device_type = (raw->msg[idx] >> 4) & 0x7;
  		repmsg->u.link_addr.ports[i].port_number = (raw->msg[idx] & 0xf);
  
  		idx++;
  		if (idx > raw->curlen)
  			goto fail_len;
  		repmsg->u.link_addr.ports[i].mcs = (raw->msg[idx] >> 7) & 0x1;
  		repmsg->u.link_addr.ports[i].ddps = (raw->msg[idx] >> 6) & 0x1;
  		if (repmsg->u.link_addr.ports[i].input_port == 0)
  			repmsg->u.link_addr.ports[i].legacy_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
  		idx++;
  		if (idx > raw->curlen)
  			goto fail_len;
  		if (repmsg->u.link_addr.ports[i].input_port == 0) {
  			repmsg->u.link_addr.ports[i].dpcd_revision = (raw->msg[idx]);
  			idx++;
  			if (idx > raw->curlen)
  				goto fail_len;
  			memcpy(repmsg->u.link_addr.ports[i].peer_guid, &raw->msg[idx], 16);
  			idx += 16;
  			if (idx > raw->curlen)
  				goto fail_len;
  			repmsg->u.link_addr.ports[i].num_sdp_streams = (raw->msg[idx] >> 4) & 0xf;
  			repmsg->u.link_addr.ports[i].num_sdp_stream_sinks = (raw->msg[idx] & 0xf);
  			idx++;
  
  		}
  		if (idx > raw->curlen)
  			goto fail_len;
  	}
  
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("link address reply parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_remote_dpcd_read(struct drm_dp_sideband_msg_rx *raw,
  						   struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;

  	repmsg->u.remote_dpcd_read_ack.port_number = raw->msg[idx] & 0xf;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];

  	idx++;

  	if (idx > raw->curlen)
  		goto fail_len;
  
  	memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_dpcd_read_ack.num_bytes);
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("link address reply parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_remote_dpcd_write(struct drm_dp_sideband_msg_rx *raw,
  						      struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;

  	repmsg->u.remote_dpcd_write_ack.port_number = raw->msg[idx] & 0xf;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_remote_i2c_read_ack(struct drm_dp_sideband_msg_rx *raw,
  						      struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;
  
  	repmsg->u.remote_i2c_read_ack.port_number = (raw->msg[idx] & 0xf);
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.remote_i2c_read_ack.num_bytes = raw->msg[idx];
  	idx++;
  	/* TODO check */
  	memcpy(repmsg->u.remote_i2c_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_i2c_read_ack.num_bytes);
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("remote i2c reply parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband_msg_rx *raw,
  							  struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;

  	repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;

  	repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1;

  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.path_resources.full_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
  	idx += 2;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.path_resources.avail_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
  	idx += 2;
  	if (idx > raw->curlen)
  		goto fail_len;
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("enum resource parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_allocate_payload_ack(struct drm_dp_sideband_msg_rx *raw,
  							  struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;

  	repmsg->u.allocate_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.allocate_payload.vcpi = raw->msg[idx];
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.allocate_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
  	idx += 2;
  	if (idx > raw->curlen)
  		goto fail_len;
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("allocate payload parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_query_payload_ack(struct drm_dp_sideband_msg_rx *raw,
  						    struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;

  	repmsg->u.query_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  	repmsg->u.query_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
  	idx += 2;
  	if (idx > raw->curlen)
  		goto fail_len;
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("query payload parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }

  static bool drm_dp_sideband_parse_power_updown_phy_ack(struct drm_dp_sideband_msg_rx *raw,
  						       struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	int idx = 1;
  
  	repmsg->u.port_number.port_number = (raw->msg[idx] >> 4) & 0xf;
  	idx++;
  	if (idx > raw->curlen) {
  		DRM_DEBUG_KMS("power up/down phy parse length fail %d %d
  ",
  			      idx, raw->curlen);
  		return false;
  	}
  	return true;
  }

  static bool
  drm_dp_sideband_parse_query_stream_enc_status(
  				struct drm_dp_sideband_msg_rx *raw,
  				struct drm_dp_sideband_msg_reply_body *repmsg)
  {
  	struct drm_dp_query_stream_enc_status_ack_reply *reply;
  
  	reply = &repmsg->u.enc_status;
  
  	reply->stream_id = raw->msg[3];
  
  	reply->reply_signed = raw->msg[2] & BIT(0);
  
  	/*
  	 * NOTE: It's my impression from reading the spec that the below parsing
  	 * is correct. However I noticed while testing with an HDCP 1.4 display
  	 * through an HDCP 2.2 hub that only bit 3 was set. In that case, I
  	 * would expect both bits to be set. So keep the parsing following the
  	 * spec, but beware reality might not match the spec (at least for some
  	 * configurations).
  	 */
  	reply->hdcp_1x_device_present = raw->msg[2] & BIT(4);
  	reply->hdcp_2x_device_present = raw->msg[2] & BIT(3);
  
  	reply->query_capable_device_present = raw->msg[2] & BIT(5);
  	reply->legacy_device_present = raw->msg[2] & BIT(6);
  	reply->unauthorizable_device_present = raw->msg[2] & BIT(7);
  
  	reply->auth_completed = !!(raw->msg[1] & BIT(3));
  	reply->encryption_enabled = !!(raw->msg[1] & BIT(4));
  	reply->repeater_present = !!(raw->msg[1] & BIT(5));
  	reply->state = (raw->msg[1] & GENMASK(7, 6)) >> 6;
  
  	return true;
  }

  static bool drm_dp_sideband_parse_reply(struct drm_dp_sideband_msg_rx *raw,
  					struct drm_dp_sideband_msg_reply_body *msg)
  {
  	memset(msg, 0, sizeof(*msg));
  	msg->reply_type = (raw->msg[0] & 0x80) >> 7;
  	msg->req_type = (raw->msg[0] & 0x7f);

  	if (msg->reply_type == DP_SIDEBAND_REPLY_NAK) {

  		memcpy(msg->u.nak.guid, &raw->msg[1], 16);
  		msg->u.nak.reason = raw->msg[17];
  		msg->u.nak.nak_data = raw->msg[18];
  		return false;
  	}
  
  	switch (msg->req_type) {
  	case DP_LINK_ADDRESS:
  		return drm_dp_sideband_parse_link_address(raw, msg);
  	case DP_QUERY_PAYLOAD:
  		return drm_dp_sideband_parse_query_payload_ack(raw, msg);
  	case DP_REMOTE_DPCD_READ:
  		return drm_dp_sideband_parse_remote_dpcd_read(raw, msg);
  	case DP_REMOTE_DPCD_WRITE:
  		return drm_dp_sideband_parse_remote_dpcd_write(raw, msg);
  	case DP_REMOTE_I2C_READ:
  		return drm_dp_sideband_parse_remote_i2c_read_ack(raw, msg);

  	case DP_REMOTE_I2C_WRITE:
  		return true; /* since there's nothing to parse */

  	case DP_ENUM_PATH_RESOURCES:
  		return drm_dp_sideband_parse_enum_path_resources_ack(raw, msg);
  	case DP_ALLOCATE_PAYLOAD:
  		return drm_dp_sideband_parse_allocate_payload_ack(raw, msg);

  	case DP_POWER_DOWN_PHY:
  	case DP_POWER_UP_PHY:
  		return drm_dp_sideband_parse_power_updown_phy_ack(raw, msg);

  	case DP_CLEAR_PAYLOAD_ID_TABLE:
  		return true; /* since there's nothing to parse */

  	case DP_QUERY_STREAM_ENC_STATUS:
  		return drm_dp_sideband_parse_query_stream_enc_status(raw, msg);

  	default:

  		DRM_ERROR("Got unknown reply 0x%02x (%s)
  ", msg->req_type,
  			  drm_dp_mst_req_type_str(msg->req_type));

  		return false;
  	}
  }
  
  static bool drm_dp_sideband_parse_connection_status_notify(struct drm_dp_sideband_msg_rx *raw,
  							   struct drm_dp_sideband_msg_req_body *msg)
  {
  	int idx = 1;
  
  	msg->u.conn_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  
  	memcpy(msg->u.conn_stat.guid, &raw->msg[idx], 16);
  	idx += 16;
  	if (idx > raw->curlen)
  		goto fail_len;
  
  	msg->u.conn_stat.legacy_device_plug_status = (raw->msg[idx] >> 6) & 0x1;
  	msg->u.conn_stat.displayport_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
  	msg->u.conn_stat.message_capability_status = (raw->msg[idx] >> 4) & 0x1;
  	msg->u.conn_stat.input_port = (raw->msg[idx] >> 3) & 0x1;
  	msg->u.conn_stat.peer_device_type = (raw->msg[idx] & 0x7);
  	idx++;
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("connection status reply parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_resource_status_notify(struct drm_dp_sideband_msg_rx *raw,
  							   struct drm_dp_sideband_msg_req_body *msg)
  {
  	int idx = 1;
  
  	msg->u.resource_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
  	idx++;
  	if (idx > raw->curlen)
  		goto fail_len;
  
  	memcpy(msg->u.resource_stat.guid, &raw->msg[idx], 16);
  	idx += 16;
  	if (idx > raw->curlen)
  		goto fail_len;
  
  	msg->u.resource_stat.available_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
  	idx++;
  	return true;
  fail_len:
  	DRM_DEBUG_KMS("resource status reply parse length fail %d %d
  ", idx, raw->curlen);
  	return false;
  }
  
  static bool drm_dp_sideband_parse_req(struct drm_dp_sideband_msg_rx *raw,
  				      struct drm_dp_sideband_msg_req_body *msg)
  {
  	memset(msg, 0, sizeof(*msg));
  	msg->req_type = (raw->msg[0] & 0x7f);
  
  	switch (msg->req_type) {
  	case DP_CONNECTION_STATUS_NOTIFY:
  		return drm_dp_sideband_parse_connection_status_notify(raw, msg);
  	case DP_RESOURCE_STATUS_NOTIFY:
  		return drm_dp_sideband_parse_resource_status_notify(raw, msg);
  	default:

