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:   sys_sysctl
 101 When:   September 2010
 102 Option: CONFIG_SYSCTL_SYSCALL
 103 Why:    The same information is available in a more convenient from
 104         /proc/sys, and none of the sysctl variables appear to be
 105         important performance wise.
 106
 107         Binary sysctls are a long standing source of subtle kernel
 108         bugs and security issues.
 109
 110         When I looked several months ago all I could find after
 111         searching several distributions were 5 user space programs and
 112         glibc (which falls back to /proc/sys) using this syscall.
 113
 114         The man page for sysctl(2) documents it as unusable for user
 115         space programs.
 116
 117         sysctl(2) is not generally ABI compatible to a 32bit user
 118         space application on a 64bit and a 32bit kernel.
 119
 120         For the last several months the policy has been no new binary
 121         sysctls and no one has put forward an argument to use them.
 122
 123         Binary sysctls issues seem to keep happening appearing so
 124         properly deprecating them (with a warning to user space) and a
 125         2 year grace warning period will mean eventually we can kill
 126         them and end the pain.
 127
 128         In the mean time individual binary sysctls can be dealt with
 129         in a piecewise fashion.
 130
 131 Who:    Eric Biederman <ebiederm@xmission.com>
 132
 133 ---------------------------
 134
 135 What:   /proc/<pid>/oom_adj
 136 When:   August 2012
 137 Why:    /proc/<pid>/oom_adj allows userspace to influence the oom killer's
 138         badness heuristic used to determine which task to kill when the kernel
 139         is out of memory.
 140
 141         The badness heuristic has since been rewritten since the introduction of
 142         this tunable such that its meaning is deprecated.  The value was
 143         implemented as a bitshift on a score generated by the badness()
 144         function that did not have any precise units of measure.  With the
 145         rewrite, the score is given as a proportion of available memory to the
 146         task allocating pages, so using a bitshift which grows the score
 147         exponentially is, thus, impossible to tune with fine granularity.
 148
 149         A much more powerful interface, /proc/<pid>/oom_score_adj, was
 150         introduced with the oom killer rewrite that allows users to increase or
 151         decrease the badness() score linearly.  This interface will replace
 152         /proc/<pid>/oom_adj.
 153
 154         A warning will be emitted to the kernel log if an application uses this
 155         deprecated interface.  After it is printed once, future warnings will be
 156         suppressed until the kernel is rebooted.
 157
 158 ---------------------------
 159
 160 What:   CS5535/CS5536 obsolete GPIO driver
 161 When:   June 2011
 162 Files:  drivers/staging/cs5535_gpio/*
 163 Check:  drivers/staging/cs5535_gpio/cs5535_gpio.c
 164 Why:    A newer driver replaces this; it is drivers/gpio/cs5535-gpio.c, and
 165         integrates with the Linux GPIO subsystem.  The old driver has been
 166         moved to staging, and will be removed altogether around 2.6.40.
 167         Please test the new driver, and ensure that the functionality you
 168         need and any bugfixes from the old driver are available in the new
 169         one.
 170 Who:    Andres Salomon <dilinger@queued.net>
 171
 172 --------------------------
 173
 174 What:   remove EXPORT_SYMBOL(kernel_thread)
 175 When:   August 2006
 176 Files:  arch/*/kernel/*_ksyms.c
 177 Check:  kernel_thread
 178 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 179         use the <linux/kthread.h> API instead which shields them from
 180         implementation details and provides a higherlevel interface that
 181         prevents bugs and code duplication
 182 Who:    Christoph Hellwig <hch@lst.de>
 183
 184 ---------------------------
 185
 186 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 187         (temporary transition config option provided until then)
 188         The transition config option will also be removed at the same time.
 189 When:   before 2.6.19
 190 Why:    Unused symbols are both increasing the size of the kernel binary
 191         and are often a sign of "wrong API"
 192 Who:    Arjan van de Ven <arjan@linux.intel.com>
 193
 194 ---------------------------
 195
 196 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 197 When:   October 2008
 198 Why:    The stacking of class devices makes these values misleading and
 199         inconsistent.
