Documentation/feature-removal-schedule.txt

   1 The following is a list of files and features that are going to be
   2 removed in the kernel source tree.  Every entry should contain what
   3 exactly is going away, why it is happening, and who is going to be doing
   4 the work.  When the feature is removed from the kernel, it should also
   5 be removed from this file.  The suggested deprecation period is 3 releases.
   6
   7 ---------------------------
   8
   9 What:   ddebug_query="query" boot cmdline param
  10 When:   v3.8
  11 Why:    obsoleted by dyndbg="query" and module.dyndbg="query"
  12 Who:    Jim Cromie <jim.cromie@gmail.com>, Jason Baron <jbaron@redhat.com>
  13
  14 ---------------------------
  15
  16 What:   CONFIG_APM_CPU_IDLE, and its ability to call APM BIOS in idle
  17 When:   2012
  18 Why:    This optional sub-feature of APM is of dubious reliability,
  19         and ancient APM laptops are likely better served by calling HLT.
  20         Deleting CONFIG_APM_CPU_IDLE allows x86 to stop exporting
  21         the pm_idle function pointer to modules.
  22 Who:    Len Brown <len.brown@intel.com>
  23
  24 ----------------------------
  25
  26 What:   x86_32 "no-hlt" cmdline param
  27 When:   2012
  28 Why:    remove a branch from idle path, simplify code used by everybody.
  29         This option disabled the use of HLT in idle and machine_halt()
  30         for hardware that was flakey 15-years ago.  Today we have
  31         "idle=poll" that removed HLT from idle, and so if such a machine
  32         is still running the upstream kernel, "idle=poll" is likely sufficient.
  33 Who:    Len Brown <len.brown@intel.com>
  34
  35 ----------------------------
  36
  37 What:   x86 "idle=mwait" cmdline param
  38 When:   2012
  39 Why:    simplify x86 idle code
  40 Who:    Len Brown <len.brown@intel.com>
  41
  42 ----------------------------
  43
  44 What:   PRISM54
  45 When:   2.6.34
  46
  47 Why:    prism54 FullMAC PCI / Cardbus devices used to be supported only by the
  48         prism54 wireless driver. After Intersil stopped selling these
  49         devices in preference for the newer more flexible SoftMAC devices
  50         a SoftMAC device driver was required and prism54 did not support
  51         them. The p54pci driver now exists and has been present in the kernel for
  52         a while. This driver supports both SoftMAC devices and FullMAC devices.
  53         The main difference between these devices was the amount of memory which
  54         could be used for the firmware. The SoftMAC devices support a smaller
  55         amount of memory. Because of this the SoftMAC firmware fits into FullMAC
  56         devices's memory. p54pci supports not only PCI / Cardbus but also USB
  57         and SPI. Since p54pci supports all devices prism54 supports
  58         you will have a conflict. I'm not quite sure how distributions are
  59         handling this conflict right now. prism54 was kept around due to
  60         claims users may experience issues when using the SoftMAC driver.
  61         Time has passed users have not reported issues. If you use prism54
  62         and for whatever reason you cannot use p54pci please let us know!
  63         E-mail us at: linux-wireless@vger.kernel.org
  64
  65         For more information see the p54 wiki page:
  66
  67         http://wireless.kernel.org/en/users/Drivers/p54
  68
  69 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  70
  71 ---------------------------
  72
  73 What:   IRQF_SAMPLE_RANDOM
  74 Check:  IRQF_SAMPLE_RANDOM
  75 When:   July 2009
  76
  77 Why:    Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
  78         sources in the kernel's current entropy model. To resolve this, every
  79         input point to the kernel's entropy pool needs to better document the
  80         type of entropy source it actually is. This will be replaced with
  81         additional add_*_randomness functions in drivers/char/random.c
  82
  83 Who:    Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
  84
  85 ---------------------------
  86
  87 What:   The ieee80211_regdom module parameter
  88 When:   March 2010 / desktop catchup
  89
  90 Why:    This was inherited by the CONFIG_WIRELESS_OLD_REGULATORY code,
  91         and currently serves as an option for users to define an
  92         ISO / IEC 3166 alpha2 code for the country they are currently
  93         present in. Although there are userspace API replacements for this
  94         through nl80211 distributions haven't yet caught up with implementing
  95         decent alternatives through standard GUIs. Although available as an
  96         option through iw or wpa_supplicant its just a matter of time before
  97         distributions pick up good GUI options for this. The ideal solution
  98         would actually consist of intelligent designs which would do this for
  99         the user automatically even when travelling through different countries.
