Just found out that the kernel option CONFIG_ECHO moved from staging to stable. Don't know when, but it's present at least in 3.19.3.
The according patch for this kernel module (echo.ko) is included in gentoo-dahdi-patchset in file 98-non-digium-hardware-and-oslec.diff for years.
My suggestion is to remove this part from the patch and implement a check for echo.ko in ebuild, with a hint for the existence of this kernel option when disabled in kernel.
Any comments, suggestions, pros and contras?
Can you please confirm if this is still a problem?
Jaco, the problem now is that ISDN - and therefore DAHDI - is dead in (mid) Europe. Therefore, I was forced to use IAX and SIP.
I think ticket can be closed.
Marking as CANTFIX since you can't test for us no more :).