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:   July 2009
 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:   PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl])
 120 When:   2.6.35/2.6.36
 121 Files:  drivers/pcmcia/: pcmcia_ioctl.c
 122 Why:    With the 16-bit PCMCIA subsystem now behaving (almost) like a
 123         normal hotpluggable bus, and with it using the default kernel
 124         infrastructure (hotplug, driver core, sysfs) keeping the PCMCIA
 125         control ioctl needed by cardmgr and cardctl from pcmcia-cs is
 126         unnecessary and potentially harmful (it does not provide for
 127         proper locking), and makes further cleanups and integration of the
 128         PCMCIA subsystem into the Linux kernel device driver model more
 129         difficult. The features provided by cardmgr and cardctl are either
 130         handled by the kernel itself now or are available in the new
 131         pcmciautils package available at
 132         http://kernel.org/pub/linux/utils/kernel/pcmcia/
 133
 134         For all architectures except ARM, the associated config symbol
 135         has been removed from kernel 2.6.34; for ARM, it will be likely
 136         be removed from kernel 2.6.35. The actual code will then likely
 137         be removed from kernel 2.6.36.
 138 Who:    Dominik Brodowski <linux@dominikbrodowski.net>
 139
 140 ---------------------------
 141
 142 What:   sys_sysctl
 143 When:   September 2010
 144 Option: CONFIG_SYSCTL_SYSCALL
 145 Why:    The same information is available in a more convenient from
 146         /proc/sys, and none of the sysctl variables appear to be
 147         important performance wise.
 148
 149         Binary sysctls are a long standing source of subtle kernel
 150         bugs and security issues.
 151
 152         When I looked several months ago all I could find after
 153         searching several distributions were 5 user space programs and
 154         glibc (which falls back to /proc/sys) using this syscall.
 155
 156         The man page for sysctl(2) documents it as unusable for user
 157         space programs.
 158
 159         sysctl(2) is not generally ABI compatible to a 32bit user
 160         space application on a 64bit and a 32bit kernel.
 161
 162         For the last several months the policy has been no new binary
 163         sysctls and no one has put forward an argument to use them.
 164
 165         Binary sysctls issues seem to keep happening appearing so
 166         properly deprecating them (with a warning to user space) and a
 167         2 year grace warning period will mean eventually we can kill
 168         them and end the pain.
 169
 170         In the mean time individual binary sysctls can be dealt with
 171         in a piecewise fashion.
 172
 173 Who:    Eric Biederman <ebiederm@xmission.com>
 174
 175 ---------------------------
 176
 177 What:   remove EXPORT_SYMBOL(kernel_thread)
 178 When:   August 2006
 179 Files:  arch/*/kernel/*_ksyms.c
 180 Check:  kernel_thread
 181 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 182         use the <linux/kthread.h> API instead which shields them from
 183         implementation details and provides a higherlevel interface that
 184         prevents bugs and code duplication
 185 Who:    Christoph Hellwig <hch@lst.de>
 186
 187 ---------------------------
 188
 189 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 190         (temporary transition config option provided until then)
 191         The transition config option will also be removed at the same time.
 192 When:   before 2.6.19
 193 Why:    Unused symbols are both increasing the size of the kernel binary
 194         and are often a sign of "wrong API"
 195 Who:    Arjan van de Ven <arjan@linux.intel.com>
 196
 197 ---------------------------
 198
 199 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 200 When:   October 2008
 201 Why:    The stacking of class devices makes these values misleading and
 202         inconsistent.
 203         Class devices should not carry any of these properties, and bus
 204         devices have SUBSYTEM and DRIVER as a replacement.
 205 Who:    Kay Sievers <kay.sievers@suse.de>
 206
 207 ---------------------------
 208
 209 What:   ACPI procfs interface
 210 When:   July 2008
 211 Why:    ACPI sysfs conversion should be finished by January 2008.
 212         ACPI procfs interface will be removed in July 2008 so that
 213         there is enough time for the user space to catch up.
 214 Who:    Zhang Rui <rui.zhang@intel.com>
 215
 216 ---------------------------
 217
 218 What:   /proc/acpi/button
 219 When:   August 2007
 220 Why:    /proc/acpi/button has been replaced by events to the input layer
 221         since 2.6.20.
 222 Who:    Len Brown <len.brown@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:   __do_IRQ all in one fits nothing interrupt handler
 317 When:   2.6.32
 318 Why:    __do_IRQ was kept for easy migration to the type flow handlers.
 319         More than two years of migration time is enough.
 320 Who:    Thomas Gleixner <tglx@linutronix.de>
 321
 322 -----------------------------
 323
 324 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 325 When:   2011
 326 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 327         represent a machine's physical PCI slots. The change in semantics
 328         had userspace implications, as the hotplug core no longer allowed
 329         drivers to create multiple sysfs files per physical slot (required
 330         for multi-function devices, e.g.). fakephp was seen as a developer's
 331         tool only, and its interface changed. Too late, we learned that
 332         there were some users of the fakephp interface.