  		DRM_ERROR("Got unknown request 0x%02x (%s)
  ", msg->req_type,
  			  drm_dp_mst_req_type_str(msg->req_type));

  		return false;
  	}
  }

  static void build_dpcd_write(struct drm_dp_sideband_msg_tx *msg,
  			     u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)

  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	req.req_type = DP_REMOTE_DPCD_WRITE;
  	req.u.dpcd_write.port_number = port_num;
  	req.u.dpcd_write.dpcd_address = offset;
  	req.u.dpcd_write.num_bytes = num_bytes;
  	req.u.dpcd_write.bytes = bytes;
  	drm_dp_encode_sideband_req(&req, msg);

  }

  static void build_link_address(struct drm_dp_sideband_msg_tx *msg)

  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	req.req_type = DP_LINK_ADDRESS;
  	drm_dp_encode_sideband_req(&req, msg);

  }

  static void build_clear_payload_id_table(struct drm_dp_sideband_msg_tx *msg)

  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	req.req_type = DP_CLEAR_PAYLOAD_ID_TABLE;
  	drm_dp_encode_sideband_req(&req, msg);

  }

  static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg,
  				     int port_num)

  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	req.req_type = DP_ENUM_PATH_RESOURCES;
  	req.u.port_num.port_number = port_num;
  	drm_dp_encode_sideband_req(&req, msg);
  	msg->path_msg = true;
  	return 0;
  }

  static void build_allocate_payload(struct drm_dp_sideband_msg_tx *msg,
  				   int port_num,
  				   u8 vcpi, uint16_t pbn,
  				   u8 number_sdp_streams,
  				   u8 *sdp_stream_sink)

  {
  	struct drm_dp_sideband_msg_req_body req;

  	memset(&req, 0, sizeof(req));
  	req.req_type = DP_ALLOCATE_PAYLOAD;
  	req.u.allocate_payload.port_number = port_num;
  	req.u.allocate_payload.vcpi = vcpi;
  	req.u.allocate_payload.pbn = pbn;

  	req.u.allocate_payload.number_sdp_streams = number_sdp_streams;
  	memcpy(req.u.allocate_payload.sdp_stream_sink, sdp_stream_sink,
  		   number_sdp_streams);

  	drm_dp_encode_sideband_req(&req, msg);
  	msg->path_msg = true;

  }

  static void build_power_updown_phy(struct drm_dp_sideband_msg_tx *msg,
  				   int port_num, bool power_up)

  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	if (power_up)
  		req.req_type = DP_POWER_UP_PHY;
  	else
  		req.req_type = DP_POWER_DOWN_PHY;
  
  	req.u.port_num.port_number = port_num;
  	drm_dp_encode_sideband_req(&req, msg);
  	msg->path_msg = true;

  }

  static int
  build_query_stream_enc_status(struct drm_dp_sideband_msg_tx *msg, u8 stream_id,
  			      u8 *q_id)
  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	req.req_type = DP_QUERY_STREAM_ENC_STATUS;
  	req.u.enc_status.stream_id = stream_id;
  	memcpy(req.u.enc_status.client_id, q_id,
  	       sizeof(req.u.enc_status.client_id));
  	req.u.enc_status.stream_event = 0;
  	req.u.enc_status.valid_stream_event = false;
  	req.u.enc_status.stream_behavior = 0;
  	req.u.enc_status.valid_stream_behavior = false;
  
  	drm_dp_encode_sideband_req(&req, msg);
  	return 0;
  }

  static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
  					struct drm_dp_vcpi *vcpi)
  {

  	int ret, vcpi_ret;

  
  	mutex_lock(&mgr->payload_lock);
  	ret = find_first_zero_bit(&mgr->payload_mask, mgr->max_payloads + 1);
  	if (ret > mgr->max_payloads) {
  		ret = -EINVAL;
  		DRM_DEBUG_KMS("out of payload ids %d
  ", ret);
  		goto out_unlock;
  	}

  	vcpi_ret = find_first_zero_bit(&mgr->vcpi_mask, mgr->max_payloads + 1);
  	if (vcpi_ret > mgr->max_payloads) {
  		ret = -EINVAL;
  		DRM_DEBUG_KMS("out of vcpi ids %d
  ", ret);
  		goto out_unlock;
  	}

  	set_bit(ret, &mgr->payload_mask);

  	set_bit(vcpi_ret, &mgr->vcpi_mask);
  	vcpi->vcpi = vcpi_ret + 1;

  	mgr->proposed_vcpis[ret - 1] = vcpi;
  out_unlock:
  	mutex_unlock(&mgr->payload_lock);
  	return ret;
  }
  
  static void drm_dp_mst_put_payload_id(struct drm_dp_mst_topology_mgr *mgr,

  				      int vcpi)

  {

  	int i;

  	if (vcpi == 0)

  		return;
  
  	mutex_lock(&mgr->payload_lock);

  	DRM_DEBUG_KMS("putting payload %d
  ", vcpi);
  	clear_bit(vcpi - 1, &mgr->vcpi_mask);
  
  	for (i = 0; i < mgr->max_payloads; i++) {

  		if (mgr->proposed_vcpis[i] &&
  		    mgr->proposed_vcpis[i]->vcpi == vcpi) {
  			mgr->proposed_vcpis[i] = NULL;
  			clear_bit(i + 1, &mgr->payload_mask);
  		}

  	}

  	mutex_unlock(&mgr->payload_lock);
  }
  
  static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr,
  			      struct drm_dp_sideband_msg_tx *txmsg)
  {

  	unsigned int state;

  
  	/*
  	 * All updates to txmsg->state are protected by mgr->qlock, and the two
  	 * cases we check here are terminal states. For those the barriers
  	 * provided by the wake_up/wait_event pair are enough.
  	 */

  	state = READ_ONCE(txmsg->state);
  	return (state == DRM_DP_SIDEBAND_TX_RX ||
  		state == DRM_DP_SIDEBAND_TX_TIMEOUT);

  }
  
  static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb,
  				    struct drm_dp_sideband_msg_tx *txmsg)
  {
  	struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;

  	unsigned long wait_timeout = msecs_to_jiffies(4000);
  	unsigned long wait_expires = jiffies + wait_timeout;

  	int ret;

  	for (;;) {
  		/*
  		 * If the driver provides a way for this, change to
  		 * poll-waiting for the MST reply interrupt if we didn't receive
  		 * it for 50 msec. This would cater for cases where the HPD
  		 * pulse signal got lost somewhere, even though the sink raised
  		 * the corresponding MST interrupt correctly. One example is the
  		 * Club 3D CAC-1557 TypeC -> DP adapter which for some reason
  		 * filters out short pulses with a duration less than ~540 usec.
  		 *
  		 * The poll period is 50 msec to avoid missing an interrupt
  		 * after the sink has cleared it (after a 110msec timeout
  		 * since it raised the interrupt).
  		 */
  		ret = wait_event_timeout(mgr->tx_waitq,
  					 check_txmsg_state(mgr, txmsg),
  					 mgr->cbs->poll_hpd_irq ?
  						msecs_to_jiffies(50) :
  						wait_timeout);
  
  		if (ret || !mgr->cbs->poll_hpd_irq ||
  		    time_after(jiffies, wait_expires))
  			break;
  
  		mgr->cbs->poll_hpd_irq(mgr);
  	}

  	mutex_lock(&mgr->qlock);

  	if (ret > 0) {
  		if (txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT) {
  			ret = -EIO;
  			goto out;
  		}
  	} else {
  		DRM_DEBUG_KMS("timedout msg send %p %d %d
  ", txmsg, txmsg->state, txmsg->seqno);
  
  		/* dump some state */
  		ret = -EIO;
  
  		/* remove from q */
  		if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED ||

  		    txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND ||
  		    txmsg->state == DRM_DP_SIDEBAND_TX_SENT)

  			list_del(&txmsg->next);

  	}
  out:

  	if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) {

  		struct drm_printer p = drm_debug_printer(DBG_PREFIX);
  
  		drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
  	}

  	mutex_unlock(&mgr->qlock);

  	drm_dp_mst_kick_tx(mgr);

  	return ret;
  }
  
  static struct drm_dp_mst_branch *drm_dp_add_mst_branch_device(u8 lct, u8 *rad)
  {
  	struct drm_dp_mst_branch *mstb;
  
  	mstb = kzalloc(sizeof(*mstb), GFP_KERNEL);
  	if (!mstb)
  		return NULL;
  
  	mstb->lct = lct;
  	if (lct > 1)
  		memcpy(mstb->rad, rad, lct / 2);
  	INIT_LIST_HEAD(&mstb->ports);

  	kref_init(&mstb->topology_kref);
  	kref_init(&mstb->malloc_kref);

  	return mstb;
  }

  static void drm_dp_free_mst_branch_device(struct kref *kref)
  {

  	struct drm_dp_mst_branch *mstb =
  		container_of(kref, struct drm_dp_mst_branch, malloc_kref);
  
  	if (mstb->port_parent)
  		drm_dp_mst_put_port_malloc(mstb->port_parent);

  	kfree(mstb);
  }

  /**
   * DOC: Branch device and port refcounting
   *
   * Topology refcount overview
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~
   *
   * The refcounting schemes for &struct drm_dp_mst_branch and &struct
   * drm_dp_mst_port are somewhat unusual. Both ports and branch devices have
   * two different kinds of refcounts: topology refcounts, and malloc refcounts.
   *
   * Topology refcounts are not exposed to drivers, and are handled internally
   * by the DP MST helpers. The helpers use them in order to prevent the
   * in-memory topology state from being changed in the middle of critical
   * operations like changing the internal state of payload allocations. This
   * means each branch and port will be considered to be connected to the rest

