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:   USER_SCHED
  10 When:   2.6.34
  11
  12 Why:    USER_SCHED was implemented as a proof of concept for group scheduling.
  13         The effect of USER_SCHED can already be achieved from userspace with
  14         the help of libcgroup. The removal of USER_SCHED will also simplify
  15         the scheduler code with the removal of one major ifdef. There are also
  16         issues USER_SCHED has with USER_NS. A decision was taken not to fix
  17         those and instead remove USER_SCHED. Also new group scheduling
  18         features will not be implemented for USER_SCHED.
  19
  20 Who:    Dhaval Giani <dhaval@linux.vnet.ibm.com>
  21
  22 ---------------------------
  23
  24 What:   PRISM54
  25 When:   2.6.34
  26
  27 Why:    prism54 FullMAC PCI / Cardbus devices used to be supported only by the
  28         prism54 wireless driver. After Intersil stopped selling these
  29         devices in preference for the newer more flexible SoftMAC devices
  30         a SoftMAC device driver was required and prism54 did not support
  31         them. The p54pci driver now exists and has been present in the kernel for
  32         a while. This driver supports both SoftMAC devices and FullMAC devices.
  33         The main difference between these devices was the amount of memory which
  34         could be used for the firmware. The SoftMAC devices support a smaller
  35         amount of memory. Because of this the SoftMAC firmware fits into FullMAC
  36         devices's memory. p54pci supports not only PCI / Cardbus but also USB
  37         and SPI. Since p54pci supports all devices prism54 supports
  38         you will have a conflict. I'm not quite sure how distributions are
  39         handling this conflict right now. prism54 was kept around due to
  40         claims users may experience issues when using the SoftMAC driver.
  41         Time has passed users have not reported issues. If you use prism54
  42         and for whatever reason you cannot use p54pci please let us know!
  43         E-mail us at: linux-wireless@vger.kernel.org
  44
  45         For more information see the p54 wiki page:
  46
  47         http://wireless.kernel.org/en/users/Drivers/p54
  48
  49 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  50
  51 ---------------------------
  52
  53 What:   IRQF_SAMPLE_RANDOM
  54 Check:  IRQF_SAMPLE_RANDOM
  55 When:   July 2009
  56
  57 Why:    Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
  58         sources in the kernel's current entropy model. To resolve this, every
  59         input point to the kernel's entropy pool needs to better document the
  60         type of entropy source it actually is. This will be replaced with
  61         additional add_*_randomness functions in drivers/char/random.c
  62
  63 Who:    Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
  64
  65 ---------------------------
  66
  67 What:   The ieee80211_regdom module parameter
  68 When:   March 2010 / desktop catchup
  69
  70 Why:    This was inherited by the CONFIG_WIRELESS_OLD_REGULATORY code,
  71         and currently serves as an option for users to define an
  72         ISO / IEC 3166 alpha2 code for the country they are currently
  73         present in. Although there are userspace API replacements for this
  74         through nl80211 distributions haven't yet caught up with implementing
  75         decent alternatives through standard GUIs. Although available as an
  76         option through iw or wpa_supplicant its just a matter of time before
  77         distributions pick up good GUI options for this. The ideal solution
  78         would actually consist of intelligent designs which would do this for
  79         the user automatically even when travelling through different countries.
  80         Until then we leave this module parameter as a compromise.
  81
  82         When userspace improves with reasonable widely-available alternatives for
  83         this we will no longer need this module parameter. This entry hopes that
  84         by the super-futuristically looking date of "March 2010" we will have
  85         such replacements widely available.
  86
  87 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  88
  89 ---------------------------
  90
  91 What:   dev->power.power_state
  92 When:   July 2007
  93 Why:    Broken design for runtime control over driver power states, confusing
  94         driver-internal runtime power management with:  mechanisms to support
  95         system-wide sleep state transitions; event codes that distinguish
  96         different phases of swsusp "sleep" transitions; and userspace policy
  97         inputs.  This framework was never widely used, and most attempts to
  98         use it were broken.  Drivers should instead be exposing domain-specific
  99         interfaces either to kernel or to userspace.
