1.. _typec: 2 3USB Type-C connector class 4========================== 5 6Introduction 7------------ 8 9The typec class is meant for describing the USB Type-C ports in a system to the 10user space in unified fashion. The class is designed to provide nothing else 11except the user space interface implementation in hope that it can be utilized 12on as many platforms as possible. 13 14The platforms are expected to register every USB Type-C port they have with the 15class. In a normal case the registration will be done by a USB Type-C or PD PHY 16driver, but it may be a driver for firmware interface such as UCSI, driver for 17USB PD controller or even driver for Thunderbolt3 controller. This document 18considers the component registering the USB Type-C ports with the class as "port 19driver". 20 21On top of showing the capabilities, the class also offer user space control over 22the roles and alternate modes of ports, partners and cable plugs when the port 23driver is capable of supporting those features. 24 25The class provides an API for the port drivers described in this document. The 26attributes are described in Documentation/ABI/testing/sysfs-class-typec. 27 28User space interface 29-------------------- 30Every port will be presented as its own device under /sys/class/typec/. The 31first port will be named "port0", the second "port1" and so on. 32 33When connected, the partner will be presented also as its own device under 34/sys/class/typec/. The parent of the partner device will always be the port it 35is attached to. The partner attached to port "port0" will be named 36"port0-partner". Full path to the device would be 37/sys/class/typec/port0/port0-partner/. 38 39The cable and the two plugs on it may also be optionally presented as their own 40devices under /sys/class/typec/. The cable attached to the port "port0" port 41will be named port0-cable and the plug on the SOP Prime end (see USB Power 42Delivery Specification ch. 2.4) will be named "port0-plug0" and on the SOP 43Double Prime end "port0-plug1". The parent of a cable will always be the port, 44and the parent of the cable plugs will always be the cable. 45 46If the port, partner or cable plug supports Alternate Modes, every supported 47Alternate Mode SVID will have their own device describing them. Note that the 48Alternate Mode devices will not be attached to the typec class. The parent of an 49alternate mode will be the device that supports it, so for example an alternate 50mode of port0-partner will be presented under /sys/class/typec/port0-partner/. 51Every mode that is supported will have its own group under the Alternate Mode 52device named "mode<index>", for example /sys/class/typec/port0/<alternate 53mode>/mode1/. The requests for entering/exiting a mode can be done with "active" 54attribute file in that group. 55 56Driver API 57---------- 58 59Registering the ports 60~~~~~~~~~~~~~~~~~~~~~ 61 62The port drivers will describe every Type-C port they control with struct 63typec_capability data structure, and register them with the following API: 64 65.. kernel-doc:: drivers/usb/typec/class.c 66 :functions: typec_register_port typec_unregister_port 67 68When registering the ports, the prefer_role member in struct typec_capability 69deserves special notice. If the port that is being registered does not have 70initial role preference, which means the port does not execute Try.SNK or 71Try.SRC by default, the member must have value TYPEC_NO_PREFERRED_ROLE. 72Otherwise if the port executes Try.SNK by default, the member must have value 73TYPEC_DEVICE, and with Try.SRC the value must be TYPEC_HOST. 74 75Registering Partners 76~~~~~~~~~~~~~~~~~~~~ 77 78After successful connection of a partner, the port driver needs to register the 79partner with the class. Details about the partner need to be described in struct 80typec_partner_desc. The class copies the details of the partner during 81registration. The class offers the following API for registering/unregistering 82partners. 83 84.. kernel-doc:: drivers/usb/typec/class.c 85 :functions: typec_register_partner typec_unregister_partner 86 87The class will provide a handle to struct typec_partner if the registration was 88successful, or NULL. 89 90If the partner is USB Power Delivery capable, and the port driver is able to 91show the result of Discover Identity command, the partner descriptor structure 92should include handle to struct usb_pd_identity instance. The class will then 93create a sysfs directory for the identity under the partner device. The result 94of Discover Identity command can then be reported with the following API: 95 96.. kernel-doc:: drivers/usb/typec/class.c 97 :functions: typec_partner_set_identity 98 99Registering Cables 100~~~~~~~~~~~~~~~~~~ 101 102After successful connection of a cable that supports USB Power Delivery 103Structured VDM "Discover Identity", the port driver needs to register the cable 104and one or two plugs, depending if there is CC Double Prime controller present 105in the cable or not. So a cable capable of SOP Prime communication, but not SOP 106Double Prime communication, should only have one plug registered. For more 107information about SOP communication, please read chapter about it from the 108latest USB Power Delivery specification. 