 100         Until then we leave this module parameter as a compromise.
 101
 102         When userspace improves with reasonable widely-available alternatives for
 103         this we will no longer need this module parameter. This entry hopes that
 104         by the super-futuristically looking date of "March 2010" we will have
 105         such replacements widely available.
 106
 107 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
 108
 109 ---------------------------
 110
 111 What:   dev->power.power_state
 112 When:   July 2007
 113 Why:    Broken design for runtime control over driver power states, confusing
 114         driver-internal runtime power management with:  mechanisms to support
 115         system-wide sleep state transitions; event codes that distinguish
 116         different phases of swsusp "sleep" transitions; and userspace policy
 117         inputs.  This framework was never widely used, and most attempts to
 118         use it were broken.  Drivers should instead be exposing domain-specific
 119         interfaces either to kernel or to userspace.
 120 Who:    Pavel Machek <pavel@ucw.cz>
 121
 122 ---------------------------
 123
 124 What:   /proc/<pid>/oom_adj
 125 When:   August 2012
 126 Why:    /proc/<pid>/oom_adj allows userspace to influence the oom killer's
 127         badness heuristic used to determine which task to kill when the kernel
 128         is out of memory.
 129
 130         The badness heuristic has since been rewritten since the introduction of
 131         this tunable such that its meaning is deprecated.  The value was
 132         implemented as a bitshift on a score generated by the badness()
 133         function that did not have any precise units of measure.  With the
 134         rewrite, the score is given as a proportion of available memory to the
 135         task allocating pages, so using a bitshift which grows the score
 136         exponentially is, thus, impossible to tune with fine granularity.
 137
 138         A much more powerful interface, /proc/<pid>/oom_score_adj, was
 139         introduced with the oom killer rewrite that allows users to increase or
 140         decrease the badness score linearly.  This interface will replace
 141         /proc/<pid>/oom_adj.
 142
 143         A warning will be emitted to the kernel log if an application uses this
 144         deprecated interface.  After it is printed once, future warnings will be
 145         suppressed until the kernel is rebooted.
 146
 147 ---------------------------
 148
 149 What:   remove EXPORT_SYMBOL(kernel_thread)
 150 When:   August 2006
 151 Files:  arch/*/kernel/*_ksyms.c
 152 Check:  kernel_thread
 153 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 154         use the <linux/kthread.h> API instead which shields them from
 155         implementation details and provides a higherlevel interface that
 156         prevents bugs and code duplication
 157 Who:    Christoph Hellwig <hch@lst.de>
 158
 159 ---------------------------
 160
 161 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 162         (temporary transition config option provided until then)
 163         The transition config option will also be removed at the same time.
 164 When:   before 2.6.19
 165 Why:    Unused symbols are both increasing the size of the kernel binary
 166         and are often a sign of "wrong API"
 167 Who:    Arjan van de Ven <arjan@linux.intel.com>
 168
 169 ---------------------------
 170
 171 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 172 When:   October 2008
 173 Why:    The stacking of class devices makes these values misleading and
 174         inconsistent.
 175         Class devices should not carry any of these properties, and bus
 176         devices have SUBSYTEM and DRIVER as a replacement.
 177 Who:    Kay Sievers <kay.sievers@suse.de>
 178
 179 ---------------------------
 180
 181 What:   ACPI procfs interface
 182 When:   July 2008
 183 Why:    ACPI sysfs conversion should be finished by January 2008.
 184         ACPI procfs interface will be removed in July 2008 so that
 185         there is enough time for the user space to catch up.