 200         Class devices should not carry any of these properties, and bus
 201         devices have SUBSYTEM and DRIVER as a replacement.
 202 Who:    Kay Sievers <kay.sievers@suse.de>
 203
 204 ---------------------------
 205
 206 What:   ACPI procfs interface
 207 When:   July 2008
 208 Why:    ACPI sysfs conversion should be finished by January 2008.
 209         ACPI procfs interface will be removed in July 2008 so that
 210         there is enough time for the user space to catch up.
 211 Who:    Zhang Rui <rui.zhang@intel.com>
 212
 213 ---------------------------
 214
 215 What:   CONFIG_ACPI_PROCFS_POWER
 216 When:   2.6.39
 217 Why:    sysfs I/F for ACPI power devices, including AC and Battery,
 218         has been working in upstream kernel since 2.6.24, Sep 2007.
 219         In 2.6.37, we make the sysfs I/F always built in and this option
 220         disabled by default.
 221         Remove this option and the ACPI power procfs interface in 2.6.39.
 222 Who:    Zhang Rui <rui.zhang@intel.com>
 223
 224 ---------------------------
 225
 226 What:   /proc/acpi/event
 227 When:   February 2008
 228 Why:    /proc/acpi/event has been replaced by events via the input layer
 229         and netlink since 2.6.23.
 230 Who:    Len Brown <len.brown@intel.com>
 231
 232 ---------------------------
 233
 234 What:   i386/x86_64 bzImage symlinks
 235 When:   April 2010
 236
 237 Why:    The i386/x86_64 merge provides a symlink to the old bzImage
 238         location so not yet updated user space tools, e.g. package
 239         scripts, do not break.
 240 Who:    Thomas Gleixner <tglx@linutronix.de>
 241
 242 ---------------------------
 243
 244 What:   GPIO autorequest on gpio_direction_{input,output}() in gpiolib
 245 When:   February 2010
 246 Why:    All callers should use explicit gpio_request()/gpio_free().
 247         The autorequest mechanism in gpiolib was provided mostly as a
 248         migration aid for legacy GPIO interfaces (for SOC based GPIOs).
 249         Those users have now largely migrated.  Platforms implementing
 250         the GPIO interfaces without using gpiolib will see no changes.
 251 Who:    David Brownell <dbrownell@users.sourceforge.net>
 252 ---------------------------
 253
 254 What:   b43 support for firmware revision < 410
 255 When:   The schedule was July 2008, but it was decided that we are going to keep the
 256         code as long as there are no major maintanance headaches.
 257         So it _could_ be removed _any_ time now, if it conflicts with something new.
 258 Why:    The support code for the old firmware hurts code readability/maintainability
 259         and slightly hurts runtime performance. Bugfixes for the old firmware
 260         are not provided by Broadcom anymore.
 261 Who:    Michael Buesch <mb@bu3sch.de>
 262
 263 ---------------------------
 264
 265 What:   /sys/o2cb symlink
 266 When:   January 2010
 267 Why:    /sys/fs/o2cb is the proper location for this information - /sys/o2cb
 268         exists as a symlink for backwards compatibility for old versions of
 269         ocfs2-tools. 2 years should be sufficient time to phase in new versions
 270         which know to look in /sys/fs/o2cb.
 271 Who:    ocfs2-devel@oss.oracle.com
 272
 273 ---------------------------
 274
 275 What:   Ability for non root users to shm_get hugetlb pages based on mlock
 276         resource limits
 277 When:   2.6.31
 278 Why:    Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
 279         have CAP_IPC_LOCK to be able to allocate shm segments backed by
 280         huge pages.  The mlock based rlimit check to allow shm hugetlb is
 281         inconsistent with mmap based allocations.  Hence it is being
 282         deprecated.