   * of the topology until its topology refcount reaches zero. Additionally,

   * for ports this means that their associated &struct drm_connector will stay
   * registered with userspace until the port's refcount reaches 0.
   *
   * Malloc refcount overview
   * ~~~~~~~~~~~~~~~~~~~~~~~~
   *
   * Malloc references are used to keep a &struct drm_dp_mst_port or &struct
   * drm_dp_mst_branch allocated even after all of its topology references have
   * been dropped, so that the driver or MST helpers can safely access each
   * branch's last known state before it was disconnected from the topology.
   * When the malloc refcount of a port or branch reaches 0, the memory
   * allocation containing the &struct drm_dp_mst_branch or &struct
   * drm_dp_mst_port respectively will be freed.
   *
   * For &struct drm_dp_mst_branch, malloc refcounts are not currently exposed
   * to drivers. As of writing this documentation, there are no drivers that
   * have a usecase for accessing &struct drm_dp_mst_branch outside of the MST
   * helpers. Exposing this API to drivers in a race-free manner would take more
   * tweaking of the refcounting scheme, however patches are welcome provided
   * there is a legitimate driver usecase for this.
   *
   * Refcount relationships in a topology
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   *
   * Let's take a look at why the relationship between topology and malloc
   * refcounts is designed the way it is.
   *
   * .. kernel-figure:: dp-mst/topology-figure-1.dot
   *
   *    An example of topology and malloc refs in a DP MST topology with two
   *    active payloads. Topology refcount increments are indicated by solid
   *    lines, and malloc refcount increments are indicated by dashed lines.
   *    Each starts from the branch which incremented the refcount, and ends at
   *    the branch to which the refcount belongs to, i.e. the arrow points the
   *    same way as the C pointers used to reference a structure.
   *
   * As you can see in the above figure, every branch increments the topology

   * refcount of its children, and increments the malloc refcount of its
   * parent. Additionally, every payload increments the malloc refcount of its

   * assigned port by 1.
   *
   * So, what would happen if MSTB #3 from the above figure was unplugged from
   * the system, but the driver hadn't yet removed payload #2 from port #3? The
   * topology would start to look like the figure below.
   *
   * .. kernel-figure:: dp-mst/topology-figure-2.dot
   *
   *    Ports and branch devices which have been released from memory are
   *    colored grey, and references which have been removed are colored red.
   *
   * Whenever a port or branch device's topology refcount reaches zero, it will
   * decrement the topology refcounts of all its children, the malloc refcount
   * of its parent, and finally its own malloc refcount. For MSTB #4 and port
   * #4, this means they both have been disconnected from the topology and freed
   * from memory. But, because payload #2 is still holding a reference to port

   * #3, port #3 is removed from the topology but its &struct drm_dp_mst_port

   * is still accessible from memory. This also means port #3 has not yet

   * decremented the malloc refcount of MSTB #3, so its &struct

   * drm_dp_mst_branch will also stay allocated in memory until port #3's
   * malloc refcount reaches 0.
   *
   * This relationship is necessary because in order to release payload #2, we
   * need to be able to figure out the last relative of port #3 that's still
   * connected to the topology. In this case, we would travel up the topology as
   * shown below.
   *
   * .. kernel-figure:: dp-mst/topology-figure-3.dot
   *
   * And finally, remove payload #2 by communicating with port #2 through
   * sideband transactions.
   */
  
  /**
   * drm_dp_mst_get_mstb_malloc() - Increment the malloc refcount of a branch
   * device
   * @mstb: The &struct drm_dp_mst_branch to increment the malloc refcount of
   *
   * Increments &drm_dp_mst_branch.malloc_kref. When
   * &drm_dp_mst_branch.malloc_kref reaches 0, the memory allocation for @mstb
   * will be released and @mstb may no longer be used.
   *
   * See also: drm_dp_mst_put_mstb_malloc()
   */
  static void
  drm_dp_mst_get_mstb_malloc(struct drm_dp_mst_branch *mstb)
  {
  	kref_get(&mstb->malloc_kref);
  	DRM_DEBUG("mstb %p (%d)
  ", mstb, kref_read(&mstb->malloc_kref));
  }
  
  /**
   * drm_dp_mst_put_mstb_malloc() - Decrement the malloc refcount of a branch
   * device
   * @mstb: The &struct drm_dp_mst_branch to decrement the malloc refcount of
   *
   * Decrements &drm_dp_mst_branch.malloc_kref. When
   * &drm_dp_mst_branch.malloc_kref reaches 0, the memory allocation for @mstb
   * will be released and @mstb may no longer be used.
   *
   * See also: drm_dp_mst_get_mstb_malloc()
   */
  static void
  drm_dp_mst_put_mstb_malloc(struct drm_dp_mst_branch *mstb)
  {
  	DRM_DEBUG("mstb %p (%d)
  ", mstb, kref_read(&mstb->malloc_kref) - 1);
  	kref_put(&mstb->malloc_kref, drm_dp_free_mst_branch_device);
  }
  
  static void drm_dp_free_mst_port(struct kref *kref)
  {
  	struct drm_dp_mst_port *port =
  		container_of(kref, struct drm_dp_mst_port, malloc_kref);
  
  	drm_dp_mst_put_mstb_malloc(port->parent);
  	kfree(port);
  }
  
  /**
   * drm_dp_mst_get_port_malloc() - Increment the malloc refcount of an MST port
   * @port: The &struct drm_dp_mst_port to increment the malloc refcount of
   *
   * Increments &drm_dp_mst_port.malloc_kref. When &drm_dp_mst_port.malloc_kref
   * reaches 0, the memory allocation for @port will be released and @port may
   * no longer be used.
   *
   * Because @port could potentially be freed at any time by the DP MST helpers
   * if &drm_dp_mst_port.malloc_kref reaches 0, including during a call to this
   * function, drivers that which to make use of &struct drm_dp_mst_port should
   * ensure that they grab at least one main malloc reference to their MST ports
   * in &drm_dp_mst_topology_cbs.add_connector. This callback is called before
   * there is any chance for &drm_dp_mst_port.malloc_kref to reach 0.
   *
   * See also: drm_dp_mst_put_port_malloc()
   */
  void
  drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port)
  {
  	kref_get(&port->malloc_kref);
  	DRM_DEBUG("port %p (%d)
  ", port, kref_read(&port->malloc_kref));
  }
  EXPORT_SYMBOL(drm_dp_mst_get_port_malloc);
  
  /**
   * drm_dp_mst_put_port_malloc() - Decrement the malloc refcount of an MST port
   * @port: The &struct drm_dp_mst_port to decrement the malloc refcount of
   *
   * Decrements &drm_dp_mst_port.malloc_kref. When &drm_dp_mst_port.malloc_kref
   * reaches 0, the memory allocation for @port will be released and @port may
   * no longer be used.
   *
   * See also: drm_dp_mst_get_port_malloc()
   */
  void
  drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port)
  {
  	DRM_DEBUG("port %p (%d)
  ", port, kref_read(&port->malloc_kref) - 1);
  	kref_put(&port->malloc_kref, drm_dp_free_mst_port);
  }
  EXPORT_SYMBOL(drm_dp_mst_put_port_malloc);

  #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
  
  #define STACK_DEPTH 8
  
  static noinline void
  __topology_ref_save(struct drm_dp_mst_topology_mgr *mgr,
  		    struct drm_dp_mst_topology_ref_history *history,
  		    enum drm_dp_mst_topology_ref_type type)

  {

  	struct drm_dp_mst_topology_ref_entry *entry = NULL;
  	depot_stack_handle_t backtrace;
  	ulong stack_entries[STACK_DEPTH];
  	uint n;
  	int i;

  	n = stack_trace_save(stack_entries, ARRAY_SIZE(stack_entries), 1);
  	backtrace = stack_depot_save(stack_entries, n, GFP_KERNEL);
  	if (!backtrace)
  		return;
  
  	/* Try to find an existing entry for this backtrace */
  	for (i = 0; i < history->len; i++) {
  		if (history->entries[i].backtrace == backtrace) {
  			entry = &history->entries[i];
  			break;
  		}

  	}

  	/* Otherwise add one */
  	if (!entry) {
  		struct drm_dp_mst_topology_ref_entry *new;
  		int new_len = history->len + 1;
  
  		new = krealloc(history->entries, sizeof(*new) * new_len,
  			       GFP_KERNEL);
  		if (!new)
  			return;
  
  		entry = &new[history->len];
  		history->len = new_len;
  		history->entries = new;
  
  		entry->backtrace = backtrace;
  		entry->type = type;
  		entry->count = 0;

  	}

  	entry->count++;
  	entry->ts_nsec = ktime_get_ns();
  }
  
  static int
  topology_ref_history_cmp(const void *a, const void *b)
  {
  	const struct drm_dp_mst_topology_ref_entry *entry_a = a, *entry_b = b;
  
  	if (entry_a->ts_nsec > entry_b->ts_nsec)
  		return 1;
  	else if (entry_a->ts_nsec < entry_b->ts_nsec)
  		return -1;
  	else
  		return 0;
  }
  
  static inline const char *
  topology_ref_type_to_str(enum drm_dp_mst_topology_ref_type type)
