ΜClinux explained

μClinux
Family:Embedded Linux
Source Model:Open source
Kernel Type:Linux kernel-fork
Userland:uClinux-dist, uClibc, BusyBox
Working State:Current
Supported Platforms:See below

μClinux is a variation of the Linux kernel, previously maintained as a fork, that targets microcontrollers without a memory management unit (MMU).[1] It was integrated into the mainline kernel as of 2.5.46;[2] the project continues to develop patches and tools for microcontrollers. The homepage lists Linux kernel releases for 2.0, 2.4 and 2.6 (all of which are end-of-life in mainline).

The letters "μC" are for "microcontroller": the name is pronounced "you-see-Linux", rather than pronouncing the letter mu as in Greek.[3]

History

μClinux was originally created by D. Jeff Dionne and Kenneth Albanowski in 1998. Initially, they targeted the Motorola DragonBall family of embedded 68k processors (specifically the 68EZ328 series used in the 3Com PalmPilot) on a 2.0.33 Linux kernel. After releasing their initial work, a developer community quickly sprang up extending their work to newer kernels and other microprocessor architectures. In early 1999, support was added for the Motorola (now NXP) ColdFire family of embedded microprocessors. ARM processor support was added later.

Although originally targeting 2.0 series Linux kernels, it now has ports based on Linux 2.4 and Linux 2.6. The Linux 2.4 ports were forward ported from the 2.0.36 Linux kernel by Michael Leslie and Evan Stawnyczy during their work at Rt-Control. There were never any μClinux extensions applied to the 2.2 series kernels.

Since version 2.5.46 of the Linux kernel, the major parts of μClinux have been integrated with the mainline kernel for a number of processor architectures.[4]

Greg Ungerer (who originally ported μClinux to the Motorola ColdFire family of processors) continued to maintain and actively push core μClinux support into the 2.6 series Linux kernels. In this regard, μClinux is essentially no longer a separate fork of Linux.

μClinux had support for many architectures, and forms the basis of many products, like network routers, security cameras, DVD or MP3 players, VoIP phone or gateways, scanners, and card readers.

Support for several of the original target architectures was dropped in 2018.[5] The obsolete CPU architectures set to be removed in Linux 4.17 and subsequent releases included ADI Blackfin, Etrax CRIS, Fujitsu FR-V, Mitsubishi M32R, Matsushita/Panasonic MN10300, Imagination META (Metag), and Tilera TILE.[6]

Hardware projects

The leanXCam was an open-source programmable smart camera used for industrial applications in the field of machine vision that ran under μClinux; the camera won an award at the 2008 VISION tradeshow.[7] As of 2015, the project was discontinued.[8]

Supported architectures

The current list includes:

No longer supported

Before Linux 4.17 the following architectures were also supported:[14]

External links

Notes and References

  1. Web site: uClinux Description. 2007-12-31. D. Jeff Dionne. Michael Durrant. live. https://web.archive.org/web/20071225125038/http://www.uclinux.org/description/. 2007-12-25.
  2. Web site: uClinux mainline Announcement. 2008-01-15. Greg Ungerer. https://web.archive.org/web/20071031135123/http://www.ucdot.org/article.pl?sid=02/11/05/0324207. 2007-10-31.
  3. Web site: μClinux. August 31, 2015. live. https://web.archive.org/web/20061004015712/http://www.uclinux.org/. October 4, 2006.
  4. Miles Gillham "uClinux and Linux set to merge", Linux.com, November 19, 2002.
  5. Linus Torvalds "Linux 4.17-rc1", LKML.ORG, 15 April 2018.
  6. Jonathan Corbet "Shedding old architectures and compilers in the kernel", LWN.net, February 26, 2018.
  7. News: Wilson . Andrew . Jan 2009 . Open-source system wins VISION Award . subscription . Vision System Design . 14 . 1 . 11–12,15 . 2023-11-29. .
  8. Web site: home . 2023-11-29 . GitHub . en.
  9. Web site: Linux for ARM® Processors www.arm.com Summer/Winter 2013 Robert Boys System Design Division, ARM . 2013-09-10 . 2014-07-17 . What about Cortex-M and Cortex-R ? /../ These can run a modified version of Linux called uClinux..
  10. Web site: Linux 2.6.27 kernel released 9 October 2008 . 2023-12-13.
  11. Web site: remove the v850 port.
  12. Web site: Linux 5.19 was released on Sunday, 31 Jul 2022. . 2023-12-24.
  13. Web site: remove the h8300 architecture.
  14. Web site: [GIT PULL] arch: remove obsolete architecture ports].
  15. https://events19.linuxfoundation.org/wp-content/uploads/2017/12/BoF-Accelerated-Linux-Build-System-Jeff-Shaw-Digi-International.pdf BoF- Accelerated Linux Build System - Jeff Shaw, Digi International