 283 Who:    Ravikiran Thirumalai <kiran@scalex86.org>
 284
 285 ---------------------------
 286
 287 What:   CONFIG_THERMAL_HWMON
 288 When:   January 2009
 289 Why:    This option was introduced just to allow older lm-sensors userspace
 290         to keep working over the upgrade to 2.6.26. At the scheduled time of
 291         removal fixed lm-sensors (2.x or 3.x) should be readily available.
 292 Who:    Rene Herman <rene.herman@gmail.com>
 293
 294 ---------------------------
 295
 296 What:   Code that is now under CONFIG_WIRELESS_EXT_SYSFS
 297         (in net/core/net-sysfs.c)
 298 When:   After the only user (hal) has seen a release with the patches
 299         for enough time, probably some time in 2010.
 300 Why:    Over 1K .text/.data size reduction, data is available in other
 301         ways (ioctls)
 302 Who:    Johannes Berg <johannes@sipsolutions.net>
 303
 304 ---------------------------
 305
 306 What:   sysfs ui for changing p4-clockmod parameters
 307 When:   September 2009
 308 Why:    See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
 309         e088e4c9cdb618675874becb91b2fd581ee707e6.
 310         Removal is subject to fixing any remaining bugs in ACPI which may
 311         cause the thermal throttling not to happen at the right time.
 312 Who:    Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
 313
 314 -----------------------------
 315
 316 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 317 When:   2011
 318 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 319         represent a machine's physical PCI slots. The change in semantics
 320         had userspace implications, as the hotplug core no longer allowed
 321         drivers to create multiple sysfs files per physical slot (required
 322         for multi-function devices, e.g.). fakephp was seen as a developer's
 323         tool only, and its interface changed. Too late, we learned that
 324         there were some users of the fakephp interface.
 325
 326         In 2.6.30, the original fakephp interface was restored. At the same
 327         time, the PCI core gained the ability that fakephp provided, namely
 328         function-level hot-remove and hot-add.
 329
 330         Since the PCI core now provides the same functionality, exposed in:
 331
 332                 /sys/bus/pci/rescan
 333                 /sys/bus/pci/devices/.../remove
 334                 /sys/bus/pci/devices/.../rescan
 335
 336         there is no functional reason to maintain fakephp as well.
 337
 338         We will keep the existing module so that 'modprobe fakephp' will
 339         present the old /sys/bus/pci/slots/... interface for compatibility,
 340         but users are urged to migrate their applications to the API above.
 341
 342         After a reasonable transition period, we will remove the legacy
 343         fakephp interface.
 344 Who:    Alex Chiang <achiang@hp.com>
 345
 346 ---------------------------
 347
 348 What:   CONFIG_RFKILL_INPUT
 349 When:   2.6.33
 350 Why:    Should be implemented in userspace, policy daemon.
 351 Who:    Johannes Berg <johannes@sipsolutions.net>
 352
 353 ----------------------------
 354
 355 What:   sound-slot/service-* module aliases and related clutters in
 356         sound/sound_core.c
 357 When:   August 2010
 358 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 359         (14) and requests modules using custom sound-slot/service-*
 360         module aliases.  The only benefit of doing this is allowing
 361         use of custom module aliases which might as well be considered
 362         a bug at this point.  This preemptive claiming prevents
 363         alternative OSS implementations.
 364
 365         Till the feature is removed, the kernel will be requesting
 366         both sound-slot/service-* and the standard char-major-* module
 367         aliases and allow turning off the pre-claiming selectively via
 368         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 369         kernel parameter.
 370
 371         After the transition phase is complete, both the custom module
 372         aliases and switches to disable it will go away.  This removal
 373         will also allow making ALSA OSS emulation independent of
 374         sound_core.  The dependency will be broken then too.
