[alsa-devel] USB audio2.0 status interrupt endpoint

[Puneet Sharma]

Hello all,

I am using the uac2 kernel driver(drivers/usb/gadget/f_uac2.c) having
kernel version 3.10.31 for an embedded board.

The board is presented as a USB device to a Linux PC having USB host
controller in it.

I have added an interrupt endpoint in the uac2 kernel driver to support the
status interrupt endpoint request as per usb audio 2.0 specification.

For the interrupt transfer to happen, I prepared the interrupt packet
structure as per audio 2.0 specification and queued the endpoint to
transfer it to the host driver.
The interrupt structure is prepared as follows:
bInfo : 0 (Interface request)
bAttribute : 0x1 (CUR request)
wValue : 0x200 (VOLUME feature unit control selector)
wIndex : 0x700 (FEATURE UNIT ID)

As per my understanding, when the above interrupt endpoint is transferred
to host in response to Interrupt IN request, the host should send me a GET
CUR volume class-specific request to further qualify the cause of interrupt.

However, I am not getting any class-specific request from host in response
to the status interrupt transferred to host.

My query is do i need to implement a mixer interface in the uac2 kernel
driver to get the request or i am doing something wrong in the process.

I am stuck onto this and cannot proceed further.

Thanks
Puneet