Hi,
The EPOS GSP 370 wireless headset has a volume control knob on the
headset. Turning this has 2 effects on Linux:
- The volume gets adjusted in firmware
- A volume up/down key event is sent to the OS and the volume is
adjustet on the OS level (the dongle registers both as a audio device
and an usb keyboard to do this)
This double volume adjust is ofc not the intended behavior and induces
all kinds of wiredness, like the os is already displaying 100% volume
but you can still turn it higher because the firmware has not yet
reached max volume.
Running Wireshark on Windows and Linux I recognized that Windows is
sending "URB_CONTROL out" events to the dongle on volume adjust, which
Linux doesn't, these events have a paylode that seems to encode a volume
value in 2 byte with little endianess.
I'm unsure if I can attach pcap file or if it will get blocked in the
list so i will send them as a reply.
So my 2 questions are:
- What are these USB "URB_CONTROL out" events? (Does not seem to be HID
reports?)
- In which subsystem would I want to implement them? Or should this be
handled in userspace?
Bast regards,
Werner