 333
 334         In 2.6.30, the original fakephp interface was restored. At the same
 335         time, the PCI core gained the ability that fakephp provided, namely
 336         function-level hot-remove and hot-add.
 337
 338         Since the PCI core now provides the same functionality, exposed in:
 339
 340                 /sys/bus/pci/rescan
 341                 /sys/bus/pci/devices/.../remove
 342                 /sys/bus/pci/devices/.../rescan
 343
 344         there is no functional reason to maintain fakephp as well.
 345
 346         We will keep the existing module so that 'modprobe fakephp' will
 347         present the old /sys/bus/pci/slots/... interface for compatibility,
 348         but users are urged to migrate their applications to the API above.
 349
 350         After a reasonable transition period, we will remove the legacy
 351         fakephp interface.
 352 Who:    Alex Chiang <achiang@hp.com>
 353
 354 ---------------------------
 355
 356 What:   CONFIG_RFKILL_INPUT
 357 When:   2.6.33
 358 Why:    Should be implemented in userspace, policy daemon.
 359 Who:    Johannes Berg <johannes@sipsolutions.net>
 360
 361 ---------------------------
 362
 363 What:   CONFIG_INOTIFY
 364 When:   2.6.33
 365 Why:    last user (audit) will be converted to the newer more generic
 366         and more easily maintained fsnotify subsystem
 367 Who:    Eric Paris <eparis@redhat.com>
 368
 369 ----------------------------
 370
 371 What:   sound-slot/service-* module aliases and related clutters in
 372         sound/sound_core.c
 373 When:   August 2010
 374 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 375         (14) and requests modules using custom sound-slot/service-*
 376         module aliases.  The only benefit of doing this is allowing
 377         use of custom module aliases which might as well be considered
 378         a bug at this point.  This preemptive claiming prevents
 379         alternative OSS implementations.
 380
 381         Till the feature is removed, the kernel will be requesting
 382         both sound-slot/service-* and the standard char-major-* module
 383         aliases and allow turning off the pre-claiming selectively via
 384         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 385         kernel parameter.
 386
 387         After the transition phase is complete, both the custom module
 388         aliases and switches to disable it will go away.  This removal
 389         will also allow making ALSA OSS emulation independent of
 390         sound_core.  The dependency will be broken then too.
 391 Who:    Tejun Heo <tj@kernel.org>
 392
 393 ----------------------------
 394
 395 What:   Support for VMware's guest paravirtuliazation technique [VMI] will be
 396         dropped.
 397 When:   2.6.37 or earlier.
 398 Why:    With the recent innovations in CPU hardware acceleration technologies
 399         from Intel and AMD, VMware ran a few experiments to compare these
 400         techniques to guest paravirtualization technique on VMware's platform.
 401         These hardware assisted virtualization techniques have outperformed the
 402         performance benefits provided by VMI in most of the workloads. VMware
 403         expects that these hardware features will be ubiquitous in a couple of
 404         years, as a result, VMware has started a phased retirement of this
 405         feature from the hypervisor. We will be removing this feature from the
 406         Kernel too. Right now we are targeting 2.6.37 but can retire earlier if
 407         technical reasons (read opportunity to remove major chunk of pvops)
 408         arise.
 409
 410         Please note that VMI has always been an optimization and non-VMI kernels
 411         still work fine on VMware's platform.
 412         Latest versions of VMware's product which support VMI are,
 413         Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence
 414         releases for these products will continue supporting VMI.
 415
 416         For more details about VMI retirement take a look at this,
 417         http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html
 418
 419 Who:    Alok N Kataria <akataria@vmware.com>
 420
 421 ----------------------------
 422
 423 What:   Support for lcd_switch and display_get in asus-laptop driver
 424 When:   March 2010
 425 Why:    These two features use non-standard interfaces. There are the
 426         only features that really need multiple path to guess what's
 427         the right method name on a specific laptop.
 428
 429         Removing them will allow to remove a lot of code an significantly
 430         clean the drivers.
 431
 432         This will affect the backlight code which won't be able to know
 433         if the backlight is on or off. The platform display file will also be
 434         write only (like the one in eeepc-laptop).
 435
 436         This should'nt affect a lot of user because they usually know
 437         when their display is on or off.
 438
 439 Who:    Corentin Chary <corentin.chary@gmail.com>
 440
 441 ----------------------------
 442
 443 What:   sysfs-class-rfkill state file
 444 When:   Feb 2014
 445 Files:  net/rfkill/core.c
 446 Why:    Documented as obsolete since Feb 2010. This file is limited to 3
 447         states while the rfkill drivers can have 4 states.
