/* $NetBSD: drm_dp_helper.c,v 1.8 2018/08/27 06:52:45 riastradh Exp $ */ /* * Copyright © 2009 Keith Packard * * Permission to use, copy, modify, distribute, and sell this software and its * documentation for any purpose is hereby granted without fee, provided that * the above copyright notice appear in all copies and that both that copyright * notice and this permission notice appear in supporting documentation, and * that the name of the copyright holders not be used in advertising or * publicity pertaining to distribution of the software without specific, * written prior permission. The copyright holders make no representations * about the suitability of this software for any purpose. It is provided "as * is" without express or implied warranty. * * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE * OF THIS SOFTWARE. */ #include __KERNEL_RCSID(0, "$NetBSD: drm_dp_helper.c,v 1.8 2018/08/27 06:52:45 riastradh Exp $"); #include #include #include #include #include #include #include #include #include #include #include #include /** * DOC: dp helpers * * These functions contain some common logic and helpers at various abstraction * levels to deal with Display Port sink devices and related things like DP aux * channel transfers, EDID reading over DP aux channels, decoding certain DPCD * blocks, ... */ /* Helpers for DP link training */ static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r) { return link_status[r - DP_LANE0_1_STATUS]; } static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE], int lane) { int i = DP_LANE0_1_STATUS + (lane >> 1); int s = (lane & 1) * 4; u8 l = dp_link_status(link_status, i); return (l >> s) & 0xf; } bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE], int lane_count) { u8 lane_align; u8 lane_status; int lane; lane_align = dp_link_status(link_status, DP_LANE_ALIGN_STATUS_UPDATED); if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0) return false; for (lane = 0; lane < lane_count; lane++) { lane_status = dp_get_lane_status(link_status, lane); if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS) return false; } return true; } EXPORT_SYMBOL(drm_dp_channel_eq_ok); bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE], int lane_count) { int lane; u8 lane_status; for (lane = 0; lane < lane_count; lane++) { lane_status = dp_get_lane_status(link_status, lane); if ((lane_status & DP_LANE_CR_DONE) == 0) return false; } return true; } EXPORT_SYMBOL(drm_dp_clock_recovery_ok); u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE], int lane) { int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1); int s = ((lane & 1) ? DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT : DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT); u8 l = dp_link_status(link_status, i); return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT; } EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage); u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE], int lane) { int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1); int s = ((lane & 1) ? DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT : DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT); u8 l = dp_link_status(link_status, i); return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT; } EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis); void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0) udelay(100); else mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4); } EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay); void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0) udelay(400); else mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4); } EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay); u8 drm_dp_link_rate_to_bw_code(int link_rate) { switch (link_rate) { case 162000: default: return DP_LINK_BW_1_62; case 270000: return DP_LINK_BW_2_7; case 540000: return DP_LINK_BW_5_4; } } EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code); int drm_dp_bw_code_to_link_rate(u8 link_bw) { switch (link_bw) { case DP_LINK_BW_1_62: default: return 162000; case DP_LINK_BW_2_7: return 270000; case DP_LINK_BW_5_4: return 540000; } } EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate); #define