/dev/usb/oh0

/dev/usb/oh0 is used to interact with the Wii's external USB bus. This interface is very similar to /dev/usb/oh1 and has two parts: the "root" or host device, and individual devices on which USB requests can be submitted.

/dev/usb/oh0 (IOS57 and newer)

In recent versions of IOS (after IOS 57), the OHCI0 module appears to implement a different interface and seems to only register this new interface of /dev/usb/oh0.

Only IOS_OPEN, IOS_CLOSE and IOS_IOCTL are valid commands. The other commands immediately return IPC_EINVAL (-4).

Additionally, /dev/usb/oh0 can only be opened from UID 0x11. Attempts to open OH0 with other UIDs will result in IPC_EACCES (-1).

Ioctl	Name	Input	Output	Notes
0	USBV2_IOCTL_GET_VERSION	-	0x20 bytes	Writes the version 0x20001 to the output buffer. This is very similar to the IOS58 version of /dev/usb/hid, which writes 0x50001 to the output buffer instead. It is also reminiscent of /dev/usb/ehc which does the same thing (but with an ioctlv).
1	?	?	?	?
2	?	?	?	?
3	?	0x20 bytes	?	?
4	?	0x20 bytes	?	?
5	?	0x20 bytes	?	?
16	?	0x20 bytes	?	?
17	?	0x20 bytes	?	?
18	?	0x20 bytes	?	Handled by the same function as for ioctl 20.
19	?	0x20 bytes	?	?
20	?	0x20 bytes	?	Handled by the same function as for ioctl 18.

/dev/usb/oh0

The OH1 module appears to be able to register itself as /dev/usb/oh0 and implements a similar set (subset?) of requests.

This list of requests is based on IOS36.

Request	Name	Input	Output	OH0/OH1	Notes
12 (ioctlv)	USBV0_IOCTLV_GETDEVLIST	2	2	Both	Returns a list of connected devices matching an interface class. struct Descriptor { u32 unknown; u16 vid; u16 pid; }; // sizeof(Descriptor) = 8 in 0: u8 - number of descriptors to return in 1: u8 - interface class io 0: u8 - number of devices io 1: u32* of size num_descriptors * 8 - device list
15 (ioctl)	? (USB_GetRhDesca)	-	4 bytes	Both	Unknown; something to do with the root hub (Desc = description?). Appears to return 02 00 03 02 regardless of the number of plugged in devices. [check]
20 (ioctlv)	USBV0_IOCTLV_GETRHPORTSTATUS	1	1	OH0	Supposedly used for getting the root hub's port status. (internal name: GetRhPortStatus) [check] in 0: u8 - ? io 0: u32 - Presumably the port status
25 (ioctlv)	USBV0_IOCTLV_SETRHPORTSTATUS	2	0	OH0	Supposedly used for setting the root hub's port status. (internal name: SetRhPortStatus) [check] in 0: u8 - ? in 1: u32 - Presumably the port status
27 (ioctlv)	USBV0_IOCTLV_DEVINSERTHOOK	2	0	OH0	Returns when a device with the requested VID/PID is plugged in, or immediately if the device is already inserted. in 0: u16 - VID in 1: u16 - PID
28 (ioctlv)	USBV0_IOCTLV_DEVICECLASSCHANGE	1	0	OH0	Has to do with device insertion hooks. Triggered on device class change (?) [check] in 0: u8 - Device class (can be zero)
30 (ioctlv)	USBV0_IOCTLV_DEVINSERTHOOKID (RegisterInsertionNotifyWithId)	3	1	OH0	Returns when a device with the requested VID/PID is plugged in. Similar to ioctlv 27, but with additional parameters. in 0: u16 - VID in 1: u16 - PID in 2: u8 - If falsy, return immediately if the device is already plugged in io 0: u32 - Overwritten with an ID to use with ioctl 31 for cancelling this insertion hook
31 (ioctl)	USBV0_IOCTL_CANCEL_INSERT_HOOK	4 bytes	-	OH0	Internal names: IUSB_CancelInsertionNotify / __ohciCancelNotifyInsertion Cancels a device insertion hook (the hook request will be replied to with return value -7022). The input buffer is the ID given in the unique output vector of ioctlv 30. Returns IPC_EINVAL if input buffer was nullptr. Otherwise, IPC_SUCCESS is returned if there was no hook; if there was a pending hook, the return value of IOS_ResourceReply(ioctlv_30_request, -7022) is used.

