In order to diagnose overall suspend/resume times, we need
basic instrumentation to break down the total time into per
device timing, similar to initcall_debug.

This patch adds the basic timing instrumentation, needed
for a scritps/bootgraph.pl equivalent or humans.
The bootgraph.pl program is still a work in progress, but
is far enough along to know that this patch is sufficient.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

This patch (as1308c) fixes __pm_runtime_get().  Currently the routine
will resume a device if the prior usage count was 0.  But this isn't
right; thanks to pm_runtime_get_noresume() the usage count can be
positive even while the device is suspended.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Nodemasks should not be allocated on the stack for large systems (when it
is larger than 256 bytes) since there is a threat of overflow.

This patch causes the unregister_mem_sect_under_nodes() nodemask to be
allocated on the stack for smaller systems and be allocated by slab for
larger systems.

GFP_KERNEL is used since remove_memory_block() can block.

Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Alex Chiang <achiang@hp.com>
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

You can discover which CPUs belong to a NUMA node by examining
/sys/devices/system/node/node#/

However, it's not convenient to go in the other direction, when looking at
/sys/devices/system/cpu/cpu#/

Yes, you can muck about in sysfs, but adding these symlinks makes life a
lot more convenient.
Signed-off-by: NAlex Chiang <achiang@hp.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

By returning early if the node is not online, we can unindent the
interesting code by two levels.

No functional change.
Signed-off-by: NAlex Chiang <achiang@hp.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

By returning early if the node is not online, we can unindent the
interesting code by one level.

No functional change.
Signed-off-by: NAlex Chiang <achiang@hp.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit c04fc586 (mm: show node to memory section relationship with
symlinks in sysfs) created symlinks from nodes to memory sections, e.g.

/sys/devices/system/node/node1/memory135 -> ../../memory/memory135

If you're examining the memory section though and are wondering what node
it might belong to, you can find it by grovelling around in sysfs, but
it's a little cumbersome.

Add a reverse symlink for each memory section that points back to the
node to which it belongs.
Signed-off-by: NAlex Chiang <achiang@hp.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Offload the registration and unregistration of per node hstate sysfs
attributes to a worker thread rather than attempt the
allocation/attachment or detachment/freeing of the attributes in the
context of the memory hotplug handler.

I don't know that this is absolutely required, but the registration can
sleep in allocations and other mem hot plug handlers do it this way.  If
it turns out this is NOT required, we can drop this patch.

N.B.,  Only tested build, boot, libhugetlbfs regression.
       i.e., no memory hotplug testing.
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Reviewed-by: NAndi Kleen <andi@firstfloor.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Eric Whitney <eric.whitney@hp.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Register per node hstate attributes only for nodes with memory.  As
suggested by David Rientjes.

With Memory Hotplug, memory can be added to a memoryless node and a node
with memory can become memoryless.  Therefore, add a memory on/off-line
notifier callback to [un]register a node's attributes on transition
to/from memoryless state.

N.B.,  Only tested build, boot, libhugetlbfs regression.
       i.e., no memory hotplug testing.
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Reviewed-by: NAndi Kleen <andi@firstfloor.org>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Eric Whitney <eric.whitney@hp.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add the per huge page size control/query attributes to the per node
sysdevs:

/sys/devices/system/node/node<ID>/hugepages/hugepages-<size>/
	nr_hugepages       - r/w
	free_huge_pages    - r/o
	surplus_huge_pages - r/o

The patch attempts to re-use/share as much of the existing global hstate
attribute initialization and handling, and the "nodes_allowed" constraint
processing as possible.

Calling set_max_huge_pages() with no node indicates a change to global
hstate parameters.  In this case, any non-default task mempolicy will be
used to generate the nodes_allowed mask.  A valid node id indicates an
update to that node's hstate parameters, and the count argument specifies
the target count for the specified node.  From this info, we compute the
target global count for the hstate and construct a nodes_allowed node mask
contain only the specified node.

Setting the node specific nr_hugepages via the per node attribute
effectively ignores any task mempolicy or cpuset constraints.

