What is the '245' in the IOKit USB libraries?

I'm getting started with IOKit on OS X, and I've been puzzled by the '2开发者_运维问答45' tagged onto data types in the IOKit USB library, such as IOUSBInterfaceInterface245. What does the 245 mean? I'm just curious what this number tacked onto the end is supposed to indicate. It seems like a version number of something.

Is there a generic version that I can use, rather than having to use a specific version?

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I believe that number refers to the IOUSBFamily version the struct is compatible with. Take a look at IOKit/usb/IOUSBLib.h for more details.

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i believe it is the usb interface interface that shipped with iousbfamily 2.4.5 ( os x tiger)

IOUSBInterfaceInterface is the 1st version and is available on every version but the newer ones like 245 add extra functionality, the number is added to the end to keep the old version for backward compatibility