linux/drivers/gpu/drm/drm_dp_helper.c
Alex Deucher 732d50b431 drm/dp/i2c: Update comments about common i2c over dp assumptions (v3)
If you are using the common dp over i2c functionality, it is
asumed that the aux transfer function does not modify the any
of the msg structure other than the reply field.  Doing so
breaks the logic in the common code.

v2: update struct drm_dp_aux comments about assumptions
v3 (chk): rebased on upstream changes

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Thierry Reding <treding@nvidia.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
2014-04-08 16:12:39 +02:00

760 lines
20 KiB
C

/*
* 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 <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <drm/drm_dp_helper.h>
#include <drm/drmP.h>
/**
* 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, ...
*/
/* Run a single AUX_CH I2C transaction, writing/reading data as necessary */
static int
i2c_algo_dp_aux_transaction(struct i2c_adapter *adapter, int mode,
uint8_t write_byte, uint8_t *read_byte)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int ret;
ret = (*algo_data->aux_ch)(adapter, mode,
write_byte, read_byte);
return ret;
}
/*
* I2C over AUX CH
*/
/*
* Send the address. If the I2C link is running, this 'restarts'
* the connection with the new address, this is used for doing
* a write followed by a read (as needed for DDC)
*/
static int
i2c_algo_dp_aux_address(struct i2c_adapter *adapter, u16 address, bool reading)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int mode = MODE_I2C_START;
int ret;
if (reading)
mode |= MODE_I2C_READ;
else
mode |= MODE_I2C_WRITE;
algo_data->address = address;
algo_data->running = true;
ret = i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
return ret;
}
/*
* Stop the I2C transaction. This closes out the link, sending
* a bare address packet with the MOT bit turned off
*/
static void
i2c_algo_dp_aux_stop(struct i2c_adapter *adapter, bool reading)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int mode = MODE_I2C_STOP;
if (reading)
mode |= MODE_I2C_READ;
else
mode |= MODE_I2C_WRITE;
if (algo_data->running) {
(void) i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
algo_data->running = false;
}
}
/*
* Write a single byte to the current I2C address, the
* the I2C link must be running or this returns -EIO
*/
static int
i2c_algo_dp_aux_put_byte(struct i2c_adapter *adapter, u8 byte)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int ret;
if (!algo_data->running)
return -EIO;
ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_WRITE, byte, NULL);
return ret;
}
/*
* Read a single byte from the current I2C address, the
* I2C link must be running or this returns -EIO
*/
static int
i2c_algo_dp_aux_get_byte(struct i2c_adapter *adapter, u8 *byte_ret)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int ret;
if (!algo_data->running)
return -EIO;
ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_READ, 0, byte_ret);
return ret;
}
static int
i2c_algo_dp_aux_xfer(struct i2c_adapter *adapter,
struct i2c_msg *msgs,
int num)
{
int ret = 0;
bool reading = false;
int m;
int b;
for (m = 0; m < num; m++) {
u16 len = msgs[m].len;
u8 *buf = msgs[m].buf;
reading = (msgs[m].flags & I2C_M_RD) != 0;
ret = i2c_algo_dp_aux_address(adapter, msgs[m].addr, reading);
if (ret < 0)
break;
if (reading) {
for (b = 0; b < len; b++) {
ret = i2c_algo_dp_aux_get_byte(adapter, &buf[b]);
if (ret < 0)
break;
}
} else {
for (b = 0; b < len; b++) {
ret = i2c_algo_dp_aux_put_byte(adapter, buf[b]);
if (ret < 0)
break;
}
}
if (ret < 0)
break;
}
if (ret >= 0)
ret = num;
i2c_algo_dp_aux_stop(adapter, reading);
DRM_DEBUG_KMS("dp_aux_xfer return %d\n", ret);
return ret;
}
static u32
i2c_algo_dp_aux_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 const struct i2c_algorithm i2c_dp_aux_algo = {
.master_xfer = i2c_algo_dp_aux_xfer,
.functionality = i2c_algo_dp_aux_functionality,
};
static void
i2c_dp_aux_reset_bus(struct i2c_adapter *adapter)
{
(void) i2c_algo_dp_aux_address(adapter, 0, false);
(void) i2c_algo_dp_aux_stop(adapter, false);
}
static int
i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
{
