bInterfaceNumber - does IF0 have to exist?

[roger]

Hi,

bInterfaceNumber is described as "Zero-based value identifying the index in the array of concurrent interfaces supported by this configuration."

My question is if it is valid to have non-contiguous interface numbers?

If I have three interfaces, which of the following respective values for bInterfaceNumber is valid:

* 0, 1, 2
* 1, 2, 0
* 1, 2, 4

[Jan Axelson]

Check the class specification or driver documentation for any limitations on this.

Jan

[Guido Koerber]

Having non-continous numbers is fine by the spec but may not be with the driver. I remember that I had problems with some version of Windows that did not work with non-continous interface numbers, though can't recall the details.

[Bret]

Unless you have a REALLY good reason to not number them sequentially starting with zero, that would be the way to do it.  You will likely save yourself all kinds of grief and compatibility problems in the future if you do it that way, even if a particular specification or driver says you don't need to.