What's going into 2.6.15

The release of the 2.6.14 kernel opened the door for new changes. Many developers have been quick to submit their patches, with the result that nearly 2000 commits have been merged for 2.6.15. The door will remain open for two weeks - until around November 11 - at which point the kernel should return to stabilization mode.

Many of the patches merged are fixes, and quite a few of them are in architecture-specific code. Among the rest, however, are the following, starting with user-visible changes:

• An update to the generic 802.11 code which includes, among other things, quality-of-service support, the ability to use hardware crypto and fragmentation offload functions, and "wireless spy" support.

• A driver for Marvell serial ATA controllers. There is also a new "ATA passthrough" ioctl() allowing arbitrary ATA commands to be sent to devices.

• The old "bluetty" driver has been removed. Everybody should be using the bluez stack for Bluetooth devices at this point.

• As a result of the device model changes, the 2.6.15 kernel will require version 071 (or higher) of the udev utility.

• A new uevent device attribute in sysfs can be used to manually force the creation of a hotplug event for an existing device. This feature can be used to regenerate hotplug events for devices which were present when the system was booted.

• The PowerPC 4xx on-chip Ethernet driver has been replaced with a completely rewritten, more efficient version.

• A new driver for the Freescale Ethernet devices found in some embedded systems.

• Support for the old Cobalt servers has been restored.

• Basic support for hot-pluggable memory.

• A big NTFS rework with much-improved write support.

• A big InfiniBand update, with support for a wider range of userspace verbs.

• Support for ARM "RealView" boards.

• A large CIFS filesystem update, with support for change notifications, mounting from "legacy" servers, case-independent file names, and more.

• DRM support for Radeon PCI Express cards

API changes and other internal patches visible to kernel developers include:

• The nested class devices patch and associated input subsystem patches. For those who are curious about where the device model work will go from here, Greg Kroah-Hartman has posted a roadmap on his weblog.

• More conversions of internal function prototypes to use the gfp_t type introduced in 2.6.14.

• A number of block layer patches, including a rework of the elevator switch code and the generic dispatch queue patch. The new I/O barrier code has not been merged as of this writing.

• A big rework of the remote procedure call code, and a number of associated NFS updates.

• Some power management changes, including a driver API change; see this article for details.

• A new mechanism allowing code to be notified when USB busses and devices come and go. Drivers do not normally need to use these notifiers, but some of the core code benefits from them.

• The driver model class "interface" add() and remove() methods have picked up a new parameter: a pointer to the actual interface structure.

• There is a new reader/writer semaphore function rwsem_is_locked(), which tests whether the rwsem is read locked without blocking.

• There is a new variant of vmalloc():

       void *vmalloc_node(unsigned long size, int node);
  

  As one might expect, it allocates memory on a specific NUMA node.

• The "reserved" bit for memory pages - used to mark pages which are not managed by the kernel page allocator (kernel text, non-memory areas, etc.) - has been all but removed. No core code uses it now, with the exception of software suspend, and that will get fixed eventually. There are reports that this change breaks VMware.

• A set of Linux security module hooks for the (relatively) new key management functions.

• A new kernel thread function:

      int kthread_stop_sem(struct task_struct *kt, struct semaphore *s);
  

  This function will stop a kernel thread which might be waiting on the given semaphore.

• A "torture test" module for the read-copy-update mechanism.

Stay tuned: there is still time for quite a few more changes to be merged before the 2.6.15 window closes.

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