 100 Who:    Pavel Machek <pavel@suse.cz>
 101
 102 ---------------------------
 103
 104 What:   Video4Linux API 1 ioctls and from Video devices.
 105 When:   July 2009
 106 Files:  include/linux/videodev.h
 107 Check:  include/linux/videodev.h
 108 Why:    V4L1 AP1 was replaced by V4L2 API during migration from 2.4 to 2.6
 109         series. The old API have lots of drawbacks and don't provide enough
 110         means to work with all video and audio standards. The newer API is
 111         already available on the main drivers and should be used instead.
 112         Newer drivers should use v4l_compat_translate_ioctl function to handle
 113         old calls, replacing to newer ones.
 114         Decoder iocts are using internally to allow video drivers to
 115         communicate with video decoders. This should also be improved to allow
 116         V4L2 calls being translated into compatible internal ioctls.
 117         Compatibility ioctls will be provided, for a while, via
 118         v4l1-compat module.
 119 Who:    Mauro Carvalho Chehab <mchehab@infradead.org>
 120
 121 ---------------------------
 122
 123 What:   PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl])
 124 When:   November 2005
 125 Files:  drivers/pcmcia/: pcmcia_ioctl.c
 126 Why:    With the 16-bit PCMCIA subsystem now behaving (almost) like a
 127         normal hotpluggable bus, and with it using the default kernel
 128         infrastructure (hotplug, driver core, sysfs) keeping the PCMCIA
 129         control ioctl needed by cardmgr and cardctl from pcmcia-cs is
 130         unnecessary, and makes further cleanups and integration of the
 131         PCMCIA subsystem into the Linux kernel device driver model more
 132         difficult. The features provided by cardmgr and cardctl are either
 133         handled by the kernel itself now or are available in the new
 134         pcmciautils package available at
 135         http://kernel.org/pub/linux/utils/kernel/pcmcia/
 136 Who:    Dominik Brodowski <linux@brodo.de>
 137
 138 ---------------------------
 139
 140 What:   sys_sysctl
 141 When:   September 2010
 142 Option: CONFIG_SYSCTL_SYSCALL
 143 Why:    The same information is available in a more convenient from
 144         /proc/sys, and none of the sysctl variables appear to be
 145         important performance wise.
 146
 147         Binary sysctls are a long standing source of subtle kernel
 148         bugs and security issues.
 149
 150         When I looked several months ago all I could find after
 151         searching several distributions were 5 user space programs and
 152         glibc (which falls back to /proc/sys) using this syscall.
 153
 154         The man page for sysctl(2) documents it as unusable for user
 155         space programs.
 156
 157         sysctl(2) is not generally ABI compatible to a 32bit user
 158         space application on a 64bit and a 32bit kernel.
 159
 160         For the last several months the policy has been no new binary
 161         sysctls and no one has put forward an argument to use them.
 162
 163         Binary sysctls issues seem to keep happening appearing so
 164         properly deprecating them (with a warning to user space) and a
 165         2 year grace warning period will mean eventually we can kill
 166         them and end the pain.
 167
 168         In the mean time individual binary sysctls can be dealt with
 169         in a piecewise fashion.
 170
 171 Who:    Eric Biederman <ebiederm@xmission.com>
 172
 173 ---------------------------
 174
 175 What:   remove EXPORT_SYMBOL(kernel_thread)
 176 When:   August 2006
 177 Files:  arch/*/kernel/*_ksyms.c
 178 Check:  kernel_thread
 179 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 180         use the <linux/kthread.h> API instead which shields them from
 181         implementation details and provides a higherlevel interface that
 182         prevents bugs and code duplication
 183 Who:    Christoph Hellwig <hch@lst.de>
 184
 185 ---------------------------
 186
 187 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 188         (temporary transition config option provided until then)
 189         The transition config option will also be removed at the same time.
 190 When:   before 2.6.19
 191 Why:    Unused symbols are both increasing the size of the kernel binary
 192         and are often a sign of "wrong API"
 193 Who:    Arjan van de Ven <arjan@linux.intel.com>
 194
 195 ---------------------------
 196
 197 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 198 When:   October 2008
 199 Why:    The stacking of class devices makes these values misleading and
 200         inconsistent.
