Document ->page_mkwrite() locking

[deliverable/linux.git] / 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:	MXSER
When:	December 2007
Why:	Old mxser driver is obsoleted by the mxser_new. Give it some time yet
	and remove it.
Who:	Jiri Slaby <jirislaby@gmail.com>

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

What:	V4L2 VIDIOC_G_MPEGCOMP and VIDIOC_S_MPEGCOMP
When:	October 2007
Why:	Broken attempt to set MPEG compression parameters. These ioctls are
	not able to implement the wide variety of parameters that can be set
	by hardware MPEG encoders. A new MPEG control mechanism was created
	in kernel 2.6.18 that replaces these ioctls. See the V4L2 specification
	(section 1.9: Extended controls) for more information on this topic.
Who:	Hans Verkuil <hverkuil@xs4all.nl> and
	Mauro Carvalho Chehab <mchehab@infradead.org>

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

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:	old NCR53C9x driver
When:	October 2007
Why:	Replaced by the much better esp_scsi driver.  Actual low-level
	driver can be ported over almost trivially.
Who:	David Miller <davem@davemloft.net>
	Christoph Hellwig <hch@lst.de>

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

What:	Video4Linux API 1 ioctls and video_decoder.h from Video devices.
When:	December 2006
Files:	include/linux/video_decoder.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.
Who:	Mauro Carvalho Chehab <mchehab@brturbo.com.br>

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

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:	remove EXPORT_SYMBOL(kernel_thread)
When:	August 2006
Files:	arch/*/kernel/*_ksyms.c
Funcs:	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:	CONFIG_FORCED_INLINING
When:	June 2006
Why:	Config option is there to see if gcc is good enough. (in january
        2006). If it is, the behavior should just be the default. If it's not,
	the option should just go away entirely.
Who:    Arjan van de Ven

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

What:   eepro100 network driver
When:   January 2007
Why:    replaced by the e100 driver
Who:    Adrian Bunk <bunk@stusta.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:	USB driver API moves to EXPORT_SYMBOL_GPL
When:	February 2008
Files:	include/linux/usb.h, drivers/usb/core/driver.c
Why:	The USB subsystem has changed a lot over time, and it has been
	possible to create userspace USB drivers using usbfs/libusb/gadgetfs
	that operate as fast as the USB bus allows.  Because of this, the USB
	subsystem will not be allowing closed source kernel drivers to
	register with it, after this grace period is over.  If anyone needs
	any help in converting their closed source drivers over to use the
	userspace filesystems, please contact the
	linux-usb-devel@lists.sourceforge.net mailing list, and the developers
	there will be glad to help you out.
Who:	Greg Kroah-Hartman <gregkh@suse.de>

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

What:	filemap_nopage, filemap_populate
When:	April 2007
Why:	These legacy interfaces no longer have any callers in the kernel and
	any functionality provided can be provided with filemap_fault. The
	removal schedule is short because they are a big maintainence burden
	and have some bugs.
Who:	Nick Piggin <npiggin@suse.de>

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

What:	vm_ops.populate, install_page
When:	April 2007
Why:	These legacy interfaces no longer have any callers in the kernel and
	any functionality provided can be provided with vm_ops.fault.
Who:	Nick Piggin <npiggin@suse.de>

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

What:	vm_ops.nopage
When:	February 2008, provided in-kernel callers have been converted
Why:	This interface is replaced by vm_ops.fault, but it has been around
	forever, is used by a lot of drivers, and doesn't cost much to
	maintain.
Who:	Nick Piggin <npiggin@suse.de>

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

What:	Interrupt only SA_* flags
When:	September 2007
Why:	The interrupt related SA_* flags are replaced by IRQF_* to move them
	out of the signal namespace.

Who:	Thomas Gleixner <tglx@linutronix.de>

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

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:	i2c-isa
When:	December 2006
Why:	i2c-isa is a non-sense and doesn't fit in the device driver
	model. Drivers relying on it are better implemented as platform
	drivers.
Who:	Jean Delvare <khali@linux-fr.org>

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

What:	i2c_adapter.list
When:	July 2007
Why:	Superfluous, this list duplicates the one maintained by the driver
	core.
Who:	Jean Delvare <khali@linux-fr.org>,
	David Brownell <dbrownell@users.sourceforge.net>

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

What:  drivers depending on OBSOLETE_OSS
When:  options in 2.6.22, code in 2.6.24
Why:   OSS drivers with ALSA replacements
Who:   Adrian Bunk <bunk@stusta.de>

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

What:	/sys/firmware/acpi/namespace
When:	2.6.21
Why:	The ACPI namespace is effectively the symbol list for
	the BIOS.  The device names are completely arbitrary
	and have no place being exposed to user-space.

