Devices With Interface-Association Descriptors

If the device includes an interface-association descriptor, the device tree can be parsed at the following three levels:

• The usb_mid(7D) USB multi-interface driver binds to device level nodes of a composite device if no vendor or class-specific driver is available.

• A client driver is bound to the interface association nodes.

• The usb_ia(7D) USB interface association driver is bound by default if no client driver is found. Then client drivers can be bound to the interface level of this interface association.

The usb_mid driver creates an ia (interface association) node for each ia. The compatible names of ia nodes generally begin with usbia. The name usb,ia is a compatible name that represents any ia as the tail of the compatible names. The usb_ia driver is bound to an ia node if no other driver has claimed this ia. The usb_ia driver creates a child node for each interface. An interface node as the child node of an ia node has the same properties with an interface node as the child of a device node.

1. 'usbia46d,8c9.5.config1.0' vend 46d, prod 8c9, rev 5, cnfg 1, first_if_in_ia 0
2. 'usbia46d,8c9.config1.0'   vend 46d, prod 8c9, cnfg 1, first_if_in_ia 0
3. 'usbia46d,classe.3.0'      vend 46d, class e, subclass 3, protocol 0
4. 'usbia46d,classe.3'        vend 46d, class e, subclass 3
5. 'usbia46d,classe'          vend 46d, class e
6. 'usbia,classe.3.0'         class e, subclass 3, protocol 0
7. 'usbia,classe.3'           class e, subclass 3
8. 'usbia,classe'             class e
9. 'usb,ia'                   by default

Use the following command to bind a vendor-specific, device-specific client driver named vendor_model_video_usb to the vendor-specific, device-specific configuration 1, first_if_in_ia 0 compatible name shown in Example 20–4:

add_drv -n -i '"usbia46d,8c9.config1.0"' vendor_model_video_usb

Use the following command to bind a class driver named video_class_usb_ia_driver to the more general class e compatible names shown in Example 20–4:

add_drv -n -i '"usbia,classee"' video_class_usb_ia_driver

In the following example, the prtconf –D command shows a device tree of a webcam with ia of video and audio. The usb_mid driver manages the device and creates two ia respectively for video and audio. A video driver usbvc is bound to the video ia, and audio drivers are bound to the interface of the audio ia.

miscellaneous, instance #28 (driver name: usb_mid)
    video, instance #24 (driver name: usbvc)
    audio, instance #30 (driver name: usb_ia)
        sound-control, instance #38 (driver name: usb_ac)
        sound, instance #47 (driver name: usb_as)