The Linux Kernel Is Moving Closer To Saying Goodbye To A Lot Of ISDN Network Code
Written by Michael Larabel in Hardware on 31 May 2019 at 10:32 AM EDT. 19 Comments
The Linux kernel will likely soon see a lot of old ISDN (Integrated Services Digital Network) subsystem/driver code deprecated and ultimately removed considering there aren't even many (or any in some places) ISDN public data networks.

Around the world most operators are abandoning ISDN in favor of VoIP over DSL lines or the like for combining voice and data on the same lines. With ISDN not having been popular for years aside from in some niche areas, the associated Linux kernel code has largely fallen into disrepair. On top of that, the Linux kernel has provided three different ISDN stacks but with two of them being at the point they should just be removed.

Arnd Bergmann is proposing that the original "isdn4linux" and CAPI ISDN stacks be deprecated with the next kernel cycle. The mISDN stack is about all the ISDN code that's seen usage in recent years and is used by some for voice-only PBX setups not on public networks. For the isdn4linux/CAPI code, there isn't much use case with minimal supported public networks.

Bergmann argues over the pull, "My proposal for this time is to kill off isdn4linux entirely, as it seems to have been unusable for quite a while. This code has been abandoned for many years and it does cause problems for treewide maintenance as it tends to do everything that we try to stop doing...CAPI in turn is not quite as obsolete, but two of the drivers (avm and hysdn) don't seem to be used at all, while another one (gigaset) will stop being maintained as Paul Bolle is no longer able to test it after the network gets shut down in September. All three are now moved into drivers/staging to let others speak up in case there are remaining users."
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