Root/Documentation/feature-removal-schedule.txt

1The following is a list of files and features that are going to be
2removed in the kernel source tree. Every entry should contain what
3exactly is going away, why it is happening, and who is going to be doing
4the work. When the feature is removed from the kernel, it should also
5be removed from this file.
6
7---------------------------
8
9What: PRISM54
10When: 2.6.34
11
12Why: 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
34Who: Luis R. Rodriguez <lrodriguez@atheros.com>
35
36---------------------------
37
38What: IRQF_SAMPLE_RANDOM
39Check: IRQF_SAMPLE_RANDOM
40When: July 2009
41
42Why: 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
48Who: Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
49
50---------------------------
51
52What: Deprecated snapshot ioctls
53When: 2.6.36
54
55Why: 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
59Who: Jiri Slaby <jirislaby@gmail.com>
60
61---------------------------
62
63What: The ieee80211_regdom module parameter
64When: March 2010 / desktop catchup
65
66Why: 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
83Who: Luis R. Rodriguez <lrodriguez@atheros.com>
84
85---------------------------
86
87What: dev->power.power_state
88When: July 2007
89Why: 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.
96Who: Pavel Machek <pavel@suse.cz>
97
98---------------------------
99
100What: Video4Linux API 1 ioctls and from Video devices.
101When: July 2009
102Files: include/linux/videodev.h
103Check: include/linux/videodev.h
104Why: 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.
115Who: Mauro Carvalho Chehab <mchehab@infradead.org>
116
117---------------------------
118
119What: PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl])
120When: 2.6.35/2.6.36
121Files: drivers/pcmcia/: pcmcia_ioctl.c
122Why: 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.
138Who: Dominik Brodowski <linux@dominikbrodowski.net>
139
140---------------------------
141
142What: sys_sysctl
143When: September 2010
144Option: CONFIG_SYSCTL_SYSCALL
145Why: 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
173Who: Eric Biederman <ebiederm@xmission.com>
174
175---------------------------
176
177What: remove EXPORT_SYMBOL(kernel_thread)
178When: August 2006
179Files: arch/*/kernel/*_ksyms.c
180Check: kernel_thread
181Why: 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
185Who: Christoph Hellwig <hch@lst.de>
186
187---------------------------
188
189What: 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.
192When: before 2.6.19
193Why: Unused symbols are both increasing the size of the kernel binary
194    and are often a sign of "wrong API"
195Who: Arjan van de Ven <arjan@linux.intel.com>
196
197---------------------------
198
199What: PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
200When: October 2008
201Why: 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.
205Who: Kay Sievers <kay.sievers@suse.de>
206
207---------------------------
208
209What: ACPI procfs interface
210When: July 2008
211Why: 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.
214Who: Zhang Rui <rui.zhang@intel.com>
215
216---------------------------
217
218What: /proc/acpi/button
219When: August 2007
220Why: /proc/acpi/button has been replaced by events to the input layer
221    since 2.6.20.
222Who: Len Brown <len.brown@intel.com>
223
224---------------------------
225
226What: /proc/acpi/event
227When: February 2008
228Why: /proc/acpi/event has been replaced by events via the input layer
229    and netlink since 2.6.23.
230Who: Len Brown <len.brown@intel.com>
231
232---------------------------
233
234What: i386/x86_64 bzImage symlinks
235When: April 2010
236
237Why: 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.
240Who: Thomas Gleixner <tglx@linutronix.de>
241
242---------------------------
243
244What (Why):
245    - xt_recent: the old ipt_recent proc dir
246      (superseded by /proc/net/xt_recent)
247
248When: January 2009 or Linux 2.7.0, whichever comes first
249Why: Superseded by newer revisions or modules
250Who: Jan Engelhardt <jengelh@computergmbh.de>
251
252---------------------------
253
254What: GPIO autorequest on gpio_direction_{input,output}() in gpiolib
255When: February 2010
256Why: All callers should use explicit gpio_request()/gpio_free().
257    The autorequest mechanism in gpiolib was provided mostly as a
258    migration aid for legacy GPIO interfaces (for SOC based GPIOs).
259    Those users have now largely migrated. Platforms implementing
260    the GPIO interfaces without using gpiolib will see no changes.
