19 October 2009, 13:50

Kernel Log: Coming in 2.6.32 (Part 1) – Network subsystem and network drivers

by Thorsten Leemhuis

Between Thursday evening and Friday morning, Linus Torvalds released the fourth release candidate of Linux version 2.6.32, although, due to the typing error in the first release candidate (RC1 was mis-labeled RC2), it is called 2.6.32-rc5 instead of 2.6.32-rc4.

Torvalds released this version only a few days after RC4, as he and many other kernel hackers will spend the weekend travelling to this year's Linux Kernel Summit held in Tokyo next week; therefore few changes are expected to make their way into the Linux kernel's source code management system during this time.

Another major SCSI driver was merged into the Linux kernel's main development branch with RC4 and RC5 offers two further network drivers. Such stragglers can be found in almost any development cycle. As usual, however, the majority of changes were incorporated during the merge window, which lasts two weeks and was closed by Torvalds with the release of the first RC at the end of September. The Kernel Log is, therefore, already in a position to provide an overview of some of the major enhancements of Linux 2.6.32, which is expected to be released at the beginning of December. We are starting our "What's coming in 2.6.32" mini series with the most important changes to the kernel's network support; major changes in other kernel areas will be discussed in further editions of the series over the next few weeks.

Wireless

The developers have re-activated the p54 driver's power saving support. While, to bypass a bug that is presumed to be hardware-related, they have done the opposite with the iwl4965 driver for Intel's Wireless Wi-Fi Link 4965AGN, and disabled it. It is yet uncertain if they will ever be able to re-activate the power saving features. However, the kernel hackers also improved the driver for Intel Wi-Fi chips, which can now automatically select the appropriate sleep state for the Wi-Fi hardware using information gathered via pm_qos (Power Management Quality of Service).

Following various restructuring measures to the ath9k driver for many recent Atheros Wi-Fi chips, the developers have extended the driver to support AR9287 Wi-Fi chips; some rudimentary first components for examining the AR9271 were also incorporated into the kernel.

The MAC8021 Wi-Fi stack now scans for Wi-Fi networks in the background, which allows access point connections to continue transmitting data. This is an interesting feature for location-based services and roaming, as highlighted in a blog post by Dan Williams, the main developer of NetworkManager.

A new addition is the wl1271 driver for the Wi-Fi part of Texas Instruments' WiLink 6.0 mobile platform used in the embedded area. The b43 driver for Wi-Fi chips by Broadcom can now also handle low power PHYs (LP-PHY) such as the BCM4312, which can be found in some notebooks and in the embedded area. The prism54 driver, which has been superseded by the p54pci driver, is now planned for removal from the kernel in version 2.6.34.

Networking

Just in time for RC5, the kernel hackers have incorporated the vmxnet3 driver into the main development branch. It is able to communicate with the "vmxnet3 virtual ethernet NIC" - a network adaptor that emulates several virtualisation solutions by VMware. In addition, Linux 2.6.32 will offer the infrastructure required for updating ("flashing") the firmware of network chips using the ethtool program.

The r8169 driver for recent network hardware by Realtek now also supports the RTL8168D chip. However, this is only one of many network drivers that have been extended to support new hardware – more information about these changes can be found in the commits in the "Minor Gems" section at the end of this article.

The btusb driver is now capable of USB autosuspending – with Bluetooth chips that don't support remote wake-up, however, the interface must be shut down for the power saving mechanisms to take effect. The btmrvl and btmrvl_sdio drivers for Bluetooth chips by Marvell (documentation) are new additions. The kernel developers also integrated several mISDN drivers:

avmfritz for AVM PCI cards in the Fritz! series
netjet for NETJet PCI cards by Traverse Technologies
mISDNinfineon for various ISDN chips by Siemens and Infineon
speedfax for the ISAR DSP chip by Siemens used in Speedfax+ hardware
w6692 for PCI cards with Winbond W6692

Another kernel first is a driver for the CAN controller on Atmel AT91SAM9263 chips, which was introduced by a Pengutronix employee (1, 2). Predominantly introduced by Oracle developers, the code that supports the Reliable Datagram Sockets (RDS) protocol created for server clusters now also supports transmissions via TCP.

Minor Gems

The kernel hackers have considerably improved the support of wireless extensions (WE) and network namespaces. Some of these and further minor, but by no means insignificant, changes can be found in the list below. Like many of the references in the text above, the links point to the relevant commit in the web front end of the main Linux development branch, where the commit comments and the patches themselves provide extensive further information on the respective changes.