	For those interested in the BIOS ACPI namespace,
	the BIOS can be extracted and disassembled with acpidump
	and iasl as documented in the pmtools package here:
	http://ftp.kernel.org/pub/linux/kernel/people/lenb/acpi/utils
Who:	Len Brown <len.brown@intel.com>

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

What:	ACPI procfs interface
When:	July 2007
Why:	After ACPI sysfs conversion, ACPI attributes will be duplicated
	in sysfs and the ACPI procfs interface should be removed.
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:	Compaq touchscreen device emulation
When:	Oct 2007
Files:	drivers/input/tsdev.c
Why:	The code says it was obsolete when it was written in 2001.
	tslib is a userspace library which does anything tsdev can do and
	much more besides in userspace where this code belongs. There is no
	longer any need for tsdev and applications should have converted to
	use tslib by now.
	The name "tsdev" is also extremely confusing and lots of people have
	it loaded when they don't need/use it.
Who:	Richard Purdie <rpurdie@rpsys.net>

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

What:	read_dev_chars(), read_conf_data{,_lpm}() (s390 common I/O layer)
When:	December 2007
Why:	These functions are a leftover from 2.4 times. They have several
	problems:
	- Duplication of checks that are done in the device driver's
	  interrupt handler
	- common I/O layer can't do device specific error recovery
	- device driver can't be notified for conditions happening during
	  execution of the function
	Device drivers should issue the read device characteristics and read
	configuration data ccws and do the appropriate error handling
	themselves.
Who:	Cornelia Huck <cornelia.huck@de.ibm.com>

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

What:	i2c-ixp2000, i2c-ixp4xx and scx200_i2c drivers
When:	September 2007
Why:	Obsolete. The new i2c-gpio driver replaces all hardware-specific
	I2C-over-GPIO drivers.
Who:	Jean Delvare <khali@linux-fr.org>

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

What:	'time' kernel boot parameter
When:	January 2008
Why:	replaced by 'printk.time=<value>' so that printk timestamps can be
	enabled or disabled as needed
Who:	Randy Dunlap <randy.dunlap@oracle.com>

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

What:  drivers depending on OSS_OBSOLETE
When:  options in 2.6.23, code in 2.6.25
Why:   obsolete OSS drivers
Who:   Adrian Bunk <bunk@stusta.de>

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

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:	Legacy RTC drivers (under drivers/i2c/chips)
When:	November 2007
Why:	Obsolete. We have a RTC subsystem with better drivers.
Who:	Jean Delvare <khali@linux-fr.org>

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

What:	iptables SAME target
When:	1.1. 2008
Files:	net/ipv4/netfilter/ipt_SAME.c, include/linux/netfilter_ipv4/ipt_SAME.h
Why:	Obsolete for multiple years now, NAT core provides the same behaviour.
	Unfixable broken wrt. 32/64 bit cleanness.
Who:	Patrick McHardy <kaber@trash.net>

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

What: The arch/ppc and include/asm-ppc directories
When: Jun 2008
Why:  The arch/powerpc tree is the merged architecture for ppc32 and ppc64
      platforms.  Currently there are efforts underway to port the remaining
      arch/ppc platforms to the merged tree.  New submissions to the arch/ppc
      tree have been frozen with the 2.6.22 kernel release and that tree will
      remain in bug-fix only mode until its scheduled removal.  Platforms
      that are not ported by June 2008 will be removed due to the lack of an
      interested maintainer.
Who:  linuxppc-dev@ozlabs.org

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

What:	mthca driver's MSI support
When:	January 2008
Files:	drivers/infiniband/hw/mthca/*.[ch]
Why:	All mthca hardware also supports MSI-X, which provides
	strictly more functionality than MSI.  So there is no point in
	having both MSI-X and MSI support in the driver.
Who:	Roland Dreier <rolandd@cisco.com>

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