 186 Who:    Zhang Rui <rui.zhang@intel.com>
 187
 188 ---------------------------
 189
 190 What:   CONFIG_ACPI_PROCFS_POWER
 191 When:   2.6.39
 192 Why:    sysfs I/F for ACPI power devices, including AC and Battery,
 193         has been working in upstream kernel since 2.6.24, Sep 2007.
 194         In 2.6.37, we make the sysfs I/F always built in and this option
 195         disabled by default.
 196         Remove this option and the ACPI power procfs interface in 2.6.39.
 197 Who:    Zhang Rui <rui.zhang@intel.com>
 198
 199 ---------------------------
 200
 201 What:   /proc/acpi/event
 202 When:   February 2008
 203 Why:    /proc/acpi/event has been replaced by events via the input layer
 204         and netlink since 2.6.23.
 205 Who:    Len Brown <len.brown@intel.com>
 206
 207 ---------------------------
 208
 209 What:   i386/x86_64 bzImage symlinks
 210 When:   April 2010
 211
 212 Why:    The i386/x86_64 merge provides a symlink to the old bzImage
 213         location so not yet updated user space tools, e.g. package
 214         scripts, do not break.
 215 Who:    Thomas Gleixner <tglx@linutronix.de>
 216
 217 ---------------------------
 218
 219 What:   GPIO autorequest on gpio_direction_{input,output}() in gpiolib
 220 When:   February 2010
 221 Why:    All callers should use explicit gpio_request()/gpio_free().
 222         The autorequest mechanism in gpiolib was provided mostly as a
 223         migration aid for legacy GPIO interfaces (for SOC based GPIOs).
 224         Those users have now largely migrated.  Platforms implementing
 225         the GPIO interfaces without using gpiolib will see no changes.
 226 Who:    David Brownell <dbrownell@users.sourceforge.net>
 227 ---------------------------
 228
 229 What:   b43 support for firmware revision < 410
 230 When:   The schedule was July 2008, but it was decided that we are going to keep the
 231         code as long as there are no major maintanance headaches.
 232         So it _could_ be removed _any_ time now, if it conflicts with something new.
 233 Why:    The support code for the old firmware hurts code readability/maintainability
 234         and slightly hurts runtime performance. Bugfixes for the old firmware
 235         are not provided by Broadcom anymore.
 236 Who:    Michael Buesch <m@bues.ch>
 237
 238 ---------------------------
 239
 240 What:   Ability for non root users to shm_get hugetlb pages based on mlock
 241         resource limits
 242 When:   2.6.31
 243 Why:    Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
 244         have CAP_IPC_LOCK to be able to allocate shm segments backed by
 245         huge pages.  The mlock based rlimit check to allow shm hugetlb is
 246         inconsistent with mmap based allocations.  Hence it is being
 247         deprecated.
 248 Who:    Ravikiran Thirumalai <kiran@scalex86.org>
 249
 250 ---------------------------
 251
 252 What:   Code that is now under CONFIG_WIRELESS_EXT_SYSFS
 253         (in net/core/net-sysfs.c)
 254 When:   3.5
 255 Why:    Over 1K .text/.data size reduction, data is available in other
 256         ways (ioctls)
 257 Who:    Johannes Berg <johannes@sipsolutions.net>
 258
 259 ---------------------------
 260
 261 What:   sysfs ui for changing p4-clockmod parameters
 262 When:   September 2009
 263 Why:    See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
 264         e088e4c9cdb618675874becb91b2fd581ee707e6.
 265         Removal is subject to fixing any remaining bugs in ACPI which may
 266         cause the thermal throttling not to happen at the right time.