261Who: David Brownell <dbrownell@users.sourceforge.net>
262---------------------------
263
264What: b43 support for firmware revision < 410
265When: The schedule was July 2008, but it was decided that we are going to keep the
266        code as long as there are no major maintanance headaches.
267    So it _could_ be removed _any_ time now, if it conflicts with something new.
268Why: The support code for the old firmware hurts code readability/maintainability
269    and slightly hurts runtime performance. Bugfixes for the old firmware
270    are not provided by Broadcom anymore.
271Who: Michael Buesch <mb@bu3sch.de>
272
273---------------------------
274
275What: /sys/o2cb symlink
276When: January 2010
277Why: /sys/fs/o2cb is the proper location for this information - /sys/o2cb
278    exists as a symlink for backwards compatibility for old versions of
279    ocfs2-tools. 2 years should be sufficient time to phase in new versions
280    which know to look in /sys/fs/o2cb.
281Who: ocfs2-devel@oss.oracle.com
282
283---------------------------
284
285What: Ability for non root users to shm_get hugetlb pages based on mlock
286    resource limits
287When: 2.6.31
288Why: Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
289    have CAP_IPC_LOCK to be able to allocate shm segments backed by
290    huge pages. The mlock based rlimit check to allow shm hugetlb is
291    inconsistent with mmap based allocations. Hence it is being
292    deprecated.
293Who: Ravikiran Thirumalai <kiran@scalex86.org>
294
295---------------------------
296
297What: CONFIG_THERMAL_HWMON
298When: January 2009
299Why: This option was introduced just to allow older lm-sensors userspace
300    to keep working over the upgrade to 2.6.26. At the scheduled time of
301    removal fixed lm-sensors (2.x or 3.x) should be readily available.
302Who: Rene Herman <rene.herman@gmail.com>
303
304---------------------------
305
306What: Code that is now under CONFIG_WIRELESS_EXT_SYSFS
307    (in net/core/net-sysfs.c)
308When: After the only user (hal) has seen a release with the patches
309    for enough time, probably some time in 2010.
310Why: Over 1K .text/.data size reduction, data is available in other
311    ways (ioctls)
312Who: Johannes Berg <johannes@sipsolutions.net>
313
314---------------------------
315
316What: CONFIG_NF_CT_ACCT
317When: 2.6.29
318Why: Accounting can now be enabled/disabled without kernel recompilation.
319      Currently used only to set a default value for a feature that is also
320      controlled by a kernel/module/sysfs/sysctl parameter.
321Who: Krzysztof Piotr Oledzki <ole@ans.pl>
322
323---------------------------
324
325What: sysfs ui for changing p4-clockmod parameters
326When: September 2009
327Why: See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
328    e088e4c9cdb618675874becb91b2fd581ee707e6.
329    Removal is subject to fixing any remaining bugs in ACPI which may
330    cause the thermal throttling not to happen at the right time.
331Who: Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
332
333-----------------------------
334
335What: __do_IRQ all in one fits nothing interrupt handler
336When: 2.6.32
337Why: __do_IRQ was kept for easy migration to the type flow handlers.
338    More than two years of migration time is enough.
339Who: Thomas Gleixner <tglx@linutronix.de>
340
341-----------------------------
342
343What: fakephp and associated sysfs files in /sys/bus/pci/slots/
344When: 2011
345Why: In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
346    represent a machine's physical PCI slots. The change in semantics
347    had userspace implications, as the hotplug core no longer allowed
348    drivers to create multiple sysfs files per physical slot (required
349    for multi-function devices, e.g.). fakephp was seen as a developer's
350    tool only, and its interface changed. Too late, we learned that
351    there were some users of the fakephp interface.
352
353    In 2.6.30, the original fakephp interface was restored. At the same
354    time, the PCI core gained the ability that fakephp provided, namely
355    function-level hot-remove and hot-add.
356
357    Since the PCI core now provides the same functionality, exposed in:
358
359        /sys/bus/pci/rescan
360        /sys/bus/pci/devices/.../remove
361        /sys/bus/pci/devices/.../rescan
362
363    there is no functional reason to maintain fakephp as well.
