1 /* 2 * Copyright © 2009 Keith Packard 3 * 4 * Permission to use, copy, modify, distribute, and sell this software and its 5 * documentation for any purpose is hereby granted without fee, provided that 6 * the above copyright notice appear in all copies and that both that copyright 7 * notice and this permission notice appear in supporting documentation, and 8 * that the name of the copyright holders not be used in advertising or 9 * publicity pertaining to distribution of the software without specific, 10 * written prior permission. The copyright holders make no representations 11 * about the suitability of this software for any purpose. It is provided "as 12 * is" without express or implied warranty. 13 * 14 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 15 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO 16 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR 17 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, 18 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER 19 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 20 * OF THIS SOFTWARE. 21 */ 22 23 #include <linux/kernel.h> 24 #include <linux/module.h> 25 #include <linux/delay.h> 26 #include <linux/errno.h> 27 #include <linux/sched.h> 28 #include <linux/i2c.h> 29 #include <drm/drm_dp_helper.h> 30 #include <drm/drmP.h> 31 32 /** 33 * DOC: dp helpers 34 * 35 * These functions contain some common logic and helpers at various abstraction 36 * levels to deal with Display Port sink devices and related things like DP aux 37 * channel transfers, EDID reading over DP aux channels, decoding certain DPCD 38 * blocks, ... 39 */ 40 41 /* Helpers for DP link training */ 42 static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r) 43 { 44 return link_status[r - DP_LANE0_1_STATUS]; 45 } 46 47 static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE], 48 int lane) 49 { 50 int i = DP_LANE0_1_STATUS + (lane >> 1); 51 int s = (lane & 1) * 4; 52 u8 l = dp_link_status(link_status, i); 53 return (l >> s) & 0xf; 54 } 55 56 bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE], 57 int lane_count) 58 { 59 u8 lane_align; 60 u8 lane_status; 61 int lane; 62 63 lane_align = dp_link_status(link_status, 64 DP_LANE_ALIGN_STATUS_UPDATED); 65 if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0) 66 return false; 67 for (lane = 0; lane < lane_count; lane++) { 68 lane_status = dp_get_lane_status(link_status, lane); 69 if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS) 70 return false; 71 } 72 return true; 73 } 74 EXPORT_SYMBOL(drm_dp_channel_eq_ok); 75 76 bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE], 77 int lane_count) 78 { 79 int lane; 80 u8 lane_status; 81 82 for (lane = 0; lane < lane_count; lane++) { 83 lane_status = dp_get_lane_status(link_status, lane); 84 if ((lane_status & DP_LANE_CR_DONE) == 0) 85 return false; 86 } 87 return true; 88 } 89 EXPORT_SYMBOL(drm_dp_clock_recovery_ok); 90 91 u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE], 92 int lane) 93 { 94 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1); 95 int s = ((lane & 1) ? 96 DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT : 97 DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT); 98 u8 l = dp_link_status(link_status, i); 99 100 return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT; 101 } 102 EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage); 103 104 u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE], 105 int lane) 106 { 107 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1); 108 int s = ((lane & 1) ? 