16 March 2009, 13:07

Kernel Log: What's new in 2.6.29 - Part 7: Audio, FireWire, USB, Video and more

On Thursday night, Linus Torvalds released an eighth pre-release version of Linux 2.6.29 and hinted that this could be the final 2.6.29 release candidate, with the main development tree now stabilising. He did not, however, completely rule out further pre-release versions, "[...]it seems to be stabilising to the point where I'm hoping that we're approaching a final 2.6.29, and this might be the last -rc. We'll have to see."). Kernel Log is taking this opportunity to continue the "What's coming in 2.6.29" series with an overview of driver news from a range of areas.

Audio and video

This development cycle once again saw hundreds of major and minor changes to the Alsa framework and drivers (including 1, 2, 3, 4, 5). According to information in the kernel, audio support in Linux 2.6.29 is now at the level of Alsa 1.0.18a, but it will in fact include many of the changes in the current 1.0.19 Alsa driver version. These include, for example, the driver for HD audio codecs being split into multiple files. As a consequence, in future, when compiling the audio drivers as a module, different, generally vendor-specific modules, will be responsible for HD audio codecs. However, these will no longer need to be loaded manually â rather the driver for the HD audio device will automatically detect which codec is connected and request the respective module.

Audio quirks Linux users with audio hardware which only works properly with the assistance of specific parameters, e.g. "model=6stack-digout" when loading "snd-hda-intel", should send this information, along with the hardware used, to the Alsa development team. They can then add to their whitelists, so that future Linux kernels will automatically use the required parameters. This will not only benefit the development team, but will also save all Linux users with the same hardware a little time by making audio hardware "just work".

The developers have also added support for audio output via HDMI with Intel and Nvidia chipsets to the HD audio driver (e.g. 1). The energy saving features for AC97 and HD audio chips are no longer considered experimental â users wanting to extend their laptop's battery life should, unless the kernel of the Linux distribution they are using has already done so, activate this feature during kernel configuration or later. The pcxhr driver for Digigram's eponymous audio chips has been substantially enhanced (1, 2). Many new drivers have also been added to the ASoC (ALSA System on Chip) framework.

As with pretty much every new kernel version, the developers have significantly extended the whitelists for automatic use of hardware specific "quirks", including in this case for the Dell Inspiron Mini9, Fujitsu-Siemens Amilo Xa3530 and HP 6730B netbooks and laptops.

V4L/DVB

It's not just the audio subsystem that's been souped up â, the video4Linux/DVB subsystem has also been extended or modified by hundreds of patches (1, 2, 3, 4, 5, 6). Two new Gspca drivers have been added â ov534 addresses the Sony Playstation EYE, whilst stv06xx is tailored to various older Logitech Quickcam cameras. Until now, these cameras have usually required one of two drivers going by the name qc-usb, which have never made the leap into the Linux main development tree. Also new are the cx24113 driver for the CX24113 chip used in the Technisat Skystar2 revision 2.8 and the omap2cam driver for the camera on the Nokia N800/N810 Internet Tablet. Many more new drivers can be located via the links below.

Latecomers and backsliders There have been several additional changes to the network subsystem beyond those previously described in the first part of the "What's coming in 2.6.29" series. The most important of these are the newly adopted HFC-USB driver for the mISDN framework integrated in 2.6.28 and the new atl1c driver for LIC series Atheros Gigabit Ethernet chips. Kernel Log also reported on changes to the p4-clockmod driver which removed the Cpufreq driver's Sysfs interface in the fourth part of the "What's coming in 2.6.29" series. This change has, after discussions in bug report 12826 on bugzilla.kernel.org, now been revised. Now in 2.6.29, as with previous kernel versions, it will remain possible to manually slow down the CPU using throttling â although this is, as previously reported, rarely worthwhile. This back-pedalling is, however, only an interim solution to allow the development team to correct certain bugs in ACPI subsystem throttle support so they can ensure the reliability of protection against CPU overheating. The plan is that the patch will be reintroduced later, with a release pencilled in for this September.

FireWire and USB

Stefan Richter has introduced numerous enhancements and extensions into the FireWire subsystem, which he maintains (e.g. 1, 2). These provide enhancements for asynchronous data transfer and remove the 800Â Mb/s maximum speed limit from the old FireWire stack. Very late in the second half of the development cycle, the firedtv (formerly firesat) V4L/DVB driver has found its way into the main development tree via the FireWire development tree. It supports the FireDTV and FloppyDTV FireWire TV hardware developed by Digital Everywhere and marketed by Elgato.

Both Wimax code and extended support for USB OTG (On-The-Go) have made their way into the main development tree via the USB development tree (1, 2, 3, 4). Other changes should accelerate data transfer via Wireless USB.

Staging driver developments

The first part of the "What's coming in 2.6.29" series mentioned a number of network and WLAN drivers which the kernel development team had included in the kernel's staging directory. These included the rt2860 and rt2870 drivers for Ralink's eponymous WLAN chips, used in many newer netbooks and laptops.

There have also been plenty of other new inclusions in the staging directory. The commit for the "openPOWERLINK Network Stack" from Systec Electronic weighs in at a massive (for the kernel) 2Â Mb. The commit which adds Meilhaus' ME-IDS drivers totals around 1.2Â Mb. The kernel development team have also included the Comedi framework and numerous kernel extensions from Google's Android in the staging directory. Details of these and other staging drivers incorporated into fpr 2.6.29 can be found in the links at the end of this article.

Even more drivers

The ps3vram driver (1, 2) allows the PS3's video RAM to be used for swapping or temporary file storage. The kernel development team is, however, planning to remove this driver shortly before 2.6.29 is released and replace it with another (1, 2).

In addition to the new features described in this article, the kernel development team has also included a large number of additional patches in 2.6.29, which add new drivers to the kernel and enhance the functionality and hardware support of existing drivers. The headings for these, perhaps less important, but in no way insignificant changes are given in the list below. The entries link to the relevant commit in the Linux source code control system, where further information on the change can be found in the commit comments and from where the patch itself can also be retrieved.

Audio

FireWire

Hardware-Monitoring, EDAC

USB

V4L/DVB

Staging

Other Drivers

Documentation

Latecomers

The Kernel Log has previously covered the updated sub-systems, but there were still late changes made to these systems worth noting:

ACPI und PCI

Graphics

Network

Generic

mISDN

LAN

WLAN

Net and Notebooks

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: