USB services

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One symbol in USB-sysmodule is: "vtable for nn::usb::detail::UsbComplexTegra21x".

usb:ds

Used for Switch<>PC USB comms, aka Switch-as-device. This service is used during factory setup by manu.

This service session is used as an IPC domain by manu. All of these {get-session} commands also return an output u8 and the u32 <domainID>, for using those sessions as domains.

Cmd Name Notes
0 #BindDevice
1 #BindClientProcess
2 #GetDsInterface
3 #GetStateChangeEvent
4 No input. Returns an output u32. Returns an error when #BindDevice wasn't used.
5 #SetVidPidBcd

Initialization done by manu:

Configuration

The following is the default USB config strings, while the usbds service isn't being used. All of the below configuration will reset to the defaults when all usbds-related sessions are closed. These can be set with #SetVidPidBcd. The default string for Product is loaded from settings config. The default is referred to by usb-sysmodule as "Dummy". 

 Product: Nintendo Switch
 Manufacturer: Nintendo
 SerialNumber: SerialNumber

The following is the default lsusb -v {...} output when the usbds service wasn't used.

The endpoints are configured using #GetDsEndpoint, the total number of endpoints is the number of open #IDsEndpoint sessions. bInterfaceNumber is {0-based index for the enabled #IDsInterface session.} Some of the interface fields are configured using #GetDsInterface.

Additional descriptors for use with interfaces/endpoints can't be configured with usbds, even though the former is used for the default HID interface. This seems to be the main(?) restriction with using usbds for Switch-as-arbitrary-devices. 

 Bus 003 Device 006: ID 057e:2000 Nintendo Co., Ltd 
 Couldn't open device, some information will be missing
 Device Descriptor:
   bLength                18
   bDescriptorType         1
   bcdUSB               2.00
   bDeviceClass            0 (Defined at Interface level)
   bDeviceSubClass         0 
   bDeviceProtocol         0 
   bMaxPacketSize0        64
   idVendor           0x057e Nintendo Co., Ltd
   idProduct          0x2000 
   bcdDevice            1.00
   iManufacturer           1 
   iProduct                2 
   iSerial                 3 
   bNumConfigurations      1
   Configuration Descriptor:
     bLength                 9
     bDescriptorType         2
     wTotalLength           34
     bNumInterfaces          1
     bConfigurationValue     1
     iConfiguration          0 
     bmAttributes         0xc0
       Self Powered
     MaxPower              {...}
     Interface Descriptor:
       bLength                 9
       bDescriptorType         4
       bInterfaceNumber        0
       bAlternateSetting       0
       bNumEndpoints           1
       bInterfaceClass         3 Human Interface Device
       bInterfaceSubClass      0 No Subclass
       bInterfaceProtocol      0 None
       iInterface              0 
         HID Device Descriptor:
           bLength                 9
           bDescriptorType        33
           bcdHID               2.00
           bCountryCode            0 Not supported
           bNumDescriptors         1
           bDescriptorType        34 Report
           wDescriptorLength      26
          Report Descriptors: 
            ** UNAVAILABLE **
       Endpoint Descriptor:
         bLength                 7
         bDescriptorType         5
         bEndpointAddress     0x81  EP 1 IN
         bmAttributes            3
           Transfer Type            Interrupt
           Synch Type               None
           Usage Type               Data
         wMaxPacketSize     0x0001  1x 1 bytes
         bInterval              16

BindDevice

Takes an u32 (complexId). Manu sends 0x02.

Binding more than once with the current session is not allowed. Once this command is used, the USB device will not be listed with lsusb until #EnableInterface is used.

BindClientProcess

Takes 1 copy-handle for the current process (0xFFFF8001).

GetDsInterface

Takes 2 type-5 buffers and returns an #IDsInterface. Manu sends a 0x09-byte command (e.g.: 0x09, 0x04, 0x04, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0x00) in the first buffer and a string ("usb") in the second buffer.

When the strlen output for the second buffer is >=0x40, size 0x40 is used instead for copying the string. This is the interface name, it's not sent over USB.

Returns an error when #BindDevice wasn't used.

Up to 4 interfaces can be used+enabled.

Structure of the first buffer(this is the same as libusb__interface__descriptor):

Offset Size Description
0x0 0x1 bLength. Must match 0x9.
0x1 0x1 bDescriptorType. Must match 0x4.
0x2 0x1 bInterfaceNumber. When 0x4, the bInterfaceNumber is automatically allocated(error will be thrown if no space). Otherwise, it's used directly and must be <=3.
0x3 0x1 bAlternateSetting. Must match 0x0.
0x4 0x1 bNumEndpoints. Ignored.
0x5 0x1 bInterfaceClass
0x6 0x1 bInterfaceSubClass
0x7 0x1 bInterfaceProtocol
0x8 0x1 iInterface. Ignored.

Only the first 0x9-bytes are used.

GetStateChangeEvent

Returns an event handle for state changes. Signalled when Switch<->host USB comms change between started/stopped. USB cable connected/disconnected while at least 1 interface was enabled, or interface enabled/disabled while the USB cable was connected which then caused USB-comms state to change.

SetVidPidBcd

Takes a type-5 buffer with 0x66 bytes of USB descriptor data (see manu).

