Brent Weatherall wrote:
I am trying to specify an extension to the UAC specification and then write a user space driver/application to use the extension when a device that supports it is available in Linux.
Can anyone assist me with the best path forward for writing user space code to use the XU I am going to define? Meaning generically speaking how to use UAC XU controls in ALSA.
XU controls cannot be used generically. The driver must be extended to create the vendor-specific controls of this particular device; or the driver could get a function to allow userspace to add such controls.
it appears that any XU controls would be processed through usbmixer.c, but I don't see how to use the code in usbmixer from user space.
That code creates mixer controls.
And so far I can't tell what source usbmixer resides in.
sound/usb/mixer.c in the kernel source, although such extensions probably belong into mixer_quirks.c.
Regards, Clemens