USB Type-C connector class¶

Introduction¶

The typec class is meant for describing the USB Type-C ports in a system to the user space in unified fashion. The class is designed to provide nothing else except the user space interface implementation in hope that it can be utilized on as many platforms as possible.

The platforms are expected to register every USB Type-C port they have with the class. In a normal case the registration will be done by a USB Type-C or PD PHY driver, but it may be a driver for firmware interface such as UCSI, driver for USB PD controller or even driver for Thunderbolt3 controller. This document considers the component registering the USB Type-C ports with the class as “port driver”.

On top of showing the capabilities, the class also offer user space control over the roles and alternate modes of ports, partners and cable plugs when the port driver is capable of supporting those features.

The class provides an API for the port drivers described in this document. The attributes are described in Documentation/ABI/testing/sysfs-class-typec.

User space interface¶

Every port will be presented as its own device under /sys/class/typec/. The first port will be named “port0”, the second “port1” and so on.

When connected, the partner will be presented also as its own device under /sys/class/typec/. The parent of the partner device will always be the port it is attached to. The partner attached to port “port0” will be named “port0-partner”. Full path to the device would be /sys/class/typec/port0/port0-partner/.

The cable and the two plugs on it may also be optionally presented as their own devices under /sys/class/typec/. The cable attached to the port “port0” port will be named port0-cable and the plug on the SOP Prime end (see USB Power Delivery Specification ch. 2.4) will be named “port0-plug0” and on the SOP Double Prime end “port0-plug1”. The parent of a cable will always be the port, and the parent of the cable plugs will always be the cable.

If the port, partner or cable plug supports Alternate Modes, every supported Alternate Mode SVID will have their own device describing them. Note that the Alternate Mode devices will not be attached to the typec class. The parent of an alternate mode will be the device that supports it, so for example an alternate mode of port0-partner will be presented under /sys/class/typec/port0-partner/. Every mode that is supported will have its own group under the Alternate Mode device named “mode<index>”, for example /sys/class/typec/port0/<alternate mode>/mode1/. The requests for entering/exiting a mode can be done with “active” attribute file in that group.

Driver API¶

Registering the ports¶

The port drivers will describe every Type-C port they control with struct typec_capability data structure, and register them with the following API:

struct typec_port * typec_register_port(struct device * parent, const struct typec_capability * cap)¶: Register a USB Type-C Port

Parameters

struct device * parent: Parent device
const struct typec_capability * cap: Description of the port

Description

Registers a device for USB Type-C Port described in cap.

Returns handle to the port on success or NULL on failure.

void typec_unregister_port(struct typec_port * port)¶: Unregister a USB Type-C Port

Parameters

struct typec_port * port: The port to be unregistered

Description

Unregister device created with typec_register_port().

When registering the ports, the prefer_role member in struct typec_capability deserves special notice. If the port that is being registered does not have initial role preference, which means the port does not execute Try.SNK or Try.SRC by default, the member must have value TYPEC_NO_PREFERRED_ROLE. Otherwise if the port executes Try.SNK by default, the member must have value TYPEC_DEVICE, and with Try.SRC the value must be TYPEC_HOST.

Registering Partners¶

After successful connection of a partner, the port driver needs to register the partner with the class. Details about the partner need to be described in struct typec_partner_desc. The class copies the details of the partner during registration. The class offers the following API for registering/unregistering partners.

struct typec_partner * typec_register_partner(struct typec_port * port, struct typec_partner_desc * desc)¶: Register a USB Type-C Partner

Parameters

struct typec_port * port: The USB Type-C Port the partner is connected to
struct typec_partner_desc * desc: Description of the partner

Description

Registers a device for USB Type-C Partner described in desc.

Returns handle to the partner on success or NULL on failure.

void typec_unregister_partner(struct typec_partner * partner)¶: Unregister a USB Type-C Partner

Parameters

struct typec_partner * partner: The partner to be unregistered

Description

Unregister device created with typec_register_partner().

The class will provide a handle to struct typec_partner if the registration was successful, or NULL.

If the partner is USB Power Delivery capable, and the port driver is able to show the result of Discover Identity command, the partner descriptor structure should include handle to struct usb_pd_identity instance. The class will then create a sysfs directory for the identity under the partner device. The result of Discover Identity command can then be reported with the following API:

int typec_partner_set_identity(struct typec_partner * partner)¶: Report result from Discover Identity command

Parameters

struct typec_partner * partner: The partner updated identity values

Description

This routine is used to report that the result of Discover Identity USB power delivery command has become available.

