Kernel Log: Linux 2.6.27 Released - The H Open: News and Features

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Wi-Fi starts to "just work"

Information from the source code repository Many links in this article point to the relevant commits in the web frontend of the Linux source code which Linus Torvalds maintains with Git. The commits usually contain a lot of extra information about the respective improvement. Particularly the middle section of the commit page displayed by Git's web frontend is often a very valuable source of additional information, as this is where the author of the patch usually explains the background for the change and what the change is supposed to achieve. Sometimes, the comments also contain references to more detailed information available elsewhere on the web as well as the results of performance tests. The bottom section of the Git web frontend offers a list of the files modified by the patch. The "diff" link behind each file name displays how the patch integrated with this commit has changed the respective file; those who want to inspect the complete patch of the commit in its raw form can access it through the

Almost every new kernel version of the main development line since Linux 2.6.22 has brought major improvements to the kernel's Wi-Fi support. The freshly released Linux version is no exception, offering two new and several extended and improved Wi-Fi drivers.

Included for the first time is the ath9k driver. It supports various of the latest Atheros Wi-Fi chips which comply with the proposed IEEE standard 802.11n. This still young driver was presented to the public only a few days after the release of Linux 2.6.26 by its developer Luis "mcgrof" Rodriguez, who has worked for Atheros for several months and had already earned a reputation for his contribution to the Linux Wi-Fi driver and infrastructure. Rodriguez and many other developers literally pounced on the driver to get it ready for integration into the kernel and they succeeded. It was only three weeks after the first release of ath9k that the kernel hackers integrated the driver into the main development branch which has now produced Linux 2.6.27.

Among the Atheros chips supported by the ath9k driver are the Wi-Fi chipsets AR5418+AR5133, AR5416+AR5133, AR5416+AR2133, AR9160, AR9280 and AR9281. These can be found in some recent notebooks and netbooks as well as on some of the PCI/PCIe cards and PC cards/minicards. The driver's wiki lists some components by Belkin, D-Link, Linksys, NEC, and Netgear. So far, however, ath9k only works in client mode (Station Mode/STA); the developers are working to integrate Mesh and AP support according to the extensive ToDo list. The definitions of constants and comments in the source code suggest that, in the long run, the developers also plan to integrate monitor mode support, which is required for tools like Wireshark or Kismet.

Like ath9k, the iwlagn driver for Intel's 802.11n chips has been included for the first time. This driver is not completely new but partly based on the code of the iwl4965 driver for Intel's first generation of 802.11n chips. The new driver not only replaces its predecessor but also supports Intel's "Wireless Wi-Fi Link 5000AGN" family of Wi-Fi modules introduced with the Centrino 2 platform this summer and part of all Centrino 2 notebooks. The new driver can't yet handle the WiMAX support offered by some of Intel's wireless modules, but this can be remedied via patches and programs which are currently being developed by Intel within the Linuxwimax.org open source project.

Extension

The ath5k driver for dated Atheros Wi-Fi chips received numerous modifications. These prompt ath5k to leave the handling of some of the 802.11n chips to the more recent ath9k driver and handle the AR2425 Atheros Wi-Fi chips integrated in the first generation of Asus Eee PCs instead (1, 2). Many distributions have so far used a snapshot from the main development branch of the madwifi driver for these chips. As planned, these and other improvements allow ath5k and ath9k to gradually replace the madwifi driver, which has a proprietary core. How much longer madwifi will be on the scene at all remains to be seen; at the time of publication of this article, the latest madwifi version 0.9.4 was already several months old and could, in some Linux 2.6.26 based distributions, only be compiled using patches from the madwifi development branch.

Kernel hackers also improved the rtl8187 driver for Realtek USB Wi-Fi chips first incorporated with Linux 2.6.23. The driver can now also handle the RTL8187B version of this chip (1, 2, 3, 4, 5, 6, 7). The developers also improved the support for power saving techniques in the latest drivers for Intel Wi-Fi modules. Apart from the new and improved Wi-Fi drivers as well as numerous improvements to the Mac80211 Wi-Fi stack, 2.6.27 also includes a greatly overhauled rfkill framework (for examples, see 1, 2, 3, documentation). The changes were made to improve hardware, kernel and userspace program interaction when Wi-Fi or Bluetooth connectivity is enabled/disabled by operating the slide switches or keyboard combinations mainly found in notebooks.