USBD_OPEN_DEVICE
Purpose
Opens a specific Universal Serial Bus (USB) logical device.
Syntax
int fp_ioctl (file, USBD_OPEN_DEVICE, arg, ext)Parameters
| Item | Description |
|---|---|
| file | File descriptor that is obtained when the USB system driver (USBD) special file was opened. |
| arg | Address of an initialized DEVOPEN structure. |
| ext | Not used and must be set to zero. |
Description
The client driver uses this fp_ioctl operation
to establish a connection to a specific USB logical device that is
identified by the information within the DEVSELECTOR structure.
A USB logical device can be opened by only one client driver at a
time. If a client opens the device, it must connect to a pipe before
the data can flow to or from the device. This data includes, but is
not limited to, the default control pipe. The client driver must close
any device that it opened by calling the usbdCloseDevice operation
when it no longer wants to manage the device. Typically, a client
driver must open the USBD, issue a USBD_OPEN_DEVICE ioctl operation
to open a specific USB device, and close the USBD. Then, the client
must communicate with the USBD by using the handle that is returned
by the USBD_OPEN_DEVICE ioctl operation
and the interface macros that are located within the usbdi.h file. To
properly track the USB device when the device needs to be moved or
replaced, the client must open the device when the client is configured,
and the client must close the USB device when the client is unconfigured.
Execution environment
This function can be called from the kernel process environment only.
Return values
| Value | Description |
|---|---|
| 0 | Success. |
| Nonzero values | Failure. |