109 110The plugs are represented as their own devices. The cable is registered first, 111followed by registration of the cable plugs. The cable will be the parent device 112for the plugs. Details about the cable need to be described in struct 113typec_cable_desc and about a plug in struct typec_plug_desc. The class copies 114the details during registration. The class offers the following API for 115registering/unregistering cables and their plugs: 116 117.. kernel-doc:: drivers/usb/typec/class.c 118 :functions: typec_register_cable typec_unregister_cable typec_register_plug typec_unregister_plug 119 120The class will provide a handle to struct typec_cable and struct typec_plug if 121the registration is successful, or NULL if it isn't. 122 123If the cable is USB Power Delivery capable, and the port driver is able to show 124the result of Discover Identity command, the cable descriptor structure should 125include handle to struct usb_pd_identity instance. The class will then create a 126sysfs directory for the identity under the cable device. The result of Discover 127Identity command can then be reported with the following API: 128 129.. kernel-doc:: drivers/usb/typec/class.c 130 :functions: typec_cable_set_identity 131 132Notifications 133~~~~~~~~~~~~~ 134 135When the partner has executed a role change, or when the default roles change 136during connection of a partner or cable, the port driver must use the following 137APIs to report it to the class: 138 139.. kernel-doc:: drivers/usb/typec/class.c 140 :functions: typec_set_data_role typec_set_pwr_role typec_set_vconn_role typec_set_pwr_opmode 141 142Alternate Modes 143~~~~~~~~~~~~~~~ 144 145USB Type-C ports, partners and cable plugs may support Alternate Modes. Each 146Alternate Mode will have identifier called SVID, which is either a Standard ID 147given by USB-IF or vendor ID, and each supported SVID can have 1 - 6 modes. The 148class provides struct typec_mode_desc for describing individual mode of a SVID, 149and struct typec_altmode_desc which is a container for all the supported modes. 150 151Ports that support Alternate Modes need to register each SVID they support with 152the following API: 153 154.. kernel-doc:: drivers/usb/typec/class.c 155 :functions: typec_port_register_altmode 156 157If a partner or cable plug provides a list of SVIDs as response to USB Power 158Delivery Structured VDM Discover SVIDs message, each SVID needs to be 159registered. 160 161API for the partners: 162 163.. kernel-doc:: drivers/usb/typec/class.c 164 :functions: typec_partner_register_altmode 165 166API for the Cable Plugs: 167 168.. kernel-doc:: drivers/usb/typec/class.c 169 :functions: typec_plug_register_altmode 170 171So ports, partners and cable plugs will register the alternate modes with their 172own functions, but the registration will always return a handle to struct 173typec_altmode on success, or NULL. The unregistration will happen with the same 174function: 175 176.. kernel-doc:: drivers/usb/typec/class.c 177 :functions: typec_unregister_altmode 178 179If a partner or cable plug enters or exits a mode, the port driver needs to 180notify the class with the following API: 181 182.. kernel-doc:: drivers/usb/typec/class.c 183 :functions: typec_altmode_update_active 184 185Multiplexer/DeMultiplexer Switches 186~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 187 188USB Type-C connectors may have one or more mux/demux switches behind them. Since 189the plugs can be inserted right-side-up or upside-down, a switch is needed to 190route the correct data pairs from the connector to the USB controllers. If 191Alternate or Accessory Modes are supported, another switch is needed that can 192route the pins on the connector to some other component besides USB. USB Type-C 193Connector Class supplies an API for registering those switches. 194 195.. kernel-doc:: drivers/usb/typec/mux.c 196 :functions: typec_switch_register typec_switch_unregister typec_mux_register typec_mux_unregister 197 198In most cases the same physical mux will handle both the orientation and mode. 199However, as the port drivers will be responsible for the orientation, and the 200alternate mode drivers for the mode, the two are always separated into their 201own logical components: "mux" for the mode and "switch" for the orientation. 202 203When a port is registered, USB Type-C Connector Class requests both the mux and 204the switch for the port. The drivers can then use the following API for 205controlling them: 206 207.. kernel-doc:: drivers/usb/typec/class.c 208 :functions: typec_set_orientation typec_set_mode 209 210If the connector is dual-role capable, there may also be a switch for the data 211role. USB Type-C Connector Class does not supply separate API for them. The 212port drivers can use USB Role Class API with those. 213 214Illustration of the muxes behind a connector that supports an alternate mode:: 215 216 ------------------------ 217 | Connector | 218 ------------------------ 219 | | 220 ------------------------ 221 \ Orientation / 222 -------------------- 223 | 224 -------------------- 225 / Mode \ 226 ------------------------ 227 / \ 228 ------------------------ -------------------- 229 | Alt Mode | / USB Role \ 230 ------------------------ ------------------------ 231 / \ 232 ------------------------ ------------------------ 233 | USB Host | | USB Device | 234 ------------------------ ------------------------ 235