109 DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT : 110 DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT); 111 u8 l = dp_link_status(link_status, i); 112 113 return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT; 114 } 115 EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis); 116 117 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { 118 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0) 119 udelay(100); 120 else 121 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4); 122 } 123 EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay); 124 125 void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { 126 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0) 127 udelay(400); 128 else 129 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4); 130 } 131 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay); 132 133 u8 drm_dp_link_rate_to_bw_code(int link_rate) 134 { 135 switch (link_rate) { 136 case 162000: 137 default: 138 return DP_LINK_BW_1_62; 139 case 270000: 140 return DP_LINK_BW_2_7; 141 case 540000: 142 return DP_LINK_BW_5_4; 143 } 144 } 145 EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code); 146 147 int drm_dp_bw_code_to_link_rate(u8 link_bw) 148 { 149 switch (link_bw) { 150 case DP_LINK_BW_1_62: 151 default: 152 return 162000; 153 case DP_LINK_BW_2_7: 154 return 270000; 155 case DP_LINK_BW_5_4: 156 return 540000; 157 } 158 } 159 EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate); 160 161 /** 162 * DOC: dp helpers 163 * 164 * The DisplayPort AUX channel is an abstraction to allow generic, driver- 165 * independent access to AUX functionality. Drivers can take advantage of 166 * this by filling in the fields of the drm_dp_aux structure. 167 * 168 * Transactions are described using a hardware-independent drm_dp_aux_msg 169 * structure, which is passed into a driver's .transfer() implementation. 170 * Both native and I2C-over-AUX transactions are supported. 171 */ 172 173 static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, 174 unsigned int offset, void *buffer, size_t size) 175 { 176 struct drm_dp_aux_msg msg; 177 unsigned int retry; 178 int err; 179 180 memset(&msg, 0, sizeof(msg)); 181 msg.address = offset; 182 msg.request = request; 183 msg.buffer = buffer; 184 msg.size = size; 185 186 /* 187 * The specification doesn't give any recommendation on how often to 188 * retry native transactions. We used to retry 7 times like for 189 * aux i2c transactions but real world devices this wasn't 190 * sufficient, bump to 32 which makes Dell 4k monitors happier. 191 */ 192 for (retry = 0; retry < 32; retry++) { 193 194 mutex_lock(&aux->hw_mutex); 195 err = aux->transfer(aux, &msg); 196 mutex_unlock(&aux->hw_mutex); 197 if (err < 0) { 198 if (err == -EBUSY) 199 continue; 200 201 return err; 202 } 203 204 205 switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) { 206 case DP_AUX_NATIVE_REPLY_ACK: 207 if (err < size) 208 return -EPROTO; 209 return err; 210 211 case DP_AUX_NATIVE_REPLY_NACK: 212 return -EIO; 213 214 case DP_AUX_NATIVE_REPLY_DEFER: 215 usleep_range(400, 500); 216 break; 217 } 218 } 219 220 DRM_DEBUG_KMS("too many retries, giving up\n"); 221 return -EIO; 222 } 223 224 /** 225 * drm_dp_dpcd_read() - read a series of bytes from the DPCD 226 * @aux: DisplayPort AUX channel 227 * @offset: address of the (first) register to read 228 * @buffer: buffer to store the register values 229 * @size: number of bytes in @buffer 230 * 231 * Returns the number of bytes transferred on success, or a negative error 232 * code on failure. -EIO is returned if the request was NAKed by the sink or 233 * if the retry count was exceeded. If not all bytes were transferred, this 234 * function returns -EPROTO. Errors from the underlying AUX channel transfer 235 * function, with the exception of -EBUSY (which causes the transaction to 236 * be retried), are propagated to the caller. 