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feature-removal-schedule.txt
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feature-removal-schedule.txt
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The following is a list of files and features that are going to be
removed in the kernel source tree. Every entry should contain what
exactly is going away, why it is happening, and who is going to be doing
the work. When the feature is removed from the kernel, it should also
be removed from this file.
---------------------------
What: CONFIG_APM_CPU_IDLE, and its ability to call APM BIOS in idle
When: 2012
Why: This optional sub-feature of APM is of dubious reliability,
and ancient APM laptops are likely better served by calling HLT.
Deleting CONFIG_APM_CPU_IDLE allows x86 to stop exporting
the pm_idle function pointer to modules.
Who: Len Brown <len.brown@intel.com>
----------------------------
What: x86_32 "no-hlt" cmdline param
When: 2012
Why: remove a branch from idle path, simplify code used by everybody.
This option disabled the use of HLT in idle and machine_halt()
for hardware that was flakey 15-years ago. Today we have
"idle=poll" that removed HLT from idle, and so if such a machine
is still running the upstream kernel, "idle=poll" is likely sufficient.
Who: Len Brown <len.brown@intel.com>
----------------------------
What: x86 "idle=mwait" cmdline param
When: 2012
Why: simplify x86 idle code
Who: Len Brown <len.brown@intel.com>
----------------------------
What: PRISM54
When: 2.6.34
Why: prism54 FullMAC PCI / Cardbus devices used to be supported only by the
prism54 wireless driver. After Intersil stopped selling these
devices in preference for the newer more flexible SoftMAC devices
a SoftMAC device driver was required and prism54 did not support
them. The p54pci driver now exists and has been present in the kernel for
a while. This driver supports both SoftMAC devices and FullMAC devices.
The main difference between these devices was the amount of memory which
could be used for the firmware. The SoftMAC devices support a smaller
amount of memory. Because of this the SoftMAC firmware fits into FullMAC
devices's memory. p54pci supports not only PCI / Cardbus but also USB
and SPI. Since p54pci supports all devices prism54 supports
you will have a conflict. I'm not quite sure how distributions are
handling this conflict right now. prism54 was kept around due to
claims users may experience issues when using the SoftMAC driver.
Time has passed users have not reported issues. If you use prism54
and for whatever reason you cannot use p54pci please let us know!
E-mail us at: linux-wireless@vger.kernel.org
For more information see the p54 wiki page:
http://wireless.kernel.org/en/users/Drivers/p54
Who: Luis R. Rodriguez <lrodriguez@atheros.com>
---------------------------
What: IRQF_SAMPLE_RANDOM
Check: IRQF_SAMPLE_RANDOM
When: July 2009
Why: Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
sources in the kernel's current entropy model. To resolve this, every
input point to the kernel's entropy pool needs to better document the
type of entropy source it actually is. This will be replaced with
additional add_*_randomness functions in drivers/char/random.c
Who: Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
---------------------------
What: Deprecated snapshot ioctls
When: 2.6.36
Why: The ioctls in kernel/power/user.c were marked as deprecated long time
ago. Now they notify users about that so that they need to replace
their userspace. After some more time, remove them completely.
Who: Jiri Slaby <jirislaby@gmail.com>
---------------------------
What: The ieee80211_regdom module parameter
When: March 2010 / desktop catchup
Why: This was inherited by the CONFIG_WIRELESS_OLD_REGULATORY code,
and currently serves as an option for users to define an
ISO / IEC 3166 alpha2 code for the country they are currently
present in. Although there are userspace API replacements for this
through nl80211 distributions haven't yet caught up with implementing
decent alternatives through standard GUIs. Although available as an
option through iw or wpa_supplicant its just a matter of time before
distributions pick up good GUI options for this. The ideal solution
would actually consist of intelligent designs which would do this for
the user automatically even when travelling through different countries.
Until then we leave this module parameter as a compromise.
When userspace improves with reasonable widely-available alternatives for
this we will no longer need this module parameter. This entry hopes that
by the super-futuristically looking date of "March 2010" we will have
such replacements widely available.
