Re: [PATCH net-deletions] net: remove ISDN subsystem and Bluetooth CMTP

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Apr 20, 2026 at 07:21:07PM -0700, Jakub Kicinski wrote:
> Remove the ISDN (mISDN, CAPI) subsystem and Bluetooth CMTP protocol
> from the kernel tree.
> 
> ISDN is a pretty old technology and it's unclear whether anyone still
> uses it. I went over the last few years of git history and all the
> commits are either tree-wide conversions or syzbot/static analyzer
> fixes.
> 
> When we discussed removal in the past IIRC there were some concerns
> about ISDN still being used in parts of Germany. Unfortunately, the
> code base is quite old, none of the current maintainers are familiar
> with it and AI tools will have a field day finding bugs here.
> 
> Delete this code and preserve it in an out-of-tree repository
> for any remaining users:
> https://github.com/linux-netdev/mod-orphan
> 
> UAPI constants AF_ISDN/PF_ISDN and the SELinux isdn_socket class
> are preserved for ABI stability, but the rest of uAPI is removed.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>