[Qemu-devel] [PATCH 0/4] usb: implement Interface Association Descriptor support

[Brad Hards]

This patchset implements Interface Association Descriptor suppoort.

These descriptors are covered in Section 9.6.4 of the USB 3.0 spec, 
but there is a better description in the Intel IAD whitepaper 
(www.usb.org/developers/whitepapers/iadclasscode_r10.pdf).

The short version is that IAD is an extra descriptor type that appears before 
a group (two or more) interface descriptors, that explains which interface 
descriptors make up a virtual device.  So it could look like:
Config Desc
IAD#0
Iface#0
Iface#1
Iface#2
IAD#1
Iface#3
Iface#4

[Check the diagram in the Intel IAD whitepaper if that makes no sense]

The implementation basically introduces the concept of a grouped of
interfaces (with an IAD header), and support for sending it to the
device.

The intended use for this is USB Video class devices, which have a
Control interface and Streaming interface that are a single logical
device.