Audio and video

Suitable for various sound cards of Creative's X-Fi series and mainly developed by Creative programmers, the snd-ctxfi driver has found its way into the kernel via the ALSA developers. This puts an end to a driver odyssey which had several, mostly half-finished, versions of both open source and proprietary drivers and in the past few years, gave us futile hopes for a half-way decent Linux driver for X-Fi sound chips. However, the newly integrated driver is not fully mature yet; for instance, it doesn't support external I/O modules.

As usual, hundreds of changes were made to the DVB/V4L subsystem. One new addition is the STV090x driver for addressing the Intersil DVB-S/S2/DSS chips found on cards like the TechnoTrend TT-budget S2-1600. Another addition is the gspca-sn9c20x driver for SN9C201 and SN9C202 USB chips, which are used in the webcams of various manufacturers. The new kernel will offer improved support for several webcams of Logitech's QuickCam Messenger series; the OV519 gspca driver now also works with the OV511 and OV518 chips.

Data Organisation

Major changes, in the form of a 350 KB patch, should significantly improve Btrfs performance by using 'mixed back references' in many areas. The patch does, however, involve a change in the structure of the file system on the storage media ('on disk format'). Kernel versions containing the new Btrfs code deal with the requisite conversion from old to new format automatically the first time the file system is mounted. However, Linux versions with older Btrfs code will thereafter no longer be able to mount file systems which have been modified by the new code.

Some other changes make Btrfs less memory hungry during long periods of high load (e.g. see 1, 2). Btrfs developers have also improved support for using SSDs (e.g. see 1, 2).

The Ext4 file system now contains code for de-fragmenting the file system while in use (online defrag). This is not, however, finished, as was recently emphasised elsewhere by Ext file system developer Theodore Tso (tytso). He goes on to say that further patches for this function still need to be evaluated and that there is still outstanding work to be done on the associated userspace program.

About the source code management system

Many of the links in this article point to the relevant commits in the web front end of Linus Torvalds' Git source code management system for Linux, because these commits tend to contain a lot more information about the respective changes. The commit comment in the mid section of the web page displayed by the Git web front end is often a particularly helpful source of further information. This is where the author of a patch usually describes the background and intended effects of the changes.

The bottom section of the Git web front end lists the files that are affected by the patch. The "diff" link behind each file name shows how the patch modifies the respective file; if you want to view the complete patch in its raw form, click on the commitdiff link. Even if you don't have any programming skills the patches are often a good source of information, because they also contain changes to the documentation and comments within the code.

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