 201         Class devices should not carry any of these properties, and bus
 202         devices have SUBSYTEM and DRIVER as a replacement.
 203 Who:    Kay Sievers <kay.sievers@suse.de>
 204
 205 ---------------------------
 206
 207 What:   ACPI procfs interface
 208 When:   July 2008
 209 Why:    ACPI sysfs conversion should be finished by January 2008.
 210         ACPI procfs interface will be removed in July 2008 so that
 211         there is enough time for the user space to catch up.
 212 Who:    Zhang Rui <rui.zhang@intel.com>
 213
 214 ---------------------------
 215
 216 What:   /proc/acpi/button
 217 When:   August 2007
 218 Why:    /proc/acpi/button has been replaced by events to the input layer
 219         since 2.6.20.
 220 Who:    Len Brown <len.brown@intel.com>
 221
 222 ---------------------------
 223
 224 What:   /proc/acpi/event
 225 When:   February 2008
 226 Why:    /proc/acpi/event has been replaced by events via the input layer
 227         and netlink since 2.6.23.
 228 Who:    Len Brown <len.brown@intel.com>
 229
 230 ---------------------------
 231
 232 What:   i386/x86_64 bzImage symlinks
 233 When:   April 2010
 234
 235 Why:    The i386/x86_64 merge provides a symlink to the old bzImage
 236         location so not yet updated user space tools, e.g. package
 237         scripts, do not break.
 238 Who:    Thomas Gleixner <tglx@linutronix.de>
 239
 240 ---------------------------
 241
 242 What (Why):
 243         - xt_recent: the old ipt_recent proc dir
 244           (superseded by /proc/net/xt_recent)
 245
 246 When:   January 2009 or Linux 2.7.0, whichever comes first
 247 Why:    Superseded by newer revisions or modules
 248 Who:    Jan Engelhardt <jengelh@computergmbh.de>
 249
 250 ---------------------------
 251
 252 What:   GPIO autorequest on gpio_direction_{input,output}() in gpiolib
 253 When:   February 2010
 254 Why:    All callers should use explicit gpio_request()/gpio_free().
 255         The autorequest mechanism in gpiolib was provided mostly as a
 256         migration aid for legacy GPIO interfaces (for SOC based GPIOs).
 257         Those users have now largely migrated.  Platforms implementing
 258         the GPIO interfaces without using gpiolib will see no changes.
 259 Who:    David Brownell <dbrownell@users.sourceforge.net>
 260 ---------------------------
 261
 262 What:   b43 support for firmware revision < 410
 263 When:   The schedule was July 2008, but it was decided that we are going to keep the
 264         code as long as there are no major maintanance headaches.
 265         So it _could_ be removed _any_ time now, if it conflicts with something new.
 266 Why:    The support code for the old firmware hurts code readability/maintainability
 267         and slightly hurts runtime performance. Bugfixes for the old firmware
 268         are not provided by Broadcom anymore.
 269 Who:    Michael Buesch <mb@bu3sch.de>
 270
 271 ---------------------------
 272
 273 What:   /sys/o2cb symlink
 274 When:   January 2010
 275 Why:    /sys/fs/o2cb is the proper location for this information - /sys/o2cb
 276         exists as a symlink for backwards compatibility for old versions of
 277         ocfs2-tools. 2 years should be sufficient time to phase in new versions
 278         which know to look in /sys/fs/o2cb.