/dev/usb/oh0/%x/%x

These devices represent an individual USB device, based on its vendor ID and product ID (in hexadecimal format without leading zeroes). It is unclear how devices with the same VID/PID can be used at the same time.

Only one device handle can be opened at the same time. Attempting to open more than one results in IPC_EEXIST (-2).

This list is based on IOS36.

Request	Name	Input	Output	OH0/OH1	Notes
0 (ioctlv)	USBV0_IOCTLV_CTRLMSG	6	1	Both	Submits a control transfer. in 0: u8 - bmRequestType in 1: u8 - bmRequest in 2: u16 - wValue (swapped) in 3: u16 - wIndex (swapped) in 4: u16 - wLength (swapped) in 5: u8 - Unknown (00) io 0: array of length wLength - Request data
1 (ioctlv)	USBV0_IOCTLV_BLKMSG	2	1	Both	Submits a bulk transfer. in 0: u8 - Endpoint in 1: u16 - Length io 0: array of length in[1] - Payload data If io_vectors[0].size and the length don't match, returns IPC_EINVAL.
2 (ioctlv)	USBV0_IOCTLV_INTRMSG	2	1	Both	Submits an interrupt transfer. in 0: u8 - Endpoint in 1: u16 - Length io 0: array of length in[1] - Payload data If io_vectors[0].size and the length don't match, returns IPC_EINVAL.
5 (ioctl)	USBV0_IOCTL_SUSPENDDEV	-	-	Both	Used to suspend a device.
6 (ioctl)	USBV0_IOCTL_RESUMEDEV	-	-	Both	Used to resume a device.
9 (ioctlv)	USBV0_IOCTLV_ISOMSG	3	2	OH0	Submits an isochronous transfer. in 0: u8 - Endpoint in 1: u16 - Length in 2: u8 - Number of isochronous packets io 0: u16* of size in[2] - Sizes of the isochronous packets io 1: array of length in[1] - Payload data
10 (ioctlv)	USBV0_IOCTLV_LBLKMSG	2	1	OH0	Submits a bulk transfer. This is the same as ioctlv 1, except that this takes a u32 for the length instead of a u16. in 0: u8 - Endpoint in 1: u32 - Length io 0: array of length in_vectors[1] - Payload data If io_vectors[0].size and the length don't match, returns IPC_EINVAL.
26 (ioctl)	USBV0_IOCTL_DEVREMOVALHOOK	-	-	Both	Returns when the device is unplugged or reset (in which cases the return value is IPC_SUCCESS / IPC_OK), or on device close (IPC_ENOENT). Only one hook is allowed at the same time. Further ioctls to set up another hook before it is triggered result in IPC_EEXIST.
29 (ioctl)	USBV0_IOCTL_RESET_DEVICE	-	-	OH0	Triggers the associated removal hook before resetting the USB device.
32 (ioctlv)	?	?	?	OH0	Unknown. [check]

Known Devices

• /dev/usb/oh0/0b95/7720: ASIX AX88772 USB2.0 to Fast Ethernet Adapter (referenced in IOS eth driver)
• /dev/usb/oh0/57e/308: Nintendo Wii Speak (microphone)
• /dev/usb/oh0/46d/a03: Logitech microphone

Errors

-4 (IPC_EINVAL): might be caused by an invalid device fd

-7003: STALL (according to gc-linux)

-7004: STALL (according to gc-linux)

-7005: NAK (according to gc-linux)

-7008

-7022