237 */ 238 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, 239 void *buffer, size_t size) 240 { 241 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, 242 size); 243 } 244 EXPORT_SYMBOL(drm_dp_dpcd_read); 245 246 /** 247 * drm_dp_dpcd_write() - write a series of bytes to the DPCD 248 * @aux: DisplayPort AUX channel 249 * @offset: address of the (first) register to write 250 * @buffer: buffer containing the values to write 251 * @size: number of bytes in @buffer 252 * 253 * Returns the number of bytes transferred on success, or a negative error 254 * code on failure. -EIO is returned if the request was NAKed by the sink or 255 * if the retry count was exceeded. If not all bytes were transferred, this 256 * function returns -EPROTO. Errors from the underlying AUX channel transfer 257 * function, with the exception of -EBUSY (which causes the transaction to 258 * be retried), are propagated to the caller. 259 */ 260 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset, 261 void *buffer, size_t size) 262 { 263 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, 264 size); 265 } 266 EXPORT_SYMBOL(drm_dp_dpcd_write); 267 268 /** 269 * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207) 270 * @aux: DisplayPort AUX channel 271 * @status: buffer to store the link status in (must be at least 6 bytes) 272 * 273 * Returns the number of bytes transferred on success or a negative error 274 * code on failure. 275 */ 276 int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, 277 u8 status[DP_LINK_STATUS_SIZE]) 278 { 279 return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status, 280 DP_LINK_STATUS_SIZE); 281 } 282 EXPORT_SYMBOL(drm_dp_dpcd_read_link_status); 283 284 /** 285 * drm_dp_link_probe() - probe a DisplayPort link for capabilities 286 * @aux: DisplayPort AUX channel 287 * @link: pointer to structure in which to return link capabilities 288 * 289 * The structure filled in by this function can usually be passed directly 290 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and 291 * configure the link based on the link's capabilities. 292 * 293 * Returns 0 on success or a negative error code on failure. 294 */ 295 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link) 296 { 297 u8 values[3]; 298 int err; 299 300 memset(link, 0, sizeof(*link)); 301 302 err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values)); 303 if (err < 0) 304 return err; 305 306 link->revision = values[0]; 307 link->rate = drm_dp_bw_code_to_link_rate(values[1]); 308 link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK; 309 310 if (values[2] & DP_ENHANCED_FRAME_CAP) 311 link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING; 312 313 return 0; 314 } 315 EXPORT_SYMBOL(drm_dp_link_probe); 316 317 /** 318 * drm_dp_link_power_up() - power up a DisplayPort link 319 * @aux: DisplayPort AUX channel 320 * @link: pointer to a structure containing the link configuration 321 * 322 * Returns 0 on success or a negative error code on failure. 323 */ 324 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link) 325 { 326 u8 value; 327 int err; 328 329 /* DP_SET_POWER register is only available on DPCD v1.1 and later */ 330 if (link->revision < 0x11) 331 return 0; 332 333 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value); 334 if (err < 0) 335 return err; 336 337 value &= ~DP_SET_POWER_MASK; 338 value |= DP_SET_POWER_D0; 339 340 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value); 341 if (err < 0) 342 return err; 343 344 /* 345 * According to the DP 1.1 specification, a "Sink Device must exit the 346 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink 347 * Control Field" (register 0x600). 348 */ 349 usleep_range(1000, 2000); 350 351 return 0; 352 } 353 EXPORT_SYMBOL(drm_dp_link_power_up); 354 355 /** 356 * drm_dp_link_power_down() - power down a DisplayPort link 357 * @aux: DisplayPort AUX channel 358 * @link: pointer to a structure containing the link configuration 359 * 360 * Returns 0 on success or a negative error code on failure. 