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:   sys_sysctl
 120 When:   September 2010
 121 Option: CONFIG_SYSCTL_SYSCALL
 122 Why:    The same information is available in a more convenient from
 123         /proc/sys, and none of the sysctl variables appear to be
 124         important performance wise.
 125
 126         Binary sysctls are a long standing source of subtle kernel
 127         bugs and security issues.
 128
 129         When I looked several months ago all I could find after
 130         searching several distributions were 5 user space programs and
 131         glibc (which falls back to /proc/sys) using this syscall.
 132
 133         The man page for sysctl(2) documents it as unusable for user
 134         space programs.
 135
 136         sysctl(2) is not generally ABI compatible to a 32bit user
 137         space application on a 64bit and a 32bit kernel.
 138
 139         For the last several months the policy has been no new binary
 140         sysctls and no one has put forward an argument to use them.
 141
 142         Binary sysctls issues seem to keep happening appearing so
 143         properly deprecating them (with a warning to user space) and a
 144         2 year grace warning period will mean eventually we can kill
 145         them and end the pain.
 146
 147         In the mean time individual binary sysctls can be dealt with
 148         in a piecewise fashion.
 149
 150 Who:    Eric Biederman <ebiederm@xmission.com>
 151
 152 ---------------------------
 153
 154 What:   remove EXPORT_SYMBOL(kernel_thread)
 155 When:   August 2006
 156 Files:  arch/*/kernel/*_ksyms.c
 157 Check:  kernel_thread
 158 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 159         use the <linux/kthread.h> API instead which shields them from
 160         implementation details and provides a higherlevel interface that
 161         prevents bugs and code duplication
 162 Who:    Christoph Hellwig <hch@lst.de>
 163
 164 ---------------------------
 165
 166 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 167         (temporary transition config option provided until then)
 168         The transition config option will also be removed at the same time.
 169 When:   before 2.6.19
 170 Why:    Unused symbols are both increasing the size of the kernel binary
 171         and are often a sign of "wrong API"
 172 Who:    Arjan van de Ven <arjan@linux.intel.com>
 173
 174 ---------------------------
 175
 176 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 177 When:   October 2008
 178 Why:    The stacking of class devices makes these values misleading and
 179         inconsistent.
 180         Class devices should not carry any of these properties, and bus
 181         devices have SUBSYTEM and DRIVER as a replacement.
 182 Who:    Kay Sievers <kay.sievers@suse.de>
 183
 184 ---------------------------
 185
 186 What:   ACPI procfs interface
 187 When:   July 2008
 188 Why:    ACPI sysfs conversion should be finished by January 2008.
 189         ACPI procfs interface will be removed in July 2008 so that
 190         there is enough time for the user space to catch up.
 191 Who:    Zhang Rui <rui.zhang@intel.com>
 192
 193 ---------------------------
 194
 195 What:   /proc/acpi/button
 196 When:   August 2007
 197 Why:    /proc/acpi/button has been replaced by events to the input layer
 198         since 2.6.20.
 199 Who:    Len Brown <len.brown@intel.com>
 200
 201 ---------------------------
 202
 203 What:   /proc/acpi/event
 204 When:   February 2008
 205 Why:    /proc/acpi/event has been replaced by events via the input layer
 206         and netlink since 2.6.23.
 207 Who:    Len Brown <len.brown@intel.com>
 208
 209 ---------------------------
 210
 211 What:   i386/x86_64 bzImage symlinks
 212 When:   April 2010
 213
 214 Why:    The i386/x86_64 merge provides a symlink to the old bzImage
 215         location so not yet updated user space tools, e.g. package
 216         scripts, do not break.
 217 Who:    Thomas Gleixner <tglx@linutronix.de>
 218
 219 ---------------------------
 220
 221 What:   GPIO autorequest on gpio_direction_{input,output}() in gpiolib
 222 When:   February 2010
 223 Why:    All callers should use explicit gpio_request()/gpio_free().
 224         The autorequest mechanism in gpiolib was provided mostly as a
 225         migration aid for legacy GPIO interfaces (for SOC based GPIOs).
 226         Those users have now largely migrated.  Platforms implementing
 227         the GPIO interfaces without using gpiolib will see no changes.