adapter->algo = &i2c_dp_aux_algo;
adapter->retries = 3;
i2c_dp_aux_reset_bus(adapter);
return 0;
}
/**
* i2c_dp_aux_add_bus() - register an i2c adapter using the aux ch helper
* @adapter: i2c adapter to register
*
* This registers an i2c adapater that uses dp aux channel as it's underlaying
* transport. The driver needs to fill out the &i2c_algo_dp_aux_data structure
* and store it in the algo_data member of the @adapter argument. This will be
* used by the i2c over dp aux algorithm to drive the hardware.
*
* RETURNS:
* 0 on success, -ERRNO on failure.
*/
int
i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
{
int error;
error = i2c_dp_aux_prepare_bus(adapter);
if (error)
return error;
error = i2c_add_adapter(adapter);
return error;
}
EXPORT_SYMBOL(i2c_dp_aux_add_bus);
/* 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);
/**
* 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;
memset(&msg, 0, sizeof(msg));
msg.address = offset;
msg.request = request;
msg.buffer = buffer;
msg.size = size;
/*
* The specification doesn't give any recommendation on how often to
* retry native transactions, so retry 7 times like for I2C-over-AUX
* transactions.
*/
for (retry = 0; retry < 7; retry++) {
err = aux->transfer(aux, &msg);
if (err < 0) {
if (err == -EBUSY)
continue;
return err;
}
switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
case DP_AUX_NATIVE_REPLY_ACK:
if (err < size)
return -EPROTO;
return err;
case DP_AUX_NATIVE_REPLY_NACK:
return -EIO;
case DP_AUX_NATIVE_REPLY_DEFER:
usleep_range(400, 500);
break;
}
}
DRM_DEBUG_KMS("too many retries, giving up\n");
return -EIO;
}
/**
* 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_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;
}
/*
* 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.
*/
static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
{
unsigned int retry;
int err;
/*
* 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.
*/
for (retry = 0; retry < 7; retry++) {
err = aux->transfer(aux, msg);
if (err < 0) {
if (err == -EBUSY)
continue;
DRM_DEBUG_KMS("transaction failed: %d\n", err);
return err;
}
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\n");
return -EREMOTEIO;
case DP_AUX_NATIVE_REPLY_DEFER:
DRM_DEBUG_KMS("native defer");
/*
* 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(500, 600);
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 (err < msg->size)
return -EPROTO;
return 0;
case DP_AUX_I2C_REPLY_NACK:
DRM_DEBUG_KMS("I2C nack\n");
return -EREMOTEIO;
case DP_AUX_I2C_REPLY_DEFER:
DRM_DEBUG_KMS("I2C defer\n");
usleep_range(400, 500);
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 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;
struct drm_dp_aux_msg msg;
int err = 0;
memset(&msg, 0, sizeof(msg));
for (i = 0; i < num; i++) {
msg.address = msgs[i].addr;
msg.request = (msgs[i].flags & I2C_M_RD) ?
DP_AUX_I2C_READ :
DP_AUX_I2C_WRITE;
msg.request |= DP_AUX_I2C_MOT;
/* 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);
if (err < 0)
break;
/*
* Many hardware implementations support FIFOs larger than a
* single byte, but it has been empirically determined that
* transferring data in larger chunks can actually lead to
* decreased performance. Therefore each message is simply
* transferred byte-by-byte.
*/
for (j = 0; j < msgs[i].len; j++) {
msg.buffer = msgs[i].buf + j;
msg.size = 1;
err = drm_dp_i2c_do_msg(aux, &msg);
if (err < 0)
break;
}
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);
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_i2c_bus() - register an I2C adapter for I2C-over-AUX
* @aux: DisplayPort AUX channel
*
* Returns 0 on success or a negative error code on failure.
*/
int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux)
{
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;
aux->ddc.dev.of_node = aux->dev->of_node;
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_i2c_bus);
/**
* drm_dp_aux_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
* @aux: DisplayPort AUX channel
*/
void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux)
{
i2c_del_adapter(&aux->ddc);
}
EXPORT_SYMBOL(drm_dp_aux_unregister_i2c_bus);