  {
  	if (type == DRM_DP_MST_TOPOLOGY_REF_GET)
  		return "get";
  	else
  		return "put";
  }
  
  static void
  __dump_topology_ref_history(struct drm_dp_mst_topology_ref_history *history,
  			    void *ptr, const char *type_str)
  {
  	struct drm_printer p = drm_debug_printer(DBG_PREFIX);
  	char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
  	int i;
  
  	if (!buf)
  		return;
  
  	if (!history->len)
  		goto out;
  
  	/* First, sort the list so that it goes from oldest to newest
  	 * reference entry
  	 */
  	sort(history->entries, history->len, sizeof(*history->entries),
  	     topology_ref_history_cmp, NULL);
  
  	drm_printf(&p, "%s (%p) topology count reached 0, dumping history:
  ",
  		   type_str, ptr);
  
  	for (i = 0; i < history->len; i++) {
  		const struct drm_dp_mst_topology_ref_entry *entry =
  			&history->entries[i];
  		ulong *entries;
  		uint nr_entries;
  		u64 ts_nsec = entry->ts_nsec;

  		u32 rem_nsec = do_div(ts_nsec, 1000000000);

  
  		nr_entries = stack_depot_fetch(entry->backtrace, &entries);
  		stack_trace_snprint(buf, PAGE_SIZE, entries, nr_entries, 4);

  		drm_printf(&p, "  %d %ss (last at %5llu.%06u):
  %s",

  			   entry->count,
  			   topology_ref_type_to_str(entry->type),
  			   ts_nsec, rem_nsec / 1000, buf);

  	}

  	/* Now free the history, since this is the only time we expose it */
  	kfree(history->entries);
  out:
  	kfree(buf);
  }

  static __always_inline void
  drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb)
  {
  	__dump_topology_ref_history(&mstb->topology_ref_history, mstb,
  				    "MSTB");
  }
  
  static __always_inline void
  drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port)
  {
  	__dump_topology_ref_history(&port->topology_ref_history, port,
  				    "Port");
  }
  
  static __always_inline void
  save_mstb_topology_ref(struct drm_dp_mst_branch *mstb,
  		       enum drm_dp_mst_topology_ref_type type)
  {
  	__topology_ref_save(mstb->mgr, &mstb->topology_ref_history, type);
  }
  
  static __always_inline void
  save_port_topology_ref(struct drm_dp_mst_port *port,
  		       enum drm_dp_mst_topology_ref_type type)
  {
  	__topology_ref_save(port->mgr, &port->topology_ref_history, type);
  }
  
  static inline void
  topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr)
  {
  	mutex_lock(&mgr->topology_ref_history_lock);
  }
  
  static inline void
  topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr)
  {
  	mutex_unlock(&mgr->topology_ref_history_lock);
  }
  #else
  static inline void
  topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr) {}
  static inline void
  topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr) {}
  static inline void
  drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb) {}
  static inline void
  drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) {}
  #define save_mstb_topology_ref(mstb, type)
  #define save_port_topology_ref(port, type)
  #endif

  static void drm_dp_destroy_mst_branch_device(struct kref *kref)
  {

  	struct drm_dp_mst_branch *mstb =
  		container_of(kref, struct drm_dp_mst_branch, topology_kref);
  	struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;

  	drm_dp_mst_dump_mstb_topology_history(mstb);

  	INIT_LIST_HEAD(&mstb->destroy_next);

  	/*
  	 * This can get called under mgr->mutex, so we need to perform the
  	 * actual destruction of the mstb in another worker
  	 */
  	mutex_lock(&mgr->delayed_destroy_lock);
  	list_add(&mstb->destroy_next, &mgr->destroy_branch_device_list);
  	mutex_unlock(&mgr->delayed_destroy_lock);

  	queue_work(mgr->delayed_destroy_wq, &mgr->delayed_destroy_work);

  }

  /**
   * drm_dp_mst_topology_try_get_mstb() - Increment the topology refcount of a

   * branch device unless it's zero

   * @mstb: &struct drm_dp_mst_branch to increment the topology refcount of
   *
   * Attempts to grab a topology reference to @mstb, if it hasn't yet been
   * removed from the topology (e.g. &drm_dp_mst_branch.topology_kref has
   * reached 0). Holding a topology reference implies that a malloc reference
   * will be held to @mstb as long as the user holds the topology reference.
   *
   * Care should be taken to ensure that the user has at least one malloc
   * reference to @mstb. If you already have a topology reference to @mstb, you
   * should use drm_dp_mst_topology_get_mstb() instead.
   *
   * See also:
   * drm_dp_mst_topology_get_mstb()
   * drm_dp_mst_topology_put_mstb()
   *
   * Returns:
   * * 1: A topology reference was grabbed successfully
   * * 0: @port is no longer in the topology, no reference was grabbed
   */
  static int __must_check
  drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb)

  {

  	int ret;

  	topology_ref_history_lock(mstb->mgr);
  	ret = kref_get_unless_zero(&mstb->topology_kref);
  	if (ret) {
  		DRM_DEBUG("mstb %p (%d)
  ",
  			  mstb, kref_read(&mstb->topology_kref));
  		save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET);
  	}
  
  	topology_ref_history_unlock(mstb->mgr);

  
  	return ret;

  }

  /**
   * drm_dp_mst_topology_get_mstb() - Increment the topology refcount of a
   * branch device
   * @mstb: The &struct drm_dp_mst_branch to increment the topology refcount of
   *
   * Increments &drm_dp_mst_branch.topology_refcount without checking whether or
   * not it's already reached 0. This is only valid to use in scenarios where
   * you are already guaranteed to have at least one active topology reference
   * to @mstb. Otherwise, drm_dp_mst_topology_try_get_mstb() must be used.
   *
   * See also:
   * drm_dp_mst_topology_try_get_mstb()
   * drm_dp_mst_topology_put_mstb()
   */
  static void drm_dp_mst_topology_get_mstb(struct drm_dp_mst_branch *mstb)
  {

  	topology_ref_history_lock(mstb->mgr);
  
  	save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET);

  	WARN_ON(kref_read(&mstb->topology_kref) == 0);
  	kref_get(&mstb->topology_kref);
  	DRM_DEBUG("mstb %p (%d)
  ", mstb, kref_read(&mstb->topology_kref));

  
  	topology_ref_history_unlock(mstb->mgr);

  }
  
  /**
   * drm_dp_mst_topology_put_mstb() - release a topology reference to a branch
   * device
   * @mstb: The &struct drm_dp_mst_branch to release the topology reference from
   *
   * Releases a topology reference from @mstb by decrementing
   * &drm_dp_mst_branch.topology_kref.
   *
   * See also:
   * drm_dp_mst_topology_try_get_mstb()
   * drm_dp_mst_topology_get_mstb()
   */
  static void
  drm_dp_mst_topology_put_mstb(struct drm_dp_mst_branch *mstb)
  {

  	topology_ref_history_lock(mstb->mgr);

  	DRM_DEBUG("mstb %p (%d)
  ",
  		  mstb, kref_read(&mstb->topology_kref) - 1);

  	save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_PUT);

  	topology_ref_history_unlock(mstb->mgr);

  	kref_put(&mstb->topology_kref, drm_dp_destroy_mst_branch_device);

  }
  
  static void drm_dp_destroy_port(struct kref *kref)
  {

  	struct drm_dp_mst_port *port =
  		container_of(kref, struct drm_dp_mst_port, topology_kref);

  	struct drm_dp_mst_topology_mgr *mgr = port->mgr;

  	drm_dp_mst_dump_port_topology_history(port);

  	/* There's nothing that needs locking to destroy an input port yet */
  	if (port->input) {
  		drm_dp_mst_put_port_malloc(port);
  		return;

  	}

  
  	kfree(port->cached_edid);
  
  	/*
  	 * we can't destroy the connector here, as we might be holding the
  	 * mode_config.mutex from an EDID retrieval
  	 */
  	mutex_lock(&mgr->delayed_destroy_lock);
  	list_add(&port->next, &mgr->destroy_port_list);
  	mutex_unlock(&mgr->delayed_destroy_lock);

  	queue_work(mgr->delayed_destroy_wq, &mgr->delayed_destroy_work);

  }
  
  /**
   * drm_dp_mst_topology_try_get_port() - Increment the topology refcount of a

   * port unless it's zero

   * @port: &struct drm_dp_mst_port to increment the topology refcount of
   *
   * Attempts to grab a topology reference to @port, if it hasn't yet been
   * removed from the topology (e.g. &drm_dp_mst_port.topology_kref has reached
   * 0). Holding a topology reference implies that a malloc reference will be
   * held to @port as long as the user holds the topology reference.
   *
   * Care should be taken to ensure that the user has at least one malloc
   * reference to @port. If you already have a topology reference to @port, you
   * should use drm_dp_mst_topology_get_port() instead.
   *
   * See also:
   * drm_dp_mst_topology_get_port()
   * drm_dp_mst_topology_put_port()
   *
   * Returns:
   * * 1: A topology reference was grabbed successfully
   * * 0: @port is no longer in the topology, no reference was grabbed
   */
  static int __must_check
  drm_dp_mst_topology_try_get_port(struct drm_dp_mst_port *port)
  {

  	int ret;

  	topology_ref_history_lock(port->mgr);
  	ret = kref_get_unless_zero(&port->topology_kref);
