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.
   6
   7 ---------------------------
   8
   9 What:   PRISM54
  10 When:   2.6.34
  11
  12 Why:    prism54 FullMAC PCI / Cardbus devices used to be supported only by the
  13         prism54 wireless driver. After Intersil stopped selling these
  14         devices in preference for the newer more flexible SoftMAC devices
  15         a SoftMAC device driver was required and prism54 did not support
  16         them. The p54pci driver now exists and has been present in the kernel for
  17         a while. This driver supports both SoftMAC devices and FullMAC devices.
  18         The main difference between these devices was the amount of memory which
  19         could be used for the firmware. The SoftMAC devices support a smaller
  20         amount of memory. Because of this the SoftMAC firmware fits into FullMAC
  21         devices's memory. p54pci supports not only PCI / Cardbus but also USB
  22         and SPI. Since p54pci supports all devices prism54 supports
  23         you will have a conflict. I'm not quite sure how distributions are
  24         handling this conflict right now. prism54 was kept around due to
  25         claims users may experience issues when using the SoftMAC driver.
  26         Time has passed users have not reported issues. If you use prism54
  27         and for whatever reason you cannot use p54pci please let us know!
  28         E-mail us at: linux-wireless@vger.kernel.org
  29
  30         For more information see the p54 wiki page:
  31
  32         http://wireless.kernel.org/en/users/Drivers/p54
  33
  34 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  35
  36 ---------------------------
  37
  38 What:   IRQF_SAMPLE_RANDOM
  39 Check:  IRQF_SAMPLE_RANDOM
  40 When:   July 2009
  41
  42 Why:    Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
  43         sources in the kernel's current entropy model. To resolve this, every
  44         input point to the kernel's entropy pool needs to better document the
  45         type of entropy source it actually is. This will be replaced with
  46         additional add_*_randomness functions in drivers/char/random.c
  47
  48 Who:    Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
  49
  50 ---------------------------
  51
  52 What:   Deprecated snapshot ioctls
  53 When:   2.6.36
  54
  55 Why:    The ioctls in kernel/power/user.c were marked as deprecated long time
  56         ago. Now they notify users about that so that they need to replace
  57         their userspace. After some more time, remove them completely.
  58
  59 Who:    Jiri Slaby <jirislaby@gmail.com>
  60
  61 ---------------------------
  62
  63 What:   The ieee80211_regdom module parameter
  64 When:   March 2010 / desktop catchup
  65
  66 Why:    This was inherited by the CONFIG_WIRELESS_OLD_REGULATORY code,
  67         and currently serves as an option for users to define an
  68         ISO / IEC 3166 alpha2 code for the country they are currently
  69         present in. Although there are userspace API replacements for this
  70         through nl80211 distributions haven't yet caught up with implementing
  71         decent alternatives through standard GUIs. Although available as an
  72         option through iw or wpa_supplicant its just a matter of time before
  73         distributions pick up good GUI options for this. The ideal solution
  74         would actually consist of intelligent designs which would do this for
  75         the user automatically even when travelling through different countries.
  76         Until then we leave this module parameter as a compromise.
  77
  78         When userspace improves with reasonable widely-available alternatives for
  79         this we will no longer need this module parameter. This entry hopes that
  80         by the super-futuristically looking date of "March 2010" we will have
  81         such replacements widely available.
  82
  83 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  84
  85 ---------------------------
  86
  87 What:   dev->power.power_state
  88 When:   July 2007
  89 Why:    Broken design for runtime control over driver power states, confusing
  90         driver-internal runtime power management with:  mechanisms to support
  91         system-wide sleep state transitions; event codes that distinguish
  92         different phases of swsusp "sleep" transitions; and userspace policy
  93         inputs.  This framework was never widely used, and most attempts to
  94         use it were broken.  Drivers should instead be exposing domain-specific
  95         interfaces either to kernel or to userspace.
