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