 228 Who:    David Brownell <dbrownell@users.sourceforge.net>
 229 ---------------------------
 230
 231 What:   b43 support for firmware revision < 410
 232 When:   The schedule was July 2008, but it was decided that we are going to keep the
 233         code as long as there are no major maintanance headaches.
 234         So it _could_ be removed _any_ time now, if it conflicts with something new.
 235 Why:    The support code for the old firmware hurts code readability/maintainability
 236         and slightly hurts runtime performance. Bugfixes for the old firmware
 237         are not provided by Broadcom anymore.
 238 Who:    Michael Buesch <mb@bu3sch.de>
 239
 240 ---------------------------
 241
 242 What:   /sys/o2cb symlink
 243 When:   January 2010
 244 Why:    /sys/fs/o2cb is the proper location for this information - /sys/o2cb
 245         exists as a symlink for backwards compatibility for old versions of
 246         ocfs2-tools. 2 years should be sufficient time to phase in new versions
 247         which know to look in /sys/fs/o2cb.
 248 Who:    ocfs2-devel@oss.oracle.com
 249
 250 ---------------------------
 251
 252 What:   Ability for non root users to shm_get hugetlb pages based on mlock
 253         resource limits
 254 When:   2.6.31
 255 Why:    Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
 256         have CAP_IPC_LOCK to be able to allocate shm segments backed by
 257         huge pages.  The mlock based rlimit check to allow shm hugetlb is
 258         inconsistent with mmap based allocations.  Hence it is being
 259         deprecated.
 260 Who:    Ravikiran Thirumalai <kiran@scalex86.org>
 261
 262 ---------------------------
 263
 264 What:   CONFIG_THERMAL_HWMON
 265 When:   January 2009
 266 Why:    This option was introduced just to allow older lm-sensors userspace
 267         to keep working over the upgrade to 2.6.26. At the scheduled time of
 268         removal fixed lm-sensors (2.x or 3.x) should be readily available.
 269 Who:    Rene Herman <rene.herman@gmail.com>
 270
 271 ---------------------------
 272
 273 What:   Code that is now under CONFIG_WIRELESS_EXT_SYSFS
 274         (in net/core/net-sysfs.c)
 275 When:   After the only user (hal) has seen a release with the patches
 276         for enough time, probably some time in 2010.
 277 Why:    Over 1K .text/.data size reduction, data is available in other
 278         ways (ioctls)
 279 Who:    Johannes Berg <johannes@sipsolutions.net>
 280
 281 ---------------------------
 282
 283 What:   sysfs ui for changing p4-clockmod parameters
 284 When:   September 2009
 285 Why:    See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
 286         e088e4c9cdb618675874becb91b2fd581ee707e6.
 287         Removal is subject to fixing any remaining bugs in ACPI which may
 288         cause the thermal throttling not to happen at the right time.
 289 Who:    Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
 290
 291 -----------------------------
 292
 293 What:   __do_IRQ all in one fits nothing interrupt handler
 294 When:   2.6.32
 295 Why:    __do_IRQ was kept for easy migration to the type flow handlers.
 296         More than two years of migration time is enough.
 297 Who:    Thomas Gleixner <tglx@linutronix.de>
 298
 299 -----------------------------
 300
 301 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 302 When:   2011
 303 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 304         represent a machine's physical PCI slots. The change in semantics
 305         had userspace implications, as the hotplug core no longer allowed
 306         drivers to create multiple sysfs files per physical slot (required
 307         for multi-function devices, e.g.). fakephp was seen as a developer's
 308         tool only, and its interface changed. Too late, we learned that
 309         there were some users of the fakephp interface.
 310
 311         In 2.6.30, the original fakephp interface was restored. At the same
 312         time, the PCI core gained the ability that fakephp provided, namely
 313         function-level hot-remove and hot-add.
 314
 315         Since the PCI core now provides the same functionality, exposed in:
 316
 317                 /sys/bus/pci/rescan
 318                 /sys/bus/pci/devices/.../remove
 319                 /sys/bus/pci/devices/.../rescan
 320
 321         there is no functional reason to maintain fakephp as well.