Who: Luis R. Rodriguez <lrodriguez@atheros.com>
---------------------------
What: dev->power.power_state
When: July 2007
Why: Broken design for runtime control over driver power states, confusing
driver-internal runtime power management with: mechanisms to support
system-wide sleep state transitions; event codes that distinguish
different phases of swsusp "sleep" transitions; and userspace policy
inputs. This framework was never widely used, and most attempts to
use it were broken. Drivers should instead be exposing domain-specific
interfaces either to kernel or to userspace.
Who: Pavel Machek <pavel@ucw.cz>
---------------------------
What: sys_sysctl
When: September 2010
Option: CONFIG_SYSCTL_SYSCALL
Why: The same information is available in a more convenient from
/proc/sys, and none of the sysctl variables appear to be
important performance wise.
Binary sysctls are a long standing source of subtle kernel
bugs and security issues.
When I looked several months ago all I could find after
searching several distributions were 5 user space programs and
glibc (which falls back to /proc/sys) using this syscall.
The man page for sysctl(2) documents it as unusable for user
space programs.
sysctl(2) is not generally ABI compatible to a 32bit user
space application on a 64bit and a 32bit kernel.
For the last several months the policy has been no new binary
sysctls and no one has put forward an argument to use them.
Binary sysctls issues seem to keep happening appearing so
properly deprecating them (with a warning to user space) and a
2 year grace warning period will mean eventually we can kill
them and end the pain.
In the mean time individual binary sysctls can be dealt with
in a piecewise fashion.
Who: Eric Biederman <ebiederm@xmission.com>
---------------------------
What: /proc/<pid>/oom_adj
When: August 2012
Why: /proc/<pid>/oom_adj allows userspace to influence the oom killer's
badness heuristic used to determine which task to kill when the kernel
is out of memory.
The badness heuristic has since been rewritten since the introduction of
this tunable such that its meaning is deprecated. The value was
implemented as a bitshift on a score generated by the badness()
function that did not have any precise units of measure. With the
rewrite, the score is given as a proportion of available memory to the
task allocating pages, so using a bitshift which grows the score
exponentially is, thus, impossible to tune with fine granularity.
A much more powerful interface, /proc/<pid>/oom_score_adj, was
introduced with the oom killer rewrite that allows users to increase or
decrease the badness() score linearly. This interface will replace
/proc/<pid>/oom_adj.
A warning will be emitted to the kernel log if an application uses this
deprecated interface. After it is printed once, future warnings will be
suppressed until the kernel is rebooted.
---------------------------
What: CS5535/CS5536 obsolete GPIO driver
When: June 2011
Files: drivers/staging/cs5535_gpio/*
Check: drivers/staging/cs5535_gpio/cs5535_gpio.c
Why: A newer driver replaces this; it is drivers/gpio/cs5535-gpio.c, and
integrates with the Linux GPIO subsystem. The old driver has been
moved to staging, and will be removed altogether around 2.6.40.
Please test the new driver, and ensure that the functionality you
need and any bugfixes from the old driver are available in the new
one.
Who: Andres Salomon <dilinger@queued.net>
--------------------------
What: remove EXPORT_SYMBOL(kernel_thread)
When: August 2006
Files: arch/*/kernel/*_ksyms.c
Check: kernel_thread
Why: kernel_thread is a low-level implementation detail. Drivers should
use the <linux/kthread.h> API instead which shields them from
implementation details and provides a higherlevel interface that
prevents bugs and code duplication
Who: Christoph Hellwig <hch@lst.de>
---------------------------
What: Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
(temporary transition config option provided until then)
The transition config option will also be removed at the same time.
When: before 2.6.19
Why: Unused symbols are both increasing the size of the kernel binary
and are often a sign of "wrong API"
Who: Arjan van de Ven <arjan@linux.intel.com>
---------------------------
What: PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
When: October 2008
Why: The stacking of class devices makes these values misleading and
inconsistent.
Class devices should not carry any of these properties, and bus
devices have SUBSYTEM and DRIVER as a replacement.
Who: Kay Sievers <kay.sievers@suse.de>
---------------------------
What: ACPI procfs interface
When: July 2008
Why: ACPI sysfs conversion should be finished by January 2008.