Offset Size Description
0x0 0x2 VID (idVendor)
0x2 0x2 PID (idProduct)
0x4 0x2 bcdUSB
0x6 0x20 Manufacturer
0x26 0x20 Product
0x46 0x20 SerialNumber

The last 3 blocks are strings. The data following each string is all-zero, for padding to size 0x20.

IDsInterface

Cmd Name Notes
0 #GetDsEndpoint
1 #GetSetupEvent
2 Takes a type-0x6 output buffer, no other output. Memcpys data to outbuf with outsize, uses size 0x8 if outsize is too large.
3 #EnableInterface
4 #DisableInterface
5 #CtrlInPostBufferAsync
6 #CtrlOutPostBufferAsync
7 #GetCtrlInCompletionEvent
8 #GetCtrlInReportData
9 #GetCtrlOutCompletionEvent
10 #GetCtrlOutReportData
11 #StallCtrl

Commands cmd2, #CtrlInPostBufferAsync, #CtrlOutPostBufferAsync, and #StallCtrl, will throw an error if the interface is not enabled. #GetDsEndpoint will throw an error if the interface is enabled.

GetDsEndpoint

Takes a type-5 buffer and returns an #IDsEndpoint. Manu uses this twice for getting two endpoint sessions, with the following 0x7-byte buffer data:

  • First endpoint: 0x07, 0x05, 0x80, 0x02, 0x00, 0x02, 0x00
    • bLength=0x7
    • bDescriptorType=LIBUSB_DT_ENDPOINT
    • bEndpointAddress=LIBUSB_ENDPOINT_IN
    • bmAttributes=LIBUSB_TRANSFER_TYPE_BULK
    • wMaxPacketSize=0x200
    • bInterval=0
  • Second endpoint: Same as above except byte2 is 0x00(bEndpointAddress=LIBUSB_ENDPOINT_OUT).

Each field is an u8, except for offset 0x4-0x5 which is an u16.

This structure matches libusb_endpoint_descriptor.

The buffer size must be >=0x7. Only the first 0x7-bytes from the buffer are used.

  • Byte0(bLength) must match 0x7.
  • Byte1(bDescriptorType) must match 0x5.
  • Byte2(bEndpointAddress) is only compared with 0x80 to determine whether to use an input or output endpoint, the actual endpoint-number is allocated automatically by checking state. Hence, all input endpoints must use bEndpointAddress==0x80. Up to endpoint-number 0xF can be allocated for each endpoint-direction, for a total of 16 endpoints including control, and 15 for non-control endpoints(#IDsEndpoint sessions for each direction). This matches the Tegra maximum.

From the Tegra datasheet: "The maximum packet size supported on any endpoint is 1024 bytes in high-speed mode, for both device and host modes."

GetSetupEvent

Returns an event handle. Unknown what triggers signalling.

EnableInterface

Takes no arguments. Enables the current interface.

Only one interface can be enabled at a time per bInterfaceNumber. When bInterfaceNumber is auto-allocate(0x4) for #GetDsEndpoint this isn't an issue since the final bInterfaceNumber will be unique.

Once enabled, the device/interface can then actually be used over USB.

DisableInterface

Takes no arguments. Disables the current interface.

CtrlInPostBufferAsync

Same as #PostBufferAsync(with same input/output), except this uses control input endpoint 0x80.

CtrlOutPostBufferAsync

Same as #PostBufferAsync(with same input/output), except this uses control output endpoint 0x00.

GetCtrlInCompletionEvent

Returns an event handle for polling the completion of input control commands. Same as #GetCompletionEvent, except this uses control input endpoint 0x80.

GetCtrlInReportData

Same as #GetReportData(with same input/output), except this uses control input endpoint 0x80.

GetCtrlOutCompletionEvent

Returns an event handle for polling the completion of output control commands. Same as #GetCompletionEvent, except this uses control output endpoint 0x00.

GetCtrlOutReportData

Same as #GetReportData(with same input/output), except this uses control output endpoint 0x00.

StallCtrl

No input/output.

Calls a function with both control endpoints(0x80 and 0x00) with the same function. From strings: "m_pProtocol->Stall(0x80)" "m_pProtocol->Stall(0x00)".

IDsEndpoint

Cmd Name Notes
0 #PostBufferAsync
1 No input/output.
2 #GetCompletionEvent
3 #GetReportData
4 #Stall
5 Takes an input u8, no output.

PostBufferAsync

Takes an u32 (size) and an u64 (buffer). Returns an output u32, this is unrelated to size.

The buffer address must be 0x1000-byte aligned. The input size doesn't matter.

Used for data-transfer with input/output endpoints.

GetCompletionEvent

No input. Returns an output event handle for polling the completion of #PostBufferAsync, even when it finished via #Stall.

GetReportData

No input. Returns 0x84 bytes of report data from the endpoint. Seems to be eventually loaded from state, since this doesn't trigger any USB bus activity.

Stall

No input/output.

Calls the same function used by #StallCtrl, except this uses the endpoint associated with the current session.

Stops in-progress data-transfer done by #PostBufferAsync.

usb:hs

General USB devices usage, used by hid-sysmodule and bsdsockets-sysmodule.

usb:pd

Only system-titles with access to this are PTM and AM.

usb:pd:c

USB-sysmodule symbols for this refer to "Cradle", which is the Dock.

usb:pm

Presumably Power Management, only system-title using this is PTM.

Retrieved from "https://switchbrew.org/w/index.php?title=USB_services&oldid=2744"