I recently had to build a couple of Asterisk servers with G400E cards, and discovered a serious problem with installing chan_extra 2.0.8 on Debian Jessie.
Due to a Linux kernel architecture change, DAHDI versions 2.8 and earlier will not build on a kernel newer than 3.13. But then chan_extra 2.0.8 (the newest version I can find) will not build against the latest DAHDI (2.10.2 + 2.10.2).
Fortunately, the motherboards were still (just about! -- they take awhile to boot) supported by Debian Wheezy; and I was able to meet the deadline by installing some older Asterisk and Dahdi versions, which do compile properly against the Wheezy stock kernel (3.2.0-4).
However, we can't rely on old kernel versions forever! Newer motherboards will have hardware which will require new drivers; and because of architecture changes, these newer drivers may not be buildable against older kernels.
Is a newer version of chan_extra available? Or will one be available soon? I can envisage some future motherboard design not working with a pre-3.13 kernel, and thus effectively obsoleting the G400 series
Well, that wasn't really the news I was wanting to hear; but at least I know now that it would not be a good idea to use these cards in new designs. Which is a bit of a shame, because they have always performed excellently once chan_extra could be persuaded to build.
I will certainly evaluate your GSM gateways for my next project.