 267 Who:    Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
 268
 269 -----------------------------
 270
 271 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 272 When:   2011
 273 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 274         represent a machine's physical PCI slots. The change in semantics
 275         had userspace implications, as the hotplug core no longer allowed
 276         drivers to create multiple sysfs files per physical slot (required
 277         for multi-function devices, e.g.). fakephp was seen as a developer's
 278         tool only, and its interface changed. Too late, we learned that
 279         there were some users of the fakephp interface.
 280
 281         In 2.6.30, the original fakephp interface was restored. At the same
 282         time, the PCI core gained the ability that fakephp provided, namely
 283         function-level hot-remove and hot-add.
 284
 285         Since the PCI core now provides the same functionality, exposed in:
 286
 287                 /sys/bus/pci/rescan
 288                 /sys/bus/pci/devices/.../remove
 289                 /sys/bus/pci/devices/.../rescan
 290
 291         there is no functional reason to maintain fakephp as well.
 292
 293         We will keep the existing module so that 'modprobe fakephp' will
 294         present the old /sys/bus/pci/slots/... interface for compatibility,
 295         but users are urged to migrate their applications to the API above.
 296
 297         After a reasonable transition period, we will remove the legacy
 298         fakephp interface.
 299 Who:    Alex Chiang <achiang@hp.com>
 300
 301 ---------------------------
 302
 303 What:   CONFIG_RFKILL_INPUT
 304 When:   2.6.33
 305 Why:    Should be implemented in userspace, policy daemon.
 306 Who:    Johannes Berg <johannes@sipsolutions.net>
 307
 308 ----------------------------
 309
 310 What:   sound-slot/service-* module aliases and related clutters in
 311         sound/sound_core.c
 312 When:   August 2010
 313 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 314         (14) and requests modules using custom sound-slot/service-*
 315         module aliases.  The only benefit of doing this is allowing
 316         use of custom module aliases which might as well be considered
 317         a bug at this point.  This preemptive claiming prevents
 318         alternative OSS implementations.
 319
 320         Till the feature is removed, the kernel will be requesting
 321         both sound-slot/service-* and the standard char-major-* module
 322         aliases and allow turning off the pre-claiming selectively via
 323         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 324         kernel parameter.
 325
 326         After the transition phase is complete, both the custom module
 327         aliases and switches to disable it will go away.  This removal
 328         will also allow making ALSA OSS emulation independent of
 329         sound_core.  The dependency will be broken then too.
 330 Who:    Tejun Heo <tj@kernel.org>
 331
 332 ----------------------------
 333
 334 What:   sysfs-class-rfkill state file
 335 When:   Feb 2014
 336 Files:  net/rfkill/core.c
 337 Why:    Documented as obsolete since Feb 2010. This file is limited to 3
 338         states while the rfkill drivers can have 4 states.
 339 Who:    anybody or Florian Mickler <florian@mickler.org>
 340
 341 ----------------------------
 342
 343 What:   sysfs-class-rfkill claim file
 344 When:   Feb 2012
 345 Files:  net/rfkill/core.c
 346 Why:    It is not possible to claim an rfkill driver since 2007. This is
 347         Documented as obsolete since Feb 2010.
 348 Who:    anybody or Florian Mickler <florian@mickler.org>
 349
 350 ----------------------------
 351
 352 What:   iwlwifi 50XX module parameters
 353 When:   3.0
 354 Why:    The "..50" modules parameters were used to configure 5000 series and
 355         up devices; different set of module parameters also available for 4965
 356         with same functionalities. Consolidate both set into single place
 357         in drivers/net/wireless/iwlwifi/iwl-agn.c
 358
 359 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 360
 361 ----------------------------
 362
 363 What:   iwl4965 alias support
 364 When:   3.0
 365 Why:    Internal alias support has been present in module-init-tools for some
 366         time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
 367         with no impact.