361 */ 362 int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link) 363 { 364 u8 value; 365 int err; 366 367 /* DP_SET_POWER register is only available on DPCD v1.1 and later */ 368 if (link->revision < 0x11) 369 return 0; 370 371 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value); 372 if (err < 0) 373 return err; 374 375 value &= ~DP_SET_POWER_MASK; 376 value |= DP_SET_POWER_D3; 377 378 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value); 379 if (err < 0) 380 return err; 381 382 return 0; 383 } 384 EXPORT_SYMBOL(drm_dp_link_power_down); 385 386 /** 387 * drm_dp_link_configure() - configure a DisplayPort link 388 * @aux: DisplayPort AUX channel 389 * @link: pointer to a structure containing the link configuration 390 * 391 * Returns 0 on success or a negative error code on failure. 392 */ 393 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) 394 { 395 u8 values[2]; 396 int err; 397 398 values[0] = drm_dp_link_rate_to_bw_code(link->rate); 399 values[1] = link->num_lanes; 400 401 if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING) 402 values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN; 403 404 err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values)); 405 if (err < 0) 406 return err; 407 408 return 0; 409 } 410 EXPORT_SYMBOL(drm_dp_link_configure); 411 412 /* 413 * I2C-over-AUX implementation 414 */ 415 416 #if 0 417 static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) 418 { 419 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 420 I2C_FUNC_SMBUS_READ_BLOCK_DATA | 421 I2C_FUNC_SMBUS_BLOCK_PROC_CALL | 422 I2C_FUNC_10BIT_ADDR; 423 } 424 425 /* 426 * Transfer a single I2C-over-AUX message and handle various error conditions, 427 * retrying the transaction as appropriate. It is assumed that the 428 * aux->transfer function does not modify anything in the msg other than the 429 * reply field. 430 * 431 * Returns bytes transferred on success, or a negative error code on failure. 432 */ 433 static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) 434 { 435 unsigned int retry; 436 int ret; 437 438 /* 439 * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device 440 * is required to retry at least seven times upon receiving AUX_DEFER 441 * before giving up the AUX transaction. 442 */ 443 for (retry = 0; retry < 7; retry++) { 444 mutex_lock(&aux->hw_mutex); 445 ret = aux->transfer(aux, msg); 446 mutex_unlock(&aux->hw_mutex); 447 if (ret < 0) { 448 if (ret == -EBUSY) 449 continue; 450 451 DRM_DEBUG_KMS("transaction failed: %d\n", ret); 452 return ret; 453 } 454 455 456 switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) { 457 case DP_AUX_NATIVE_REPLY_ACK: 458 /* 459 * For I2C-over-AUX transactions this isn't enough, we 460 * need to check for the I2C ACK reply. 461 */ 462 break; 463 464 case DP_AUX_NATIVE_REPLY_NACK: 465 DRM_DEBUG_KMS("native nack (result=%d, size=%zu)\n", ret, msg->size); 466 return -EREMOTEIO; 467 468 case DP_AUX_NATIVE_REPLY_DEFER: 469 DRM_DEBUG_KMS("native defer"); 470 /* 471 * We could check for I2C bit rate capabilities and if 472 * available adjust this interval. We could also be 473 * more careful with DP-to-legacy adapters where a 474 * long legacy cable may force very low I2C bit rates. 475 * 476 * For now just defer for long enough to hopefully be 477 * safe for all use-cases. 478 */ 479 usleep_range(500, 600); 480 continue; 481 482 default: 483 DRM_ERROR("invalid native reply %#04x\n", msg->reply); 484 return -EREMOTEIO; 485 } 486 487 switch (msg->reply & DP_AUX_I2C_REPLY_MASK) { 488 case DP_AUX_I2C_REPLY_ACK: 489 /* 490 * Both native ACK and I2C ACK replies received. We 491 * can assume the transfer was successful. 492 */ 493 return ret; 494 495 case DP_AUX_I2C_REPLY_NACK: 496 DRM_DEBUG_KMS("I2C nack (result=%d, size=%zu\n", ret, msg->size); 497 aux->i2c_nack_count++; 498 return -EREMOTEIO; 499 500 case DP_AUX_I2C_REPLY_DEFER: 501 DRM_DEBUG_KMS("I2C defer\n"); 502 aux->i2c_defer_count++; 503 usleep_range(400, 500); 504 continue; 505 506 default: 507 DRM_ERROR("invalid I2C reply %#04x\n", msg->reply); 508 return -EREMOTEIO; 509 } 510 } 511 512 DRM_DEBUG_KMS("too many retries, giving up\n"); 513 return -EREMOTEIO; 514 } 515 516 /* 517 * Keep retrying drm_dp_i2c_do_msg until all data has been transferred. 518 * 519 * Returns an error code on failure, or a recommended transfer size on success. 520 */ 521 static int drm_dp_i2c_drain_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *orig_msg) 522 { 523 int err, ret = orig_msg->size; 524 struct drm_dp_aux_msg msg = *orig_msg; 525 526 while (msg.size > 0) { 527 err = drm_dp_i2c_do_msg(aux, &msg); 528 if (err <= 0) 529 return err == 0 ? -EPROTO : err; 530 531 if (err < msg.size && err < ret) { 532 DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n", 533 msg.size, err); 534 ret = err; 535 } 536 537 msg.size -= err; 538 msg.buffer += err; 539 } 540 541 return ret; 542 } 543 544 /* 545 * Bizlink designed DP->DVI-D Dual Link adapters require the I2C over AUX 546 * packets to be as large as possible. If not, the I2C transactions never 547 * succeed. Hence the default is maximum. 548 */ 549 static int dp_aux_i2c_transfer_size __read_mostly = DP_AUX_MAX_PAYLOAD_BYTES; 550 module_param_unsafe(dp_aux_i2c_transfer_size, int, 0644); 551 MODULE_PARM_DESC(dp_aux_i2c_transfer_size, 552 "Number of bytes to transfer in a single I2C over DP AUX CH message, (1-16, default 16)"); 553 554 static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, 555 int num) 556 { 557 struct drm_dp_aux *aux = adapter->algo_data; 558 unsigned int i, j; 559 unsigned transfer_size; 560 struct drm_dp_aux_msg msg; 561 int err = 0; 562 563 dp_aux_i2c_transfer_size = clamp(dp_aux_i2c_transfer_size, 1, DP_AUX_MAX_PAYLOAD_BYTES); 564 565 memset(&msg, 0, sizeof(msg)); 566 567 for (i = 0; i < num; i++) { 568 msg.address = msgs[i].addr; 569 msg.request = (msgs[i].flags & I2C_M_RD) ? 570 DP_AUX_I2C_READ : 571 DP_AUX_I2C_WRITE; 572 msg.request |= DP_AUX_I2C_MOT; 573 /* Send a bare address packet to start the transaction. 574 * Zero sized messages specify an address only (bare 575 * address) transaction. 576 */ 577 msg.buffer = NULL; 578 msg.size = 0; 579 err = drm_dp_i2c_do_msg(aux, &msg); 580 if (err < 0) 581 break; 582 /* We want each transaction to be as large as possible, but 583 * we'll go to smaller sizes if the hardware gives us a 584 * short reply. 585 */ 586 transfer_size = dp_aux_i2c_transfer_size; 587 for (j = 0; j < msgs[i].len; j += msg.size) { 588 msg.buffer = msgs[i].buf + j; 589 msg.size = min(transfer_size, msgs[i].len - j); 590 591 err = drm_dp_i2c_drain_msg(aux, &msg); 592 if (err < 0) 593 break; 594 transfer_size = err; 595 } 596 if (err < 0) 597 break; 598 } 599 if (err >= 0) 600 err = num; 601 /* Send a bare address packet to close out the transaction. 602 * Zero sized messages specify an address only (bare 603 * address) transaction. 604 */ 605 msg.request &= ~DP_AUX_I2C_MOT; 606 msg.buffer = NULL; 607 msg.size = 0; 608 (void)drm_dp_i2c_do_msg(aux, &msg); 609 610 return err; 611 } 612 613 static const struct i2c_algorithm drm_dp_i2c_algo = { 614 .functionality = drm_dp_i2c_functionality, 615 .master_xfer = drm_dp_i2c_xfer, 616 }; 617 618 /** 619 * drm_dp_aux_register() - initialise and register aux channel 620 * @aux: DisplayPort AUX channel 621 * 622 * Returns 0 on success or a negative error code on failure. 623 */ 624 int drm_dp_aux_register(struct drm_dp_aux *aux) 625 { 626 lockinit(&aux->hw_mutex, "ahm", 0, LK_CANRECURSE); 627 628 aux->ddc.algo = &drm_dp_i2c_algo; 629 aux->ddc.algo_data = aux; 630 aux->ddc.retries = 3; 631 632 aux->ddc.class = I2C_CLASS_DDC; 633 aux->ddc.owner = THIS_MODULE; 634 aux->ddc.dev.parent = aux->dev; 635 aux->ddc.dev.of_node = aux->dev->of_node; 636 637 strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev), 638 sizeof(aux->ddc.name)); 639 640 return i2c_add_adapter(&aux->ddc); 641 } 642 EXPORT_SYMBOL(drm_dp_aux_register); 643 #endif 644 645 /** 646 * drm_dp_aux_unregister() - unregister an AUX adapter 647 * @aux: DisplayPort AUX channel 648 */ 649 void drm_dp_aux_unregister(struct drm_dp_aux *aux) 650 { 651 #if 0 652 i2c_del_adapter(&aux->ddc); 653 #endif 654 } 655 EXPORT_SYMBOL(drm_dp_aux_unregister); 656