 448 Who:    anybody or Florian Mickler <florian@mickler.org>
 449
 450 ----------------------------
 451
 452 What:   sysfs-class-rfkill claim file
 453 When:   Feb 2012
 454 Files:  net/rfkill/core.c
 455 Why:    It is not possible to claim an rfkill driver since 2007. This is
 456         Documented as obsolete since Feb 2010.
 457 Who:    anybody or Florian Mickler <florian@mickler.org>
 458
 459 ----------------------------
 460
 461 What:   capifs
 462 When:   February 2011
 463 Files:  drivers/isdn/capi/capifs.*
 464 Why:    udev fully replaces this special file system that only contains CAPI
 465         NCCI TTY device nodes. User space (pppdcapiplugin) works without
 466         noticing the difference.
 467 Who:    Jan Kiszka <jan.kiszka@web.de>
 468
 469 ----------------------------
 470
 471 What:   xtime, wall_to_monotonic
 472 When:   2.6.36+
 473 Files:  kernel/time/timekeeping.c include/linux/time.h
 474 Why:    Cleaning up timekeeping internal values. Please use
 475         existing timekeeping accessor functions to access
 476         the equivalent functionality.
 477 Who:    John Stultz <johnstul@us.ibm.com>
 478
 479 ----------------------------
 480
 481 What:   KVM paravirt mmu host support
 482 When:   January 2011
 483 Why:    The paravirt mmu host support is slower than non-paravirt mmu, both
 484         on newer and older hardware.  It is already not exposed to the guest,
 485         and kept only for live migration purposes.
 486 Who:    Avi Kivity <avi@redhat.com>
 487
 488 ----------------------------
 489
 490 What:   iwlwifi 50XX module parameters
 491 When:   2.6.40
 492 Why:    The "..50" modules parameters were used to configure 5000 series and
 493         up devices; different set of module parameters also available for 4965
 494         with same functionalities. Consolidate both set into single place
 495         in drivers/net/wireless/iwlwifi/iwl-agn.c
 496
 497 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 498
 499 ----------------------------
 500
 501 What:   iwl4965 alias support
 502 When:   2.6.40
 503 Why:    Internal alias support has been present in module-init-tools for some
 504         time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
 505         with no impact.
 506
 507 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 508
 509 ---------------------------
 510
 511 What:   xt_NOTRACK
 512 Files:  net/netfilter/xt_NOTRACK.c
 513 When:   April 2011
 514 Why:    Superseded by xt_CT
 515 Who:    Netfilter developer team <netfilter-devel@vger.kernel.org>
 516
 517 ---------------------------
 518
 519 What:   video4linux /dev/vtx teletext API support
 520 When:   2.6.35
 521 Files:  drivers/media/video/saa5246a.c drivers/media/video/saa5249.c
 522         include/linux/videotext.h
 523 Why:    The vtx device nodes have been superseded by vbi device nodes
 524         for many years. No applications exist that use the vtx support.
 525         Of the two i2c drivers that actually support this API the saa5249
 526         has been impossible to use for a year now and no known hardware
 527         that supports this device exists. The saa5246a is theoretically
 528         supported by the old mxb boards, but it never actually worked.
 529
 530         In summary: there is no hardware that can use this API and there
 531         are no applications actually implementing this API.
 532
 533         The vtx support still reserves minors 192-223 and we would really
 534         like to reuse those for upcoming new functionality. In the unlikely
 535         event that new hardware appears that wants to use the functionality
 536         provided by the vtx API, then that functionality should be build
 537         around the sliced VBI API instead.
 538 Who:    Hans Verkuil <hverkuil@xs4all.nl>
 539
 540 ----------------------------
 541
 542 What:   IRQF_DISABLED
 543 When:   2.6.36
 544 Why:    The flag is a NOOP as we run interrupt handlers with interrupts disabled
 545 Who:    Thomas Gleixner <tglx@linutronix.de>
 546
 547 ----------------------------
 548
 549 What:   old ieee1394 subsystem (CONFIG_IEEE1394)
 550 When:   2.6.37
 551 Files:  drivers/ieee1394/ except init_ohci1394_dma.c
 552 Why:    superseded by drivers/firewire/ (CONFIG_FIREWIRE) which offers more
 553         features, better performance, and better security, all with smaller
 554         and more modern code base
 555 Who:    Stefan Richter <stefanr@s5r6.in-berlin.de>
 556
 557 ----------------------------
 558
 559 What:   The acpi_sleep=s4_nonvs command line option
 560 When:   2.6.37
 561 Files:  arch/x86/kernel/acpi/sleep.c
 562 Why:    superseded by acpi_sleep=nonvs
 563 Who:    Rafael J. Wysocki <rjw@sisk.pl>
 564
 565 ----------------------------