ACPI procfs interface will be removed in July 2008 so that
there is enough time for the user space to catch up.
Who: Zhang Rui <rui.zhang@intel.com>
---------------------------
What: CONFIG_ACPI_PROCFS_POWER
When: 2.6.39
Why: sysfs I/F for ACPI power devices, including AC and Battery,
has been working in upstream kernel since 2.6.24, Sep 2007.
In 2.6.37, we make the sysfs I/F always built in and this option
disabled by default.
Remove this option and the ACPI power procfs interface in 2.6.39.
Who: Zhang Rui <rui.zhang@intel.com>
---------------------------
What: /proc/acpi/event
When: February 2008
Why: /proc/acpi/event has been replaced by events via the input layer
and netlink since 2.6.23.
Who: Len Brown <len.brown@intel.com>
---------------------------
What: i386/x86_64 bzImage symlinks
When: April 2010
Why: The i386/x86_64 merge provides a symlink to the old bzImage
location so not yet updated user space tools, e.g. package
scripts, do not break.
Who: Thomas Gleixner <tglx@linutronix.de>
---------------------------
What: GPIO autorequest on gpio_direction_{input,output}() in gpiolib
When: February 2010
Why: All callers should use explicit gpio_request()/gpio_free().
The autorequest mechanism in gpiolib was provided mostly as a
migration aid for legacy GPIO interfaces (for SOC based GPIOs).
Those users have now largely migrated. Platforms implementing
the GPIO interfaces without using gpiolib will see no changes.
Who: David Brownell <dbrownell@users.sourceforge.net>
---------------------------
What: b43 support for firmware revision < 410
When: The schedule was July 2008, but it was decided that we are going to keep the
code as long as there are no major maintanance headaches.
So it _could_ be removed _any_ time now, if it conflicts with something new.
Why: The support code for the old firmware hurts code readability/maintainability
and slightly hurts runtime performance. Bugfixes for the old firmware
are not provided by Broadcom anymore.
Who: Michael Buesch <mb@bu3sch.de>
---------------------------
What: Ability for non root users to shm_get hugetlb pages based on mlock
resource limits
When: 2.6.31
Why: Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
have CAP_IPC_LOCK to be able to allocate shm segments backed by
huge pages. The mlock based rlimit check to allow shm hugetlb is
inconsistent with mmap based allocations. Hence it is being
deprecated.
Who: Ravikiran Thirumalai <kiran@scalex86.org>
---------------------------
What: CONFIG_THERMAL_HWMON
When: January 2009
Why: This option was introduced just to allow older lm-sensors userspace
to keep working over the upgrade to 2.6.26. At the scheduled time of
removal fixed lm-sensors (2.x or 3.x) should be readily available.
Who: Rene Herman <rene.herman@gmail.com>
---------------------------
What: Code that is now under CONFIG_WIRELESS_EXT_SYSFS
(in net/core/net-sysfs.c)
When: After the only user (hal) has seen a release with the patches
for enough time, probably some time in 2010.
Why: Over 1K .text/.data size reduction, data is available in other
ways (ioctls)
Who: Johannes Berg <johannes@sipsolutions.net>
---------------------------
What: sysfs ui for changing p4-clockmod parameters
When: September 2009
Why: See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
e088e4c9cdb618675874becb91b2fd581ee707e6.
Removal is subject to fixing any remaining bugs in ACPI which may
cause the thermal throttling not to happen at the right time.
Who: Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
-----------------------------
What: fakephp and associated sysfs files in /sys/bus/pci/slots/
When: 2011
Why: In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
represent a machine's physical PCI slots. The change in semantics
had userspace implications, as the hotplug core no longer allowed
drivers to create multiple sysfs files per physical slot (required
for multi-function devices, e.g.). fakephp was seen as a developer's
tool only, and its interface changed. Too late, we learned that
there were some users of the fakephp interface.
In 2.6.30, the original fakephp interface was restored. At the same
time, the PCI core gained the ability that fakephp provided, namely
function-level hot-remove and hot-add.