Registering Cables¶

After successful connection of a cable that supports USB Power Delivery Structured VDM “Discover Identity”, the port driver needs to register the cable and one or two plugs, depending if there is CC Double Prime controller present in the cable or not. So a cable capable of SOP Prime communication, but not SOP Double Prime communication, should only have one plug registered. For more information about SOP communication, please read chapter about it from the latest USB Power Delivery specification.

The plugs are represented as their own devices. The cable is registered first, followed by registration of the cable plugs. The cable will be the parent device for the plugs. Details about the cable need to be described in struct typec_cable_desc and about a plug in struct typec_plug_desc. The class copies the details during registration. The class offers the following API for registering/unregistering cables and their plugs:

The class will provide a handle to struct typec_cable and struct typec_plug if the registration is successful, or NULL if it isn’t.

If the cable is USB Power Delivery capable, and the port driver is able to show the result of Discover Identity command, the cable descriptor structure should include handle to struct usb_pd_identity instance. The class will then create a sysfs directory for the identity under the cable device. The result of Discover Identity command can then be reported with the following API:

int typec_cable_set_identity(struct typec_cable * cable)¶: Report result from Discover Identity command

Parameters

struct typec_cable * cable: The cable updated identity values

Description

This routine is used to report that the result of Discover Identity USB power delivery command has become available.

Notifications¶

When the partner has executed a role change, or when the default roles change during connection of a partner or cable, the port driver must use the following APIs to report it to the class:

Alternate Modes¶

USB Type-C ports, partners and cable plugs may support Alternate Modes. Each Alternate Mode will have identifier called SVID, which is either a Standard ID given by USB-IF or vendor ID, and each supported SVID can have 1 - 6 modes. The class provides struct typec_mode_desc for describing individual mode of a SVID, and struct typec_altmode_desc which is a container for all the supported modes.

Ports that support Alternate Modes need to register each SVID they support with the following API:

struct typec_altmode * typec_port_register_altmode(struct typec_port * port, struct typec_altmode_desc * desc)¶: Register USB Type-C Port Alternate Mode

Parameters

struct typec_port * port: USB Type-C Port that supports the alternate mode
struct typec_altmode_desc * desc: Description of the alternate mode

Description

This routine is used to register an alternate mode that port is capable of supporting.

Returns handle to the alternate mode on success or NULL on failure.

If a partner or cable plug provides a list of SVIDs as response to USB Power Delivery Structured VDM Discover SVIDs message, each SVID needs to be registered.

API for the partners:

struct typec_altmode * typec_partner_register_altmode(struct typec_partner * partner, struct typec_altmode_desc * desc)¶: Register USB Type-C Partner Alternate Mode

Parameters

struct typec_partner * partner: USB Type-C Partner that supports the alternate mode
struct typec_altmode_desc * desc: Description of the alternate mode

Description

This routine is used to register each alternate mode individually that partner has listed in response to Discover SVIDs command. The modes for a SVID listed in response to Discover Modes command need to be listed in an array in desc.

Returns handle to the alternate mode on success or NULL on failure.

API for the Cable Plugs:

struct typec_altmode * typec_plug_register_altmode(struct typec_plug * plug, struct typec_altmode_desc * desc)¶: Register USB Type-C Cable Plug Alternate Mode

Parameters

struct typec_plug * plug: USB Type-C Cable Plug that supports the alternate mode
struct typec_altmode_desc * desc: Description of the alternate mode

Description

This routine is used to register each alternate mode individually that plug has listed in response to Discover SVIDs command. The modes for a SVID that the plug lists in response to Discover Modes command need to be listed in an array in desc.

Returns handle to the alternate mode on success or NULL on failure.

So ports, partners and cable plugs will register the alternate modes with their own functions, but the registration will always return a handle to struct typec_altmode on success, or NULL. The unregistration will happen with the same function:

void typec_unregister_altmode(struct typec_altmode * alt)¶: Unregister Alternate Mode

Parameters

struct typec_altmode * alt: The alternate mode to be unregistered

Description

Unregister device created with typec_partner_register_altmode(), typec_plug_register_altmode() or typec_port_register_altmode().

If a partner or cable plug enters or exits a mode, the port driver needs to notify the class with the following API:

void typec_altmode_update_active(struct typec_altmode * alt, int mode, bool active)¶: Report Enter/Exit mode

Parameters

struct typec_altmode * alt: Handle to the alternate mode
int mode: Mode index
bool active: True when the mode has been entered

Description

If a partner or cable plug executes Enter/Exit Mode command successfully, the drivers use this routine to report the updated state of the mode.