1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

"Very Disruptive" Change Hurts ARM Linux Support

Linux Kernel

Published on 10 April 2013 01:49 PM EDT
Written by Michael Larabel in Linux Kernel
55 Comments

The Linux kernel is having to remove support for NWFPE and VFP emulation code due to a licensing conflict. Removing NWFPE and VFP from the kernel will effectively render older ARM hardware on Linux useless until a solution is determined.

Russell King, the maintainer of the ARM code for the Linux kernel, announced this removal on the linux-arm-kernel mailing list. The NWFPE (NetWinder Floating Point Emulator) and VFP (Vector Floating Point) code is for emulating floating-point operations within the kernel. While this code is critical to ARM hardware without hardware floating-point support, the code needs to be dropped due to a licensing conflict.

It turns out that the softfloat library used by NWFPE and VFP is incompatible with the GPLv2 license, for which the Linux kernel is licensed. The softfloat library has an indemnification clause, which the Free Software Foundation considers to be an "additional restriction" and thereby renders it incompatible with the GPLv2.

The Softfloat library either needs to be re-licensed without the indemnification clause, a clean-room GPLv2-compatible Softfloat library needs to be written not based upon the current code, or some alternative plan needs to be devised.

Russel King admits, "This will be very disruptive for ARMv4 and ARMv5 CPUs, which will no longer be able to run userspace with NWFPE support removed...The situation with VFP is likely less disruptive - only instructions which aren't implemented in hardware (or, for example, if you ask for inexact exceptions to be enabled) which are bounced to the software support code will be affected. I think OMAP should get away unscathed, but ARM's implementation will bounce if inexact exceptions are enabled or in a few corner cases. Qualcomm is likely to be the worst affected by this."

Those wanting more details on the Softfloat library can visit its web-page.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. MSI X99S SLI PLUS On Linux
  2. NVIDIA GeForce GTX 970 Offers Great Linux Performance
  3. CompuLab Intense-PC2: An Excellent, Fanless, Mini PC Powered By Intel's i7 Haswell
  4. From The Atom 330 To Haswell ULT: Intel Linux Performance Benchmarks
Latest Linux Articles
  1. Open-Source Radeon 2D Performance Is Better With Ubuntu 14.10
  2. RunAbove: A POWER8 Compute Cloud With Offerings Up To 176 Threads
  3. 6-Way Ubuntu 14.10 Linux Desktop Benchmarks
  4. Ubuntu 14.10 XMir System Compositor Benchmarks
Latest Linux News
  1. Dead Island GOTY Now Available On Linux/SteamOS
  2. Ubuntu 14.04 In The Power8 Cloud From RunAbove
  3. KDE With Theoretical Client-Side Decorations, Windows 10 Influence
  4. Sandusky Lee: Great Cabinets For Storing All Your Computer Gear
  5. Fedora 21 Beta & Final Release Slip Further
  6. Mesa 10.3.2 Has A Couple Bug-Fixes
  7. RadeonSI/R600g HyperZ Support Gets Turned Back On
  8. openSUSE Factory & Tumbleweed Are Merging
  9. More Fedora Delays: Fedora 21 Beta Slips
  10. Mono Brings C# To The Unreal Engine 4
Latest Forum Discussions
  1. HOPE: The Ease Of Python With The Speed Of C++
  2. Use Ubuntu MATE 14.10 Make it an official distro.
  3. Users/Developers Threatening Fork Of Debian GNU/Linux
  4. Debian Is Back To Discussing Init Systems, Freedom of Choice
  5. AMD Radeon VDPAU Video Performance With Gallium3D
  6. Updated and Optimized Ubuntu Free Graphics Drivers
  7. Ubuntu 16.04 Might Be The Distribution's Last 32-Bit Release
  8. Linux hacker compares Solaris kernel code: