Question: gadget: How to realize uvc and uac composite function?

[app l]

Hi,
Version: 4.9 and uac1 driver is V5.9. I tested it based on 4.9 with
backported dwc3 driver frome v5.9.
1. According to configfs-usb-gadget-uvc, PC(Windows 10) can get ISO
data normally;
2. According to configfs-usb-gadget-uac1, PC(Windows 10) can  install
audio driver normally(AC Interface,/Captue Input terminal/Speaker);
3、uvc+uac1 composite device, PC(Windows 10) can get ISO data normally,
but PC shows that the uac1 driver installation failed(AC
Interface/Capture Inactive/Playback Inactive). AC Interface/Capture
Inactive/Playback Inactive all show the device cannot start code 10,
The settings of the I/O device are incorrect or the configuration
parameters of the driver are incorrect. Through the USB analyzer to
capture the packet, I found that the Index value seems to be wrong
when PC host to get the descriptor. The acquisition is Playback
Inactive and Capture Inactive, and the PC did not send the command
packet about uac1. It is difficult to debug it.
I suspect that some parts of the uac1 descriptor need to be modified,
but I don’t know which one to modify.
I sincerely hope that everyone can give some suggestions or related
patches to help me. Thanks very much!

Regards,
pengcheng