 279 Who:    ocfs2-devel@oss.oracle.com
 280
 281 ---------------------------
 282
 283 What:   Ability for non root users to shm_get hugetlb pages based on mlock
 284         resource limits
 285 When:   2.6.31
 286 Why:    Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
 287         have CAP_IPC_LOCK to be able to allocate shm segments backed by
 288         huge pages.  The mlock based rlimit check to allow shm hugetlb is
 289         inconsistent with mmap based allocations.  Hence it is being
 290         deprecated.
 291 Who:    Ravikiran Thirumalai <kiran@scalex86.org>
 292
 293 ---------------------------
 294
 295 What:   CONFIG_THERMAL_HWMON
 296 When:   January 2009
 297 Why:    This option was introduced just to allow older lm-sensors userspace
 298         to keep working over the upgrade to 2.6.26. At the scheduled time of
 299         removal fixed lm-sensors (2.x or 3.x) should be readily available.
 300 Who:    Rene Herman <rene.herman@gmail.com>
 301
 302 ---------------------------
 303
 304 What:   Code that is now under CONFIG_WIRELESS_EXT_SYSFS
 305         (in net/core/net-sysfs.c)
 306 When:   After the only user (hal) has seen a release with the patches
 307         for enough time, probably some time in 2010.
 308 Why:    Over 1K .text/.data size reduction, data is available in other
 309         ways (ioctls)
 310 Who:    Johannes Berg <johannes@sipsolutions.net>
 311
 312 ---------------------------
 313
 314 What: CONFIG_NF_CT_ACCT
 315 When: 2.6.29
 316 Why:  Accounting can now be enabled/disabled without kernel recompilation.
 317       Currently used only to set a default value for a feature that is also
 318       controlled by a kernel/module/sysfs/sysctl parameter.
 319 Who:  Krzysztof Piotr Oledzki <ole@ans.pl>
 320
 321 ---------------------------
 322
 323 What:   sysfs ui for changing p4-clockmod parameters
 324 When:   September 2009
 325 Why:    See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
 326         e088e4c9cdb618675874becb91b2fd581ee707e6.
 327         Removal is subject to fixing any remaining bugs in ACPI which may
 328         cause the thermal throttling not to happen at the right time.
 329 Who:    Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
 330
 331 -----------------------------
 332
 333 What:   __do_IRQ all in one fits nothing interrupt handler
 334 When:   2.6.32
 335 Why:    __do_IRQ was kept for easy migration to the type flow handlers.
 336         More than two years of migration time is enough.
 337 Who:    Thomas Gleixner <tglx@linutronix.de>
 338
 339 -----------------------------
 340
 341 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 342 When:   2011
 343 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 344         represent a machine's physical PCI slots. The change in semantics
 345         had userspace implications, as the hotplug core no longer allowed
 346         drivers to create multiple sysfs files per physical slot (required
 347         for multi-function devices, e.g.). fakephp was seen as a developer's
 348         tool only, and its interface changed. Too late, we learned that
 349         there were some users of the fakephp interface.
 350
 351         In 2.6.30, the original fakephp interface was restored. At the same
 352         time, the PCI core gained the ability that fakephp provided, namely
 353         function-level hot-remove and hot-add.
 354
 355         Since the PCI core now provides the same functionality, exposed in:
 356
 357                 /sys/bus/pci/rescan
 358                 /sys/bus/pci/devices/.../remove
 359                 /sys/bus/pci/devices/.../rescan
 360
 361         there is no functional reason to maintain fakephp as well.
 362
 363         We will keep the existing module so that 'modprobe fakephp' will
 364         present the old /sys/bus/pci/slots/... interface for compatibility,
 365         but users are urged to migrate their applications to the API above.
 366
 367         After a reasonable transition period, we will remove the legacy
 368         fakephp interface.
