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14 November 2008, 12:51

Kernel Log: What's coming in 2.6.28 - Part 5: updates for netbooks and notebooks

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Following the kernel developers' addition of a driver to the kernel supporting the ACPI Integrated Graphics Device OpRegion Specification, as we reported previously, thanks to ACPI developers, a change to the driver found its way into the kernel on Wednesday night. The modification tells the driver to give preference to ACPI for controlling backlighting in notebook displays. Netbook and notebook drivers for Asus – 1, 2, Compal, Fujitsu, MSI, Sony and IBM/Lenovo now no longer control brightness if it can be handled by ACPI. These two processes sometimes butted heads in the past.

During the merge window, kernel hackers had already incorporated the panasonic-laptop driver for Let's Note series Panasonic laptops that allows display brightness to be adjusted and activates previously useless function keys. The Toshiba notebook driver can now toggle Bluetooth on and off using the rfkill framework.

Range hrtimers reduce CPU power consumption, increasing battery life for notebooks. They allow the kernel to perform tasks, which can be run a few fractions of a second earlier or later, sometime within a specified time window. That makes it easier for the kernel to bundle several tasks and perform them in one fell swoop, lengthening the time in which the CPU operates in the power-saving sleep mode; that makes it possible to switch to yet deeper CPU sleep modes that save even more power – see also, article on range hrtimers.

Some other changes to the CPUFreq framework, for instance, 1, 2, will reduce power consumption for idling CPUs even more. Version 2.6.28 will include a special driver for notebooks equipped with Elantech touchpads – many of Asus' EeePCs among them – that, along with current versions of the Synaptics driver for X, enable extended touchpad features. Also, the framebuffer driver for Intel graphics chipsets now supports the 945GME installed in the Eee 901.

Once again, there were numerous small changes to Alsa project maintained audio drivers. The updated drivers have lengthened the list of devices on which the sound drivers automatically activate special handling for audio hardware needed on some notebooks. Among the devices that will profit from this are the Acer Aspire 5920G, Medion MD96630, HP EliteBook 8530p, Toshiba RX1 and Toshiba L305.

Following kernel developers' inclusion of libata and IDE support for disk shock protection at the beginning of the current development cycle, a driver for the acceleration sensors built into various HP notebooks also recently made its way into the kernel. Using the sensor data, the driver lets a userspace program park the hard drive's write/read heads for an impending shock the way "HP Mobile Data Protection System 3D" and "HP 3D driveguard" do under Windows.

Additional comments related to notebook drivers, ACPI and power saving technology can be found here:

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 heise open:

Older Kernel logs can be found in the archives or by using the search function at heise open. (thl/c't)


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