AUX_RETRY_INTERVAL 500 /* us */ /** * DOC: dp helpers * * The DisplayPort AUX channel is an abstraction to allow generic, driver- * independent access to AUX functionality. Drivers can take advantage of * this by filling in the fields of the drm_dp_aux structure. * * Transactions are described using a hardware-independent drm_dp_aux_msg * structure, which is passed into a driver's .transfer() implementation. * Both native and I2C-over-AUX transactions are supported. */ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, unsigned int offset, void *buffer, size_t size) { struct drm_dp_aux_msg msg; unsigned int retry; int err = 0; memset(&msg, 0, sizeof(msg)); msg.address = offset; msg.request = request; msg.buffer = buffer; msg.size = size; mutex_lock(&aux->hw_mutex); /* * The specification doesn't give any recommendation on how often to * retry native transactions. We used to retry 7 times like for * aux i2c transactions but real world devices this wasn't * sufficient, bump to 32 which makes Dell 4k monitors happier. */ for (retry = 0; retry < 32; retry++) { err = aux->transfer(aux, &msg); if (err < 0) { if (err == -EBUSY) continue; goto unlock; } switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) { case DP_AUX_NATIVE_REPLY_ACK: if (err < size) err = -EPROTO; goto unlock; case DP_AUX_NATIVE_REPLY_NACK: err = -EIO; goto unlock; case DP_AUX_NATIVE_REPLY_DEFER: usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100); break; } } DRM_DEBUG_KMS("too many retries, giving up\n"); err = -EIO; unlock: mutex_unlock(&aux->hw_mutex); return err; } /** * drm_dp_dpcd_read() - read a series of bytes from the DPCD * @aux: DisplayPort AUX channel * @offset: address of the (first) register to read * @buffer: buffer to store the register values * @size: number of bytes in @buffer * * Returns the number of bytes transferred on success, or a negative error * code on failure. -EIO is returned if the request was NAKed by the sink or * if the retry count was exceeded. If not all bytes were transferred, this * function returns -EPROTO. Errors from the underlying AUX channel transfer * function, with the exception of -EBUSY (which causes the transaction to * be retried), are propagated to the caller. */ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size) { return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, size); } EXPORT_SYMBOL(drm_dp_dpcd_read); /** * drm_dp_dpcd_write() - write a series of bytes to the DPCD * @aux: DisplayPort AUX channel * @offset: address of the (first) register to write * @buffer: buffer containing the values to write * @size: number of bytes in @buffer * * Returns the number of bytes transferred on success, or a negative error * code on failure. -EIO is returned if the request was NAKed by the sink or * if the retry count was exceeded. If not all bytes were transferred, this * function returns -EPROTO. Errors from the underlying AUX channel transfer * function, with the exception of -EBUSY (which causes the transaction to * be retried), are propagated to the caller. */ ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size) { return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, size); } EXPORT_SYMBOL(drm_dp_dpcd_write); /** * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207) * @aux: DisplayPort AUX channel * @status: buffer to store the link status in (must be at least 6 bytes) * * Returns the number of bytes transferred on success or a negative error * code on failure. */ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, u8 status[DP_LINK_STATUS_SIZE]) { return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status, DP_LINK_STATUS_SIZE); } EXPORT_SYMBOL(drm_dp_dpcd_read_link_status); /** * drm_dp_link_probe() - probe a DisplayPort link for capabilities * @aux: DisplayPort AUX channel * @link: pointer to structure in which to return link capabilities * * The structure filled in by this function can usually be passed directly * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and * configure the link based on the link's capabilities. * * Returns 0 on success or a negative error code on failure. */ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link) { u8 