perf_counter: documentation update

[linux-2.6] / Documentation / feature-removal-schedule.txt

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:   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:   CONFIG_WIRELESS_OLD_REGULATORY - old static regulatory information
When:   March 2010 / desktop catchup

Why:    The old regulatory infrastructure has been replaced with a new one
        which does not require statically defined regulatory domains. We do
        not want to keep static regulatory domains in the kernel due to the
        the dynamic nature of regulatory law and localization. We kept around
        the old static definitions for the regulatory domains of:

                * US
                * JP
                * EU

        and used by default the US when CONFIG_WIRELESS_OLD_REGULATORY was
        set. We will remove this option once the standard Linux desktop catches
        up with the new userspace APIs we have implemented.

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@suse.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:   PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl])
When:   November 2005
Files:  drivers/pcmcia/: pcmcia_ioctl.c
Why:    With the 16-bit PCMCIA subsystem now behaving (almost) like a
        normal hotpluggable bus, and with it using the default kernel
        infrastructure (hotplug, driver core, sysfs) keeping the PCMCIA
        control ioctl needed by cardmgr and cardctl from pcmcia-cs is
        unnecessary, and makes further cleanups and integration of the
        PCMCIA subsystem into the Linux kernel device driver model more
        difficult. The features provided by cardmgr and cardctl are either
        handled by the kernel itself now or are available in the new
        pcmciautils package available at
        http://kernel.org/pub/linux/utils/kernel/pcmcia/
Who:    Dominik Brodowski <linux@brodo.de>

---------------------------

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:   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: libata spindown skipping and warning
When: Dec 2008
Why:  Some halt(8) implementations synchronize caches for and spin
      down libata disks because libata didn't use to spin down disk on
      system halt (only synchronized caches).
      Spin down on system halt is now implemented.  sysfs node
      /sys/class/scsi_disk/h:c:i:l/manage_start_stop is present if
      spin down support is available.
      Because issuing spin down command to an already spun down disk
      makes some disks spin up just to spin down again, libata tracks
      device spindown status to skip the extra spindown command and
      warn about it.
      This is to give userspace tools the time to get updated and will
      be removed after userspace is reasonably updated.
Who:  Tejun Heo <htejun@gmail.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 (Why):
        - include/linux/netfilter_ipv4/ipt_TOS.h ipt_tos.h header files
          (superseded by xt_TOS/xt_tos target & match)

        - "forwarding" header files like ipt_mac.h in
          include/linux/netfilter_ipv4/ and include/linux/netfilter_ipv6/

        - xt_CONNMARK match revision 0
          (superseded by xt_CONNMARK match revision 1)

        - xt_MARK target revisions 0 and 1
          (superseded by xt_MARK match revision 2)

        - xt_connmark match revision 0
          (superseded by xt_connmark match revision 1)

        - xt_conntrack match revision 0
          (superseded by xt_conntrack match revision 1)

        - xt_iprange match revision 0,
          include/linux/netfilter_ipv4/ipt_iprange.h
          (superseded by xt_iprange match revision 1)

        - xt_mark match revision 0
          (superseded by xt_mark match revision 1)

        - xt_recent: the old ipt_recent proc dir
          (superseded by /proc/net/xt_recent)

When:   January 2009 or Linux 2.7.0, whichever comes first
Why:    Superseded by newer revisions or modules
Who:    Jan Engelhardt <jengelh@computergmbh.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:   usedac i386 kernel parameter
When:   2.6.27
Why:    replaced by allowdac and no dac combination
Who:    Glauber Costa <gcosta@redhat.com>

---------------------------

What: print_fn_descriptor_symbol()
When: October 2009
Why:  The %pF vsprintf format provides the same functionality in a
      simpler way.  print_fn_descriptor_symbol() is deprecated but
      still present to give out-of-tree modules time to change.
Who:  Bjorn Helgaas <bjorn.helgaas@hp.com>

---------------------------

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:   SCTP_GET_PEER_ADDRS_NUM_OLD, SCTP_GET_PEER_ADDRS_OLD,
        SCTP_GET_LOCAL_ADDRS_NUM_OLD, SCTP_GET_LOCAL_ADDRS_OLD
When:   June 2009
Why:    A newer version of the options have been introduced in 2005 that
        removes the limitions of the old API.  The sctp library has been
        converted to use these new options at the same time.  Any user
        space app that directly uses the old options should convert to using
        the new options.
Who:    Vlad Yasevich <vladislav.yasevich@hp.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: CONFIG_NF_CT_ACCT
When: 2.6.29
Why:  Accounting can now be enabled/disabled without kernel recompilation.
      Currently used only to set a default value for a feature that is also
      controlled by a kernel/module/sysfs/sysctl parameter.
Who:  Krzysztof Piotr Oledzki <ole@ans.pl>

---------------------------

What:   i2c_attach_client(), i2c_detach_client(), i2c_driver->detach_client(),
        i2c_adapter->client_register(), i2c_adapter->client_unregister
When:   2.6.30
Check:  i2c_attach_client i2c_detach_client
Why:    Deprecated by the new (standard) device driver binding model. Use
        i2c_driver->probe() and ->remove() instead.
Who:    Jean Delvare <khali@linux-fr.org>

---------------------------

What:   fscher and fscpos drivers
When:   June 2009
Why:    Deprecated by the new fschmd driver.
Who:    Hans de Goede <hdegoede@redhat.com>
        Jean Delvare <khali@linux-fr.org>

---------------------------

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:   obsolete generic irq defines and typedefs
When:   2.6.30
Why:    The defines and typedefs (hw_interrupt_type, no_irq_type, irq_desc_t)
        have been kept around for migration reasons. After more than two years
        it's time to remove them finally
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:   i2c-voodoo3 driver
When:   October 2009
Why:    Superseded by tdfxfb. I2C/DDC support used to live in a separate
        driver but this caused driver conflicts.
Who:    Jean Delvare <khali@linux-fr.org>
        Krzysztof Helt <krzysztof.h1@wp.pl>