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diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt new file mode 100644 index 00000000..842aa9de --- /dev/null +++ b/Documentation/feature-removal-schedule.txt @@ -0,0 +1,566 @@ +The following is a list of files and features that are going to be +removed in the kernel source tree. Every entry should contain what +exactly is going away, why it is happening, and who is going to be doing +the work. When the feature is removed from the kernel, it should also +be removed from this file. + +--------------------------- + +What: PRISM54 +When: 2.6.34 + +Why: prism54 FullMAC PCI / Cardbus devices used to be supported only by the + prism54 wireless driver. After Intersil stopped selling these + devices in preference for the newer more flexible SoftMAC devices + a SoftMAC device driver was required and prism54 did not support + them. The p54pci driver now exists and has been present in the kernel for + a while. This driver supports both SoftMAC devices and FullMAC devices. + The main difference between these devices was the amount of memory which + could be used for the firmware. The SoftMAC devices support a smaller + amount of memory. Because of this the SoftMAC firmware fits into FullMAC + devices's memory. p54pci supports not only PCI / Cardbus but also USB + and SPI. Since p54pci supports all devices prism54 supports + you will have a conflict. I'm not quite sure how distributions are + handling this conflict right now. prism54 was kept around due to + claims users may experience issues when using the SoftMAC driver. + Time has passed users have not reported issues. If you use prism54 + and for whatever reason you cannot use p54pci please let us know! + E-mail us at: linux-wireless@vger.kernel.org + + For more information see the p54 wiki page: + + http://wireless.kernel.org/en/users/Drivers/p54 + +Who: Luis R. Rodriguez <lrodriguez@atheros.com> + +--------------------------- + +What: IRQF_SAMPLE_RANDOM +Check: IRQF_SAMPLE_RANDOM +When: July 2009 + +Why: Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy + sources in the kernel's current entropy model. To resolve this, every + input point to the kernel's entropy pool needs to better document the + type of entropy source it actually is. This will be replaced with + additional add_*_randomness functions in drivers/char/random.c + +Who: Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com> + +--------------------------- + +What: Deprecated snapshot ioctls +When: 2.6.36 + +Why: The ioctls in kernel/power/user.c were marked as deprecated long time + ago. Now they notify users about that so that they need to replace + their userspace. After some more time, remove them completely. + +Who: Jiri Slaby <jirislaby@gmail.com> + +--------------------------- + +What: The ieee80211_regdom module parameter +When: March 2010 / desktop catchup + +Why: This was inherited by the CONFIG_WIRELESS_OLD_REGULATORY code, + and currently serves as an option for users to define an + ISO / IEC 3166 alpha2 code for the country they are currently + present in. Although there are userspace API replacements for this + through nl80211 distributions haven't yet caught up with implementing + decent alternatives through standard GUIs. Although available as an + option through iw or wpa_supplicant its just a matter of time before + distributions pick up good GUI options for this. The ideal solution + would actually consist of intelligent designs which would do this for + the user automatically even when travelling through different countries. + Until then we leave this module parameter as a compromise. + + When userspace improves with reasonable widely-available alternatives for + this we will no longer need this module parameter. This entry hopes that + by the super-futuristically looking date of "March 2010" we will have + such replacements widely available. + +Who: Luis R. Rodriguez <lrodriguez@atheros.com> + +--------------------------- + +What: dev->power.power_state +When: July 2007 +Why: Broken design for runtime control over driver power states, confusing + driver-internal runtime power management with: mechanisms to support + system-wide sleep state transitions; event codes that distinguish + different phases of swsusp "sleep" transitions; and userspace policy + inputs. This framework was never widely used, and most attempts to + use it were broken. Drivers should instead be exposing domain-specific + interfaces either to kernel or to userspace. +Who: Pavel Machek <pavel@ucw.cz> + +--------------------------- + +What: Video4Linux API 1 ioctls and from Video devices. +When: July 2009 +Files: include/linux/videodev.h +Check: include/linux/videodev.h +Why: V4L1 AP1 was replaced by V4L2 API during migration from 2.4 to 2.6 + series. The old API have lots of drawbacks and don't provide enough + means to work with all video and audio standards. The newer API is + already available on the main drivers and should be used instead. + Newer drivers should use v4l_compat_translate_ioctl function to handle + old calls, replacing to newer ones. + Decoder iocts are using internally to allow video drivers to + communicate with video decoders. This should also be improved to allow + V4L2 calls being translated into compatible internal ioctls. + Compatibility ioctls will be provided, for a while, via + v4l1-compat module. +Who: Mauro Carvalho Chehab <mchehab@infradead.org> + +--------------------------- + +What: sys_sysctl +When: September 2010 +Option: CONFIG_SYSCTL_SYSCALL +Why: The same information is available in a more convenient from + /proc/sys, and none of the sysctl variables appear to be + important performance wise. + + Binary sysctls are a long standing source of subtle kernel + bugs and security issues. + + When I looked several months ago all I could find after + searching several distributions were 5 user space programs and + glibc (which falls back to /proc/sys) using this syscall. + + The man page for sysctl(2) documents it as unusable for user + space programs. + + sysctl(2) is not generally ABI compatible to a 32bit user + space application on a 64bit and a 32bit kernel. + + For the last several months the policy has been no new binary + sysctls and no one has put forward an argument to use them. + + Binary sysctls issues seem to keep happening appearing so + properly deprecating them (with a warning to user space) and a + 2 year grace warning period will mean eventually we can kill + them and end the pain. + + In the mean time individual binary sysctls can be dealt with + in a piecewise fashion. + +Who: Eric Biederman <ebiederm@xmission.com> + +--------------------------- + +What: /proc/<pid>/oom_adj +When: August 2012 +Why: /proc/<pid>/oom_adj allows userspace to influence the oom killer's + badness heuristic used to determine which task to kill when the kernel + is out of memory. + + The badness heuristic has since been rewritten since the introduction of + this tunable such that its meaning is deprecated. The value was + implemented as a bitshift on a score generated by the badness() + function that did not have any precise units of measure. With the + rewrite, the score is given as a proportion of available memory to the + task allocating pages, so using a bitshift which grows the score + exponentially is, thus, impossible to tune with fine granularity. + + A much more powerful interface, /proc/<pid>/oom_score_adj, was + introduced with the oom killer rewrite that allows users to increase or + decrease the badness() score linearly. This interface will replace + /proc/<pid>/oom_adj. + + A warning will be emitted to the kernel log if an application uses this + deprecated interface. After it is printed once, future warnings will be + suppressed until the kernel is rebooted. + +--------------------------- + +What: remove EXPORT_SYMBOL(kernel_thread) +When: August 2006 +Files: arch/*/kernel/*_ksyms.c +Check: kernel_thread +Why: kernel_thread is a low-level implementation detail. Drivers should + use the <linux/kthread.h> API instead which shields them from + implementation details and provides a higherlevel interface that + prevents bugs and code duplication +Who: Christoph Hellwig <hch@lst.de> + +--------------------------- + +What: Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports + (temporary transition config option provided until then) + The transition config option will also be removed at the same time. +When: before 2.6.19 +Why: Unused symbols are both increasing the size of the kernel binary + and are often a sign of "wrong API" +Who: Arjan van de Ven <arjan@linux.intel.com> + +--------------------------- + +What: PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment +When: October 2008 +Why: The stacking of class devices makes these values misleading and + inconsistent. + Class devices should not carry any of these properties, and bus + devices have SUBSYTEM and DRIVER as a replacement. +Who: Kay Sievers <kay.sievers@suse.de> + +--------------------------- + +What: ACPI procfs interface +When: July 2008 +Why: ACPI sysfs conversion should be finished by January 2008. + ACPI procfs interface will be removed in July 2008 so that + there is enough time for the user space to catch up. +Who: Zhang Rui <rui.zhang@intel.com> + +--------------------------- + +What: /proc/acpi/button +When: August 2007 +Why: /proc/acpi/button has been replaced by events to the input layer + since 2.6.20. +Who: Len Brown <len.brown@intel.com> + +--------------------------- + +What: /proc/acpi/event +When: February 2008 +Why: /proc/acpi/event has been replaced by events via the input layer + and netlink since 2.6.23. +Who: Len Brown <len.brown@intel.com> + +--------------------------- + +What: i386/x86_64 bzImage symlinks +When: April 2010 + +Why: The i386/x86_64 merge provides a symlink to the old bzImage + location so not yet updated user space tools, e.g. package + scripts, do not break. +Who: Thomas Gleixner <tglx@linutronix.de> + +--------------------------- + +What: GPIO autorequest on gpio_direction_{input,output}() in gpiolib +When: February 2010 +Why: All callers should use explicit gpio_request()/gpio_free(). + The autorequest mechanism in gpiolib was provided mostly as a + migration aid for legacy GPIO interfaces (for SOC based GPIOs). + Those users have now largely migrated. Platforms implementing + the GPIO interfaces without using gpiolib will see no changes. +Who: David Brownell <dbrownell@users.sourceforge.net> +--------------------------- + +What: b43 support for firmware revision < 410 +When: The schedule was July 2008, but it was decided that we are going to keep the + code as long as there are no major maintanance headaches. + So it _could_ be removed _any_ time now, if it conflicts with something new. +Why: The support code for the old firmware hurts code readability/maintainability + and slightly hurts runtime performance. Bugfixes for the old firmware + are not provided by Broadcom anymore. +Who: Michael Buesch <mb@bu3sch.de> + +--------------------------- + +What: /sys/o2cb symlink +When: January 2010 +Why: /sys/fs/o2cb is the proper location for this information - /sys/o2cb + exists as a symlink for backwards compatibility for old versions of + ocfs2-tools. 2 years should be sufficient time to phase in new versions + which know to look in /sys/fs/o2cb. +Who: ocfs2-devel@oss.oracle.com + +--------------------------- + +What: Ability for non root users to shm_get hugetlb pages based on mlock + resource limits +When: 2.6.31 +Why: Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or + have CAP_IPC_LOCK to be able to allocate shm segments backed by + huge pages. The mlock based rlimit check to allow shm hugetlb is + inconsistent with mmap based allocations. Hence it is being + deprecated. +Who: Ravikiran Thirumalai <kiran@scalex86.org> + +--------------------------- + +What: CONFIG_THERMAL_HWMON +When: January 2009 +Why: This option was introduced just to allow older lm-sensors userspace + to keep working over the upgrade to 2.6.26. At the scheduled time of + removal fixed lm-sensors (2.x or 3.x) should be readily available. +Who: Rene Herman <rene.herman@gmail.com> + +--------------------------- + +What: Code that is now under CONFIG_WIRELESS_EXT_SYSFS + (in net/core/net-sysfs.c) +When: After the only user (hal) has seen a release with the patches + for enough time, probably some time in 2010. +Why: Over 1K .text/.data size reduction, data is available in other + ways (ioctls) +Who: Johannes Berg <johannes@sipsolutions.net> + +--------------------------- + +What: sysfs ui for changing p4-clockmod parameters +When: September 2009 +Why: See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and + e088e4c9cdb618675874becb91b2fd581ee707e6. + Removal is subject to fixing any remaining bugs in ACPI which may + cause the thermal throttling not to happen at the right time. +Who: Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com> + +----------------------------- + +What: __do_IRQ all in one fits nothing interrupt handler +When: 2.6.32 +Why: __do_IRQ was kept for easy migration to the type flow handlers. + More than two years of migration time is enough. +Who: Thomas Gleixner <tglx@linutronix.de> + +----------------------------- + +What: fakephp and associated sysfs files in /sys/bus/pci/slots/ +When: 2011 +Why: In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to + represent a machine's physical PCI slots. The change in semantics + had userspace implications, as the hotplug core no longer allowed + drivers to create multiple sysfs files per physical slot (required + for multi-function devices, e.g.). fakephp was seen as a developer's + tool only, and its interface changed. Too late, we learned that + there were some users of the fakephp interface. + + In 2.6.30, the original fakephp interface was restored. At the same + time, the PCI core gained the ability that fakephp provided, namely + function-level hot-remove and hot-add. + + Since the PCI core now provides the same functionality, exposed in: + + /sys/bus/pci/rescan + /sys/bus/pci/devices/.../remove + /sys/bus/pci/devices/.../rescan + + there is no functional reason to maintain fakephp as well. + + We will keep the existing module so that 'modprobe fakephp' will + present the old /sys/bus/pci/slots/... interface for compatibility, + but users are urged to migrate their applications to the API above. + + After a reasonable transition period, we will remove the legacy + fakephp interface. +Who: Alex Chiang <achiang@hp.com> + +--------------------------- + +What: CONFIG_RFKILL_INPUT +When: 2.6.33 +Why: Should be implemented in userspace, policy daemon. +Who: Johannes Berg <johannes@sipsolutions.net> + +---------------------------- + +What: sound-slot/service-* module aliases and related clutters in + sound/sound_core.c +When: August 2010 +Why: OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR + (14) and requests modules using custom sound-slot/service-* + module aliases. The only benefit of doing this is allowing + use of custom module aliases which might as well be considered + a bug at this point. This preemptive claiming prevents + alternative OSS implementations. + + Till the feature is removed, the kernel will be requesting + both sound-slot/service-* and the standard char-major-* module + aliases and allow turning off the pre-claiming selectively via + CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss + kernel parameter. + + After the transition phase is complete, both the custom module + aliases and switches to disable it will go away. This removal + will also allow making ALSA OSS emulation independent of + sound_core. The dependency will be broken then too. +Who: Tejun Heo <tj@kernel.org> + +---------------------------- + +What: Support for VMware's guest paravirtuliazation technique [VMI] will be + dropped. +When: 2.6.37 or earlier. +Why: With the recent innovations in CPU hardware acceleration technologies + from Intel and AMD, VMware ran a few experiments to compare these + techniques to guest paravirtualization technique on VMware's platform. + These hardware assisted virtualization techniques have outperformed the + performance benefits provided by VMI in most of the workloads. VMware + expects that these hardware features will be ubiquitous in a couple of + years, as a result, VMware has started a phased retirement of this + feature from the hypervisor. We will be removing this feature from the + Kernel too. Right now we are targeting 2.6.37 but can retire earlier if + technical reasons (read opportunity to remove major chunk of pvops) + arise. + + Please note that VMI has always been an optimization and non-VMI kernels + still work fine on VMware's platform. + Latest versions of VMware's product which support VMI are, + Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence + releases for these products will continue supporting VMI. + + For more details about VMI retirement take a look at this, + http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html + +Who: Alok N Kataria <akataria@vmware.com> + +---------------------------- + +What: Support for lcd_switch and display_get in asus-laptop driver +When: March 2010 +Why: These two features use non-standard interfaces. There are the + only features that really need multiple path to guess what's + the right method name on a specific laptop. + + Removing them will allow to remove a lot of code an significantly + clean the drivers. + + This will affect the backlight code which won't be able to know + if the backlight is on or off. The platform display file will also be + write only (like the one in eeepc-laptop). + + This should'nt affect a lot of user because they usually know + when their display is on or off. + +Who: Corentin Chary <corentin.chary@gmail.com> + +---------------------------- + +What: sysfs-class-rfkill state file +When: Feb 2014 +Files: net/rfkill/core.c +Why: Documented as obsolete since Feb 2010. This file is limited to 3 + states while the rfkill drivers can have 4 states. +Who: anybody or Florian Mickler <florian@mickler.org> + +---------------------------- + +What: sysfs-class-rfkill claim file +When: Feb 2012 +Files: net/rfkill/core.c +Why: It is not possible to claim an rfkill driver since 2007. This is + Documented as obsolete since Feb 2010. +Who: anybody or Florian Mickler <florian@mickler.org> + +---------------------------- + +What: capifs +When: February 2011 +Files: drivers/isdn/capi/capifs.* +Why: udev fully replaces this special file system that only contains CAPI + NCCI TTY device nodes. User space (pppdcapiplugin) works without + noticing the difference. +Who: Jan Kiszka <jan.kiszka@web.de> + +---------------------------- + +What: KVM paravirt mmu host support +When: January 2011 +Why: The paravirt mmu host support is slower than non-paravirt mmu, both + on newer and older hardware. It is already not exposed to the guest, + and kept only for live migration purposes. +Who: Avi Kivity <avi@redhat.com> + +---------------------------- + +What: iwlwifi 50XX module parameters +When: 2.6.40 +Why: The "..50" modules parameters were used to configure 5000 series and + up devices; different set of module parameters also available for 4965 + with same functionalities. Consolidate both set into single place + in drivers/net/wireless/iwlwifi/iwl-agn.c + +Who: Wey-Yi Guy <wey-yi.w.guy@intel.com> + +---------------------------- + +What: iwl4965 alias support +When: 2.6.40 +Why: Internal alias support has been present in module-init-tools for some + time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed + with no impact. + +Who: Wey-Yi Guy <wey-yi.w.guy@intel.com> + +--------------------------- + +What: xt_NOTRACK +Files: net/netfilter/xt_NOTRACK.c +When: April 2011 +Why: Superseded by xt_CT +Who: Netfilter developer team <netfilter-devel@vger.kernel.org> + +--------------------------- + +What: video4linux /dev/vtx teletext API support +When: 2.6.35 +Files: drivers/media/video/saa5246a.c drivers/media/video/saa5249.c + include/linux/videotext.h +Why: The vtx device nodes have been superseded by vbi device nodes + for many years. No applications exist that use the vtx support. + Of the two i2c drivers that actually support this API the saa5249 + has been impossible to use for a year now and no known hardware + that supports this device exists. The saa5246a is theoretically + supported by the old mxb boards, but it never actually worked. + + In summary: there is no hardware that can use this API and there + are no applications actually implementing this API. + + The vtx support still reserves minors 192-223 and we would really + like to reuse those for upcoming new functionality. In the unlikely + event that new hardware appears that wants to use the functionality + provided by the vtx API, then that functionality should be build + around the sliced VBI API instead. +Who: Hans Verkuil <hverkuil@xs4all.nl> + +---------------------------- + +What: IRQF_DISABLED +When: 2.6.36 +Why: The flag is a NOOP as we run interrupt handlers with interrupts disabled +Who: Thomas Gleixner <tglx@linutronix.de> + +---------------------------- + +What: old ieee1394 subsystem (CONFIG_IEEE1394) +When: 2.6.37 +Files: drivers/ieee1394/ except init_ohci1394_dma.c +Why: superseded by drivers/firewire/ (CONFIG_FIREWIRE) which offers more + features, better performance, and better security, all with smaller + and more modern code base +Who: Stefan Richter <stefanr@s5r6.in-berlin.de> + +---------------------------- + +What: The acpi_sleep=s4_nonvs command line option +When: 2.6.37 +Files: arch/x86/kernel/acpi/sleep.c +Why: superseded by acpi_sleep=nonvs +Who: Rafael J. Wysocki <rjw@sisk.pl> + +---------------------------- + +What: PCI DMA unmap state API +When: August 2012 +Why: PCI DMA unmap state API (include/linux/pci-dma.h) was replaced + with DMA unmap state API (DMA unmap state API can be used for + any bus). +Who: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> + +---------------------------- + +What: DMA_xxBIT_MASK macros +When: Jun 2011 +Why: DMA_xxBIT_MASK macros were replaced with DMA_BIT_MASK() macros. +Who: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> + +---------------------------- + |