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Wi-Fi drivers

Sponsored by Broadcom, the brcmsmac Wi-Fi driver now uses the bcma driver, which has been part of the kernel for some time, to address the Wi-Fi components of chips that use Broadcom's AMBA Interconnect technology; together with another modification, this prevents potential conflicts caused by two drivers trying to address the same hardware.

The ath9k Atheros driver has been modified to support Dynamic Frequency Selection (DFS). This technology prevents Wi-Fi networks from using certain frequencies in the 5 GHz range if this interferes with the radar used at airports, military facilities and meteorological stations. Full DFS support for the Wi-Fi subsystem is still in development; background information on DFS is available in the Linux Wireless wiki and on LWN.net.

LAN drivers

Having spent years in the staging area, the hv_netvsc network driver for Microsoft's Hyper-V virtualisation interface has now matured sufficiently to be moved to the network subsystem; it should soon appear in the kernels of distributions that rarely, or never, include drivers from the area for insufficiently developed code.

The tg3 driver now supports Broadcom's 57766 chip, while the ixgbe driver addresses two new variants of Intel's 82599 (1, 2). The virtio-net driver that allows host and guest systems to exchange paravirtualised network data now supports ACPI S4 (standby/hibernate).

Overload protection

The network code for Active Queue Management (AQM) now uses an "Adaptive RED" (Random Early Detection) mechanism that dynamically adapts random-drop/tail-drop thresholds to data traffic volumes. As explained in a paper on Adaptive REDPDF presented in 2001, this approach aims to improve the robustness of this technology used by routers to protect themselves against overload.

Network subsystem maintainer David Miller explains many of these changes, as well as various others, in his main Git-Pull request for Linux 3.3. For example, he mentions the new Netlink Socket Dumping support for UDP and AF_UNIX sockets (1, 2, 3, 4, 5).

Minor gems

Many further minor, but by no means insignificant, changes can be found in the list below, which contains the commit headers referring to the respective change. Like many of the references in the text above, the links point to the relevant commit in the web front end of the Git branch for the "official" kernel sources maintained by Linus Torvalds at kernel.org. The commit comments available at these links and the patches themselves provide extensive further information on the respective changes.

Every link is preceded by various letters and numbers in square brackets. The letter "C" identifies patches that modify Kconfig files, which contain the help texts and configuration options displayed by "make menuconfig", "make xconfig" and similar tools during kernel configuration. "D" is used for patches that modify the documentation available under Documentation/ in the kernel branch. "N" identifies changes which create a new file. The numbers provide a rough idea of the patch size: For instance, "1" is used for changes between 10 and 20 KBytes including comment, "2" for patches between 20 and 30 KBytes; changes without a number are less than 10 KBytes, while patches marked "9" are 90 KBytes or more.

LAN

WLAN

Various

Further background information about the developments in the Linux kernel area can be found using the search function at The H Open Source. Information about previous Linux kernel releases can be found in The H's Linux Kernel History. New editions of Kernel Logs are also mentioned on Identi.ca and Twitter by @kernellog2. The Kernel Log author also posts updates about various topics on Identi.ca and Twitter as @kernellogauthor.

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