values[3]; int err; memset(link, 0, sizeof(*link)); err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values)); if (err < 0) return err; link->revision = values[0]; link->rate = drm_dp_bw_code_to_link_rate(values[1]); link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK; if (values[2] & DP_ENHANCED_FRAME_CAP) link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING; return 0; } EXPORT_SYMBOL(drm_dp_link_probe); /** * drm_dp_link_power_up() - power up a DisplayPort link * @aux: DisplayPort AUX channel * @link: pointer to a structure containing the link configuration * * Returns 0 on success or a negative error code on failure. */ int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link) { u8 value; int err; /* DP_SET_POWER register is only available on DPCD v1.1 and later */ if (link->revision < 0x11) return 0; err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value); if (err < 0) return err; value &= ~DP_SET_POWER_MASK; value |= DP_SET_POWER_D0; err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value); if (err < 0) return err; /* * According to the DP 1.1 specification, a "Sink Device must exit the * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink * Control Field" (register 0x600). */ usleep_range(1000, 2000); return 0; } EXPORT_SYMBOL(drm_dp_link_power_up); /** * drm_dp_link_power_down() - power down a DisplayPort link * @aux: DisplayPort AUX channel * @link: pointer to a structure containing the link configuration * * Returns 0 on success or a negative error code on failure. */ int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link) { u8 value; int err; /* DP_SET_POWER register is only available on DPCD v1.1 and later */ if (link->revision < 0x11) return 0; err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value); if (err < 0) return err; value &= ~DP_SET_POWER_MASK; value |= DP_SET_POWER_D3; err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value); if (err < 0) return err; return 0; } EXPORT_SYMBOL(drm_dp_link_power_down); /** * drm_dp_link_configure() - configure a DisplayPort link * @aux: DisplayPort AUX channel * @link: pointer to a structure containing the link configuration * * Returns 0 on success or a negative error code on failure. */ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) { u8 values[2]; int err; values[0] = drm_dp_link_rate_to_bw_code(link->rate); values[1] = link->num_lanes; if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING) values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN; err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values)); if (err < 0) return err; return 0; } EXPORT_SYMBOL(drm_dp_link_configure); /* * I2C-over-AUX implementation */ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) { return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_READ_BLOCK_DATA | I2C_FUNC_SMBUS_BLOCK_PROC_CALL | I2C_FUNC_10BIT_ADDR; } static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg) { /* * In case of i2c defer or short i2c ack reply to a write, * we need to switch to WRITE_STATUS_UPDATE to drain the * rest of the message */ if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE) { msg->request &= DP_AUX_I2C_MOT; msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE; } } #define AUX_PRECHARGE_LEN 10 /* 10 to 16 */ #define AUX_SYNC_LEN (16 + 4) /* preamble + AUX_SYNC_END */ #define AUX_STOP_LEN 4 #define AUX_CMD_LEN 4 #define AUX_ADDRESS_LEN 20 #define AUX_REPLY_PAD_LEN 4 #define AUX_LENGTH_LEN 8 /* * Calculate the duration of the AUX request/reply in usec. Gives the * "best" case estimate, ie. successful while as short as possible. */ static int drm_dp_aux_req_duration(const struct drm_dp_aux_msg *msg) { int len = AUX_PRECHARGE_LEN + AUX_SYNC_LEN + AUX_STOP_LEN + AUX_CMD_LEN + AUX_ADDRESS_LEN + AUX_LENGTH_LEN; if ((msg->request & DP_AUX_I2C_READ) == 0) len += msg->size * 8; return len; } static int drm_dp_aux_reply_duration(const struct drm_dp_aux_msg *msg) { int len = AUX_PRECHARGE_LEN + AUX_SYNC_LEN + AUX_STOP_LEN + AUX_CMD_LEN + AUX_REPLY_PAD_LEN; /* * For read we expect what was asked. For writes there will * be 0 or 1 data bytes. Assume 0 for the "best" case. */ if (msg->request & DP_AUX_I2C_READ) len += msg->size * 8; return len; } #define I2C_START_LEN 1 #define I2C_STOP_LEN 1 #define I2C_ADDR_LEN 9 /* ADDRESS + R/W + ACK/NACK */ #define I2C_DATA_LEN 9 /* DATA + ACK/NACK */ /* * Calculate the length of the i2c transfer in usec, assuming * the i2c bus speed is as specified. Gives the the "worst" * case estimate, ie. successful while as long as possible. * Doesn't account the the "MOT" bit, and instead assumes each * message includes a START, ADDRESS and STOP. Neither does it * account for additional random variables such as clock stretching. */ static int drm_dp_i2c_msg_duration(const struct drm_dp_aux_msg *msg, int i2c_speed_khz) { /* AUX bitrate is 1MHz, i2c bitrate as specified */ return DIV_ROUND_UP((I2C_START_LEN + I2C_ADDR_LEN + msg->size * I2C_DATA_LEN + I2C_STOP_LEN) * 1000, i2c_speed_khz); } /* * Deterine how many retries should be attempted to successfully transfer * the specified message, based on the estimated durations of the * i2c and AUX transfers. */ static int drm_dp_i2c_retry_count(const struct drm_dp_aux_msg *msg, int i2c_speed_khz) { int aux_time_us = drm_dp_aux_req_duration(msg) + drm_dp_aux_reply_duration(msg); int i2c_time_us = drm_dp_i2c_msg_duration(msg, i2c_speed_khz); return DIV_ROUND_UP(i2c_time_us, aux_time_us + AUX_RETRY_INTERVAL); } /* * FIXME currently assumes 10 kHz as some real world devices seem * to require it. We should query/set the speed via DPCD if supported. */ static int dp_aux_i2c_speed_khz __read_mostly = 10; module_param_unsafe(dp_aux_i2c_speed_khz, int, 0644); MODULE_PARM_DESC(dp_aux_i2c_speed_khz, "Assumed speed of the i2c bus in kHz, (1-400, default 10)"); /* * Transfer a single I2C-over-AUX message and handle various error conditions, * retrying the transaction as appropriate. It is assumed that the * aux->transfer function does not modify anything in the msg other than the * reply field. * * Returns bytes transferred on success, or a negative error code on failure. */ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { unsigned int retry, defer_i2c; int ret; /* * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device * is required to retry at least seven times upon receiving AUX_DEFER * before giving up the AUX transaction. * * We also try to account for the i2c bus speed. */ int max_retries = max(7, drm_dp_i2c_retry_count(msg, dp_aux_i2c_speed_khz)); for (retry = 0, defer_i2c = 0; retry < (max_retries + defer_i2c); retry++) { ret = aux->transfer(aux, msg); if (ret < 0) { if (ret == -EBUSY) continue; DRM_DEBUG_KMS("transaction failed: %d\n", ret); return ret; } switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) { case DP_AUX_NATIVE_REPLY_ACK: /* * For I2C-over-AUX transactions this isn't enough, we * need to check for the I2C ACK reply. */ break; case DP_AUX_NATIVE_REPLY_NACK: DRM_DEBUG_KMS("native nack (result=%d, size=%zu)\n", ret, msg->size); return -EREMOTEIO; case DP_AUX_NATIVE_REPLY_DEFER: DRM_DEBUG_KMS("native defer\n"); /* * We could check for I2C bit rate capabilities and if * available adjust this interval. We could also be * more careful with DP-to-legacy adapters where a * long legacy cable may force very low I2C bit rates. * * For now just defer for long enough to hopefully be * safe for all use-cases. */ usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100); continue; default: DRM_ERROR("invalid native reply %#04x\n", msg->reply); return -EREMOTEIO; } switch (msg->reply & DP_AUX_I2C_REPLY_MASK) { case DP_AUX_I2C_REPLY_ACK: /* * Both native ACK and I2C ACK replies received. We * can assume the transfer was successful. */ if (ret != msg->size) drm_dp_i2c_msg_write_status_update(msg); return ret; case DP_AUX_I2C_REPLY_NACK: DRM_DEBUG_KMS("I2C nack (result=%d, size=%zu\n", ret, msg->size); aux->i2c_nack_count++; return -EREMOTEIO; case DP_AUX_I2C_REPLY_DEFER: DRM_DEBUG_KMS("I2C defer\n"); /* DP Compliance Test 4.2.2.5 Requirement: * Must have at least 7 retries for I2C defers on the * transaction to pass this test */ aux->i2c_defer_count++; if (defer_i2c < 7) defer_i2c++; usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100); drm_dp_i2c_msg_write_status_update(msg); continue; default: DRM_ERROR("invalid I2C reply %#04x\n", msg->reply); return -EREMOTEIO; } } DRM_DEBUG_KMS("too many retries, giving up\n"); return -EREMOTEIO; } static void drm_dp_i2c_msg_set_request(struct drm_dp_aux_msg *msg, const struct i2c_msg *i2c_msg) { msg->request = (i2c_msg->flags & I2C_M_RD) ? DP_AUX_I2C_READ : DP_AUX_I2C_WRITE; msg->request |= DP_AUX_I2C_MOT; } /* * Keep retrying drm_dp_i2c_do_msg until all data has been transferred. * * Returns an error code on failure, or a recommended transfer size on success. */ static int drm_dp_i2c_drain_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *orig_msg) { int err, ret = orig_msg->size; struct drm_dp_aux_msg msg = *orig_msg; while (msg.size > 0) { err = drm_dp_i2c_do_msg(aux, &msg); if (err <= 0) return err == 0 ? -EPROTO : err; if (err < msg.size && err < ret) { DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n", msg.size, err); ret = err; } msg.size -= err; msg.buffer = (void *)((char *)msg.buffer + err); } return ret; } /* * Bizlink designed DP->DVI-D Dual Link adapters require the I2C over AUX * packets to be as large as possible. If not, the I2C transactions never * succeed. Hence the default is maximum. */ static int dp_aux_i2c_transfer_size __read_mostly = DP_AUX_MAX_PAYLOAD_BYTES; module_param_unsafe(dp_aux_i2c_transfer_size, int, 0644); MODULE_PARM_DESC(dp_aux_i2c_transfer_size, "Number of bytes to transfer in a single I2C over DP AUX CH message, (1-16, default 16)"); static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num) { struct drm_dp_aux *aux = adapter->algo_data; unsigned int i, j; unsigned transfer_size; struct drm_dp_aux_msg msg; int err = 0; dp_aux_i2c_transfer_size = clamp(dp_aux_i2c_transfer_size, 1, DP_AUX_MAX_PAYLOAD_BYTES); memset(&msg, 0, sizeof(msg)); mutex_lock(&aux->hw_mutex); for (i = 0; i < num; i++) { msg.address = msgs[i].addr; drm_dp_i2c_msg_set_request(&msg, &msgs[i]); /* Send a bare address packet to start the transaction. * Zero sized messages specify an address only (bare * address) transaction. */ msg.buffer = NULL; msg.size = 0; err = drm_dp_i2c_do_msg(aux, &msg); /* * Reset msg.request in case in case it got * changed into a WRITE_STATUS_UPDATE. */ drm_dp_i2c_msg_set_request(&msg, &msgs[i]); if (err < 0) break; /* We want each transaction to be as large as possible, but * we'll go to smaller sizes if the hardware gives us a * short reply. */ transfer_size = dp_aux_i2c_transfer_size; for (j = 0; j < msgs[i].len; j += msg.size) { msg.buffer = msgs[i].buf + j; msg.size = min(transfer_size, msgs[i].len - j); err = drm_dp_i2c_drain_msg(aux, &msg); /* * Reset msg.request in case in case it got * changed into a WRITE_STATUS_UPDATE. */ drm_dp_i2c_msg_set_request(&msg, &msgs[i]); if (err < 0) break; transfer_size = err; } if (err < 0) break; } if (err >= 0) err = num; /* Send a bare address packet to close out the transaction. * Zero sized messages specify an address only (bare * address) transaction. */ msg.request &= ~DP_AUX_I2C_MOT; msg.buffer = NULL; msg.size = 0; (void)drm_dp_i2c_do_msg(aux, &msg); mutex_unlock(&aux->hw_mutex); return err; } static const struct i2c_algorithm drm_dp_i2c_algo = { .functionality = drm_dp_i2c_functionality, .master_xfer = drm_dp_i2c_xfer, }; /** * drm_dp_aux_register() - initialise and register aux channel * @aux: DisplayPort AUX channel * * Returns 0 on success or a negative error code on failure. */ int drm_dp_aux_register(struct drm_dp_aux *aux) { #ifdef __NetBSD__ linux_mutex_init(&aux->hw_mutex); #else mutex_init(&aux->hw_mutex); #endif aux->ddc.algo = &drm_dp_i2c_algo; aux->ddc.algo_data = aux; aux->ddc.retries = 3; aux->ddc.class = I2C_CLASS_DDC; aux->ddc.owner = THIS_MODULE; aux->ddc.dev.parent = aux->dev; #ifndef __NetBSD__ aux->ddc.dev.of_node = aux->dev->of_node; #endif strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev), sizeof(aux->ddc.name)); return i2c_add_adapter(&aux->ddc); } EXPORT_SYMBOL(drm_dp_aux_register); /** * drm_dp_aux_unregister() - unregister an AUX adapter * @aux: DisplayPort AUX channel */ void drm_dp_aux_unregister(struct drm_dp_aux *aux) { i2c_del_adapter(&aux->ddc); #ifdef __NetBSD__ linux_mutex_destroy(&aux->hw_mutex); #else mutex_destroy(&aux->hw_mutex); #endif } EXPORT_SYMBOL(drm_dp_aux_unregister);