 368
 369 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 370
 371 ---------------------------
 372
 373 What:   xt_NOTRACK
 374 Files:  net/netfilter/xt_NOTRACK.c
 375 When:   April 2011
 376 Why:    Superseded by xt_CT
 377 Who:    Netfilter developer team <netfilter-devel@vger.kernel.org>
 378
 379 ----------------------------
 380
 381 What:   IRQF_DISABLED
 382 When:   2.6.36
 383 Why:    The flag is a NOOP as we run interrupt handlers with interrupts disabled
 384 Who:    Thomas Gleixner <tglx@linutronix.de>
 385
 386 ----------------------------
 387
 388 What:   PCI DMA unmap state API
 389 When:   August 2012
 390 Why:    PCI DMA unmap state API (include/linux/pci-dma.h) was replaced
 391         with DMA unmap state API (DMA unmap state API can be used for
 392         any bus).
 393 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 394
 395 ----------------------------
 396
 397 What:   iwlwifi disable_hw_scan module parameters
 398 When:   3.0
 399 Why:    Hareware scan is the prefer method for iwlwifi devices for
 400         scanning operation. Remove software scan support for all the
 401         iwlwifi devices.
 402
 403 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 404
 405 ----------------------------
 406
 407 What:   Legacy, non-standard chassis intrusion detection interface.
 408 When:   June 2011
 409 Why:    The adm9240, w83792d and w83793 hardware monitoring drivers have
 410         legacy interfaces for chassis intrusion detection. A standard
 411         interface has been added to each driver, so the legacy interface
 412         can be removed.
 413 Who:    Jean Delvare <khali@linux-fr.org>
 414
 415 ----------------------------
 416
 417 What:   xt_connlimit rev 0
 418 When:   2012
 419 Who:    Jan Engelhardt <jengelh@medozas.de>
 420 Files:  net/netfilter/xt_connlimit.c
 421
 422 ----------------------------
 423
 424 What:   ipt_addrtype match include file
 425 When:   2012
 426 Why:    superseded by xt_addrtype
 427 Who:    Florian Westphal <fw@strlen.de>
 428 Files:  include/linux/netfilter_ipv4/ipt_addrtype.h
 429
 430 ----------------------------
 431
 432 What:   i2c_driver.attach_adapter
 433         i2c_driver.detach_adapter
 434 When:   September 2011
 435 Why:    These legacy callbacks should no longer be used as i2c-core offers
 436         a variety of preferable alternative ways to instantiate I2C devices.
 437 Who:    Jean Delvare <khali@linux-fr.org>
 438
 439 ----------------------------
 440
 441 What:   Opening a radio device node will no longer automatically switch the
 442         tuner mode from tv to radio.
 443 When:   3.3
 444 Why:    Just opening a V4L device should not change the state of the hardware
 445         like that. It's very unexpected and against the V4L spec. Instead, you
 446         switch to radio mode by calling VIDIOC_S_FREQUENCY. This is the second
 447         and last step of the move to consistent handling of tv and radio tuners.
 448 Who:    Hans Verkuil <hans.verkuil@cisco.com>
 449
 450 ----------------------------
 451
 452 What:   g_file_storage driver
 453 When:   3.8
 454 Why:    This driver has been superseded by g_mass_storage.
 455 Who:    Alan Stern <stern@rowland.harvard.edu>
 456
 457 ----------------------------
 458
 459 What:   threeg and interface sysfs files in /sys/devices/platform/acer-wmi
 460 When:   2012
 461 Why:    In 3.0, we can now autodetect internal 3G device and already have
 462         the threeg rfkill device. So, we plan to remove threeg sysfs support
 463         for it's no longer necessary.
 464
 465         We also plan to remove interface sysfs file that exposed which ACPI-WMI
 466         interface that was used by acer-wmi driver. It will replaced by
 467         information log when acer-wmi initial.
 468 Who:    Lee, Chun-Yi <jlee@novell.com>
 469
 470 ---------------------------
 471
 472 What:   /sys/devices/platform/_UDC_/udc/_UDC_/is_dualspeed file and
 473         is_dualspeed line in /sys/devices/platform/ci13xxx_*/udc/device file.
 474 When:   3.8
 475 Why:    The is_dualspeed file is superseded by maximum_speed in the same
 476         directory and is_dualspeed line in device file is superseded by
 477         max_speed line in the same file.