  	if (ret) {
  		DRM_DEBUG("port %p (%d)
  ",
  			  port, kref_read(&port->topology_kref));
  		save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET);
  	}

  	topology_ref_history_unlock(port->mgr);

  	return ret;

  }

  /**
   * drm_dp_mst_topology_get_port() - Increment the topology refcount of a port
   * @port: The &struct drm_dp_mst_port to increment the topology refcount of
   *
   * Increments &drm_dp_mst_port.topology_refcount without checking whether or
   * not it's already reached 0. This is only valid to use in scenarios where
   * you are already guaranteed to have at least one active topology reference
   * to @port. Otherwise, drm_dp_mst_topology_try_get_port() must be used.
   *
   * See also:
   * drm_dp_mst_topology_try_get_port()
   * drm_dp_mst_topology_put_port()
   */
  static void drm_dp_mst_topology_get_port(struct drm_dp_mst_port *port)
  {

  	topology_ref_history_lock(port->mgr);

  	WARN_ON(kref_read(&port->topology_kref) == 0);
  	kref_get(&port->topology_kref);
  	DRM_DEBUG("port %p (%d)
  ", port, kref_read(&port->topology_kref));

  	save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET);
  
  	topology_ref_history_unlock(port->mgr);

  }
  
  /**
   * drm_dp_mst_topology_put_port() - release a topology reference to a port
   * @port: The &struct drm_dp_mst_port to release the topology reference from
   *
   * Releases a topology reference from @port by decrementing
   * &drm_dp_mst_port.topology_kref.
   *
   * See also:
   * drm_dp_mst_topology_try_get_port()
   * drm_dp_mst_topology_get_port()
   */

  static void drm_dp_mst_topology_put_port(struct drm_dp_mst_port *port)

  {

  	topology_ref_history_lock(port->mgr);

  	DRM_DEBUG("port %p (%d)
  ",
  		  port, kref_read(&port->topology_kref) - 1);

  	save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_PUT);
  
  	topology_ref_history_unlock(port->mgr);

  	kref_put(&port->topology_kref, drm_dp_destroy_port);

  }

  static struct drm_dp_mst_branch *
  drm_dp_mst_topology_get_mstb_validated_locked(struct drm_dp_mst_branch *mstb,
  					      struct drm_dp_mst_branch *to_find)

  {
  	struct drm_dp_mst_port *port;
  	struct drm_dp_mst_branch *rmstb;

  
  	if (to_find == mstb)

  		return mstb;

  	list_for_each_entry(port, &mstb->ports, next) {
  		if (port->mstb) {

  			rmstb = drm_dp_mst_topology_get_mstb_validated_locked(
  			    port->mstb, to_find);

  			if (rmstb)
  				return rmstb;
  		}
  	}
  	return NULL;
  }

  static struct drm_dp_mst_branch *
  drm_dp_mst_topology_get_mstb_validated(struct drm_dp_mst_topology_mgr *mgr,
  				       struct drm_dp_mst_branch *mstb)

  {
  	struct drm_dp_mst_branch *rmstb = NULL;

  	mutex_lock(&mgr->lock);

  	if (mgr->mst_primary) {

  		rmstb = drm_dp_mst_topology_get_mstb_validated_locked(
  		    mgr->mst_primary, mstb);

  
  		if (rmstb && !drm_dp_mst_topology_try_get_mstb(rmstb))
  			rmstb = NULL;
  	}

  	mutex_unlock(&mgr->lock);
  	return rmstb;
  }

  static struct drm_dp_mst_port *
  drm_dp_mst_topology_get_port_validated_locked(struct drm_dp_mst_branch *mstb,
  					      struct drm_dp_mst_port *to_find)

  {
  	struct drm_dp_mst_port *port, *mport;
  
  	list_for_each_entry(port, &mstb->ports, next) {

  		if (port == to_find)

  			return port;

  		if (port->mstb) {

  			mport = drm_dp_mst_topology_get_port_validated_locked(
  			    port->mstb, to_find);

  			if (mport)
  				return mport;
  		}
  	}
  	return NULL;
  }

  static struct drm_dp_mst_port *
  drm_dp_mst_topology_get_port_validated(struct drm_dp_mst_topology_mgr *mgr,
  				       struct drm_dp_mst_port *port)

  {
  	struct drm_dp_mst_port *rport = NULL;

  	mutex_lock(&mgr->lock);

  	if (mgr->mst_primary) {
  		rport = drm_dp_mst_topology_get_port_validated_locked(
  		    mgr->mst_primary, port);
  
  		if (rport && !drm_dp_mst_topology_try_get_port(rport))
  			rport = NULL;
  	}

  	mutex_unlock(&mgr->lock);
  	return rport;
  }
  
  static struct drm_dp_mst_port *drm_dp_get_port(struct drm_dp_mst_branch *mstb, u8 port_num)
  {
  	struct drm_dp_mst_port *port;

  	int ret;

  
  	list_for_each_entry(port, &mstb->ports, next) {
  		if (port->port_num == port_num) {

  			ret = drm_dp_mst_topology_try_get_port(port);
  			return ret ? port : NULL;

  		}
  	}
  
  	return NULL;
  }
  
  /*
   * calculate a new RAD for this MST branch device
   * if parent has an LCT of 2 then it has 1 nibble of RAD,
   * if parent has an LCT of 3 then it has 2 nibbles of RAD,
   */
  static u8 drm_dp_calculate_rad(struct drm_dp_mst_port *port,
  				 u8 *rad)
  {

  	int parent_lct = port->parent->lct;

  	int shift = 4;

  	int idx = (parent_lct - 1) / 2;

  	if (parent_lct > 1) {
  		memcpy(rad, port->parent->rad, idx + 1);
  		shift = (parent_lct % 2) ? 4 : 0;

  	} else
  		rad[0] = 0;
  
  	rad[idx] |= port->port_num << shift;

  	return parent_lct + 1;

  }

  static bool drm_dp_mst_is_end_device(u8 pdt, bool mcs)

  {
  	switch (pdt) {
  	case DP_PEER_DEVICE_DP_LEGACY_CONV:
  	case DP_PEER_DEVICE_SST_SINK:
  		return true;
  	case DP_PEER_DEVICE_MST_BRANCHING:
  		/* For sst branch device */
  		if (!mcs)
  			return true;
  
  		return false;
  	}
  	return true;
  }
  
  static int
  drm_dp_port_set_pdt(struct drm_dp_mst_port *port, u8 new_pdt,
  		    bool new_mcs)

  {

  	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
  	struct drm_dp_mst_branch *mstb;
  	u8 rad[8], lct;
  	int ret = 0;

  	if (port->pdt == new_pdt && port->mcs == new_mcs)

  		return 0;
  
  	/* Teardown the old pdt, if there is one */

  	if (port->pdt != DP_PEER_DEVICE_NONE) {

  		if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {

  			/*
  			 * If the new PDT would also have an i2c bus,
  			 * don't bother with reregistering it
  			 */
  			if (new_pdt != DP_PEER_DEVICE_NONE &&

  			    drm_dp_mst_is_end_device(new_pdt, new_mcs)) {

  				port->pdt = new_pdt;
  				port->mcs = new_mcs;
  				return 0;
  			}

  			/* remove i2c over sideband */

  			drm_dp_mst_unregister_i2c_bus(port);

  		} else {
  			mutex_lock(&mgr->lock);
  			drm_dp_mst_topology_put_mstb(port->mstb);
  			port->mstb = NULL;
  			mutex_unlock(&mgr->lock);
  		}

  	}
  
  	port->pdt = new_pdt;

  	port->mcs = new_mcs;

  	if (port->pdt != DP_PEER_DEVICE_NONE) {

  		if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {

  			/* add i2c over sideband */

  			ret = drm_dp_mst_register_i2c_bus(port);

  		} else {
  			lct = drm_dp_calculate_rad(port, rad);
  			mstb = drm_dp_add_mst_branch_device(lct, rad);
  			if (!mstb) {
  				ret = -ENOMEM;
  				DRM_ERROR("Failed to create MSTB for port %p",
  					  port);
  				goto out;
  			}

  			mutex_lock(&mgr->lock);
  			port->mstb = mstb;
  			mstb->mgr = port->mgr;
  			mstb->port_parent = port;

  			/*
  			 * Make sure this port's memory allocation stays
  			 * around until its child MSTB releases it
  			 */
  			drm_dp_mst_get_port_malloc(port);
  			mutex_unlock(&mgr->lock);

  			/* And make sure we send a link address for this */
  			ret = 1;
  		}

  	}

  
  out:
  	if (ret < 0)
  		port->pdt = DP_PEER_DEVICE_NONE;
  	return ret;

  }

  /**
   * drm_dp_mst_dpcd_read() - read a series of bytes from the DPCD via sideband
   * @aux: Fake sideband AUX CH
   * @offset: address of the (first) register to read
   * @buffer: buffer to store the register values
   * @size: number of bytes in @buffer
   *
   * Performs the same functionality for remote devices via
   * sideband messaging as drm_dp_dpcd_read() does for local
   * devices via actual AUX CH.
   *
   * Return: Number of bytes read, or negative error code on failure.
   */
  ssize_t drm_dp_mst_dpcd_read(struct drm_dp_aux *aux,
  			     unsigned int offset, void *buffer, size_t size)
  {
  	struct drm_dp_mst_port *port = container_of(aux, struct drm_dp_mst_port,
  						    aux);
  
  	return drm_dp_send_dpcd_read(port->mgr, port,
  				     offset, size, buffer);
  }
  
  /**
   * drm_dp_mst_dpcd_write() - write a series of bytes to the DPCD via sideband
   * @aux: Fake sideband AUX CH
   * @offset: address of the (first) register to write
   * @buffer: buffer containing the values to write
   * @size: number of bytes in @buffer
   *
   * Performs the same functionality for remote devices via
   * sideband messaging as drm_dp_dpcd_write() does for local
   * devices via actual AUX CH.
   *

   * Return: number of bytes written on success, negative error code on failure.

   */
  ssize_t drm_dp_mst_dpcd_write(struct drm_dp_aux *aux,
  			      unsigned int offset, void *buffer, size_t size)
  {
  	struct drm_dp_mst_port *port = container_of(aux, struct drm_dp_mst_port,
  						    aux);
  
  	return drm_dp_send_dpcd_write(port->mgr, port,
  				      offset, size, buffer);
