Add FreeBSD support

[valpackett]

(re: #283)

• OSS backend works fine
• ALSA backend is crackling (probably resampling related; that happens other apps too), do not use (wasn't used in jack1 either)
• D-Bus works fine
• tested with Carla, Cadence, qjackctl
• using POSIX semaphores because I'm currently too lazy to write a thing for umtx (futex equivalent)
  • does any platform need O_RDWR in semaphores?
  • would any platform complain about beginning the semaphore path with /?
• also needs -fPIC to build the OSS adapter, I'm not sure where in waf I should enable PIC

[7890]

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[7890]

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[7890]

This PR looks good to me, I think we should probably merge it away. Are there any opinions from other FreeBSD users? If possible please also attach a full verbose build log.

[falkTX]

We need to figure out something better for this

[7890]

I don't understand. Is this about naming, licenses and such or about technical shortcomings?

[yurivict]

@myfreeweb Could you please squash all commits into one?

[valpackett]

@yurivict hmm, why?

@7890 @falkTX can someone please answer the questions from the original post:

does any platform need O_RDWR in semaphores?

would any platform complain about beginning the semaphore path with /?

I'm not sure where in waf I should enable PIC

[yurivict]

@yurivict hmm, why?

Difficult to add 6 lines, need to maintain the proper order of patches, etc.
I tried to add them into the port but there are patching problems. You probably need to rebase.

Also, __FreeBSD_kernel__ isn't needed.

[valpackett]

If you want to test in ports, you can just fetch from my branch. If you want to commit a port already… isn't it a bit early? :)

[7890]

From man sem_open:

Both read and write permission should be granted to each class of user that will access  the  semaphore.

This hints at that O_RDWR is correct.

From man sem_overview:

Named semaphores
A named semaphore is identified by a name of the form /somename; that is, a  null-terminated string  of  up to NAME_MAX-4 (i.e., 251) characters consisting of an initial slash, followed by one or more characters, none of which are slashes.

Like shared memory handles for shm_open, semaphores should start with a slash. I think this rule isn't strictly enforced, any name without slashes in the middle should work. I speculate that using a leading slash wouldn't be problematic on any platform. However there are different semaphore name length limits on different platforms (see OSX max. client name length).

[0EVSG]

@falkTX Could you please elaborate on your review above (freebsd/driver.h, Feb 6. 2019)?

If it's about using symlinks, there's the option of a relay #include with relative path.

Otherwise, it's probably also acceptable to drop the ALSA backend on FreeBSD, which refers to driver.h. As for uptime.h, either just duplicate it (it's small), or add the linux directory to the include paths when compiling the DBUS controller?

FYI, jack2 v1.9.16 is now in the FreeBSD ports, taken from a branch in my repo. It is based on these commits plus a separate, overhauled OSS driver taylored to FreeBSD. I intend to make an up-to-date pull request for that, thus my interest in how to fix this.

[yurivict]

FYI: Jack2 is now available in FreeBSD ports: https://www.freshports.org/audio/jack/

[0EVSG]

Closing this, superseded by #800 which includes most of the work in this pull request.
Thanks everybody for your contributions!