Re: [Jack-Devel] incompatible version of ffado error message

On Mon, Apr 30, 2012 at 03:35:54PM +0200, Adrian Knoth wrote:
> On Mon, Apr 30, 2012 at 11:26:32PM +1000, Allan Klinbail wrote:
> > I've been using jack with ffado as the driver for a few years now.
> > Today, after upgrading ffado to the latest svn , (then tested working).
> > I then upgraded to the latest jack svn version. Following this I started
> > receiving the following incompatible error message. 
> 
> You were doing it in the wrong order.
> 
> FFADO detects the jackd version at compile time. If it's a new jackd
> version supporting the new API, it switches to the new API.

Similarly, if there is no jackd installed at compile time ffado assumes that
the jackd which will ultimately be available will support the new API.

So in Allan's case, he compiled a new FFADO against an old jack, which
resulted in a FFADO which uses the old API.  The old jack was happy with
this and everything worked.

> You've just told FFADO to adjust itself to an old jackd version.
> Simply compile FFADO again.

Yep, that should work.

However, from a development point of view I'm a little surprised that the
latest jackd didn't simply accept FFADO as it was.  The relevant line in
current jack1 is drivers/firewire/ffado_driver.c, line 786 and following.

  if(ffado_get_api_version() < FIREWIRE_REQUIRED_FFADO_API_VERSION) {
    printError("Incompatible libffado version! ...
  }

The same conditional is used in jack2, so the following analysis applies
equally to that.

In Allen's case, ffado_get_api_version() would return 8 (the old version).
FIREWIRE_REQUIRED_FFADO_API_VERSION is defined as 8, so this conditional
*should* have failed and the "Incompatible libffado version" message should
never have been displayed.

Oh hang on: Allan, you said "the latest jack svn version".  Did you
literally use jack's subversion repository?  That is no longer carrying the
latest jackd source as far as I know: if you want the latest jackd you need
to get it using git.  This is described at

  http://jackaudio.org/download

Look for the "JACK Source Code Repository" section about half-way down.

I don't know the state of jack's ffado driver in the old svn repository, but
the use of the older jack code (which could be in an unstable intermediate
state with respect to ffado driver updates) may explain the symptoms
described.

Regards
  jonathan

1335830891.32369_0.ltw:2, <20120501000801.GA20808 at marvin dot atrad dot com dot au>