 322
 323         We will keep the existing module so that 'modprobe fakephp' will
 324         present the old /sys/bus/pci/slots/... interface for compatibility,
 325         but users are urged to migrate their applications to the API above.
 326
 327         After a reasonable transition period, we will remove the legacy
 328         fakephp interface.
 329 Who:    Alex Chiang <achiang@hp.com>
 330
 331 ---------------------------
 332
 333 What:   CONFIG_RFKILL_INPUT
 334 When:   2.6.33
 335 Why:    Should be implemented in userspace, policy daemon.
 336 Who:    Johannes Berg <johannes@sipsolutions.net>
 337
 338 ---------------------------
 339
 340 What:   CONFIG_INOTIFY
 341 When:   2.6.33
 342 Why:    last user (audit) will be converted to the newer more generic
 343         and more easily maintained fsnotify subsystem
 344 Who:    Eric Paris <eparis@redhat.com>
 345
 346 ----------------------------
 347
 348 What:   sound-slot/service-* module aliases and related clutters in
 349         sound/sound_core.c
 350 When:   August 2010
 351 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 352         (14) and requests modules using custom sound-slot/service-*
 353         module aliases.  The only benefit of doing this is allowing
 354         use of custom module aliases which might as well be considered
 355         a bug at this point.  This preemptive claiming prevents
 356         alternative OSS implementations.
 357
 358         Till the feature is removed, the kernel will be requesting
 359         both sound-slot/service-* and the standard char-major-* module
 360         aliases and allow turning off the pre-claiming selectively via
 361         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 362         kernel parameter.
 363
 364         After the transition phase is complete, both the custom module
 365         aliases and switches to disable it will go away.  This removal
 366         will also allow making ALSA OSS emulation independent of
 367         sound_core.  The dependency will be broken then too.
 368 Who:    Tejun Heo <tj@kernel.org>
 369
 370 ----------------------------
 371
 372 What:   Support for VMware's guest paravirtuliazation technique [VMI] will be
 373         dropped.
 374 When:   2.6.37 or earlier.
 375 Why:    With the recent innovations in CPU hardware acceleration technologies
 376         from Intel and AMD, VMware ran a few experiments to compare these
 377         techniques to guest paravirtualization technique on VMware's platform.
 378         These hardware assisted virtualization techniques have outperformed the
 379         performance benefits provided by VMI in most of the workloads. VMware
 380         expects that these hardware features will be ubiquitous in a couple of
 381         years, as a result, VMware has started a phased retirement of this
 382         feature from the hypervisor. We will be removing this feature from the
 383         Kernel too. Right now we are targeting 2.6.37 but can retire earlier if
 384         technical reasons (read opportunity to remove major chunk of pvops)
 385         arise.
 386
 387         Please note that VMI has always been an optimization and non-VMI kernels
 388         still work fine on VMware's platform.
 389         Latest versions of VMware's product which support VMI are,
 390         Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence
 391         releases for these products will continue supporting VMI.
 392
 393         For more details about VMI retirement take a look at this,
 394         http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html
 395
 396 Who:    Alok N Kataria <akataria@vmware.com>
 397
 398 ----------------------------
 399
 400 What:   Support for lcd_switch and display_get in asus-laptop driver
 401 When:   March 2010
 402 Why:    These two features use non-standard interfaces. There are the
 403         only features that really need multiple path to guess what's
 404         the right method name on a specific laptop.
 405
 406         Removing them will allow to remove a lot of code an significantly
 407         clean the drivers.
 408
 409         This will affect the backlight code which won't be able to know
 410         if the backlight is on or off. The platform display file will also be
 411         write only (like the one in eeepc-laptop).
 412
 413         This should'nt affect a lot of user because they usually know
 414         when their display is on or off.
 415
 416 Who:    Corentin Chary <corentin.chary@gmail.com>
 417
 418 ----------------------------
 419
 420 What:   sysfs-class-rfkill state file
 421 When:   Feb 2014
 422 Files:  net/rfkill/core.c
 423 Why:    Documented as obsolete since Feb 2010. This file is limited to 3
 424         states while the rfkill drivers can have 4 states.
