This term refers to code that aimed to replace the proprietary, closed-source HAL we had on MadWiFi. The code is based on Reyk Floeter's ar5k, part of OpenBSD's 'ath' driver for Atheros wireless cards and evolved by Nick Kossifidis through further reverse engineering (using MMIO trace, IDA pro with Hex-rays and other techniques). The MadWiFi team also provided assistance, bug fixes and helped with reverse engineering, we even created madwifi-trace to let users also participate in the process by providing register dumps. Finally many people/companies helped through donations of hw.
Claims that the OpenBSD ar5k code (and thus also OpenHAL) contained code said to be copied without authorization loomed throughout the Internet since about summer 2005. This had essentially created Fear, Uncertainty and Doubt over its use to base the OpenHAL efforts upon and even caused the work on it to stall.
Because of these doubts the Linux wireless developers contacted the Software Freedom Law Center (SFLC) for assistance. On November 14, 2006 a press release was made by Linux wireless kernel maintainer, John W. Linville, in which he indicated that the SFLC had assisted the Linux wireless developers in evaluating the development history of Reyk Floeter's OpenBSD reverse-engineered Atheros HAL. He stated:
SFLC's assessment leads to the conclusion that free software developers should not be worried about using/extending ar5k or porting ar5k to other platforms.
SFLC has made independent inquiries with the OpenBSD team regarding the development history of ar5k source. The responses received provide a reasonable basis for SFLC to believe that the OpenBSD developers who worked on ar5k did not misappropriate code, and that the ar5k implementation is OpenBSD's original copyrighted work.
Some, however, still remained skeptic... so an agreement was made between Atheros and the Linux wireless developers to do an audit, "carefully comparing OpenHAL to Atheros' proprietary HAL code." The audit was completed and a conclusion published by the SFLC, released on July 31, 2007, stated:
... SFLC concluded that OpenHAL does not infringe copyrights held by Atheros. As a result, OpenHAL development can now continue safely, unencumbered by legal uncertainty so long as the OpenHAL developers continue their work in isolation from Atheros' proprietary code.
The name originally was introduced by John Bicket, who did a first port of the OpenBSD ar5k driver to Linux, but his work soon ceased. In an independent effort Nick Kossifidis also ported ar5k to Linux and made it available for the first time on February 23, 2006. The name OpenHAL was orphaned, so it was adapted for Nick's work. The work then ceased for a while because of claimed copyright violations (see above).
Beginning with changeset 2232, OpenHAL diverted from ar5k and was converted to a different layout: common code for all chipsets was centralized, code was cleaned and adjusted for the Linux kernel coding style, documentation was added, and so on. Also we added support for new chips (mostly PHY chips) and features. Every fix as well as many bug reports were shared with Reyk, and some of them have been added to the OpenBSD CVS repository. We even introduced the Changes-licensed-under tag when sending patches on linux-wireless for ath5k to maintain the initial ISC license and let OpenBSD benefit from our work.
On Fri, 26 Sep 2008 Atheros announced the release of legacy-HAL, an open source version of the binary HAL, in order to help ath5k development process so OpenHAL became obsolete. Later Sam Leffler also released his open source version of HAL that we now use on MadWiFi and it's being used on FreeBSD.
On 25/07/2008 Atheros released ath9k a fully open-source driver for their new 11n chips.