"There is one high-profile holdout, though: the Linux Infrared Remote Control (LIRC) subsystem. LIRC is used to obtain input events from remote control devices and feed them through to applications; Linux-based digital video recorder systems are heavy LIRC users, but there are others as well. Back in October, Jarod Wilson posted a new version of LIRC for consideration. One month later, the kernel developers have started talking about it; what they lack in punctuality has been more than made up for in volume.
"One might think that merging this longstanding, heavily-used project into the mainline would not require a great deal of discussion. The problem is that LIRC brings with it a new ABI. Since user-space interfaces must be supported indefinitely, they tend to come under a higher degree of scrutiny than other parts of the code. LIRC has never had to freeze its ABI during its many years of out-of-tree existence, a freedom which has made life easier for its developers. But LIRC in mainline would not have this freedom, so any incompatible ABI changes need to be made prior to merging. And, as it happens, some developers would like to see significant changes.
"One would think that an IR receiver would be a simple device; all it must do is report button press and release events, much like a keyboard. Often, it seems, the simplest devices are the most complex to deal with. Some receivers have decoders built into them, allowing them to pass scan codes to the driver, which can then map them onto key codes to pass to applications."
