Lucent Technologies USS-720 manual Ioctlreadinterruptpipe, Byte Description

USS-720	Preliminary User Guide, Rev. 2
USB Device Driver	February 1999

4 I/O Control Codes (continued)

4.17 IOCTL_READ_INTERRUPT_PIPE

IOCTL_READ_INTERRUPT_PIPE reports changes on the parallel port and buffer status when they occur. Details regarding parameters and error codes follow.

4.17.1 Parameters

lpInBuffer—Points to an input buffer. Not used with this operation. Set to NULL.

nInBufferSize—Specifies the size (in bytes) of the buffer pointed to by lpInBuffer. Not used with this operation. Set to zero.

lpOutBuffer—Points to an output buffer that will receive four status bytes reflecting changes in the parallel port and buffer status as follows (see the USS-720USB-to-IEEE 1284 Bridge Preliminary Data Sheet, “Registers”):

Byte Description

0Status.

1Control.

2Extended control.

3USS-720 control.

nOutBufferSize—Specifies the size (in bytes) of the buffer pointed to by lpOutBuffer, which must be large enough to contain 4 bytes.

lpBytesReturned—Points to a DWORD that receives the actual size (in bytes) of the data stored into lpOutBuffer.

4.17.2 Notes

None.

4.17.3 Error Codes

ERROR_INVALID_ALTERNATESETTING—The command is only supported in ALT_INTERFACE_2 (see Section 4.9 of this document).

ERROR_NOT_ENOUGH_BUFFER—lpOutBuffer needs to be large enough to receive the status bytes.

STATUS_INSUFFICIENT_RESOURCES—Not enough memory to perform the request on this device instance.

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