  96 Who:    Pavel Machek <pavel@ucw.cz>
  97
  98 ---------------------------
  99
 100 What:   Video4Linux API 1 ioctls and from Video devices.
 101 When:   kernel 2.6.38
 102 Files:  include/linux/videodev.h
 103 Check:  include/linux/videodev.h
 104 Why:    V4L1 AP1 was replaced by V4L2 API during migration from 2.4 to 2.6
 105         series. The old API have lots of drawbacks and don't provide enough
 106         means to work with all video and audio standards. The newer API is
 107         already available on the main drivers and should be used instead.
 108         Newer drivers should use v4l_compat_translate_ioctl function to handle
 109         old calls, replacing to newer ones.
 110         Decoder iocts are using internally to allow video drivers to
 111         communicate with video decoders. This should also be improved to allow
 112         V4L2 calls being translated into compatible internal ioctls.
 113         Compatibility ioctls will be provided, for a while, via
 114         v4l1-compat module.
 115 Who:    Mauro Carvalho Chehab <mchehab@infradead.org>
 116
 117 ---------------------------
 118
 119 What:   Video4Linux obsolete drivers using V4L1 API
 120 When:   kernel 2.6.38
 121 Files:  drivers/staging/cpia/* drivers/staging/stradis/*
 122 Check:  drivers/staging/cpia/cpia.c drivers/staging/stradis/stradis.c
 123 Why:    There are some drivers still using V4L1 API, despite all efforts we've done
 124         to migrate. Those drivers are for obsolete hardware that the old maintainer
 125         didn't care (or not have the hardware anymore), and that no other developer
 126         could find any hardware to buy. They probably have no practical usage today,
 127         and people with such old hardware could probably keep using an older version
 128         of the kernel. Those drivers will be moved to staging on 2.6.37 and, if nobody
 129         care enough to port and test them with V4L2 API, they'll be removed on 2.6.38.
 130 Who:    Mauro Carvalho Chehab <mchehab@infradead.org>
 131
 132 ---------------------------
 133
 134 What:   sys_sysctl
 135 When:   September 2010
 136 Option: CONFIG_SYSCTL_SYSCALL
 137 Why:    The same information is available in a more convenient from
 138         /proc/sys, and none of the sysctl variables appear to be
 139         important performance wise.
 140
 141         Binary sysctls are a long standing source of subtle kernel
 142         bugs and security issues.
 143
 144         When I looked several months ago all I could find after
 145         searching several distributions were 5 user space programs and
 146         glibc (which falls back to /proc/sys) using this syscall.
 147
 148         The man page for sysctl(2) documents it as unusable for user
 149         space programs.
 150
 151         sysctl(2) is not generally ABI compatible to a 32bit user
 152         space application on a 64bit and a 32bit kernel.
 153
 154         For the last several months the policy has been no new binary
 155         sysctls and no one has put forward an argument to use them.
 156
 157         Binary sysctls issues seem to keep happening appearing so
 158         properly deprecating them (with a warning to user space) and a
 159         2 year grace warning period will mean eventually we can kill
 160         them and end the pain.
 161
 162         In the mean time individual binary sysctls can be dealt with
 163         in a piecewise fashion.
 164
 165 Who:    Eric Biederman <ebiederm@xmission.com>
 166
 167 ---------------------------
 168
 169 What:   /proc/<pid>/oom_adj
 170 When:   August 2012
 171 Why:    /proc/<pid>/oom_adj allows userspace to influence the oom killer's
 172         badness heuristic used to determine which task to kill when the kernel
 173         is out of memory.
 174
 175         The badness heuristic has since been rewritten since the introduction of
 176         this tunable such that its meaning is deprecated.  The value was
 177         implemented as a bitshift on a score generated by the badness()
 178         function that did not have any precise units of measure.  With the
 179         rewrite, the score is given as a proportion of available memory to the
 180         task allocating pages, so using a bitshift which grows the score
 181         exponentially is, thus, impossible to tune with fine granularity.