With this patch:

(me):ls /sys/devices/system/node/node0/hugepages/hugepages-2048kB
./  ../  free_hugepages  nr_hugepages  surplus_hugepages

Starting from:
Node 0 HugePages_Total:     0
Node 0 HugePages_Free:      0
Node 0 HugePages_Surp:      0
Node 1 HugePages_Total:     0
Node 1 HugePages_Free:      0
Node 1 HugePages_Surp:      0
Node 2 HugePages_Total:     0
Node 2 HugePages_Free:      0
Node 2 HugePages_Surp:      0
Node 3 HugePages_Total:     0
Node 3 HugePages_Free:      0
Node 3 HugePages_Surp:      0
vm.nr_hugepages = 0

Allocate 16 persistent huge pages on node 2:
(me):echo 16 >/sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages

[Note that this is equivalent to:
	numactl -m 2 hugeadmin --pool-pages-min 2M:+16
]

Yields:
Node 0 HugePages_Total:     0
Node 0 HugePages_Free:      0
Node 0 HugePages_Surp:      0
Node 1 HugePages_Total:     0
Node 1 HugePages_Free:      0
Node 1 HugePages_Surp:      0
Node 2 HugePages_Total:    16
Node 2 HugePages_Free:     16
Node 2 HugePages_Surp:      0
Node 3 HugePages_Total:     0
Node 3 HugePages_Free:      0
Node 3 HugePages_Surp:      0
vm.nr_hugepages = 16

Global controls work as expected--reduce pool to 8 persistent huge pages:
(me):echo 8 >/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages

Node 0 HugePages_Total:     0
Node 0 HugePages_Free:      0
Node 0 HugePages_Surp:      0
Node 1 HugePages_Total:     0
Node 1 HugePages_Free:      0
Node 1 HugePages_Surp:      0
Node 2 HugePages_Total:     8
Node 2 HugePages_Free:      8
Node 2 HugePages_Surp:      0
Node 3 HugePages_Total:     0
Node 3 HugePages_Free:      0
Node 3 HugePages_Surp:      0
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NAndi Kleen <andi@firstfloor.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Eric Whitney <eric.whitney@hp.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch (as1310) works around a race in dev_driver_string().  If
the device is unbound while the function is running, dev->driver might
become NULL after we test it and before we dereference it.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Add early_platform_init_buffer() support and update the
early platform driver code to allow passing parameters
to the driver on the kernel command line.

early_platform_init_buffer() simply allows early platform
drivers to provide a pointer and length to a memory area
where the remaining part of the kernel command line option
will be stored.

Needed to pass baud rate and other serial port options
to the reworked early serial console code on SuperH.
Signed-off-by: NMagnus Damm <damm@opensource.se>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

device_shutdown is defined to just shutdown the hardware and to not
clean up any kernel data structures.  Therefore don't put the kobjects
for /sys/dev and /sys/dev/block and /sys/dev/char.

This ensures we don't remove /sys/dev/block and /sys/dev/char while
we still have symlinks from there to the actual devices.
Acked-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NEric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Unfortunately, one cannot hold on to the struct firmware
that request_firmware_nowait() hands off, which is needed
in some cases. Allow this by requiring the callback to
free it (via release_firmware).

Additionally, give it a gfp_t parameter -- all the current
users call it from a GFP_KERNEL context so the GFP_ATOMIC
isn't necessary. This also marks an API break which is
useful in a sense, although that is obviously not the
primary purpose of this change.
Signed-off-by: NJohannes Berg <johannes@sipsolutions.net>
Acked-by: NMarcel Holtmann <marcel@holtmann.org>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Woodhouse <David.Woodhouse@intel.com>
Cc: Pavel Roskin <proski@gnu.org>
Cc: Abhay Salunke <abhay_salunke@dell.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Cc: Mark Rosenstand <rosenstand@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Currently the cpu-allocation/deallocation process comprises of two steps:
- Set the indicators and to update the device tree with DLPAR node
  information.

- Online/offline the allocated/deallocated CPU.

This is achieved by writing to the sysfs tunables "probe" during allocation
and "release" during deallocation.

At the sametime, the userspace can independently online/offline the CPUs of
the system using the sysfs tunable "online".

It is quite possible that when a userspace tool offlines a CPU
for the purpose of deallocation and is in the process of updating the device
tree, some other userspace tool could bring the CPU back online by writing to
the "online" sysfs tunable thereby causing the deallocate process to fail.