Since the PCI core now provides the same functionality, exposed in:
/sys/bus/pci/rescan
/sys/bus/pci/devices/.../remove
/sys/bus/pci/devices/.../rescan
there is no functional reason to maintain fakephp as well.
We will keep the existing module so that 'modprobe fakephp' will
present the old /sys/bus/pci/slots/... interface for compatibility,
but users are urged to migrate their applications to the API above.
After a reasonable transition period, we will remove the legacy
fakephp interface.
Who: Alex Chiang <achiang@hp.com>
---------------------------
What: CONFIG_RFKILL_INPUT
When: 2.6.33
Why: Should be implemented in userspace, policy daemon.
Who: Johannes Berg <johannes@sipsolutions.net>
----------------------------
What: sound-slot/service-* module aliases and related clutters in
sound/sound_core.c
When: August 2010
Why: OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
(14) and requests modules using custom sound-slot/service-*
module aliases. The only benefit of doing this is allowing
use of custom module aliases which might as well be considered
a bug at this point. This preemptive claiming prevents
alternative OSS implementations.
Till the feature is removed, the kernel will be requesting
both sound-slot/service-* and the standard char-major-* module
aliases and allow turning off the pre-claiming selectively via
CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
kernel parameter.
After the transition phase is complete, both the custom module
aliases and switches to disable it will go away. This removal
will also allow making ALSA OSS emulation independent of
sound_core. The dependency will be broken then too.
Who: Tejun Heo <tj@kernel.org>
----------------------------
What: sysfs-class-rfkill state file
When: Feb 2014
Files: net/rfkill/core.c
Why: Documented as obsolete since Feb 2010. This file is limited to 3
states while the rfkill drivers can have 4 states.
Who: anybody or Florian Mickler <florian@mickler.org>
----------------------------
What: sysfs-class-rfkill claim file
When: Feb 2012
Files: net/rfkill/core.c
Why: It is not possible to claim an rfkill driver since 2007. This is
Documented as obsolete since Feb 2010.
Who: anybody or Florian Mickler <florian@mickler.org>
----------------------------
What: KVM paravirt mmu host support
When: January 2011
Why: The paravirt mmu host support is slower than non-paravirt mmu, both
on newer and older hardware. It is already not exposed to the guest,
and kept only for live migration purposes.
Who: Avi Kivity <avi@redhat.com>
----------------------------
What: iwlwifi 50XX module parameters
When: 2.6.40
Why: The "..50" modules parameters were used to configure 5000 series and
up devices; different set of module parameters also available for 4965
with same functionalities. Consolidate both set into single place
in drivers/net/wireless/iwlwifi/iwl-agn.c
Who: Wey-Yi Guy <wey-yi.w.guy@intel.com>
----------------------------
What: iwl4965 alias support
When: 2.6.40
Why: Internal alias support has been present in module-init-tools for some
time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
with no impact.
Who: Wey-Yi Guy <wey-yi.w.guy@intel.com>
---------------------------
What: xt_NOTRACK
Files: net/netfilter/xt_NOTRACK.c
When: April 2011
Why: Superseded by xt_CT
Who: Netfilter developer team <netfilter-devel@vger.kernel.org>
----------------------------
What: IRQF_DISABLED
When: 2.6.36
Why: The flag is a NOOP as we run interrupt handlers with interrupts disabled
Who: Thomas Gleixner <tglx@linutronix.de>
----------------------------
What: PCI DMA unmap state API
When: August 2012
Why: PCI DMA unmap state API (include/linux/pci-dma.h) was replaced
with DMA unmap state API (DMA unmap state API can be used for
any bus).
Who: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
----------------------------
What: DMA_xxBIT_MASK macros
When: Jun 2011
Why: DMA_xxBIT_MASK macros were replaced with DMA_BIT_MASK() macros.
Who: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
----------------------------
What: iwlwifi disable_hw_scan module parameters
When: 2.6.40
Why: Hareware scan is the prefer method for iwlwifi devices for
scanning operation. Remove software scan support for all the
iwlwifi devices.
