---
title: Open
framework: usbdriverkit
role: symbol
role_heading: Instance Method
path: usbdriverkit/iousbhostdevice/open
---

# Open

Opens a session to a host device.

## Declaration

```occ
virtual kern_return_t Open(IOService *forClient, IOOptionBits options, uintptr_t arg);
```

## Parameters

- `forClient`: The service object that is opening the session.
- `options`: The options to use when opening the session. Specify 0 for this parameter.
- `arg`: Additional arguments to the function. Specify NULL for this parameter.

## Return Value

Return Value kIOReturnSuccess on success, or another value if an error occurs. See Error Codes.

## Discussion

Discussion This method opens a session to the IOUSBHostDevice, and acquires the service’s workloop lock. Child IOUSBHostInterface objects may open simultaneous sessions, but only one IOUSBHostDevice object at a time may open a session to the device.

## See Also

### Managing the Device Session

- [Close](usbdriverkit/iousbhostdevice/close.md)
- [Reset](usbdriverkit/iousbhostdevice/reset.md)