 375 Who:    Tejun Heo <tj@kernel.org>
 376
 377 ----------------------------
 378
 379 What:   sysfs-class-rfkill state file
 380 When:   Feb 2014
 381 Files:  net/rfkill/core.c
 382 Why:    Documented as obsolete since Feb 2010. This file is limited to 3
 383         states while the rfkill drivers can have 4 states.
 384 Who:    anybody or Florian Mickler <florian@mickler.org>
 385
 386 ----------------------------
 387
 388 What:   sysfs-class-rfkill claim file
 389 When:   Feb 2012
 390 Files:  net/rfkill/core.c
 391 Why:    It is not possible to claim an rfkill driver since 2007. This is
 392         Documented as obsolete since Feb 2010.
 393 Who:    anybody or Florian Mickler <florian@mickler.org>
 394
 395 ----------------------------
 396
 397 What:   KVM paravirt mmu host support
 398 When:   January 2011
 399 Why:    The paravirt mmu host support is slower than non-paravirt mmu, both
 400         on newer and older hardware.  It is already not exposed to the guest,
 401         and kept only for live migration purposes.
 402 Who:    Avi Kivity <avi@redhat.com>
 403
 404 ----------------------------
 405
 406 What:   iwlwifi 50XX module parameters
 407 When:   2.6.40
 408 Why:    The "..50" modules parameters were used to configure 5000 series and
 409         up devices; different set of module parameters also available for 4965
 410         with same functionalities. Consolidate both set into single place
 411         in drivers/net/wireless/iwlwifi/iwl-agn.c
 412
 413 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 414
 415 ----------------------------
 416
 417 What:   iwl4965 alias support
 418 When:   2.6.40
 419 Why:    Internal alias support has been present in module-init-tools for some
 420         time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
 421         with no impact.
 422
 423 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 424
 425 ---------------------------
 426
 427 What:   xt_NOTRACK
 428 Files:  net/netfilter/xt_NOTRACK.c
 429 When:   April 2011
 430 Why:    Superseded by xt_CT
 431 Who:    Netfilter developer team <netfilter-devel@vger.kernel.org>
 432
 433 ----------------------------
 434
 435 What:   IRQF_DISABLED
 436 When:   2.6.36
 437 Why:    The flag is a NOOP as we run interrupt handlers with interrupts disabled
 438 Who:    Thomas Gleixner <tglx@linutronix.de>
 439
 440 ----------------------------
 441
 442 What:   PCI DMA unmap state API
 443 When:   August 2012
 444 Why:    PCI DMA unmap state API (include/linux/pci-dma.h) was replaced
 445         with DMA unmap state API (DMA unmap state API can be used for
 446         any bus).
 447 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 448
 449 ----------------------------
 450
 451 What:   DMA_xxBIT_MASK macros
 452 When:   Jun 2011
 453 Why:    DMA_xxBIT_MASK macros were replaced with DMA_BIT_MASK() macros.
 454 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 455
 456 ----------------------------
 457
 458 What:   namespace cgroup (ns_cgroup)
 459 When:   2.6.38
 460 Why:    The ns_cgroup leads to some problems:
 461         * cgroup creation is out-of-control
 462         * cgroup name can conflict when pids are looping
 463         * it is not possible to have a single process handling
 464         a lot of namespaces without falling in a exponential creation time
 465         * we may want to create a namespace without creating a cgroup
 466
 467         The ns_cgroup is replaced by a compatibility flag 'clone_children',
 468         where a newly created cgroup will copy the parent cgroup values.
 469         The userspace has to manually create a cgroup and add a task to
 470         the 'tasks' file.
 471 Who:    Daniel Lezcano <daniel.lezcano@free.fr>
 472
 473 ----------------------------
 474
 475 What:   iwlwifi disable_hw_scan module parameters
 476 When:   2.6.40
 477 Why:    Hareware scan is the prefer method for iwlwifi devices for
 478         scanning operation. Remove software scan support for all the
 479         iwlwifi devices.
