Re: Need information to implement correct handling of the GSP 370 wireless headset

[Werner Sembach <werner@rdorf.de>]

Am 07.07.23 um 23:12 schrieb Werner Sembach:
> 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.
As I thought: The pcapng files are to big for the mailing list. When 
someone is interested let me know how I can send them (should I open a 
Bugzilla Ticket for it?).
>
> 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
>