 369 Who:    Alex Chiang <achiang@hp.com>
 370
 371 ---------------------------
 372
 373 What:   CONFIG_RFKILL_INPUT
 374 When:   2.6.33
 375 Why:    Should be implemented in userspace, policy daemon.
 376 Who:    Johannes Berg <johannes@sipsolutions.net>
 377
 378 ---------------------------
 379
 380 What:   CONFIG_INOTIFY
 381 When:   2.6.33
 382 Why:    last user (audit) will be converted to the newer more generic
 383         and more easily maintained fsnotify subsystem
 384 Who:    Eric Paris <eparis@redhat.com>
 385
 386 ----------------------------
 387
 388 What:   lock_policy_rwsem_* and unlock_policy_rwsem_* will not be
 389         exported interface anymore.
 390 When:   2.6.33
 391 Why:    cpu_policy_rwsem has a new cleaner definition making it local to
 392         cpufreq core and contained inside cpufreq.c. Other dependent
 393         drivers should not use it in order to safely avoid lockdep issues.
 394 Who:    Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 395
 396 ----------------------------
 397
 398 What:   sound-slot/service-* module aliases and related clutters in
 399         sound/sound_core.c
 400 When:   August 2010
 401 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 402         (14) and requests modules using custom sound-slot/service-*
 403         module aliases.  The only benefit of doing this is allowing
 404         use of custom module aliases which might as well be considered
 405         a bug at this point.  This preemptive claiming prevents
 406         alternative OSS implementations.
 407
 408         Till the feature is removed, the kernel will be requesting
 409         both sound-slot/service-* and the standard char-major-* module
 410         aliases and allow turning off the pre-claiming selectively via
 411         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 412         kernel parameter.
 413
 414         After the transition phase is complete, both the custom module
 415         aliases and switches to disable it will go away.  This removal
 416         will also allow making ALSA OSS emulation independent of
 417         sound_core.  The dependency will be broken then too.
 418 Who:    Tejun Heo <tj@kernel.org>
 419
 420 ----------------------------
 421
 422 What:   Support for VMware's guest paravirtuliazation technique [VMI] will be
 423         dropped.
 424 When:   2.6.37 or earlier.
 425 Why:    With the recent innovations in CPU hardware acceleration technologies
 426         from Intel and AMD, VMware ran a few experiments to compare these
 427         techniques to guest paravirtualization technique on VMware's platform.
 428         These hardware assisted virtualization techniques have outperformed the
 429         performance benefits provided by VMI in most of the workloads. VMware
 430         expects that these hardware features will be ubiquitous in a couple of
 431         years, as a result, VMware has started a phased retirement of this
 432         feature from the hypervisor. We will be removing this feature from the
 433         Kernel too. Right now we are targeting 2.6.37 but can retire earlier if
 434         technical reasons (read opportunity to remove major chunk of pvops)
 435         arise.
 436
 437         Please note that VMI has always been an optimization and non-VMI kernels
 438         still work fine on VMware's platform.
 439         Latest versions of VMware's product which support VMI are,
 440         Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence
 441         releases for these products will continue supporting VMI.
 442
 443         For more details about VMI retirement take a look at this,
 444         http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html
 445
 446 Who:    Alok N Kataria <akataria@vmware.com>
 447
 448 ----------------------------
 449
 450 What:   adt7473 hardware monitoring driver
 451 When:   February 2010
 452 Why:    Obsoleted by the adt7475 driver.
 453 Who:    Jean Delvare <khali@linux-fr.org>
 454
 455 ---------------------------
 456 What:   Support for lcd_switch and display_get in asus-laptop driver
 457 When:   March 2010
 458 Why:    These two features use non-standard interfaces. There are the
 459         only features that really need multiple path to guess what's
 460         the right method name on a specific laptop.
 461
 462         Removing them will allow to remove a lot of code an significantly
 463         clean the drivers.
 464
 465         This will affect the backlight code which won't be able to know
 466         if the backlight is on or off. The platform display file will also be
 467         write only (like the one in eeepc-laptop).
 468
 469         This should'nt affect a lot of user because they usually know
 470         when their display is on or off.
 471
 472 Who:    Corentin Chary <corentin.chary@gmail.com>
 473
 474 ----------------------------