17 April 2009, 10:51

Kernel Log: What's coming in 2.6.30 - Network: New Wi-Fi drivers and other network novelties

Kernel Log Penguin The next major Linux version will include new Wi-Fi drivers for chips from Atheros, Intel, Intersil/Prism and Marvell and new drivers for Intel LAN chips. The kernel will also in future make better use of energy saving features in the latest Wi-Fi hardware and Oracle is contributing code for the Reliable Datagram Sockets (RDS) cluster protocol.

As with previous kernel versions, the recent release of the second pre-release version of Linux 2.6.30 saw a good few major patches which had missed the merge window find their way into the main Linux development tree. Further major changes are rare in the second phase of the development cycle, so that the second pre-release version should now contain all the major changes for the next major kernel revision.

The Kernel Log on The H is taking the opportunity to open the "What's coming in 2.6.30" series with a description of the major networking-related changes and will be extended with further instalments over the next few weeks, building up to a detailed description of all the major changes in 2.6.30 in the various functional areas within the Linux kernel, until Linus Torvalds releases Linux kernel 2.6.30 in around seven to ten weeks time.

Code recycling

In version 2.6.30, Linux will for the first time include the ar9170 Wi-Fi driver for Atheros' eponymous 802.11n USB chip set (1, 2, 3, 4, 5, 6). The driver is brand spanking new, but re-uses some of the code from Atheros' otus driver, which was released a few months ago. The latter was added to the staging area in Linux 2.6.29; in the opinion of some Wi-Fi driver developers, however, re-jigging and improving the staging driver to meet kernel hacker quality standards would have taken more work than writing a new driver tailored to the kernel's Wi-Fi stack, resulting in the development of the new driver.

Also making its debut, driven largely by Marvell developers, is the mwl8k driver for Marvell 88w8xxx (Topdog) series PCI and PCIe Wi-Fi chips. Currently, however, it only supports the 88w8687 Wi-Fi chip in STA mode on channels 1 to 11. Also still some way off technical maturity is the new at76c50x-usb driver for Atmel's old at76c503, at76c505 and at76c505a Wi-Fi chips. In the long term it is intended to replace the at76_usb driver, which was incorporated into the kernel's staging area in 2.6.28. As with otus and ar9170, some of the old driver code has found its way into the new driver, which is based on the kernel's Mac80211 Wi-Fi stack.

Clean up work and energy saving functions

To simplify maintenance, the kernel development team has combined parts of the iwl3945 driver with the files for drivers for newer Intel Wi-Fi chips (e.g. 1, 2, 3, 4). The latter have been extended to include support for Intel's 1000, 6000 and 6050 Wi-Fi chips (1, 2, 3, 4).

The kernel hackers have also improved support for runtime energy saving features in modern Wi-Fi hardware in both the Mac80211 Wi-Fi stack and in some drivers (e.g. 1, 2, 3; further commits can be found in the list at the end of this article). There have also been enhancements to the code for suspending to, and resuming from, RAM and disk.

Wired

The kernel development team have added support for the Generic Receive Offload (GRO) infrastructure, introduced in 2.6.29, to many LAN drivers. These include the igbvf network driver for Intel's 82576, ethoc for OpenCores' 10/100 Mbit LAN Chip and vxge for Neterion's X3100 series 10GbE PCIe I/O Virtualized Server adapters (e.g. 1, 2, Documentation).

Also new in 2.6.30 is code introduced by one Oracle developer (Documentation) to provide support for the Reliable Datagram Sockets (RDS) server cluster protocol. This was originally developed jointly by Cisco Systems and Oracle, before being transferred to the Open Fabrics Alliance software stack.

In Brief

LAN

Having offloaded the firmware code for many network drivers into separate files in 2.6.27, .28 and .29, the kernel developers are continuing the process in 2.6.30.

Wi-Fi

The new libertas_spi drivers for the Marvell 8686 and the experimental p54spi driver for Prism's stlc4550 and stlc4560 chips, designed for Nokia's N800 and N810 devices, are tailored to Wi-Fi chips with SPI (Serial Peripheral Interface).
Cfg80211 and nl80211 now include autonomous support for scanning for Wi-Fi networks.

Netfilter

The packet filter code now offers a userspace interface allowing packets to be time stamped.

Miscellaneous

Bluetooth: Kernel hackers have adapted the Bluetooth stack security model for the changes made in Bluetooth 2.1, as a result of which the kernel can now utilise Secure Simple Pairing.

Minor gems

The changes described are just some of the more significant changes recently undertaken by kernel hackers in the networking field. The following list includes numerous further major commits for 2.6.30 in the main Linux development tree; the links lead directly to the Git version control system web interface, where comments on the commits and patches themselves provide wide-ranging information on the less important, but far from insignificant, changes.

Network

Most relevant Git-Pull-Request:

Network: 1, 2, 3, 4, 5

Infiniband: 1

LAN

Wi-Fi

RDS

Others

Further background and information about developments in the Linux kernel and its environment can also be found in previous issues of the Kernel Log at The H Open Source:

Older Kernel logs can be found in the archives or by using the search function at The H Open Source. (thl/c't)

(djwm)

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