The kernel's Radeon graphics driver now supports the Oland graphics chips that are used on series 8500 and 8600 Radeon HD cards (1, 2, 3). The kernel now also supports AMD's soon-to-be-expected Richland APU generation (1, 2). The Nouveau driver now offers various experimental automatic and manual fan control features for the NV40 and NV50 GPUs that are used on GeForce series 6xxx to 9xxx and 1xx to 3xx graphics chips (1, 2, 3, 4). NVIDIA developer Aaron Plattner got his "prime helpers" integrated, which are being used by a beta of a new NVIDIA graphics driver to provide Optimus support for the first time. The graphics driver for Intel's soon-to-be-expected Haswell processors has been enhanced to configure these processors' graphics core to use less power when only one display pipe is used with the Embedded DisplayPort (EDP); this is sometimes the case in notebooks.
Linux 3.9 will include a driver for Intel's series 7000 Wi-Fi components; apparently, these components will support the fast IEEE 802.11ac transmission modes (1, 2). It seems that the company is planning to introduce them in a few months – probably together with the Haswell-based notebook processors that are expected to become available this summer.
Major changes to the driver code for configuring the HD audio codecs that are used in many modern desktop PCs and notebooks are said to make this code leaner and more robust. The libata drivers now support zero power optical device drives (ZPODD) (optical drives which are able to almost completely power down to save power when there is no CD or DVD in the drive) (1, 2 and others).
Among the platform driver modifications, the kernel developers have added a driver that supports Chromebooks by various manufacturers including, for example, the Chromebook Pixel (1, 2, 3). Another new addition is a driver for Cypress APA I2C trackpads; these trackpads are included in Samsung's ARM Series 3 Chromebook, which is currently a popular test item for Linux developers who have an interest in ARM. Also new is a driver for the Cypress PS/2 trackpad that Dell is using in its developer-oriented Ultrabook with Ubuntu 12.04.
As planned, the Linux developers have removed the CONFIG_EXPERIMENTAL kernel configuration option (1, 2). Experimental features could originally only be activated during kernel building if this option was enabled. However, the kernel developers often forgot to remove the CONFIG_EXPERIMENTAL dependency once features had matured. Kernel builders spent many years having to enable the CONFIG_EXPERIMENTAL options, almost as a default, in order to build a kernel for modern hardware components and distributions – the kernel developers have picked up on that and are now dropping this approach. The status of truly experimental features is now only indicated in the help texts that are displayed during configuration and in additions such as "(EXPERIMENTAL)" to the short descriptions.
The list of supported CPU architectures includes two new entries because Linux now runs on Synopsys ARC processors as well as Imagination Meta ATP (Meta 1) and HTP (Meta 2) processor cores. The developers have updated the code for compressing and decompressing LZO to provide significantly faster processing speeds; according to a merge comment, the feature is now as much as twice as fast on some processors.
The kernel's KVM hypervisor will support the virtualisation features of Cortex A15 processors. This will, for the first time, allow KVM to work under ARM cores. The kernel's Xen support now includes drivers for hotplugging processors and memory components (1, 2, 3); removing these components at runtime is not possible at present. The integration of the drivers for VMware's VMCI (Virtual Machine Communication Interface) and the VMCI Sockets that are based on it promises to improve the general support for VMware's virtualisation solutions (1 2, 3). VMware products use these technologies to provide communication and data exchanges between hosts and guests.
Linux 3.9 will support a "lightweight suspend" or "suspend freeze" mode that will cause the kernel to send all hardware components into their deepest sleep state. Unlike suspend-to-RAM (ACPI S3), this feature doesn't power down the components so they are quicker to resume operation when they are needed. While the resulting power consumption will be higher than with suspend-to-RAM, it is still designed to be lower than during the normal idle state because the processor can sleep longer and more deeply. The freeze state tends to be less relevant for PCs and notebooks, discounting certain special cases such as systems that must wake up from suspend particularly quickly, that need to respond to keyboard inputs or network traffic, or don't offer suspend-to-RAM. However, the developers say that the new suspend mode will make a difference with some smartphones and tablets that will consume almost as little power as when they are put into the deeper and less responsive suspend-to-RAM state.