 478
 479         The maximum_speed/max_speed specifies maximum speed supported by UDC.
 480         To check if dualspeeed is supported, check if the value is >= 3.
 481         Various possible speeds are defined in <linux/usb/ch9.h>.
 482 Who:    Michal Nazarewicz <mina86@mina86.com>
 483
 484 ----------------------------
 485
 486 What:   The XFS nodelaylog mount option
 487 When:   3.3
 488 Why:    The delaylog mode that has been the default since 2.6.39 has proven
 489         stable, and the old code is in the way of additional improvements in
 490         the log code.
 491 Who:    Christoph Hellwig <hch@lst.de>
 492
 493 ----------------------------
 494
 495 What:   iwlagn alias support
 496 When:   3.5
 497 Why:    The iwlagn module has been renamed iwlwifi.  The alias will be around
 498         for backward compatibility for several cycles and then dropped.
 499 Who:    Don Fry <donald.h.fry@intel.com>
 500
 501 ----------------------------
 502
 503 What:   pci_scan_bus_parented()
 504 When:   3.5
 505 Why:    The pci_scan_bus_parented() interface creates a new root bus.  The
 506         bus is created with default resources (ioport_resource and
 507         iomem_resource) that are always wrong, so we rely on arch code to
 508         correct them later.  Callers of pci_scan_bus_parented() should
 509         convert to using pci_scan_root_bus() so they can supply a list of
 510         bus resources when the bus is created.
 511 Who:    Bjorn Helgaas <bhelgaas@google.com>
 512
 513 ----------------------------
 514
 515 What:   Low Performance USB Block driver ("CONFIG_BLK_DEV_UB")
 516 When:   3.6
 517 Why:    This driver provides support for USB storage devices like "USB
 518         sticks". As of now, it is deactivated in Debian, Fedora and
 519         Ubuntu. All current users can switch over to usb-storage
 520         (CONFIG_USB_STORAGE) which only drawback is the additional SCSI
 521         stack.
 522 Who:    Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
 523
 524 ----------------------------
 525
 526 What:   kmap_atomic(page, km_type)
 527 When:   3.5
 528 Why:    The old kmap_atomic() with two arguments is deprecated, we only
 529         keep it for backward compatibility for few cycles and then drop it.
 530 Who:    Cong Wang <amwang@redhat.com>
 531
 532 ----------------------------
 533
 534 What:   get_robust_list syscall
 535 When:   2013
 536 Why:    There appear to be no production users of the get_robust_list syscall,
 537         and it runs the risk of leaking address locations, allowing the bypass
 538         of ASLR. It was only ever intended for debugging, so it should be
 539         removed.
 540 Who:    Kees Cook <keescook@chromium.org>
 541
 542 ----------------------------
 543
 544 What:   setitimer accepts user NULL pointer (value)
 545 When:   3.6
 546 Why:    setitimer is not returning -EFAULT if user pointer is NULL. This
 547         violates the spec.
 548 Who:    Sasikantha Babu <sasikanth.v19@gmail.com>
 549
 550 ----------------------------
 551
 552 What:   V4L2_CID_HCENTER, V4L2_CID_VCENTER V4L2 controls
 553 When:   3.7
 554 Why:    The V4L2_CID_VCENTER, V4L2_CID_HCENTER controls have been deprecated
 555         for about 4 years and they are not used by any mainline driver.
 556         There are newer controls (V4L2_CID_PAN*, V4L2_CID_TILT*) that provide
 557         similar functionality.
 558 Who:    Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
 559
 560 ----------------------------
 561
 562 What:   cgroup option updates via remount
 563 When:   March 2013
 564 Why:    Remount currently allows changing bound subsystems and
 565         release_agent.  Rebinding is hardly useful as it only works
 566         when the hierarchy is empty and release_agent itself should be
 567         replaced with conventional fsnotify.
 568
 569 ----------------------------