Introduced in 2.6.39, the kernel's ipset support has been improved to provide filter information that grants simpler and more flexible access to the tables that are consulted by the firewall code. For instance, addresses and interface names can now be submitted in pairs with their own names, which is interesting for egress and ingress filtering tasks; furthermore, the kernel can now automatically convert any addresses that have been submitted as an IP range to the correct subnet definitions. The networking code is being extended to include a subsystem for Near Field Communication (NFC), a technology that is used by many contactless payment systems (documentation, 1, 2, 3, 4).
Torvalds has merged a 660 KB patch, which lifts LIO (linux-iscsi.org), the iSCSI target framework merged in 2.6.38, to LIO version 4.1 (1, 2). The kernel code for software RAID now offers bad block management for RAID levels 1, 4, 5 and 6. This detects and avoids known bad areas on the RAID disks (for example 1, 2, 3). Dm-crypt is now able to forward discard commands to the underlying disk. This is useful for SSDs, as it allows them to be informed of freed blocks via ATA trim, improving both speed and lifespan. For security reasons – to prevent attackers from being able to make inferences from the extent of disk use – this function is deactivated by default.
Like Ext4, the Ext3 filesystem will in future use write barriers by default. This adversely affects speed, but improves robustness in the event of a crash. Changes to the btrfs locking mechanism can make the experimental filesystem significantly faster during read-heavy workloads. Kernel developers have extended pstore (platform persistent storage), which was merged into Linux 2.6.39, in order to be able to retain data for analysing crashes in non-volatile memory areas used by UEFI (1, 2).
Audio and video drivers
The snd-ctxfi audio driver does now support the Creative Titanium HD. The media subsystem with its drivers for remote controls and for DVB, radio and video hardware was extended to include drivers for the Micronas DRX-K DVB-C/T demodulator and the TDA18271C2 tuner (for example 1, 2, 3, 4). Another kernel addition is the Ddbridge driver, which supports video hardware with Ddbridge components by Digital Devices – such as the Octopus, Octopus mini, Octopus LE and cineS2(v6) with DuoFlex S2 and/or DuoFlex CT Tuner (1, 2, 3). Also new is the ir-mce_kbd-decoder driver that allows the Windows Media Center edition of the Microsoft Remote Keyboard to be used with a normal IR receiver.
Architecture and Infrastructure
Together with a patch that has been integrated for Linux 3.1, the tool Uname26 can instruct the kernel to present version numbers that begin with "2.6." to other programs. This makes some software co-operate that struggle with the current kernel's two-figure version numbers that begin with 3. Linux 3.1 will be the first version to support the OpenRISC architecture (for example 1); find further changes in the "minor gems" section). OpenRISC is an open source processor architecture with a set of RISC instructions that was originally developed within OpenCores.org but is temporarily being developed in the context of the OpenRISC.net project. From Linux 3.1, the tools directory with kernel-related userland software will contain the "cpupower" diagnostic tool. A successor to cpufrequtils, the tool monitors whether the power saving and frequency changing functions of modern processors are being used fully – for instance, whether Intel processors switch to the highest clock speed via TurboBoost when only one or a small number of processor cores are busy.