DeviceRequest
Sends a synchronous request to the device on the default control endpoint.
Declaration
virtual kern_return_t DeviceRequest(IOService *forClient, uint8_t bmRequestType, uint8_t bRequest, uint16_t wValue, uint16_t wIndex, uint16_t wLength, IOMemoryDescriptor *dataBuffer, uint16_t *bytesTransferred, uint32_t completionTimeoutMs);Parameters
- bmRequestType:
The characteristics of the device request. See the Usbmakebmrequesttype macro for information about how to construct this request.
- bRequest:
The request you want to make.
- wValue:
Request-specific data.
- wIndex:
Request-specific data.
- wLength:
The number of bytes to transfer, if there’s a data stage.
- dataBuffer:
The memory descriptor to use for the request’s data phase, if any.
- bytesTransferred:
A pointer to a variable. On return, this variable contains the number of bytes that the method actually transferred during the data phase.
- completionTimeoutMs:
The timeout duration in milliseconds. If you specify
0, the request never times out.
Return Value
kIOReturnSuccess on success, or another value if an error occurs. See Error Codes.
Discussion
This method acquires the service’s workloop lock and performs a USB device request (USB 2.0, section 9.3). The method waits for the request to complete, and may call commandSleep during that time.