  }

  static int drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid)

  {

  	int ret = 0;

  
  	memcpy(mstb->guid, guid, 16);
  
  	if (!drm_dp_validate_guid(mstb->mgr, mstb->guid)) {
  		if (mstb->port_parent) {

  			ret = drm_dp_send_dpcd_write(mstb->mgr,
  						     mstb->port_parent,
  						     DP_GUID, 16, mstb->guid);

  		} else {

  			ret = drm_dp_dpcd_write(mstb->mgr->aux,
  						DP_GUID, mstb->guid, 16);

  		}
  	}

  	if (ret < 16 && ret > 0)
  		return -EPROTO;
  
  	return ret == 16 ? 0 : ret;

  }

  static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
  				int pnum,

  				char *proppath,
  				size_t proppath_size)

  {
  	int i;
  	char temp[8];

  	snprintf(proppath, proppath_size, "mst:%d", mstb->mgr->conn_base_id);

  	for (i = 0; i < (mstb->lct - 1); i++) {
  		int shift = (i % 2) ? 0 : 4;

  		int port_num = (mstb->rad[i / 2] >> shift) & 0xf;

  		snprintf(temp, sizeof(temp), "-%d", port_num);
  		strlcat(proppath, temp, proppath_size);

  	}

  	snprintf(temp, sizeof(temp), "-%d", pnum);

  	strlcat(proppath, temp, proppath_size);

  }

  /**
   * drm_dp_mst_connector_late_register() - Late MST connector registration

   * @connector: The MST connector

   * @port: The MST port for this connector
   *
   * Helper to register the remote aux device for this MST port. Drivers should
   * call this from their mst connector's late_register hook to enable MST aux
   * devices.
   *
   * Return: 0 on success, negative error code on failure.
   */
  int drm_dp_mst_connector_late_register(struct drm_connector *connector,
  				       struct drm_dp_mst_port *port)
  {
  	DRM_DEBUG_KMS("registering %s remote bus for %s
  ",
  		      port->aux.name, connector->kdev->kobj.name);
  
  	port->aux.dev = connector->kdev;
  	return drm_dp_aux_register_devnode(&port->aux);
  }
  EXPORT_SYMBOL(drm_dp_mst_connector_late_register);
  
  /**
   * drm_dp_mst_connector_early_unregister() - Early MST connector unregistration

   * @connector: The MST connector

   * @port: The MST port for this connector
   *
   * Helper to unregister the remote aux device for this MST port, registered by
   * drm_dp_mst_connector_late_register(). Drivers should call this from their mst
   * connector's early_unregister hook.
   */
  void drm_dp_mst_connector_early_unregister(struct drm_connector *connector,
  					   struct drm_dp_mst_port *port)
  {
  	DRM_DEBUG_KMS("unregistering %s remote bus for %s
  ",
  		      port->aux.name, connector->kdev->kobj.name);
  	drm_dp_aux_unregister_devnode(&port->aux);
  }
  EXPORT_SYMBOL(drm_dp_mst_connector_early_unregister);

  static void

  drm_dp_mst_port_add_connector(struct drm_dp_mst_branch *mstb,
  			      struct drm_dp_mst_port *port)
  {
  	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
  	char proppath[255];
  	int ret;
  
  	build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath));
  	port->connector = mgr->cbs->add_connector(mgr, port, proppath);
  	if (!port->connector) {
  		ret = -ENOMEM;
  		goto error;
  	}

  	if (port->pdt != DP_PEER_DEVICE_NONE &&

  	    drm_dp_mst_is_end_device(port->pdt, port->mcs)) {

  		port->cached_edid = drm_get_edid(port->connector,
  						 &port->aux.ddc);
  		drm_connector_set_tile_property(port->connector);
  	}

  	drm_connector_register(port->connector);

  	return;
  
  error:
  	DRM_ERROR("Failed to create connector for port %p: %d
  ", port, ret);
  }
  
  /*
   * Drop a topology reference, and unlink the port from the in-memory topology
   * layout
   */
  static void
  drm_dp_mst_topology_unlink_port(struct drm_dp_mst_topology_mgr *mgr,
  				struct drm_dp_mst_port *port)
  {
  	mutex_lock(&mgr->lock);

  	port->parent->num_ports--;

  	list_del(&port->next);
  	mutex_unlock(&mgr->lock);
  	drm_dp_mst_topology_put_port(port);
  }
  
  static struct drm_dp_mst_port *
  drm_dp_mst_add_port(struct drm_device *dev,
  		    struct drm_dp_mst_topology_mgr *mgr,
  		    struct drm_dp_mst_branch *mstb, u8 port_number)
  {
  	struct drm_dp_mst_port *port = kzalloc(sizeof(*port), GFP_KERNEL);
  
  	if (!port)
  		return NULL;
  
  	kref_init(&port->topology_kref);
  	kref_init(&port->malloc_kref);
  	port->parent = mstb;
  	port->port_num = port_number;
  	port->mgr = mgr;
  	port->aux.name = "DPMST";
  	port->aux.dev = dev->dev;
  	port->aux.is_remote = true;

  	/* initialize the MST downstream port's AUX crc work queue */
  	drm_dp_remote_aux_init(&port->aux);

  	/*
  	 * Make sure the memory allocation for our parent branch stays
  	 * around until our own memory allocation is released
  	 */
  	drm_dp_mst_get_mstb_malloc(mstb);
  
  	return port;
  }

  static int

  drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
  				    struct drm_device *dev,
  				    struct drm_dp_link_addr_reply_port *port_msg)

  {

  	struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;

  	struct drm_dp_mst_port *port;

  	int old_ddps = 0, ret;
  	u8 new_pdt = DP_PEER_DEVICE_NONE;

  	bool new_mcs = 0;

  	bool created = false, send_link_addr = false, changed = false;

  	port = drm_dp_get_port(mstb, port_msg->port_number);
  	if (!port) {

  		port = drm_dp_mst_add_port(dev, mgr, mstb,
  					   port_msg->port_number);

  		if (!port)

  			return -ENOMEM;

  		created = true;

  		changed = true;
  	} else if (!port->input && port_msg->input_port && port->connector) {
  		/* Since port->connector can't be changed here, we create a
  		 * new port if input_port changes from 0 to 1

  		 */

  		drm_dp_mst_topology_unlink_port(mgr, port);
  		drm_dp_mst_topology_put_port(port);

  		port = drm_dp_mst_add_port(dev, mgr, mstb,
  					   port_msg->port_number);
  		if (!port)

  			return -ENOMEM;
  		changed = true;

  		created = true;

  	} else if (port->input && !port_msg->input_port) {
  		changed = true;
  	} else if (port->connector) {
  		/* We're updating a port that's exposed to userspace, so do it
  		 * under lock

  		 */
  		drm_modeset_lock(&mgr->base.lock, NULL);

  		old_ddps = port->ddps;

  		changed = port->ddps != port_msg->ddps ||
  			(port->ddps &&
  			 (port->ldps != port_msg->legacy_device_plug_status ||
  			  port->dpcd_rev != port_msg->dpcd_revision ||
  			  port->mcs != port_msg->mcs ||
  			  port->pdt != port_msg->peer_device_type ||
  			  port->num_sdp_stream_sinks !=
  			  port_msg->num_sdp_stream_sinks));

  	}

  	port->input = port_msg->input_port;

  	if (!port->input)
  		new_pdt = port_msg->peer_device_type;

  	new_mcs = port_msg->mcs;

  	port->ddps = port_msg->ddps;
  	port->ldps = port_msg->legacy_device_plug_status;
  	port->dpcd_rev = port_msg->dpcd_revision;
  	port->num_sdp_streams = port_msg->num_sdp_streams;
  	port->num_sdp_stream_sinks = port_msg->num_sdp_stream_sinks;

  
  	/* manage mstb port lists with mgr lock - take a reference
  	   for this list */
  	if (created) {

  		mutex_lock(&mgr->lock);

  		drm_dp_mst_topology_get_port(port);

  		list_add(&port->next, &mstb->ports);

  		mstb->num_ports++;

  		mutex_unlock(&mgr->lock);

  	}

  	/*
  	 * Reprobe PBN caps on both hotplug, and when re-probing the link
  	 * for our parent mstb
  	 */
  	if (old_ddps != port->ddps || !created) {
  		if (port->ddps && !port->input) {
  			ret = drm_dp_send_enum_path_resources(mgr, mstb,
  							      port);
  			if (ret == 1)
  				changed = true;

  		} else {

  			port->full_pbn = 0;

  		}

  	}

  	ret = drm_dp_port_set_pdt(port, new_pdt, new_mcs);

  	if (ret == 1) {
  		send_link_addr = true;
  	} else if (ret < 0) {
  		DRM_ERROR("Failed to change PDT on port %p: %d
  ",
  			  port, ret);
  		goto fail;

  	}

  	/*
  	 * If this port wasn't just created, then we're reprobing because
  	 * we're coming out of suspend. In this case, always resend the link
  	 * address if there's an MSTB on this port
  	 */

  	if (!created && port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
  	    port->mcs)

  		send_link_addr = true;
  
  	if (port->connector)

  		drm_modeset_unlock(&mgr->base.lock);

  	else if (!port->input)

  		drm_dp_mst_port_add_connector(mstb, port);

  	if (send_link_addr && port->mstb) {
  		ret = drm_dp_send_link_address(mgr, port->mstb);
  		if (ret == 1) /* MSTB below us changed */
  			changed = true;
  		else if (ret < 0)
  			goto fail_put;

  	}

  	/* put reference to this port */

  	drm_dp_mst_topology_put_port(port);

  	return changed;

  
  fail:

  	drm_dp_mst_topology_unlink_port(mgr, port);

  	if (port->connector)

  		drm_modeset_unlock(&mgr->base.lock);

  fail_put:
  	drm_dp_mst_topology_put_port(port);
  	return ret;

  }

  static void
  drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
  			    struct drm_dp_connection_status_notify *conn_stat)

  {

  	struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;

