2.6.27: what's coming (part 1)

Linus wasted no time after the 2.6.26 release; he opened the 2.6.27 merge window less than 24 hours later. As of this writing, the process has barely begun with a mere 3000 changesets merged. So we do not have a complete picture of what will be in the next kernel release. But we can look at what has been merged so far.

User-visible changes include:

• New drivers for CompuLab EM-x270 audio devices (as found on the Toshiba e800 PDA), Philips UDA1380 codecs, Wolfson Micro WM8510 and WM8990 codecs, Atmel AT32 audio devices, AK4535 codecs, SGI HAL2 audio devices (as found in Indy and Indigo2 workstations), SGI O2 audio boards, crypto engines found in Intel IXP4xx processors, Freescale Security Engine processors, AMD I/O memory management units, Marvell Loki (88RC8480), Kirkwood (88F6000), and Discovery Duo (MV78xx0) system-on-chip processors, IBM Power Virtual Fibre Channel Adapters, and GEFanuc C2K cPCI single-board computers.

• The old "ppc" architecture has been removed; all platforms are now supported by the integrated "powerpc" architecture code.

• The SCSI command filter - which controls which SCSI commands can be sent to a device by which kind of user - is now per-device and can be changed via sysfs.

• The block subsystem now has support for hardware which can perform data integrity checking; this will allow some kinds of errors to be caught before the associated data is lost forever. See this article for more information on the block-layer integrity feature.

• The "dummy" Linux security module has been removed; the default module is now the capabilities module.

• The crypto code has gained support for the RIPEMD-128, RIPEMD-160, RIPEMD-256, and RIPEMD-320 hash algorithms. Asynchronous hashing is now supported and is implemented by the "cryptd" software crypto daemon.

• Xen now has support for the saving and restoring of virtual machines - possibly migrating them to different hosts in between.

• The new virtual file /sys/firmware/memmap shows the memory map as it was configured by the system BIOS before the kernel booted.

• The ftrace lightweight tracing framework has been merged. See Documentation/ftrace.txt for more information on ftrace.

• The mmiotrace tool has been merged. Mmiotrace will capture and print out memory-mapped I/O accesses, making it a useful tool for the reverse-engineering of binary drivers.

• The ARM and powerpc architectures now support the latencytop tool.

• The RDMA code has acquired support for the InfiniBand "base memory management extension" operations. The IP-over-InfiniBand code can now perform large receive offload (LRO).

• Delayed allocation support has been added to the ext4 filesystem, which is getting quite close to its target feature set.

• The SATA layer now has enclosure management support; this allows the system to do things like blink an LED to indicate a specific drive in a large enclosure.

• The SGI IRIX binary compatibility layer has been removed.

Changes visible to kernel developers include:

• The register_security() function has been removed. Security modules which wish to implement stacking must now do so explicitly.

• The request_queue_t type is gone at last; block drivers should use struct request_queue instead.

• Quite a bit of big kernel lock removal work has been merged. For char devices, the open() method from struct file_operations is no longer protected by the BKL. Calls to fasync() have also lost BKL protection.

• Many drivers have been converted to use the firmware loader, making it possible to strip the firmware from the kernel for those who are inclined to do so. See this article for more information on the firmware work.

• The API work in the i2c layer continues; there is now an autodetection capability which allows new-style drivers to detect devices on their buses automatically.

• The SCSI layer has gained new support for "device handlers," which are mostly concerned with multipath management. Some of this code has been moved over from the device mapper.

Come back next week for the next episode in the "what's coming in 2.6.27" series.

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