 425 Who:    anybody or Florian Mickler <florian@mickler.org>
 426
 427 ----------------------------
 428
 429 What:   sysfs-class-rfkill claim file
 430 When:   Feb 2012
 431 Files:  net/rfkill/core.c
 432 Why:    It is not possible to claim an rfkill driver since 2007. This is
 433         Documented as obsolete since Feb 2010.
 434 Who:    anybody or Florian Mickler <florian@mickler.org>
 435
 436 ----------------------------
 437
 438 What:   capifs
 439 When:   February 2011
 440 Files:  drivers/isdn/capi/capifs.*
 441 Why:    udev fully replaces this special file system that only contains CAPI
 442         NCCI TTY device nodes. User space (pppdcapiplugin) works without
 443         noticing the difference.
 444 Who:    Jan Kiszka <jan.kiszka@web.de>
 445
 446 ----------------------------
 447
 448 What:   KVM paravirt mmu host support
 449 When:   January 2011
 450 Why:    The paravirt mmu host support is slower than non-paravirt mmu, both
 451         on newer and older hardware.  It is already not exposed to the guest,
 452         and kept only for live migration purposes.
 453 Who:    Avi Kivity <avi@redhat.com>
 454
 455 ----------------------------
 456
 457 What:   iwlwifi 50XX module parameters
 458 When:   2.6.40
 459 Why:    The "..50" modules parameters were used to configure 5000 series and
 460         up devices; different set of module parameters also available for 4965
 461         with same functionalities. Consolidate both set into single place
 462         in drivers/net/wireless/iwlwifi/iwl-agn.c
 463
 464 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 465
 466 ----------------------------
 467
 468 What:   iwl4965 alias support
 469 When:   2.6.40
 470 Why:    Internal alias support has been present in module-init-tools for some
 471         time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
 472         with no impact.
 473
 474 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 475
 476 ---------------------------
 477
 478 What:   xt_NOTRACK
 479 Files:  net/netfilter/xt_NOTRACK.c
 480 When:   April 2011
 481 Why:    Superseded by xt_CT
 482 Who:    Netfilter developer team <netfilter-devel@vger.kernel.org>
 483
 484 ---------------------------
 485
 486 What:   video4linux /dev/vtx teletext API support
 487 When:   2.6.35
 488 Files:  drivers/media/video/saa5246a.c drivers/media/video/saa5249.c
 489         include/linux/videotext.h
 490 Why:    The vtx device nodes have been superseded by vbi device nodes
 491         for many years. No applications exist that use the vtx support.
 492         Of the two i2c drivers that actually support this API the saa5249
 493         has been impossible to use for a year now and no known hardware
 494         that supports this device exists. The saa5246a is theoretically
 495         supported by the old mxb boards, but it never actually worked.
 496
 497         In summary: there is no hardware that can use this API and there
 498         are no applications actually implementing this API.
 499
 500         The vtx support still reserves minors 192-223 and we would really
 501         like to reuse those for upcoming new functionality. In the unlikely
 502         event that new hardware appears that wants to use the functionality
 503         provided by the vtx API, then that functionality should be build
 504         around the sliced VBI API instead.
 505 Who:    Hans Verkuil <hverkuil@xs4all.nl>
 506
 507 ----------------------------
 508
 509 What:   IRQF_DISABLED
 510 When:   2.6.36
 511 Why:    The flag is a NOOP as we run interrupt handlers with interrupts disabled
 512 Who:    Thomas Gleixner <tglx@linutronix.de>
 513
 514 ----------------------------
 515
 516 What:   old ieee1394 subsystem (CONFIG_IEEE1394)
 517 When:   2.6.37
 518 Files:  drivers/ieee1394/ except init_ohci1394_dma.c
 519 Why:    superseded by drivers/firewire/ (CONFIG_FIREWIRE) which offers more
 520         features, better performance, and better security, all with smaller
 521         and more modern code base
 522 Who:    Stefan Richter <stefanr@s5r6.in-berlin.de>
 523
 524 ----------------------------
 525
 526 What:   The acpi_sleep=s4_nonvs command line option
 527 When:   2.6.37
 528 Files:  arch/x86/kernel/acpi/sleep.c
 529 Why:    superseded by acpi_sleep=nonvs
 530 Who:    Rafael J. Wysocki <rjw@sisk.pl>
 531
 532 ----------------------------