Re: [FFADO-user] jackd - without ffado/ firewire support...?

[Jonathan W. <jw...@ju...>]

Hi Morgan

On Wed, Apr 29, 2020 at 10:55:51PM +0100, Morgan Read via FFADO-user wrote:
> I wish...
> 
> $ jackd -d firewire --help
> jackdmp 1.9.12
> :
> Unknown driver "firewire"
> $
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1829403#c1
> 
> --- Comment #1 from Guido Aulisi <gui...@gm...> ---
> That's because there is no ffado package in epel8.
> 
> 
> And, I guess that's because there's no libxml++

As David pointed out, jackd wouldn't list the "firewire" backend if its
package hadn't been installed.  However, since it seems rhel8 doesn't
include a libffado package, it also cannot have an equivalent of the
jackd2-firewire package.  Whether the decision to omit FFADO was due to
libxml++ I do not know.  Whatever the case, clearly there's no
distribution-level support for the jackd firewire backend on your
distribution.

There are two ways to proceed.  The first is to see if someone has already
prepared a jackd package for rhel8 which includes the "firewire" backend. 
They also presumedly would have needed to prepare a libffado and libxml++
packages too.  I don't use RH and are not familiar of where one might go to
find such packages, but a quick web search didn't turn anything up (although
there's a hint that it was available in RHEL7).

If this is the case then you'll need to prepare your own version of jackd2.
As I eluded to earlier, this is not quite as simple as it seems: removing
the existing jackd2 package will also cause RH to remove every package which
flags jackd2 as a dependency.  In practice this will cause most of your
jack-enabled programs to disappear.

In the past the way this sort of thing has been dealt with is to arrange for
the replacement jackd to simply install over the top of the existing one.
For this to work the jackd2 installation directories need to be configured
the same as was used by RHEL8.  On many distributions in the past it was
sufficient to specify

  --prefix=/usr

when running jackd2's "configure" script.  Jackd2 now uses the waf build
system, so you'd need to find the equivalent option in that.  I don't know
whether simply setting the prefix to /usr is sufficient for RHEL8; you may
have to consult the source-RPM for RHEL8's jackd2 package and see how they
configured the package.

Since your system has libffado, jackd2's build system should discover this
and automatically enable the "firewire" backend.  At least in theory, once
this is compiled and installed you should have access to the "firewire"
backend when starting jackd through the command line or qjackctl.

Obviously I cannot give any watertight guarantees about the above
information; without a RHEL8 system (or any direct RH experience) I have no
way to test it myself.

Regards
  jonathan