 182
 183         A much more powerful interface, /proc/<pid>/oom_score_adj, was
 184         introduced with the oom killer rewrite that allows users to increase or
 185         decrease the badness() score linearly.  This interface will replace
 186         /proc/<pid>/oom_adj.
 187
 188         A warning will be emitted to the kernel log if an application uses this
 189         deprecated interface.  After it is printed once, future warnings will be
 190         suppressed until the kernel is rebooted.
 191
 192 ---------------------------
 193
 194 What:   remove EXPORT_SYMBOL(kernel_thread)
 195 When:   August 2006
 196 Files:  arch/*/kernel/*_ksyms.c
 197 Check:  kernel_thread
 198 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 199         use the <linux/kthread.h> API instead which shields them from
 200         implementation details and provides a higherlevel interface that
 201         prevents bugs and code duplication
 202 Who:    Christoph Hellwig <hch@lst.de>
 203
 204 ---------------------------
 205
 206 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 207         (temporary transition config option provided until then)
 208         The transition config option will also be removed at the same time.
 209 When:   before 2.6.19
 210 Why:    Unused symbols are both increasing the size of the kernel binary
 211         and are often a sign of "wrong API"
 212 Who:    Arjan van de Ven <arjan@linux.intel.com>
 213
 214 ---------------------------
 215
 216 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 217 When:   October 2008
 218 Why:    The stacking of class devices makes these values misleading and
 219         inconsistent.
 220         Class devices should not carry any of these properties, and bus
 221         devices have SUBSYTEM and DRIVER as a replacement.
 222 Who:    Kay Sievers <kay.sievers@suse.de>
 223
 224 ---------------------------
 225
 226 What:   ACPI procfs interface
 227 When:   July 2008
 228 Why:    ACPI sysfs conversion should be finished by January 2008.
 229         ACPI procfs interface will be removed in July 2008 so that
 230         there is enough time for the user space to catch up.
 231 Who:    Zhang Rui <rui.zhang@intel.com>
 232
 233 ---------------------------
 234
 235 What:   CONFIG_ACPI_PROCFS_POWER
 236 When:   2.6.39
 237 Why:    sysfs I/F for ACPI power devices, including AC and Battery,
 238         has been working in upstream kenrel since 2.6.24, Sep 2007.
 239         In 2.6.37, we make the sysfs I/F always built in and this option
 240         disabled by default.
 241         Remove this option and the ACPI power procfs interface in 2.6.39.
 242 Who:    Zhang Rui <rui.zhang@intel.com>
 243
 244 ---------------------------
 245
 246 What:   /proc/acpi/button
 247 When:   August 2007
 248 Why:    /proc/acpi/button has been replaced by events to the input layer
 249         since 2.6.20.
 250 Who:    Len Brown <len.brown@intel.com>
 251
 252 ---------------------------
 253
 254 What:   /proc/acpi/event
 255 When:   February 2008
 256 Why:    /proc/acpi/event has been replaced by events via the input layer
 257         and netlink since 2.6.23.
 258 Who:    Len Brown <len.brown@intel.com>
 259
 260 ---------------------------
 261
 262 What:   i386/x86_64 bzImage symlinks
 263 When:   April 2010
 264
 265 Why:    The i386/x86_64 merge provides a symlink to the old bzImage
 266         location so not yet updated user space tools, e.g. package
 267         scripts, do not break.
 268 Who:    Thomas Gleixner <tglx@linutronix.de>
 269
 270 ---------------------------
 271
 272 What:   GPIO autorequest on gpio_direction_{input,output}() in gpiolib
 273 When:   February 2010
 274 Why:    All callers should use explicit gpio_request()/gpio_free().
 275         The autorequest mechanism in gpiolib was provided mostly as a
 276         migration aid for legacy GPIO interfaces (for SOC based GPIOs).
 277         Those users have now largely migrated.  Platforms implementing
 278         the GPIO interfaces without using gpiolib will see no changes.