Who: Wey-Yi Guy <wey-yi.w.guy@intel.com>
----------------------------
What: access to nfsd auth cache through sys_nfsservctl or '.' files
in the 'nfsd' filesystem.
When: 2.6.40
Why: This is a legacy interface which have been replaced by a more
dynamic cache. Continuing to maintain this interface is an
unnecessary burden.
Who: NeilBrown <neilb@suse.de>
----------------------------
What: cancel_rearming_delayed_work[queue]()
When: 2.6.39
Why: The functions have been superceded by cancel_delayed_work_sync()
quite some time ago. The conversion is trivial and there is no
in-kernel user left.
Who: Tejun Heo <tj@kernel.org>
----------------------------
What: Legacy, non-standard chassis intrusion detection interface.
When: June 2011
Why: The adm9240, w83792d and w83793 hardware monitoring drivers have
legacy interfaces for chassis intrusion detection. A standard
interface has been added to each driver, so the legacy interface
can be removed.
Who: Jean Delvare <khali@linux-fr.org>
----------------------------
What: xt_connlimit rev 0
When: 2012
Who: Jan Engelhardt <jengelh@medozas.de>
Files: net/netfilter/xt_connlimit.c
----------------------------
What: noswapaccount kernel command line parameter
When: 2.6.40
Why: The original implementation of memsw feature enabled by
CONFIG_CGROUP_MEM_RES_CTLR_SWAP could be disabled by the noswapaccount
kernel parameter (introduced in 2.6.29-rc1). Later on, this decision
turned out to be not ideal because we cannot have the feature compiled
in and disabled by default and let only interested to enable it
(e.g. general distribution kernels might need it). Therefore we have
added swapaccount[=0|1] parameter (introduced in 2.6.37) which provides
the both possibilities. If we remove noswapaccount we will have
less command line parameters with the same functionality and we
can also cleanup the parameter handling a bit ().
Who: Michal Hocko <mhocko@suse.cz>
----------------------------
What: ipt_addrtype match include file
When: 2012
Why: superseded by xt_addrtype
Who: Florian Westphal <fw@strlen.de>
Files: include/linux/netfilter_ipv4/ipt_addrtype.h
----------------------------
What: i2c_driver.attach_adapter
i2c_driver.detach_adapter
When: September 2011
Why: These legacy callbacks should no longer be used as i2c-core offers
a variety of preferable alternative ways to instantiate I2C devices.
Who: Jean Delvare <khali@linux-fr.org>
----------------------------
What: Support for UVCIOC_CTRL_ADD in the uvcvideo driver
When: 2.6.42
Why: The information passed to the driver by this ioctl is now queried
dynamically from the device.
Who: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
----------------------------
What: Support for UVCIOC_CTRL_MAP_OLD in the uvcvideo driver
When: 2.6.42
Why: Used only by applications compiled against older driver versions.
Superseded by UVCIOC_CTRL_MAP which supports V4L2 menu controls.
Who: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
----------------------------
What: Support for UVCIOC_CTRL_GET and UVCIOC_CTRL_SET in the uvcvideo driver
When: 2.6.42
Why: Superseded by the UVCIOC_CTRL_QUERY ioctl.
Who: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
----------------------------
What: For VIDIOC_S_FREQUENCY the type field must match the device node's type.
If not, return -EINVAL.
When: 3.2
Why: It makes no sense to switch the tuner to radio mode by calling
VIDIOC_S_FREQUENCY on a video node, or to switch the tuner to tv mode by
calling VIDIOC_S_FREQUENCY on a radio node. This is the first step of a
move to more consistent handling of tv and radio tuners.
Who: Hans Verkuil <hans.verkuil@cisco.com>
----------------------------
What: Opening a radio device node will no longer automatically switch the
tuner mode from tv to radio.
When: 3.3
Why: Just opening a V4L device should not change the state of the hardware
like that. It's very unexpected and against the V4L spec. Instead, you
switch to radio mode by calling VIDIOC_S_FREQUENCY. This is the second
and last step of the move to consistent handling of tv and radio tuners.
Who: Hans Verkuil <hans.verkuil@cisco.com>
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