The solution to this is to serialize writes to the "probe/release" sysfs
tunable with the writes to the "online" sysfs tunable.

This patch employs a mutex to provide this serialization, which is a no-op on
all architectures except PPC_PSERIES
Signed-off-by: NGautham R Shenoy <ego@in.ibm.com>
Acked-by: NVaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Version 3 of this patch is updated with documentation added to
Documentation/ABI.  There are no changes to any of the C code from v2
of the patch.

In order to support kernel DLPAR of CPU resources we need to provide an
interface to add (probe) and remove (release) the resource from the system.
This patch Creates new generic probe and release sysfs files to facilitate
cpu probe/release.  The probe/release interface provides for allowing each
arch to supply their own routines for implementing the backend of adding
and removing cpus to/from the system.

This also creates the powerpc specific stubs to handle the arch callouts
from writes to the sysfs files.

The creation and use of these files is regulated by the
CONFIG_ARCH_CPU_PROBE_RELEASE option so that only architectures that need the
capability will have the files created.
Signed-off-by: NNathan Fontenot <nfont@austin.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Some braces in __pm_runtime_set_status() are not necessary, so
remove them.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The runtime PM core code assumes that dev->power.timer_expires is
nonzero when the timer is scheduled, but it may become zero
incidentally in pm_schedule_suspend().  Prevent this from happening
by bumping dev->power.timer_expires up to 1 if it's 0 before calling
mod_timer().
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Reported-by: NAlan Stern <stern@rowland.harvard.edu>

This patch (as1307) adds a small optimization to
__pm_request_resume().  If the device is currently being suspended,
there's no need to queue a work routine to resume it.  Setting the
deferred_resume flag will suffice.  (There's also a minor improvement
to the function's code layout: An unnecessary "else" is removed.)

Also, the patch clarifies the usage of the deferred_resume flag.  It
is meaningful only while a suspend is in progress, so it should be
cleared just before a suspend starts, not just after one ends.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Lockdep complains about taking the parent lock in
__pm_runtime_set_status(), so mark it as nested.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Reported-by: NAlan Stern <stern@rowland.harvard.edu>
Cc: stable@kernel.org

That is "success", "unknown", "through", "performance", "[re|un]mapping"
, "access", "default", "reasonable", "[con]currently", "temperature"
, "channel", "[un]used", "application", "example","hierarchy", "therefore"
, "[over|under]flow", "contiguous", "threshold", "enough" and others.
Signed-off-by: NAndré Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

This patch (as1305) fixes a bug in the irq-enable settings and removes
some related overhead in the runtime PM code.

	In __pm_runtime_resume(), within the scope of the original
	spin_lock_irq(), we know that irqs are disabled.  There's no
	reason to go through a pair of enable/disable cycles when
	acquiring and releasing the parent's lock.

	In __pm_runtime_set_status(), irqs are already disabled when
	the parent's lock is acquired, and they must remain disabled
	when it is released.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

o kdump functionality reserves a per cpu area at boot time and exports the
  physical address of that area to user space through sys interface. This
  area stores some dump related information like cpu register states etc
  at the time of crash.

o We were assuming that per cpu area always come from linearly mapped meory
  region and using __pa() to determine physical address.
  With percpu_alloc=page, per cpu area can come from vmalloc region also and
  __pa() breaks.

o This patch implments a new function to convert per cpu address to
  physical address.

Before the patch, crash_notes addresses looked as follows.

cpu0 60fffff49800
cpu1 60fffff60800
cpu2 60fffff77800

These are bogus phsyical addresses.

After the patch, address are following.

cpu0 13eb44000
cpu1 13eb43000
cpu2 13eb42000
cpu3 13eb41000

These look fine. I got 4G of memory and /proc/iomem tell me following.

100000000-13fffffff : System RAM

tj: * added missing asm/io.h include reported by Stephen Rothwell
    * repositioned per_cpu_ptr_phys() in percpu.c and added comment.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>

pm_runtime_idle() is somewhat noisy. Remove debug prints.
Signed-off-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Fixes the point where we need to complete the power transition when
device suspend fails, so that we don't print warnings about devices
added to the device hierarchy after a failing suspend.