364
365    We will keep the existing module so that 'modprobe fakephp' will
366    present the old /sys/bus/pci/slots/... interface for compatibility,
367    but users are urged to migrate their applications to the API above.
368
369    After a reasonable transition period, we will remove the legacy
370    fakephp interface.
371Who: Alex Chiang <achiang@hp.com>
372
373---------------------------
374
375What: CONFIG_RFKILL_INPUT
376When: 2.6.33
377Why: Should be implemented in userspace, policy daemon.
378Who: Johannes Berg <johannes@sipsolutions.net>
379
380---------------------------
381
382What: CONFIG_INOTIFY
383When: 2.6.33
384Why: last user (audit) will be converted to the newer more generic
385    and more easily maintained fsnotify subsystem
386Who: Eric Paris <eparis@redhat.com>
387
388----------------------------
389
390What: lock_policy_rwsem_* and unlock_policy_rwsem_* will not be
391    exported interface anymore.
392When: 2.6.33
393Why: cpu_policy_rwsem has a new cleaner definition making it local to
394    cpufreq core and contained inside cpufreq.c. Other dependent
395    drivers should not use it in order to safely avoid lockdep issues.
396Who: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
397
398----------------------------
399
400What: sound-slot/service-* module aliases and related clutters in
401    sound/sound_core.c
402When: August 2010
403Why: OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
404    (14) and requests modules using custom sound-slot/service-*
405    module aliases. The only benefit of doing this is allowing
406    use of custom module aliases which might as well be considered
407    a bug at this point. This preemptive claiming prevents
408    alternative OSS implementations.
409
410    Till the feature is removed, the kernel will be requesting
411    both sound-slot/service-* and the standard char-major-* module
412    aliases and allow turning off the pre-claiming selectively via
413    CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
414    kernel parameter.
415
416    After the transition phase is complete, both the custom module
417    aliases and switches to disable it will go away. This removal
418    will also allow making ALSA OSS emulation independent of
419    sound_core. The dependency will be broken then too.
420Who: Tejun Heo <tj@kernel.org>
421
422----------------------------
423
424What: Support for VMware's guest paravirtuliazation technique [VMI] will be
425    dropped.
426When: 2.6.37 or earlier.
427Why: With the recent innovations in CPU hardware acceleration technologies
428    from Intel and AMD, VMware ran a few experiments to compare these
429    techniques to guest paravirtualization technique on VMware's platform.
430    These hardware assisted virtualization techniques have outperformed the
431    performance benefits provided by VMI in most of the workloads. VMware
432    expects that these hardware features will be ubiquitous in a couple of
433    years, as a result, VMware has started a phased retirement of this
434    feature from the hypervisor. We will be removing this feature from the
435    Kernel too. Right now we are targeting 2.6.37 but can retire earlier if
436    technical reasons (read opportunity to remove major chunk of pvops)
437    arise.
438
439    Please note that VMI has always been an optimization and non-VMI kernels
440    still work fine on VMware's platform.
441    Latest versions of VMware's product which support VMI are,
442    Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence
443    releases for these products will continue supporting VMI.
444
445    For more details about VMI retirement take a look at this,
446    http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html
447
448Who: Alok N Kataria <akataria@vmware.com>
449
450----------------------------
451
452What: Support for lcd_switch and display_get in asus-laptop driver
453When: March 2010
454Why: These two features use non-standard interfaces. There are the
455    only features that really need multiple path to guess what's
456    the right method name on a specific laptop.
457
458    Removing them will allow to remove a lot of code an significantly
459    clean the drivers.
460
461    This will affect the backlight code which won't be able to know
462    if the backlight is on or off. The platform display file will also be
463    write only (like the one in eeepc-laptop).
464
465    This should'nt affect a lot of user because they usually know
466    when their display is on or off.
