Mini TTY In Development For The Linux Kernel

Linaro and other ARM/embedded developers continue working on minitty, a minimal TTY implementation for the Linux kernel that's targeting embedded systems.

The mini TTY implementation is designed for systems not needing the full TTY layer. The minitty code only supports serial port outputs with no VTs or PTYs, no job control support, no hung-up state, and various other features have been stripped out. The motivation for this is reducing the size of the kernel and dynamic memory requirements when using Linux on embedded systems. Beyond that, "the existing TTY code is quite large and complex", per Linaro's Nicolas Pitre.

Writing this minimal TTY implementation has turned out to be easier than putting the current TTY code on a diet. "The existing TTY code is quite large and complex. Trying to shrink it is risky as the potential for breakage is non negligeable, and its interchangeable layers impose a lower limit on the code to implement it. Therefore, the approach used here consists in the creation of a parallel implementation with the very minimal amount of code collapsed together that interfaces with existing UART drivers directly and provides TTY-like character devices to user space. When the regular TTY layer is disabled, then this minitty alternative layer is proposed by Kconfig."

Those potentially interested in this mini TTY implementation for the Linux kernel can find the details via this patch series. Minitty in its current form is less than three thousand lines of new code.