the 3.4-rc1 release and the
closing of the merge window on March 31. At the outset, he had said
that this merge window could run a little longer than usual; in fact, at 13
days, it was slightly shorter. One should not conclude that there was not
much to pull, though; some 9,248 non-merge changesets went into the
mainline before 3.4-rc1, and a couple of significant features have sneaked
their way in afterward as well.
User-visible features merged since last week's
- The device mapper "thin provisioning" target now supports discard
requests, a feature which should help it to use the underlying storage
- The dm-verity device mapper target has
been merged. This target manages a read-only device where all blocks
are checked against a cryptographic hash maintained elsewhere; it thus
provides a certain degree of tampering detection. Details can be
found in Documentation/device-mapper/verity.txt
- Support for the x32 ABI has been
merged into the kernel. Getting support into the compiler and the C
library is an ongoing project, and the creation of distributions using
this ABI will take even longer, but the foundation, at least, is now
- The "high-speed synchronous serial interface" (HSI) framework has been
merged. HSI is an interface that is mainly used to connect processors
with cellular modem engines; it will be used for handset support in
future kernel releases.
- New drivers include:
- Processors and platforms:
Samsung EXYNOS5 SoCs, and NVIDIA Tegra3 SoCs.
SMI-attached SPEAR MTD NOR controllers,
DiskOnChip G4 NAND flash devices, and
Universal Flash Storage host controllers (details in Documentation/scsi/ufs.txt).
Apple "gmux" display multiplexers,
Intel Sodaville GPIO controllers,
TI TPS65217 and TPS65090 power management controllers,
Ricoh RC5T583 power management system devices,
Freescale i.MX on-chip ANATOP controllers,
Summit Microelectronics SMB347 battery chargers, and
ST Ericsson AB8500 battery management controllers.
Changes visible to kernel developers include:
- The "common clock framework" unifies the handling of subsystem clocks,
especially on the ARM architecture (though it is not limited to ARM).
See Documentation/clk.txt for more
- The DMA buffer sharing API has been extended to allow CPU access to
the buffers; see the updated Documentation/dma-buf-sharing.txt file
- The direct rendering subsystem has gained initial support for the DMA
buffer sharing mechanism. No drivers use it yet, but having this
support in the mainline will ease the development of driver support
for future kernels.
- The massive <asm/system.h> include file has been split
into several smaller files and removed; in-tree users have been fixed.
- The new /proc/dma-mappings file on the ARM architecture
displays the currently-active coherent DMA mappings. Since such
mappings tend to be in short supply on ARM, this can be a useful
- The ARM architecture has gained jump label ("static branch") support.
- The just-in-time compiler for BPF packet filters has been ported to
the ARM architecture.
There are a couple of other features that Linus may still be considering
merging as of this writing, though the chances of them getting in would
appear to be diminishing. One is the DMA
mapping rework; Linus has been asking for potential users of this
change to speak up, but few have done so. In other words, if there are
developers out there who would like to see the improved DMA subsystem in
the 3.4 release, you are running out of time to make that desire known.
The other is POHMELFS, which has had some
review snags and which also seems to lack a vocal community clamoring for
Beyond those possibilities, though, the time for new features to go into
the 3.4 development cycle has now passed. The stabilization process has
begun, with a probable final release in late May or early June.
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