Get rid of Documentation/feature-removal.txt (9c0ece06) · Commits · 戴 / test

Documentation/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. The suggested deprecation period is 3 releases.

		---------------------------

		What: ddebug_query="query" boot cmdline param
		When: v3.8
		Why: obsoleted by dyndbg="query" and module.dyndbg="query"
		Who: Jim Cromie <jim.cromie@gmail.com>, Jason Baron <jbaron@redhat.com>

		---------------------------

		What: /proc/sys/vm/nr_pdflush_threads
		When: 2012
		Why: Since pdflush is deprecated, the interface exported in /proc/sys/vm/
		should be removed.
		Who: Wanpeng Li <liwp@linux.vnet.ibm.com>

		---------------------------

		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: 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: /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: 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 <m@bues.ch>

		---------------------------

		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: 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: 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: iwlwifi 50XX module parameters
		When: 3.0
		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: 3.0
		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: iwlwifi disable_hw_scan module parameters
		When: 3.0
		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: 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: 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>

		----------------------------

		What: CONFIG_CFG80211_WEXT
		When: as soon as distributions ship new wireless tools, ie. wpa_supplicant 1.0
		and NetworkManager/connman/etc. that are able to use nl80211
		Why: Wireless extensions are deprecated, and userland tools are moving to
		using nl80211. New drivers are no longer using wireless extensions,
		and while there might still be old drivers, both new drivers and new
		userland no longer needs them and they can't be used for an feature
		developed in the past couple of years. As such, compatibility with
		wireless extensions in new drivers will be removed.
		Who: Johannes Berg <johannes@sipsolutions.net>

		----------------------------

		What: g_file_storage driver
		When: 3.8
		Why: This driver has been superseded by g_mass_storage.
		Who: Alan Stern <stern@rowland.harvard.edu>

		----------------------------

		What: threeg and interface sysfs files in /sys/devices/platform/acer-wmi
		When: 2012
		Why: In 3.0, we can now autodetect internal 3G device and already have
		the threeg rfkill device. So, we plan to remove threeg sysfs support
		for it's no longer necessary.

		We also plan to remove interface sysfs file that exposed which ACPI-WMI
		interface that was used by acer-wmi driver. It will replaced by
		information log when acer-wmi initial.
		Who: Lee, Chun-Yi <jlee@novell.com>

		---------------------------

		What: /sys/devices/platform/_UDC_/udc/_UDC_/is_dualspeed file and
		is_dualspeed line in /sys/devices/platform/ci13xxx_*/udc/device file.
		When: 3.8
		Why: The is_dualspeed file is superseded by maximum_speed in the same
		directory and is_dualspeed line in device file is superseded by
		max_speed line in the same file.

		The maximum_speed/max_speed specifies maximum speed supported by UDC.
		To check if dualspeeed is supported, check if the value is >= 3.
		Various possible speeds are defined in <linux/usb/ch9.h>.
		Who: Michal Nazarewicz <mina86@mina86.com>

		----------------------------

		What: The XFS nodelaylog mount option
		When: 3.3
		Why: The delaylog mode that has been the default since 2.6.39 has proven
		stable, and the old code is in the way of additional improvements in
		the log code.
		Who: Christoph Hellwig <hch@lst.de>

		----------------------------

		What: iwlagn alias support
		When: 3.5
		Why: The iwlagn module has been renamed iwlwifi. The alias will be around
		for backward compatibility for several cycles and then dropped.
		Who: Don Fry <donald.h.fry@intel.com>

		----------------------------

		What: pci_scan_bus_parented()
		When: 3.5
		Why: The pci_scan_bus_parented() interface creates a new root bus. The
		bus is created with default resources (ioport_resource and
		iomem_resource) that are always wrong, so we rely on arch code to
		correct them later. Callers of pci_scan_bus_parented() should
		convert to using pci_scan_root_bus() so they can supply a list of
		bus resources when the bus is created.
		Who: Bjorn Helgaas <bhelgaas@google.com>

		----------------------------

		What: get_robust_list syscall
		When: 2013
		Why: There appear to be no production users of the get_robust_list syscall,
		and it runs the risk of leaking address locations, allowing the bypass
		of ASLR. It was only ever intended for debugging, so it should be
		removed.
		Who: Kees Cook <keescook@chromium.org>

		----------------------------

		What: Removing the pn544 raw driver.
		When: 3.6
		Why: With the introduction of the NFC HCI and SHDL kernel layers, pn544.c
		is being replaced by pn544_hci.c which is accessible through the netlink
		and socket NFC APIs. Moreover, pn544.c is outdated and does not seem to
		work properly with the latest Android stacks.
		Having 2 drivers for the same hardware is confusing and as such we
		should only keep the one following the kernel NFC APIs.
		Who: Samuel Ortiz <sameo@linux.intel.com>

		----------------------------

		What: setitimer accepts user NULL pointer (value)
		When: 3.6
		Why: setitimer is not returning -EFAULT if user pointer is NULL. This
		violates the spec.
		Who: Sasikantha Babu <sasikanth.v19@gmail.com>

		----------------------------

		What: remove bogus DV presets V4L2_DV_1080I29_97, V4L2_DV_1080I30 and
		V4L2_DV_1080I25
		When: 3.6
		Why: These HDTV formats do not exist and were added by a confused mind
		(that was me, to be precise...)
		Who: Hans Verkuil <hans.verkuil@cisco.com>

		----------------------------

		What: V4L2_CID_HCENTER, V4L2_CID_VCENTER V4L2 controls
		When: 3.7
		Why: The V4L2_CID_VCENTER, V4L2_CID_HCENTER controls have been deprecated
		for about 4 years and they are not used by any mainline driver.
		There are newer controls (V4L2_CID_PAN, V4L2_CID_TILT) that provide
		similar functionality.
		Who: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>

		----------------------------

		What: cgroup option updates via remount
		When: March 2013
		Why: Remount currently allows changing bound subsystems and
		release_agent. Rebinding is hardly useful as it only works
		when the hierarchy is empty and release_agent itself should be
		replaced with conventional fsnotify.

		----------------------------

		What: xt_recent rev 0
		When: 2013
		Who: Pablo Neira Ayuso <pablo@netfilter.org>
		Files: net/netfilter/xt_recent.c

		----------------------------

		What: KVM debugfs statistics
		When: 2013
		Why: KVM tracepoints provide mostly equivalent information in a much more
		flexible fashion.

		----------------------------

		What: at91-mci driver ("CONFIG_MMC_AT91")
		When: 3.8
		Why: There are two mci drivers: at91-mci and atmel-mci. The PDC support
		was added to atmel-mci as a first step to support more chips.
		Then at91-mci was kept only for old IP versions (on at91rm9200 and
		at91sam9261). The support of these IP versions has just been added
		to atmel-mci, so atmel-mci can be used for all chips.
		Who: Ludovic Desroches <ludovic.desroches@atmel.com>

		----------------------------

		What: net/wanrouter/
		When: June 2013
		Why: Unsupported/unmaintained/unused since 2.6

		----------------------------

		What: V4L2 selections API target rectangle and flags unification, the
		following definitions will be removed: V4L2_SEL_TGT_CROP_ACTIVE,
		V4L2_SEL_TGT_COMPOSE_ACTIVE, V4L2_SUBDEV_SEL_, V4L2_SUBDEV_SEL_FLAG_
		in favor of common V4L2_SEL_TGT_* and V4L2_SEL_FLAG_* definitions.
		For more details see include/linux/v4l2-common.h.
		When: 3.8
		Why: The regular V4L2 selections and the subdev selection API originally
		defined distinct names for the target rectangles and flags - V4L2_SEL_*
		and V4L2_SUBDEV_SEL_*. Although, it turned out that the meaning of these
		target rectangles is virtually identical and the APIs were consolidated
		to use single set of names - V4L2_SEL_*. This didn't involve any ABI
		changes. Alias definitions were created for the original ones to avoid
		any instabilities in the user space interface. After few cycles these
		backward compatibility definitions will be removed.
		Who: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>

		----------------------------

		What: Using V4L2_CAP_VIDEO_CAPTURE and V4L2_CAP_VIDEO_OUTPUT flags
		to indicate a V4L2 memory-to-memory device capability
		When: 3.8
		Why: New drivers should use new V4L2_CAP_VIDEO_M2M capability flag
		to indicate a V4L2 video memory-to-memory (M2M) device and
		applications can now identify a M2M video device by checking
		for V4L2_CAP_VIDEO_M2M, with VIDIOC_QUERYCAP ioctl. Using ORed
		V4L2_CAP_VIDEO_CAPTURE and V4L2_CAP_VIDEO_OUTPUT flags for M2M
		devices is ambiguous and may lead, for example, to identifying
		a M2M device as a video capture or output device.
		Who: Sylwester Nawrocki <s.nawrocki@samsung.com>

		----------------------------

		What: OMAP private DMA implementation
		When: 2013
		Why: We have a DMA engine implementation; all users should be updated
		to use this rather than persisting with the old APIs. The old APIs
		block merging the old DMA engine implementation into the DMA
		engine driver.
		Who: Russell King <linux@arm.linux.org.uk>,
		Santosh Shilimkar <santosh.shilimkar@ti.com>

		----------------------------

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