  	struct drm_dp_mst_port *port;

  	int old_ddps, old_input, ret, i;

  	u8 new_pdt;

  	bool new_mcs;

  	bool dowork = false, create_connector = false;

  	port = drm_dp_get_port(mstb, conn_stat->port_number);
  	if (!port)
  		return;

  	if (port->connector) {
  		if (!port->input && conn_stat->input_port) {
  			/*
  			 * We can't remove a connector from an already exposed
  			 * port, so just throw the port out and make sure we
  			 * reprobe the link address of it's parent MSTB
  			 */
  			drm_dp_mst_topology_unlink_port(mgr, port);
  			mstb->link_address_sent = false;
  			dowork = true;
  			goto out;
  		}
  
  		/* Locking is only needed if the port's exposed to userspace */

  		drm_modeset_lock(&mgr->base.lock, NULL);

  	} else if (port->input && !conn_stat->input_port) {
  		create_connector = true;
  		/* Reprobe link address so we get num_sdp_streams */
  		mstb->link_address_sent = false;
  		dowork = true;
  	}

  	old_ddps = port->ddps;

  	old_input = port->input;

  	port->input = conn_stat->input_port;

  	port->ldps = conn_stat->legacy_device_plug_status;
  	port->ddps = conn_stat->displayport_device_plug_status;
  
  	if (old_ddps != port->ddps) {

  		if (port->ddps && !port->input)
  			drm_dp_send_enum_path_resources(mgr, mstb, port);
  		else

  			port->full_pbn = 0;

  	}

  	new_pdt = port->input ? DP_PEER_DEVICE_NONE : conn_stat->peer_device_type;

  	new_mcs = conn_stat->message_capability_status;
  	ret = drm_dp_port_set_pdt(port, new_pdt, new_mcs);

  	if (ret == 1) {
  		dowork = true;
  	} else if (ret < 0) {
  		DRM_ERROR("Failed to change PDT for port %p: %d
  ",
  			  port, ret);
  		dowork = false;

  	}

  	if (!old_input && old_ddps != port->ddps && !port->ddps) {
  		for (i = 0; i < mgr->max_payloads; i++) {
  			struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i];
  			struct drm_dp_mst_port *port_validated;
  
  			if (!vcpi)
  				continue;
  
  			port_validated =
  				container_of(vcpi, struct drm_dp_mst_port, vcpi);
  			port_validated =
  				drm_dp_mst_topology_get_port_validated(mgr, port_validated);
  			if (!port_validated) {
  				mutex_lock(&mgr->payload_lock);
  				vcpi->num_slots = 0;
  				mutex_unlock(&mgr->payload_lock);
  			} else {
  				drm_dp_mst_topology_put_port(port_validated);
  			}
  		}
  	}

  	if (port->connector)
  		drm_modeset_unlock(&mgr->base.lock);

  	else if (create_connector)
  		drm_dp_mst_port_add_connector(mstb, port);

  out:

  	drm_dp_mst_topology_put_port(port);

  	if (dowork)
  		queue_work(system_long_wq, &mstb->mgr->work);

  }
  
  static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_topology_mgr *mgr,
  							       u8 lct, u8 *rad)
  {
  	struct drm_dp_mst_branch *mstb;
  	struct drm_dp_mst_port *port;

  	int i, ret;

  	/* find the port by iterating down */

  
  	mutex_lock(&mgr->lock);

  	mstb = mgr->mst_primary;

  	if (!mstb)
  		goto out;

  	for (i = 0; i < lct - 1; i++) {
  		int shift = (i % 2) ? 0 : 4;

  		int port_num = (rad[i / 2] >> shift) & 0xf;

  
  		list_for_each_entry(port, &mstb->ports, next) {
  			if (port->port_num == port_num) {

  				mstb = port->mstb;
  				if (!mstb) {

  					DRM_ERROR("failed to lookup MSTB with lct %d, rad %02x
  ", lct, rad[0]);

  					goto out;

  				}

  				break;
  			}
  		}
  	}

  	ret = drm_dp_mst_topology_try_get_mstb(mstb);
  	if (!ret)
  		mstb = NULL;

  out:

  	mutex_unlock(&mgr->lock);

  	return mstb;
  }

  static struct drm_dp_mst_branch *get_mst_branch_device_by_guid_helper(
  	struct drm_dp_mst_branch *mstb,

  	const uint8_t *guid)

  {
  	struct drm_dp_mst_branch *found_mstb;
  	struct drm_dp_mst_port *port;

  	if (memcmp(mstb->guid, guid, 16) == 0)
  		return mstb;

  	list_for_each_entry(port, &mstb->ports, next) {
  		if (!port->mstb)
  			continue;

  		found_mstb = get_mst_branch_device_by_guid_helper(port->mstb, guid);
  
  		if (found_mstb)
  			return found_mstb;
  	}
  
  	return NULL;
  }

  static struct drm_dp_mst_branch *
  drm_dp_get_mst_branch_device_by_guid(struct drm_dp_mst_topology_mgr *mgr,

  				     const uint8_t *guid)

  {
  	struct drm_dp_mst_branch *mstb;

  	int ret;

  
  	/* find the port by iterating down */
  	mutex_lock(&mgr->lock);

  	mstb = get_mst_branch_device_by_guid_helper(mgr->mst_primary, guid);

  	if (mstb) {
  		ret = drm_dp_mst_topology_try_get_mstb(mstb);
  		if (!ret)
  			mstb = NULL;
  	}

  
  	mutex_unlock(&mgr->lock);
  	return mstb;
  }

  static int drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr,

  					       struct drm_dp_mst_branch *mstb)
  {
  	struct drm_dp_mst_port *port;

  	int ret;
  	bool changed = false;

  	if (!mstb->link_address_sent) {
  		ret = drm_dp_send_link_address(mgr, mstb);
  		if (ret == 1)
  			changed = true;
  		else if (ret < 0)
  			return ret;
  	}

  	list_for_each_entry(port, &mstb->ports, next) {

  		struct drm_dp_mst_branch *mstb_child = NULL;

  		if (port->input || !port->ddps)

  			continue;

  		if (port->mstb)

  			mstb_child = drm_dp_mst_topology_get_mstb_validated(
  			    mgr, port->mstb);

  
  		if (mstb_child) {

  			ret = drm_dp_check_and_send_link_address(mgr,
  								 mstb_child);

  			drm_dp_mst_topology_put_mstb(mstb_child);

  			if (ret == 1)
  				changed = true;
  			else if (ret < 0)
  				return ret;

  		}

  	}

  
  	return changed;

  }
  
  static void drm_dp_mst_link_probe_work(struct work_struct *work)
  {

  	struct drm_dp_mst_topology_mgr *mgr =
  		container_of(work, struct drm_dp_mst_topology_mgr, work);
  	struct drm_device *dev = mgr->dev;

  	struct drm_dp_mst_branch *mstb;

  	int ret;

  	bool clear_payload_id_table;

  	mutex_lock(&mgr->probe_lock);

  	mutex_lock(&mgr->lock);

  	clear_payload_id_table = !mgr->payload_id_table_cleared;
  	mgr->payload_id_table_cleared = true;

  	mstb = mgr->mst_primary;
  	if (mstb) {

  		ret = drm_dp_mst_topology_try_get_mstb(mstb);
  		if (!ret)
  			mstb = NULL;

  	}
  	mutex_unlock(&mgr->lock);

  	if (!mstb) {
  		mutex_unlock(&mgr->probe_lock);
  		return;

  	}

  	/*
  	 * Certain branch devices seem to incorrectly report an available_pbn
  	 * of 0 on downstream sinks, even after clearing the
  	 * DP_PAYLOAD_ALLOCATE_* registers in
  	 * drm_dp_mst_topology_mgr_set_mst(). Namely, the CableMatters USB-C
  	 * 2x DP hub. Sending a CLEAR_PAYLOAD_ID_TABLE message seems to make
  	 * things work again.
  	 */
  	if (clear_payload_id_table) {
  		DRM_DEBUG_KMS("Clearing payload ID table
  ");
  		drm_dp_send_clear_payload_id_table(mgr, mstb);

  	}

  	ret = drm_dp_check_and_send_link_address(mgr, mstb);

  	drm_dp_mst_topology_put_mstb(mstb);

  	mutex_unlock(&mgr->probe_lock);

  	if (ret)
  		drm_kms_helper_hotplug_event(dev);

  }
  
  static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
  				 u8 *guid)
  {

  	u64 salt;

  	if (memchr_inv(guid, 0, 16))
  		return true;
  
  	salt = get_jiffies_64();
  
  	memcpy(&guid[0], &salt, sizeof(u64));
  	memcpy(&guid[8], &salt, sizeof(u64));
  
  	return false;

  }

  static void build_dpcd_read(struct drm_dp_sideband_msg_tx *msg,
  			    u8 port_num, u32 offset, u8 num_bytes)

  {
  	struct drm_dp_sideband_msg_req_body req;
  
  	req.req_type = DP_REMOTE_DPCD_READ;
  	req.u.dpcd_read.port_number = port_num;
  	req.u.dpcd_read.dpcd_address = offset;
  	req.u.dpcd_read.num_bytes = num_bytes;
  	drm_dp_encode_sideband_req(&req, msg);

  }

  
  static int drm_dp_send_sideband_msg(struct drm_dp_mst_topology_mgr *mgr,
  				    bool up, u8 *msg, int len)
  {
  	int ret;
  	int regbase = up ? DP_SIDEBAND_MSG_UP_REP_BASE : DP_SIDEBAND_MSG_DOWN_REQ_BASE;
  	int tosend, total, offset;
  	int retries = 0;
  
  retry:
  	total = len;
  	offset = 0;
  	do {
  		tosend = min3(mgr->max_dpcd_transaction_bytes, 16, total);
  
  		ret = drm_dp_dpcd_write(mgr->aux, regbase + offset,
  					&msg[offset],
  					tosend);
  		if (ret != tosend) {
  			if (ret == -EIO && retries < 5) {
  				retries++;
  				goto retry;
  			}
  			DRM_DEBUG_KMS("failed to dpcd write %d %d
  ", tosend, ret);

  
  			return -EIO;
  		}
  		offset += tosend;
  		total -= tosend;
  	} while (total > 0);
  	return 0;
  }
  
  static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr,
  				  struct drm_dp_sideband_msg_tx *txmsg)
  {
  	struct drm_dp_mst_branch *mstb = txmsg->dst;

  	u8 req_type;

  	req_type = txmsg->msg[0] & 0x7f;
  	if (req_type == DP_CONNECTION_STATUS_NOTIFY ||
  		req_type == DP_RESOURCE_STATUS_NOTIFY)
  		hdr->broadcast = 1;
  	else
  		hdr->broadcast = 0;

  	hdr->path_msg = txmsg->path_msg;
  	hdr->lct = mstb->lct;
  	hdr->lcr = mstb->lct - 1;
  	if (mstb->lct > 1)
  		memcpy(hdr->rad, mstb->rad, mstb->lct / 2);

  	return 0;
  }
  /*