 480
 481 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 482
 483 ----------------------------
 484
 485 What:   access to nfsd auth cache through sys_nfsservctl or '.' files
 486         in the 'nfsd' filesystem.
 487 When:   2.6.40
 488 Why:    This is a legacy interface which have been replaced by a more
 489         dynamic cache.  Continuing to maintain this interface is an
 490         unnecessary burden.
 491 Who:    NeilBrown <neilb@suse.de>
 492
 493 ----------------------------
 494
 495 What:   cancel_rearming_delayed_work[queue]()
 496 When:   2.6.39
 497
 498 Why:    The functions have been superceded by cancel_delayed_work_sync()
 499         quite some time ago.  The conversion is trivial and there is no
 500         in-kernel user left.
 501 Who:    Tejun Heo <tj@kernel.org>
 502
 503 ----------------------------
 504
 505 What:   Legacy, non-standard chassis intrusion detection interface.
 506 When:   June 2011
 507 Why:    The adm9240, w83792d and w83793 hardware monitoring drivers have
 508         legacy interfaces for chassis intrusion detection. A standard
 509         interface has been added to each driver, so the legacy interface
 510         can be removed.
 511 Who:    Jean Delvare <khali@linux-fr.org>
 512
 513 ----------------------------
 514
 515 What:   xt_connlimit rev 0
 516 When:   2012
 517 Who:    Jan Engelhardt <jengelh@medozas.de>
 518 Files:  net/netfilter/xt_connlimit.c
 519
 520 ----------------------------
 521
 522 What:   noswapaccount kernel command line parameter
 523 When:   2.6.40
 524 Why:    The original implementation of memsw feature enabled by
 525         CONFIG_CGROUP_MEM_RES_CTLR_SWAP could be disabled by the noswapaccount
 526         kernel parameter (introduced in 2.6.29-rc1). Later on, this decision
 527         turned out to be not ideal because we cannot have the feature compiled
 528         in and disabled by default and let only interested to enable it
 529         (e.g. general distribution kernels might need it). Therefore we have
 530         added swapaccount[=0|1] parameter (introduced in 2.6.37) which provides
 531         the both possibilities. If we remove noswapaccount we will have
 532         less command line parameters with the same functionality and we
 533         can also cleanup the parameter handling a bit ().
 534 Who:    Michal Hocko <mhocko@suse.cz>
 535
 536 ----------------------------
 537
 538 What:   ipt_addrtype match include file
 539 When:   2012
 540 Why:    superseded by xt_addrtype
 541 Who:    Florian Westphal <fw@strlen.de>
 542 Files:  include/linux/netfilter_ipv4/ipt_addrtype.h
 543
 544 ----------------------------
 545
 546 What:   i2c_driver.attach_adapter
 547         i2c_driver.detach_adapter
 548 When:   September 2011
 549 Why:    These legacy callbacks should no longer be used as i2c-core offers
 550         a variety of preferable alternative ways to instantiate I2C devices.
 551 Who:    Jean Delvare <khali@linux-fr.org>
 552
 553 ----------------------------
 554
 555 What:   Support for UVCIOC_CTRL_ADD in the uvcvideo driver
 556 When:   2.6.42
 557 Why:    The information passed to the driver by this ioctl is now queried
 558         dynamically from the device.
 559 Who:    Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 560
 561 ----------------------------
 562
 563 What:   Support for UVCIOC_CTRL_MAP_OLD in the uvcvideo driver
 564 When:   2.6.42
 565 Why:    Used only by applications compiled against older driver versions.
 566         Superseded by UVCIOC_CTRL_MAP which supports V4L2 menu controls.
 567 Who:    Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 568
 569 ----------------------------
 570
 571 What:   Support for UVCIOC_CTRL_GET and UVCIOC_CTRL_SET in the uvcvideo driver
 572 When:   2.6.42
 573 Why:    Superseded by the UVCIOC_CTRL_QUERY ioctl.
 574 Who:    Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 575
 576 ----------------------------