General¶

By default, the alternate mode drivers are responsible for entering the mode.It is also possible to leave the decision about entering the mode to the userspace (See Documentation/ABI/testing/sysfs-class-typec). Port drivers should notenter any modes on their own.

->vdm is the most important callback in the operation callbacks vector. Itwill be used to deliver all the SVID specific commands from the partner to thealternate mode driver, and vice versa in case of port drivers. The drivers sendthe SVID specific commands to each other usingtypec_altmode_vdm().

If the communication with the partner using the SVID specific commands resultsin need to reconfigure the pins on the connector, the alternate mode driverneeds to notify the bus usingtypec_altmode_notify(). The driverpasses the negotiated SVID specific pin configuration value to the function asparameter. The bus driver will then configure the mux behind the connector usingthat value as the state value for the mux.

NOTE: The SVID specific pin configuration values must always start fromTYPEC_STATE_MODAL. USB Type-C specification defines two default states forthe connector:TYPEC_STATE_USB andTYPEC_STATE_SAFE. These values arereserved by the bus as the first possible values for the state. When thealternate mode is entered, the bus will put the connector intoTYPEC_STATE_SAFE before sending Enter or Exit Mode command as defined in USBType-C Specification, and also put the connector back toTYPEC_STATE_USBafter the mode has been exited.

An example of working definitions for SVID specific pin configurations wouldlook like this:

enum {    ALTMODEX_CONF_A = TYPEC_STATE_MODAL,    ALTMODEX_CONF_B,    ...};

Helper macroTYPEC_MODAL_STATE() can also be used:

#define ALTMODEX_CONF_A = TYPEC_MODAL_STATE(0);#define ALTMODEX_CONF_B = TYPEC_MODAL_STATE(1);

Cable plug alternate modes¶

The alternate mode drivers are not bound to cable plug alternate mode devices,only to the partner alternate mode devices. If the alternate mode supports, orrequires, a cable that responds to SOP Prime, and optionally SOP Double Primemessages, the driver for that alternate mode must request handle to the cableplug alternate modes usingtypec_altmode_get_plug(), and take overtheir control.

Alternate mode driver registering/unregistering¶

Alternate mode driver operations¶

inttypec_altmode_notify(struct typec_altmode * adev, unsigned long conf, void * data)¶

Communication between the OS and alternate mode driver

Parameters

structtypec_altmode*adev

Handle to the alternate mode

unsignedlongconf

Alternate mode specific configuration value

void*data

Alternate mode specific data

Description

The primary purpose for this function is to allow the alternate mode driversto tell which pin configuration has been negotiated with the partner. Thatinformation will then be used for example to configure the muxes.Communication to the other direction is also possible, and low level devicedrivers can also send notifications to the alternate mode drivers. The actualcommunication will be specific for every SVID.

inttypec_altmode_enter(struct typec_altmode * adev, u32 * vdo)¶

Enter Mode

Parameters

structtypec_altmode*adev

The alternate mode

u32*vdo

VDO for the Enter Mode command

Description

The alternate mode drivers use this function to enter mode. The port driversuse this to inform the alternate mode drivers that the partner has initiatedEnter Mode command. If the alternate mode does not require VDO,vdo must beNULL.

inttypec_altmode_exit(struct typec_altmode * adev)¶

Exit Mode

Parameters

structtypec_altmode*adev

The alternate mode

Description

The partner ofadev has initiated Exit Mode command.

voidtypec_altmode_attention(struct typec_altmode * adev, u32 vdo)¶

Attention command

Parameters

structtypec_altmode*adev

The alternate mode

u32vdo

VDO for the Attention command

Description

Notifies the partner ofadev about Attention command.

inttypec_altmode_vdm(struct typec_altmode * adev, const u32 header, const u32 * vdo, int count)¶

Send Vendor Defined Messages (VDM) to the partner

Parameters

structtypec_altmode*adev

Alternate mode handle

constu32header

VDM Header

constu32*vdo

Array of Vendor Defined Data Objects

intcount

Number of Data Objects

Description

The alternate mode drivers use this function for SVID specific communicationwith the partner. The port drivers use it to deliver the Structured VDMsreceived from the partners to the alternate mode drivers.

API for the port drivers¶

struct typec_altmode *typec_match_altmode(struct typec_altmode ** altmodes, size_t n, u16 svid, u8 mode)¶

Match SVID and mode to an array of alternate modes

Parameters

structtypec_altmode**altmodes

Array of alternate modes

size_tn

Number of elements in the array, or -1 for NULL terminated arrays

u16svid

Standard or Vendor ID to match with

u8mode

Mode to match with

Description

Return pointer to an alternate mode with SVID matchingsvid, or NULL when nomatch is found.

Cable Plug operations¶

struct typec_altmode *typec_altmode_get_plug(struct typec_altmode * adev, enum typec_plug_index index)¶

Find cable plug alternate mode

Parameters

structtypec_altmode*adev

Handle to partner alternate mode

enumtypec_plug_indexindex

Cable plug index

Description

Increment reference count for cable plug alternate mode device. Returnshandle to the cable plug alternate mode, or NULL if none is found.

voidtypec_altmode_put_plug(struct typec_altmode * plug)¶

Decrement cable plug alternate mode reference count

Parameters

structtypec_altmode*plug

Handle to the cable plug alternate mode