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Suitably configured

Kernel testers can now use the new 'localmodconfig' make target to, relatively simply, create a kernel configuration attuned to the distribution and hardware being used, and which does not compile any unneeded modules. This uses the configuration file for the currently running kernel and deactivates all modules which are not loaded in the kernel when it is run.

As a consequence, drivers for hardware which is not connected when the make is called, such as USB devices, may be omitted. For testers, however, it has the potential to save a bunch of time when generating a kernel, as explained in a git pull request by Steven Rostedt, the kernel hacker responsible for this change. Rostedt also explains how it works and describes the 'localyesconfig' make target, which generates a kernel configuration into which all modules loaded when it is called are compiled.



This article can only provide an overview of the most important changes of Linux version 2.6.32. More detailed information can be found in the various parts of the Kernel Log's "What's coming in 2.6.32" mini series released over the past few weeks on The H Open and which form the basis of this article.

In these articles, you will find the main sections that make up this article and an "In Brief" section which details important changes. There is also the "Minor gems" section which lists the many other changes which are not mentioned in the main article but for many users are still of great significance.

For example, in the article on Graphics, "Minor gems" lists the numerous patches to support the video hardware on different PCs, notebooks and motherboards, and lists the changes to the V4L/DVB subsystem, which includes the addition of product names for TV hardware that the Linux kernel now recognises.

It will in future be possible to read certain information on AHCI capabilities – such as whether a port is hot-pluggable or is an eSATA connector – via sysfs. Userspace applications should be able to use this information to make better decisions on optimal behaviours, e.g. when configuring ALPM (Aggressive Link Power Management). These now include support for AMD's SB900 southbridge, which, as things stand at present, still looks several months away from a release date.

A 1.4 MB patch for the bfa driver for Brocade FC and FCOE host adapters has been merged into the SCSI subsystem. Much more lightweight are the new be2iscsi driver for iSCSI functionality for ServerEngines' 10Gbps BladeEngine 2 storage adapter and pmcraid driver for PMC Sierra's MaxRAID series 6Gb/s SAS adapters.

There have been a number of changes to the MD code and other kernel subsystems to improve the ability to offload calculations for RAID 6 to dedicated hardware. There have also been changes to the still fresh MD code for supporting the various options for modifying and converting software RAID arrays – e.g. for converting a RAID 1 to a RAID 5, to a RAID 6 and back again. Such conversions can be carried out by mdadm versions 3.1.x.

Audio and video

The kernel's audio drivers are now at the same level as ALSA 1.0.21. The driver for HD audio hardware now supports now supports a type of "firmware" that allows special hardware requirements ("quirks") to be dynamically communicated to the driver if the BIOS provides insufficient or incorrect codec configuration details. There were many improvements to the codec configuration in Dell and HP notebooks in general and the audio drivers are now said to configure Realtek codecs more reliably. The developers also improved the drivers for the Intel chip-sets used on LGA1156 boards (P55/IbexPeak).

Among the new additions in the V4L/DVB subsystem is the CX25821 driver for TV cards based on the chip of the same name. Also new is the SAA7164 driver for the chip installed on the Hauppauge HVR 2200 and 2250. The uvcvideo driver for USB webcams that comply with the USB Device Class Definition for Video Devices now supports multiple simultaneous streams (1, 2) and programmers can now find API information about the V4L/DVB subsystem in the kernel documentation. The V4L/DVB subsystem now also supports the ISDB-T (terrestrial TV) and ISDB-S (satellite) transmission standards, which are mainly used in Japan and South America. The developers have also given the code for infra-red remote controls a makeover and unified some key mappings that were previously driver specific.

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