 279 Who:    David Brownell <dbrownell@users.sourceforge.net>
 280 ---------------------------
 281
 282 What:   b43 support for firmware revision < 410
 283 When:   The schedule was July 2008, but it was decided that we are going to keep the
 284         code as long as there are no major maintanance headaches.
 285         So it _could_ be removed _any_ time now, if it conflicts with something new.
 286 Why:    The support code for the old firmware hurts code readability/maintainability
 287         and slightly hurts runtime performance. Bugfixes for the old firmware
 288         are not provided by Broadcom anymore.
 289 Who:    Michael Buesch <mb@bu3sch.de>
 290
 291 ---------------------------
 292
 293 What:   /sys/o2cb symlink
 294 When:   January 2010
 295 Why:    /sys/fs/o2cb is the proper location for this information - /sys/o2cb
 296         exists as a symlink for backwards compatibility for old versions of
 297         ocfs2-tools. 2 years should be sufficient time to phase in new versions
 298         which know to look in /sys/fs/o2cb.
 299 Who:    ocfs2-devel@oss.oracle.com
 300
 301 ---------------------------
 302
 303 What:   Ability for non root users to shm_get hugetlb pages based on mlock
 304         resource limits
 305 When:   2.6.31
 306 Why:    Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
 307         have CAP_IPC_LOCK to be able to allocate shm segments backed by
 308         huge pages.  The mlock based rlimit check to allow shm hugetlb is
 309         inconsistent with mmap based allocations.  Hence it is being
 310         deprecated.
 311 Who:    Ravikiran Thirumalai <kiran@scalex86.org>
 312
 313 ---------------------------
 314
 315 What:   CONFIG_THERMAL_HWMON
 316 When:   January 2009
 317 Why:    This option was introduced just to allow older lm-sensors userspace
 318         to keep working over the upgrade to 2.6.26. At the scheduled time of
 319         removal fixed lm-sensors (2.x or 3.x) should be readily available.
 320 Who:    Rene Herman <rene.herman@gmail.com>
 321
 322 ---------------------------
 323
 324 What:   Code that is now under CONFIG_WIRELESS_EXT_SYSFS
 325         (in net/core/net-sysfs.c)
 326 When:   After the only user (hal) has seen a release with the patches
 327         for enough time, probably some time in 2010.
 328 Why:    Over 1K .text/.data size reduction, data is available in other
 329         ways (ioctls)
 330 Who:    Johannes Berg <johannes@sipsolutions.net>
 331
 332 ---------------------------
 333
 334 What:   sysfs ui for changing p4-clockmod parameters
 335 When:   September 2009
 336 Why:    See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
 337         e088e4c9cdb618675874becb91b2fd581ee707e6.
 338         Removal is subject to fixing any remaining bugs in ACPI which may
 339         cause the thermal throttling not to happen at the right time.
 340 Who:    Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
 341
 342 -----------------------------
 343
 344 What:   __do_IRQ all in one fits nothing interrupt handler
 345 When:   2.6.32
 346 Why:    __do_IRQ was kept for easy migration to the type flow handlers.
 347         More than two years of migration time is enough.
 348 Who:    Thomas Gleixner <tglx@linutronix.de>
 349
 350 -----------------------------
 351
 352 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 353 When:   2011
 354 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 355         represent a machine's physical PCI slots. The change in semantics
 356         had userspace implications, as the hotplug core no longer allowed
 357         drivers to create multiple sysfs files per physical slot (required
 358         for multi-function devices, e.g.). fakephp was seen as a developer's
 359         tool only, and its interface changed. Too late, we learned that
 360         there were some users of the fakephp interface.
 361
 362         In 2.6.30, the original fakephp interface was restored. At the same
 363         time, the PCI core gained the ability that fakephp provided, namely
 364         function-level hot-remove and hot-add.
 365
 366         Since the PCI core now provides the same functionality, exposed in:
 367
 368                 /sys/bus/pci/rescan
 369                 /sys/bus/pci/devices/.../remove
 370                 /sys/bus/pci/devices/.../rescan
 371
 372         there is no functional reason to maintain fakephp as well.