[rjw: Modified changelog.]
Signed-off-by: NRomit Dasgupta <romit@ti.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Platform drivers registered via platform_driver_probe() can be bound
to devices only once, upon registration, because discard their probe()
routines to save memory. Unbinding the driver through sysfs 'unbind'
leaves the device stranded and confuses users so let's not create
bind and unbind attributes for such drivers.
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>
Cc: Éric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

In this patch:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=16dc42e018c2868211b4928f20a957c0c216126c
the check was added for another driver to already claim the same device
on the same bus. But the returned error code was wrong: to modprobe, the
-EEXIST means that _this_ driver is already installed. It therefore
doesn't produce the needed error message when _another_ driver is trying
to register for the same device.  Returning -EBUSY fixes the problem.
Signed-off-by: NStas Sergeev <stsp@aknet.ru>
Cc: stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Recently we encountered OOM problems due to memory use of the GEM cache.
Generally a large amuont of Shmem/Tmpfs pages tend to create a memory
shortage problem.

We often use the following calculation to determine the amount of shmem
pages:

shmem = NR_ACTIVE_ANON + NR_INACTIVE_ANON - NR_ANON_PAGES

however the expression does not consider isolated and mlocked pages.

This patch adds explicit accounting for pages used by shmem and tmpfs.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NRik van Riel <riel@redhat.com>
Reviewed-by: NChristoph Lameter <cl@linux-foundation.org>
Acked-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The amount of memory allocated to kernel stacks can become significant and
cause OOM conditions.  However, we do not display the amount of memory
consumed by stacks.

Add code to display the amount of memory used for stacks in /proc/meminfo.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NChristoph Lameter <cl@linux-foundation.org>
Reviewed-by: NMinchan Kim <minchan.kim@gmail.com>
Reviewed-by: NRik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This allows subsytems to provide devtmpfs with non-default permissions
for the device node. Instead of the default mode of 0600, null, zero,
random, urandom, full, tty, ptmx now have a mode of 0666, which allows
non-privileged processes to access standard device nodes in case no
other userspace process applies the expected permissions.

This also fixes a wrong assignment in pktcdvd and a checkpatch.pl complain.
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Devtmpfs lets the kernel create a tmpfs instance called devtmpfs
very early at kernel initialization, before any driver-core device
is registered. Every device with a major/minor will provide a
device node in devtmpfs.

Devtmpfs can be changed and altered by userspace at any time,
and in any way needed - just like today's udev-mounted tmpfs.
Unmodified udev versions will run just fine on top of it, and will
recognize an already existing kernel-created device node and use it.
The default node permissions are root:root 0600. Proper permissions
and user/group ownership, meaningful symlinks, all other policy still
needs to be applied by userspace.

If a node is created by devtmps, devtmpfs will remove the device node
when the device goes away. If the device node was created by
userspace, or the devtmpfs created node was replaced by userspace, it
will no longer be removed by devtmpfs.

If it is requested to auto-mount it, it makes init=/bin/sh work
without any further userspace support. /dev will be fully populated
and dynamic, and always reflect the current device state of the kernel.
With the commonly used dynamic device numbers, it solves the problem
where static devices nodes may point to the wrong devices.

It is intended to make the initial bootup logic simpler and more robust,
by de-coupling the creation of the inital environment, to reliably run
userspace processes, from a complex userspace bootstrap logic to provide
a working /dev.
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NJan Blunck <jblunck@suse.de>
Tested-By: NHarald Hoyer <harald@redhat.com>
Tested-By: NScott James Remnant <scott@ubuntu.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Instead of open-coding it.
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

When turning class devices into bus devices, we may need to
temporarily add links in sysfs so that user-space applications
are not confused. This is done by adding the following API:

* Functions to register and unregister compatibility classes.
  These appear in sysfs at the same location as regular classes, but
  instead of class devices, they contain links to bus devices.
* Functions to create and delete such links. Additionally, the caller
  can optionally pass a target device to which a "device" link should
  point (typically that would be the device's parent), to fully emulate
  the original class device.

The i2c subsystem will be the first user of this API, as i2c adapters
are being converted from class devices to bus devices.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>

Placing dma-coherent.c in driver/base is better than in kernel,
since it contains code to do per-device coherent dma memory
handling.
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>