KDBUS Submitted For Review To The Mainline Linux Kernel
Written by Michael Larabel in systemd on 29 October 2014 at 06:28 PM EDT. 13 Comments
SYSTEMD --
It looks like KDBUS, the Linux kernel D-Bus implementation, is posed to be added to the next kernel release after Greg Kroah-Hartman sent out its patches today.

Back in February we reported that KDBUS would try to be mainlined this year and it looks like that's holding true. Greg KH sent out the KDBUS kernel-side patches to the kernel mailing list today for review and discussion. While KDBUS doesn't touch any existing kernel code, we're now well past the Linux 3.18 kernel merge window so Linus Torvalds is very unlikely to accept it at this point for 3.18, not to mention the lack of upstream discussion and review surrounding this work. It's most likely that the KDBUS code will be merged then for the Linux 3.19 kernel that will get underway in just under two months.

For over four years Linux developers have been talking about bringing D-Bus into the kernel as a low-level, native kernel DuB-s transport for inter-process communication (IPC). The KDBUS work has been closely aligned with systemd development and systemd already supports KDBUS. Last year when using the development code was when it finally reached a state of yielding a working system with the various Git repositories and with mainline Linux 3.17 is when memfd support was added as a KDBUS requirement.

KDBUS is implemented as a char driver, supports peer-to-peer unicast and multi-cast messages, eavesdropping of busses when debugging, support for passing file descriptors and sealed memfs, etc. About KDBUS Greg KH says in the patch series, "This is the first submission of kdbus by the kernel community. It was developed in its own repository for well more than a year, and has been tested on x64-64, i686 and ARM architectures in various use cases. The driver is totally non-intrusive and doesn't touch a single line of existing kernel code."

This implementation measures in at around eleven thousand lines of code and the developers consider the API/ABI mostly stable at this point. The KDBUS code has been added to Greg's char-misc Git repository at Kernel.org. More information on it can be learned from the in-kernel documentation.
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