USBFindNextAssociatedDescriptor

You use the USBFindNextAssociatedDescriptor function to find a specific interface or pipe descriptor, or any descriptor associated with the interface or endpoint. For example, a HID interface driver could use this function to find HID descriptors.

OSStatus USBFindNextAssociatedDescriptor(USBPB *pb);

Required fields required the USBPB parameter block for the USBFindNextAssociatedDescriptor function are

--> pbLength

Length of parameter block

--> pbVersion

Parameter block version number

--> usbCompletion

The completion routine

--> usbRefcon

General-purpose value passed back to the completion routine

--> usbReference

Interface or pipe reference

<--> usbWIndex

Descriptor index start at zero

--> usbBuffer

Descriptor buffer

--> usbReqCount

Size of buffer

<-- usbActCount

Size of the descriptor returned

<--> usbOther

Descriptor type (a value of 0 matches any)

The USBFindNextAssociatedDescriptor function steps through the descriptors following the relevant interface or endpoint descriptor, and returns the descriptors matching the given parameters. If usbReference is an interface reference, all the descriptors are returned until the next interface descriptor is found, or until the end of the configuration descriptor is reached. If usbReference is a pipe reference, all of the descriptors are returned until the next endpoint or interface descriptor is found, or until the end of the configuration descriptor is reached.

The usbWIndex field provides an index into all the available descriptors. A value of 1 describes the interface or endpoint descriptor itself, so passing 0 allows the interface or endpoint descriptor to be returned. If usbWIndex is passed back in the next call untouched, the function returns the next available matching descriptor.

The usbOther field contains a descriptor type to match. If searching for any type ( usbOther set to 0) all descriptors are matched. To use this method of search again for all descriptors, the usbOther field has to be set to 0 each time the function is called.

The errors returned by the USBFindNextAssociatedDescriptor function include:

kUSBUnknownInterfaceErr	-6978	usbReference does not refer to a current interface or pipe
kUSBInternalErr, paramErr	-6999	internal configuration descriptor cache corrupted
kUSBNotFound	-6987	interface or configuration specified is not in configuration descriptor

USBDisposeInterfaceRef

The USBDisposeInterfaceRef function closes the specified interface currently opened. The interface reference obtained with the USBNewInterfaceRef function for this interface is no longer valid after the call USBDisposeInterfaceRef call completes.

OSStatus USBDisposeInterfaceRef(USBPS *pb);

Required fields in the USBPB parameter block for the USBDisposeInterfaceRef function are

--> pbLength

Length of parameter block

--> pbVersion

Parameter block version number

--> usbCompletion

The completion routine

--> usbRefcon

General-purpose value passed back to the completion routine

--> usbReference

Interface reference for the interface to close.

--> usbFlags

Should be set to 0

If the usbCompletion field is set to kUSBNoCallBack, the call back mechanism is not invoked. This is useful for finalization routines which need to clean up immediately and can't wait for a callback routine to complete.

If the no call back option ( kUSBNoCallBack ) is used, the parameter block is free as soon as the USBDisposeInterfaceRef call returns.

Errors returned by the USBDisposeInterfaceRef function include

kUSBUnknownInterfaceErr

-6978

usbReference does not refer to a current interface