   * process a single block of the next message in the sideband queue
   */
  static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
  				   struct drm_dp_sideband_msg_tx *txmsg,
  				   bool up)
  {
  	u8 chunk[48];
  	struct drm_dp_sideband_msg_hdr hdr;
  	int len, space, idx, tosend;
  	int ret;

  	if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT)
  		return 0;

  	memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr));

  	if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED)

  		txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND;

  	/* make hdr from dst mst */

  	ret = set_hdr_from_dst_qlock(&hdr, txmsg);
  	if (ret < 0)
  		return ret;
  
  	/* amount left to send in this message */
  	len = txmsg->cur_len - txmsg->cur_offset;
  
  	/* 48 - sideband msg size - 1 byte for data CRC, x header bytes */
  	space = 48 - 1 - drm_dp_calc_sb_hdr_size(&hdr);
  
  	tosend = min(len, space);
  	if (len == txmsg->cur_len)
  		hdr.somt = 1;
  	if (space >= len)
  		hdr.eomt = 1;
  
  
  	hdr.msg_len = tosend + 1;
  	drm_dp_encode_sideband_msg_hdr(&hdr, chunk, &idx);
  	memcpy(&chunk[idx], &txmsg->msg[txmsg->cur_offset], tosend);
  	/* add crc at end */
  	drm_dp_crc_sideband_chunk_req(&chunk[idx], tosend);
  	idx += tosend + 1;
  
  	ret = drm_dp_send_sideband_msg(mgr, up, chunk, idx);

  	if (unlikely(ret) && drm_debug_enabled(DRM_UT_DP)) {

  		struct drm_printer p = drm_debug_printer(DBG_PREFIX);
  
  		drm_printf(&p, "sideband msg failed to send
  ");
  		drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);

  		return ret;
  	}
  
  	txmsg->cur_offset += tosend;
  	if (txmsg->cur_offset == txmsg->cur_len) {
  		txmsg->state = DRM_DP_SIDEBAND_TX_SENT;
  		return 1;
  	}
  	return 0;
  }

  static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr)
  {
  	struct drm_dp_sideband_msg_tx *txmsg;
  	int ret;

  	WARN_ON(!mutex_is_locked(&mgr->qlock));

  	/* construct a chunk from the first msg in the tx_msg queue */

  	if (list_empty(&mgr->tx_msg_downq))

  		return;

  	txmsg = list_first_entry(&mgr->tx_msg_downq,
  				 struct drm_dp_sideband_msg_tx, next);

  	ret = process_single_tx_qlock(mgr, txmsg, false);

  	if (ret < 0) {

  		DRM_DEBUG_KMS("failed to send msg in q %d
  ", ret);
  		list_del(&txmsg->next);

  		txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT;

  		wake_up_all(&mgr->tx_waitq);

  	}

  }

  static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr,
  				 struct drm_dp_sideband_msg_tx *txmsg)
  {
  	mutex_lock(&mgr->qlock);
  	list_add_tail(&txmsg->next, &mgr->tx_msg_downq);

  	if (drm_debug_enabled(DRM_UT_DP)) {

  		struct drm_printer p = drm_debug_printer(DBG_PREFIX);
  
  		drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
  	}

  	if (list_is_singular(&mgr->tx_msg_downq))

  		process_single_down_tx_qlock(mgr);
  	mutex_unlock(&mgr->qlock);
  }

  static void
  drm_dp_dump_link_address(struct drm_dp_link_address_ack_reply *reply)
  {
  	struct drm_dp_link_addr_reply_port *port_reply;
  	int i;
  
  	for (i = 0; i < reply->nports; i++) {
  		port_reply = &reply->ports[i];
  		DRM_DEBUG_KMS("port %d: input %d, pdt: %d, pn: %d, dpcd_rev: %02x, mcs: %d, ddps: %d, ldps %d, sdp %d/%d
  ",
  			      i,
  			      port_reply->input_port,
  			      port_reply->peer_device_type,
  			      port_reply->port_number,
  			      port_reply->dpcd_revision,
  			      port_reply->mcs,
  			      port_reply->ddps,
  			      port_reply->legacy_device_plug_status,
  			      port_reply->num_sdp_streams,
  			      port_reply->num_sdp_stream_sinks);
  	}
  }

  static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,

  				     struct drm_dp_mst_branch *mstb)

  {

  	struct drm_dp_sideband_msg_tx *txmsg;

  	struct drm_dp_link_address_ack_reply *reply;

  	struct drm_dp_mst_port *port, *tmp;

  	int i, ret, port_mask = 0;

  	bool changed = false;

  
  	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
  	if (!txmsg)

  		return -ENOMEM;

  
  	txmsg->dst = mstb;

  	build_link_address(txmsg);

  	mstb->link_address_sent = true;

  	drm_dp_queue_down_tx(mgr, txmsg);

  	/* FIXME: Actually do some real error handling here */

  	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);

  	if (ret <= 0) {
  		DRM_ERROR("Sending link address failed with %d
  ", ret);
  		goto out;
  	}
  	if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
  		DRM_ERROR("link address NAK received
  ");
  		ret = -EIO;
  		goto out;
  	}

  	reply = &txmsg->reply.u.link_addr;
  	DRM_DEBUG_KMS("link address reply: %d
  ", reply->nports);
  	drm_dp_dump_link_address(reply);

  	ret = drm_dp_check_mstb_guid(mstb, reply->guid);

  	if (ret) {
  		char buf[64];
  
  		drm_dp_mst_rad_to_str(mstb->rad, mstb->lct, buf, sizeof(buf));
  		DRM_ERROR("GUID check on %s failed: %d
  ",
  			  buf, ret);

  		goto out;

  	}

  	for (i = 0; i < reply->nports; i++) {
  		port_mask |= BIT(reply->ports[i].port_number);
  		ret = drm_dp_mst_handle_link_address_port(mstb, mgr->dev,
  							  &reply->ports[i]);
  		if (ret == 1)
  			changed = true;
  		else if (ret < 0)
  			goto out;
  	}

  	/* Prune any ports that are currently a part of mstb in our in-memory
  	 * topology, but were not seen in this link address. Usually this
  	 * means that they were removed while the topology was out of sync,
  	 * e.g. during suspend/resume
  	 */
  	mutex_lock(&mgr->lock);
  	list_for_each_entry_safe(port, tmp, &mstb->ports, next) {
  		if (port_mask & BIT(port->port_num))
  			continue;
  
  		DRM_DEBUG_KMS("port %d was not in link address, removing
  ",
  			      port->port_num);
  		list_del(&port->next);
  		drm_dp_mst_topology_put_port(port);
  		changed = true;
  	}
  	mutex_unlock(&mgr->lock);

  out:
  	if (ret <= 0)
  		mstb->link_address_sent = false;

  	kfree(txmsg);

  	return ret < 0 ? ret : changed;

  }

  static void
  drm_dp_send_clear_payload_id_table(struct drm_dp_mst_topology_mgr *mgr,
  				   struct drm_dp_mst_branch *mstb)

  {
  	struct drm_dp_sideband_msg_tx *txmsg;

  	int ret;

  
  	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
  	if (!txmsg)
  		return;
  
  	txmsg->dst = mstb;

  	build_clear_payload_id_table(txmsg);

  
  	drm_dp_queue_down_tx(mgr, txmsg);
  
  	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
  	if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
  		DRM_DEBUG_KMS("clear payload table id nak received
  ");
  
  	kfree(txmsg);
  }

  static int
  drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
  				struct drm_dp_mst_branch *mstb,
  				struct drm_dp_mst_port *port)

  {

  	struct drm_dp_enum_path_resources_ack_reply *path_res;

  	struct drm_dp_sideband_msg_tx *txmsg;
  	int ret;
  
  	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
  	if (!txmsg)
  		return -ENOMEM;
  
  	txmsg->dst = mstb;

  	build_enum_path_resources(txmsg, port->port_num);

  
  	drm_dp_queue_down_tx(mgr, txmsg);
  
  	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
  	if (ret > 0) {

  		ret = 0;

  		path_res = &txmsg->reply.u.path_resources;

  		if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {

  			DRM_DEBUG_KMS("enum path resources nak received
  ");

  		} else {

  			if (port->port_num != path_res->port_number)

  				DRM_ERROR("got incorrect port in response
  ");

  
  			DRM_DEBUG_KMS("enum path resources %d: %d %d
  ",
  				      path_res->port_number,
  				      path_res->full_payload_bw_number,
  				      path_res->avail_payload_bw_number);

  
  			/*
  			 * If something changed, make sure we send a
  			 * hotplug
  			 */
  			if (port->full_pbn != path_res->full_payload_bw_number ||
  			    port->fec_capable != path_res->fec_capable)
  				ret = 1;

  			port->full_pbn = path_res->full_payload_bw_number;

  			port->fec_capable = path_res->fec_capable;

  		}
  	}
  
  	kfree(txmsg);

  	return ret;

  }

  static struct drm_dp_mst_port *drm_dp_get_last_connected_port_to_mstb(struct drm_dp_mst_branch *mstb)
  {
  	if (!mstb->port_parent)
  		return NULL;
  
  	if (mstb->port_parent->mstb != mstb)
  		return mstb->port_parent;
  
  	return drm_dp_get_last_connected_port_to_mstb(mstb->port_parent->parent);
  }

  /*
   * Searches upwards in the topology starting from mstb to try to find the
   * closest available parent of mstb that's still connected to the rest of the
   * topology. This can be used in order to perform operations like releasing
   * payloads, where the branch device which owned the payload may no longer be
   * around and thus would require that the payload on the last living relative
   * be freed instead.
   */
  static struct drm_dp_mst_branch *
  drm_dp_get_last_connected_port_and_mstb(struct drm_dp_mst_topology_mgr *mgr,
  					struct drm_dp_mst_branch *mstb,
  					int *port_num)