 373
 374         We will keep the existing module so that 'modprobe fakephp' will
 375         present the old /sys/bus/pci/slots/... interface for compatibility,
 376         but users are urged to migrate their applications to the API above.
 377
 378         After a reasonable transition period, we will remove the legacy
 379         fakephp interface.
 380 Who:    Alex Chiang <achiang@hp.com>
 381
 382 ---------------------------
 383
 384 What:   CONFIG_RFKILL_INPUT
 385 When:   2.6.33
 386 Why:    Should be implemented in userspace, policy daemon.
 387 Who:    Johannes Berg <johannes@sipsolutions.net>
 388
 389 ----------------------------
 390
 391 What:   sound-slot/service-* module aliases and related clutters in
 392         sound/sound_core.c
 393 When:   August 2010
 394 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 395         (14) and requests modules using custom sound-slot/service-*
 396         module aliases.  The only benefit of doing this is allowing
 397         use of custom module aliases which might as well be considered
 398         a bug at this point.  This preemptive claiming prevents
 399         alternative OSS implementations.
 400
 401         Till the feature is removed, the kernel will be requesting
 402         both sound-slot/service-* and the standard char-major-* module
 403         aliases and allow turning off the pre-claiming selectively via
 404         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 405         kernel parameter.
 406
 407         After the transition phase is complete, both the custom module
 408         aliases and switches to disable it will go away.  This removal
 409         will also allow making ALSA OSS emulation independent of
 410         sound_core.  The dependency will be broken then too.
 411 Who:    Tejun Heo <tj@kernel.org>
 412
 413 ----------------------------
 414
 415 What:   Support for lcd_switch and display_get in asus-laptop driver
 416 When:   March 2010
 417 Why:    These two features use non-standard interfaces. There are the
 418         only features that really need multiple path to guess what's
 419         the right method name on a specific laptop.
 420
 421         Removing them will allow to remove a lot of code an significantly
 422         clean the drivers.
 423
 424         This will affect the backlight code which won't be able to know
 425         if the backlight is on or off. The platform display file will also be
 426         write only (like the one in eeepc-laptop).
 427
 428         This should'nt affect a lot of user because they usually know
 429         when their display is on or off.
 430
 431 Who:    Corentin Chary <corentin.chary@gmail.com>
 432
 433 ----------------------------
 434
 435 What:   sysfs-class-rfkill state file
 436 When:   Feb 2014
 437 Files:  net/rfkill/core.c
 438 Why:    Documented as obsolete since Feb 2010. This file is limited to 3
 439         states while the rfkill drivers can have 4 states.
 440 Who:    anybody or Florian Mickler <florian@mickler.org>
 441
 442 ----------------------------
 443
 444 What:   sysfs-class-rfkill claim file
 445 When:   Feb 2012
 446 Files:  net/rfkill/core.c
 447 Why:    It is not possible to claim an rfkill driver since 2007. This is
 448         Documented as obsolete since Feb 2010.
 449 Who:    anybody or Florian Mickler <florian@mickler.org>
 450
 451 ----------------------------
 452
 453 What:   capifs
 454 When:   February 2011
 455 Files:  drivers/isdn/capi/capifs.*
 456 Why:    udev fully replaces this special file system that only contains CAPI
 457         NCCI TTY device nodes. User space (pppdcapiplugin) works without
 458         noticing the difference.
 459 Who:    Jan Kiszka <jan.kiszka@web.de>
 460
 461 ----------------------------
 462
 463 What:   KVM paravirt mmu host support
 464 When:   January 2011
 465 Why:    The paravirt mmu host support is slower than non-paravirt mmu, both
 466         on newer and older hardware.  It is already not exposed to the guest,
 467         and kept only for live migration purposes.