467
468Who: Corentin Chary <corentin.chary@gmail.com>
469
470----------------------------
471
472What: usbvideo quickcam_messenger driver
473When: 2.6.35
474Files: drivers/media/video/usbvideo/quickcam_messenger.[ch]
475Why: obsolete v4l1 driver replaced by gspca_stv06xx
476Who: Hans de Goede <hdegoede@redhat.com>
477
478----------------------------
479
480What: ov511 v4l1 driver
481When: 2.6.35
482Files: drivers/media/video/ov511.[ch]
483Why: obsolete v4l1 driver replaced by gspca_ov519
484Who: Hans de Goede <hdegoede@redhat.com>
485
486----------------------------
487
488What: w9968cf v4l1 driver
489When: 2.6.35
490Files: drivers/media/video/w9968cf*.[ch]
491Why: obsolete v4l1 driver replaced by gspca_ov519
492Who: Hans de Goede <hdegoede@redhat.com>
493
494----------------------------
495
496What: ovcamchip sensor framework
497When: 2.6.35
498Files: drivers/media/video/ovcamchip/*
499Why: Only used by obsoleted v4l1 drivers
500Who: Hans de Goede <hdegoede@redhat.com>
501
502----------------------------
503
504What: stv680 v4l1 driver
505When: 2.6.35
506Files: drivers/media/video/stv680.[ch]
507Why: obsolete v4l1 driver replaced by gspca_stv0680
508Who: Hans de Goede <hdegoede@redhat.com>
509
510----------------------------
511
512What: zc0301 v4l driver
513When: 2.6.35
514Files: drivers/media/video/zc0301/*
515Why: Duplicate functionality with the gspca_zc3xx driver, zc0301 only
516    supports 2 USB-ID's (because it only supports a limited set of
517    sensors) wich are also supported by the gspca_zc3xx driver
518    (which supports 53 USB-ID's in total)
519Who: Hans de Goede <hdegoede@redhat.com>
520
521----------------------------
522
523What: corgikbd, spitzkbd, tosakbd driver
524When: 2.6.35
525Files: drivers/input/keyboard/{corgi,spitz,tosa}kbd.c
526Why: We now have a generic GPIO based matrix keyboard driver that
527    are fully capable of handling all the keys on these devices.
528    The original drivers manipulate the GPIO registers directly
529    and so are difficult to maintain.
530Who: Eric Miao <eric.y.miao@gmail.com>
531
532----------------------------
533
534What: corgi_ssp and corgi_ts driver
535When: 2.6.35
536Files: arch/arm/mach-pxa/corgi_ssp.c, drivers/input/touchscreen/corgi_ts.c
537Why: The corgi touchscreen is now deprecated in favour of the generic
538    ads7846.c driver. The noise reduction technique used in corgi_ts.c,
539    that's to wait till vsync before ADC sampling, is also integrated into
540    ads7846 driver now. Provided that the original driver is not generic
541    and is difficult to maintain, it will be removed later.
542Who: Eric Miao <eric.y.miao@gmail.com>
543
544----------------------------
545
546What: capifs
547When: February 2011
548Files: drivers/isdn/capi/capifs.*
549Why: udev fully replaces this special file system that only contains CAPI
550    NCCI TTY device nodes. User space (pppdcapiplugin) works without
551    noticing the difference.
552Who: Jan Kiszka <jan.kiszka@web.de>
553
554----------------------------
555
556What: KVM memory aliases support
557When: July 2010
558Why: Memory aliasing support is used for speeding up guest vga access
559    through the vga windows.
560
561    Modern userspace no longer uses this feature, so it's just bitrotted
562    code and can be removed with no impact.
563Who: Avi Kivity <avi@redhat.com>
564
565----------------------------
566
567What: KVM kernel-allocated memory slots
568When: July 2010
569Why: Since 2.6.25, kvm supports user-allocated memory slots, which are
570    much more flexible than kernel-allocated slots. All current userspace
571    supports the newer interface and this code can be removed with no
572    impact.
573Who: Avi Kivity <avi@redhat.com>
574
575----------------------------
576
577What: KVM paravirt mmu host support
578When: January 2011
579Why: The paravirt mmu host support is slower than non-paravirt mmu, both
580    on newer and older hardware. It is already not exposed to the guest,
581    and kept only for live migration purposes.
582Who: Avi Kivity <avi@redhat.com>
583
584----------------------------
585
586What: "acpi=ht" boot option
587When: 2.6.35
588Why: Useful in 2003, implementation is a hack.
589    Generally invoked by accident today.
590    Seen as doing more harm than good.
591Who: Len Brown <len.brown@intel.com>
592

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