Extending [some level of] support to earlier macOS

[barracuda156]

@mrmidi Hi, Alexander! Great to see this project!
It will be awesome to retain FireWire Audio support in macOS.

Do you consider extending support to older macOS versions too (without prioritizing them, of course)?
It is sensible, since device drivers, which existed, are no longer updated, and many macOS versions never even received the latest releases (and since the code was proprietary, there is no chance of building those from source). As an example at hand, my Weiss Int202 DDC does not have drivers for modern arm64, but also never got updated drivers for powerpc.
If that can be considered in principle, I can join in; while I have no experience or expertise with writing low-level stuff, I can do testing and some code fix-ups if needed.

I am also interested in support for modern macOS versions, of course, but for that I can only be a consumer LOL
My work in development has only been focused on powerpc systems.

[barracuda156]

Looks like AudioServerPlugIn and XPC are stoppers with no direct fallbacks :(

[mrmidi]

I don't sure actually. XPC is still required: otherwise you couldn't control your hw, but FireWire stack probably could move into ASP itself if possible. I remember I had some problems with it. Otherwise shared memory approach is wrong: I suppose core audio could use IOBifferMemoryDescroptor instead of custom shared memory workaround that is aimed to share memory between DCLs and core audio. Some other core audio contracts are broken here, now I understand architecture a bit better. :)

[barracuda156]

Will this work to substitute for XPC? https://github.com/PureDarwin/XPC
Apple one does not exist before 10.7 and some APIs used here before 10.8, apparently.

[mrmidi]

Which Mac OS version you are aiming? If it's PowerPC era ASPL is wrong direction. Briefly - I think you could leverage AppleFWAudio.kext for audio streaming and some custom DICE init with IOFireWireFamily. Probably kextless driver. You probably still may need IPC. I'm pretty sure xpc had existed, but without nice obj-c abstractions Apple introduced later - just type 'man xpc' in terminal. It will be hardcore plain c, but it's doable and easier than mach ports. Probably you don't need xpc at all and could use unix sockets for IPC - you don't need something ultra high speed low latency high bandwidth that xpc provides :), only init the hw, start the streams, control it, etc. And unix sockets is easier than plain c xpc. I've created this project to replace AppleFWAudio.kext for Ventura+ when it was completely removed. Otherwise it's possible to bring up any firewire audio device on older Macs in my opinion. If you will download FireWire SDK from Apple's developers portal - you could find some very nice examples how to use AppleFWAudio user client. See AVCVideoServices. My guess For 10.7 and 10.8 intel it's doable. It's more natural way to use fw audio kext instead of inventing the wheel.

[barracuda156]

My baseline is 10.6 on powerpc (never released, but we have it now). That makes difference from 10.5 in regards of CoreAudio APIs and libdispatch, but obviously it won’t have 10.7–10.8 stuff that is used here.

I know the project target is modern macOS where Apple, sadly, dropped FW, and it is indeed more important to support FW there, I just thought it will be nice to have a supported and open-source FW implementation on older OS too.

My Weiss DDC has archaic driver for powerpc and never officially supported on Catalina (which is what I use on x86), though older x86 driver seems working. Both are proprietary and long out of support.

[mrmidi]

Join discord: https://discord.gg/c82rmSEEPY or drop me a line on telegram https://t.me/mrmidi - it's better to chat about it I guess.