During this GSoC period, I focused on developing the virtio sound driver for Haiku, aiming to enhance its performance as a guest OS in virtualized environments. This journey began with some challenges, for example, initially, I missed a small detail in the driver module path, which prevented the driver from loading.
Thanks a lot for your contribution! Hope you can stick around a bit longer to do follow ups here. 
Thanks for your contribution to Haiku and for the detailed report that was very interesting to read.
Thanks! Beside improving user experience in VM, as a good part of upcoming sound drivers will probably use hmulti_audio, Iād say that your guide itself is priceless.
You create documentation based on your findings, could you explain what is missing in the documentation and unclear points?
Hi, @marcoapc.
While working on this driver, I can truly say to you, that a lot of time went into understanding hmulti_audio.
If you try to search of any documentation of multi_audio, youāll likely come across (although even trying to find this back took me a little while) this mail thread: ā[ā¦] Iām afraid no spec documentation is available, reading the sources might help. [ā¦]ā and a link to an old newsletter.
The ācompleteā documentation for the driver API is included in three files:
multi_audio.h,multi_audio.gb, andmulti_audio.txt. To get these files, write to trinity [at] be [dot] com
Only multi_audio.h remains, the others are sadly lost to time.
While the newsletter gives a bit of information about BUFFER_EXCHANGE, it only serves at that. Everything else, shall be inferred from previous drivers and multi_audio code.
Some structs, contain members of which I thought to be important and even defining for what other members should be read, are completely ignored. (See flags in BUFFER_EXCHANGE, playback_latency, record_latency, etc.)
While reading multi_audio.h helped a lot, if you only keep that, youād never know that B_MULTI_GET_ENABLED_CHANNELS and B_MULTI_SET_ENABLED_CHANNELS are actually required to be implemented; multi_audio.h only warns about B_MULTI_SET_GLOBAL_FORMAT as required to be implemented.
Many little cases like the above exist.
But I think I went a bit long. I hope I cleared it up!
I do happen to have that file right here. What I do not have anymore, is a working copy of GoBe Productive to open it and convert it to something else.
Hereās the zipped multi_audio.gb. (not sure how long it last onlineā¦ used the first site that worked for me).
Edit: seems the above auto-deletes after the first download 
Hereās a different one that should last for 6 days at least.
Why not use 0x0.st?
It has my IP range blocked for some reason.
Great job, thank you.
You have clarified a lot, thank you very much for your work and time dedicated.
Ahoy @leavengood ,
Is there a chance you know this trinity from Be Inc. ?
Iām asking because he possibly could provide the third file :ā> ``multi_audio.txt`
Only this 1 file is missing from the mentioned 3 files now - if you followed the conversation above.
Thanks in advance
if you can make Diegoās work easier to better understand / able to re-create/complete documentation about āmulti_audioā driver and the driver itself.
Kind regards`
Seriously, what are the chances this would work? They wrote this file 25 years ago. Do you hold on to documentation for things you worked on in a past job a quarter of a century ago? I certainly donāt (well, I have not been in this job for 25 years, but even if you asked me about things I did 10 years ago, that all stayed at the company when I left)
Well, fortunately it is not needed anymore.
I understand your reasonig too - I may not composed my sentence well.
I should have write to ask about file availability ā¦
Mea culpa !..
The transfer you requested has been deleted.