 468 Who:    Avi Kivity <avi@redhat.com>
 469
 470 ----------------------------
 471
 472 What:   iwlwifi 50XX module parameters
 473 When:   2.6.40
 474 Why:    The "..50" modules parameters were used to configure 5000 series and
 475         up devices; different set of module parameters also available for 4965
 476         with same functionalities. Consolidate both set into single place
 477         in drivers/net/wireless/iwlwifi/iwl-agn.c
 478
 479 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 480
 481 ----------------------------
 482
 483 What:   iwl4965 alias support
 484 When:   2.6.40
 485 Why:    Internal alias support has been present in module-init-tools for some
 486         time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
 487         with no impact.
 488
 489 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 490
 491 ---------------------------
 492
 493 What:   xt_NOTRACK
 494 Files:  net/netfilter/xt_NOTRACK.c
 495 When:   April 2011
 496 Why:    Superseded by xt_CT
 497 Who:    Netfilter developer team <netfilter-devel@vger.kernel.org>
 498
 499 ----------------------------
 500
 501 What:   IRQF_DISABLED
 502 When:   2.6.36
 503 Why:    The flag is a NOOP as we run interrupt handlers with interrupts disabled
 504 Who:    Thomas Gleixner <tglx@linutronix.de>
 505
 506 ----------------------------
 507
 508 What:   The acpi_sleep=s4_nonvs command line option
 509 When:   2.6.37
 510 Files:  arch/x86/kernel/acpi/sleep.c
 511 Why:    superseded by acpi_sleep=nonvs
 512 Who:    Rafael J. Wysocki <rjw@sisk.pl>
 513
 514 ----------------------------
 515
 516 What:   PCI DMA unmap state API
 517 When:   August 2012
 518 Why:    PCI DMA unmap state API (include/linux/pci-dma.h) was replaced
 519         with DMA unmap state API (DMA unmap state API can be used for
 520         any bus).
 521 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 522
 523 ----------------------------
 524
 525 What:   DMA_xxBIT_MASK macros
 526 When:   Jun 2011
 527 Why:    DMA_xxBIT_MASK macros were replaced with DMA_BIT_MASK() macros.
 528 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 529
 530 ----------------------------
 531
 532 What:   namespace cgroup (ns_cgroup)
 533 When:   2.6.38
 534 Why:    The ns_cgroup leads to some problems:
 535         * cgroup creation is out-of-control
 536         * cgroup name can conflict when pids are looping
 537         * it is not possible to have a single process handling
 538         a lot of namespaces without falling in a exponential creation time
 539         * we may want to create a namespace without creating a cgroup
 540
 541         The ns_cgroup is replaced by a compatibility flag 'clone_children',
 542         where a newly created cgroup will copy the parent cgroup values.
 543         The userspace has to manually create a cgroup and add a task to
 544         the 'tasks' file.
 545 Who:    Daniel Lezcano <daniel.lezcano@free.fr>
 546
 547 ----------------------------
 548
 549 What:   iwlwifi disable_hw_scan module parameters
 550 When:   2.6.40
 551 Why:    Hareware scan is the prefer method for iwlwifi devices for
 552         scanning operation. Remove software scan support for all the
 553         iwlwifi devices.
 554
 555 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 556
 557 ----------------------------
 558
 559 What:   access to nfsd auth cache through sys_nfsservctl or '.' files
 560         in the 'nfsd' filesystem.
 561 When:   2.6.40
 562 Why:    This is a legacy interface which have been replaced by a more
 563         dynamic cache.  Continuing to maintain this interface is an
 564         unnecessary burden.
 565 Who:    NeilBrown <neilb@suse.de>
 566
 567 ----------------------------
 568
 569 What:   i2c_adapter.id
 570 When:   June 2011
 571 Why:    This field is deprecated. I2C device drivers shouldn't change their
 572         behavior based on the underlying I2C adapter. Instead, the I2C
 573         adapter driver should instantiate the I2C devices and provide the
 574         needed platform-specific information.
 575 Who:    Jean Delvare <khali@linux-fr.org>
 576
 577 ----------------------------