Commit 23db9f43 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

Merge branch 'linus' into perfcounters/core 



Merge reason: merge almost-rc8 into perfcounters/core, which was -rc6
              based - to pick up the latest upstream fixes.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parents 27b9613b 3218911f

Documentation/ABI/testing/sysfs-kernel-slab

0 → 100644
+479 −0
Original line number Diff line number Diff line 
What:		/sys/kernel/slab

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The /sys/kernel/slab directory contains a snapshot of the

		internal state of the SLUB allocator for each cache.  Certain

		files may be modified to change the behavior of the cache (and

		any cache it aliases, if any).

Users:		kernel memory tuning tools



What:		/sys/kernel/slab/cache/aliases

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The aliases file is read-only and specifies how many caches

		have merged into this cache.



What:		/sys/kernel/slab/cache/align

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The align file is read-only and specifies the cache's object

		alignment in bytes.



What:		/sys/kernel/slab/cache/alloc_calls

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The alloc_calls file is read-only and lists the kernel code

		locations from which allocations for this cache were performed.

		The alloc_calls file only contains information if debugging is

		enabled for that cache (see Documentation/vm/slub.txt).



What:		/sys/kernel/slab/cache/alloc_fastpath

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The alloc_fastpath file is read-only and specifies how many

		objects have been allocated using the fast path.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/alloc_from_partial

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The alloc_from_partial file is read-only and specifies how

		many times a cpu slab has been full and it has been refilled

		by using a slab from the list of partially used slabs.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/alloc_refill

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The alloc_refill file is read-only and specifies how many

		times the per-cpu freelist was empty but there were objects

		available as the result of remote cpu frees.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/alloc_slab

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The alloc_slab file is read-only and specifies how many times

		a new slab had to be allocated from the page allocator.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/alloc_slowpath

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The alloc_slowpath file is read-only and specifies how many

		objects have been allocated using the slow path because of a

		refill or allocation from a partial or new slab.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/cache_dma

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The cache_dma file is read-only and specifies whether objects

		are from ZONE_DMA.

		Available when CONFIG_ZONE_DMA is enabled.



What:		/sys/kernel/slab/cache/cpu_slabs

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The cpu_slabs file is read-only and displays how many cpu slabs

		are active and their NUMA locality.



What:		/sys/kernel/slab/cache/cpuslab_flush

Date:		April 2009

KernelVersion:	2.6.31

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file cpuslab_flush is read-only and specifies how many

		times a cache's cpu slabs have been flushed as the result of

		destroying or shrinking a cache, a cpu going offline, or as

		the result of forcing an allocation from a certain node.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/ctor

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The ctor file is read-only and specifies the cache's object

		constructor function, which is invoked for each object when a

		new slab is allocated.



What:		/sys/kernel/slab/cache/deactivate_empty

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file deactivate_empty is read-only and specifies how many

		times an empty cpu slab was deactivated.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/deactivate_full

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file deactivate_full is read-only and specifies how many

		times a full cpu slab was deactivated.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/deactivate_remote_frees

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file deactivate_remote_frees is read-only and specifies how

		many times a cpu slab has been deactivated and contained free

		objects that were freed remotely.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/deactivate_to_head

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file deactivate_to_head is read-only and specifies how

		many times a partial cpu slab was deactivated and added to the

		head of its node's partial list.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/deactivate_to_tail

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file deactivate_to_tail is read-only and specifies how

		many times a partial cpu slab was deactivated and added to the

		tail of its node's partial list.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/destroy_by_rcu

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The destroy_by_rcu file is read-only and specifies whether

		slabs (not objects) are freed by rcu.



What:		/sys/kernel/slab/cache/free_add_partial

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file free_add_partial is read-only and specifies how many

		times an object has been freed in a full slab so that it had to

		added to its node's partial list.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/free_calls

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The free_calls file is read-only and lists the locations of

		object frees if slab debugging is enabled (see

		Documentation/vm/slub.txt).



What:		/sys/kernel/slab/cache/free_fastpath

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The free_fastpath file is read-only and specifies how many

		objects have been freed using the fast path because it was an

		object from the cpu slab.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/free_frozen

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The free_frozen file is read-only and specifies how many

		objects have been freed to a frozen slab (i.e. a remote cpu

		slab).

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/free_remove_partial

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file free_remove_partial is read-only and specifies how

		many times an object has been freed to a now-empty slab so

		that it had to be removed from its node's partial list.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/free_slab

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The free_slab file is read-only and specifies how many times an

		empty slab has been freed back to the page allocator.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/free_slowpath

Date:		February 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The free_slowpath file is read-only and specifies how many

		objects have been freed using the slow path (i.e. to a full or

		partial slab).

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/hwcache_align

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The hwcache_align file is read-only and specifies whether

		objects are aligned on cachelines.



What:		/sys/kernel/slab/cache/min_partial

Date:		February 2009

KernelVersion:	2.6.30

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		David Rientjes <rientjes@google.com>

Description:

		The min_partial file specifies how many empty slabs shall

		remain on a node's partial list to avoid the overhead of

		allocating new slabs.  Such slabs may be reclaimed by utilizing

		the shrink file.



What:		/sys/kernel/slab/cache/object_size

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The object_size file is read-only and specifies the cache's

		object size.



What:		/sys/kernel/slab/cache/objects

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The objects file is read-only and displays how many objects are

		active and from which nodes they are from.



What:		/sys/kernel/slab/cache/objects_partial

Date:		April 2008

KernelVersion:	2.6.26

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The objects_partial file is read-only and displays how many

		objects are on partial slabs and from which nodes they are

		from.



What:		/sys/kernel/slab/cache/objs_per_slab

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file objs_per_slab is read-only and specifies how many

		objects may be allocated from a single slab of the order

		specified in /sys/kernel/slab/cache/order.



What:		/sys/kernel/slab/cache/order

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The order file specifies the page order at which new slabs are

		allocated.  It is writable and can be changed to increase the

		number of objects per slab.  If a slab cannot be allocated

		because of fragmentation, SLUB will retry with the minimum order

		possible depending on its characteristics.



What:		/sys/kernel/slab/cache/order_fallback

Date:		April 2008

KernelVersion:	2.6.26

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file order_fallback is read-only and specifies how many

		times an allocation of a new slab has not been possible at the

		cache's order and instead fallen back to its minimum possible

		order.

		Available when CONFIG_SLUB_STATS is enabled.



What:		/sys/kernel/slab/cache/partial

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The partial file is read-only and displays how long many

		partial slabs there are and how long each node's list is.



What:		/sys/kernel/slab/cache/poison

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The poison file specifies whether objects should be poisoned

		when a new slab is allocated.



What:		/sys/kernel/slab/cache/reclaim_account

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The reclaim_account file specifies whether the cache's objects

		are reclaimable (and grouped by their mobility).



What:		/sys/kernel/slab/cache/red_zone

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The red_zone file specifies whether the cache's objects are red

		zoned.



What:		/sys/kernel/slab/cache/remote_node_defrag_ratio

Date:		January 2008

KernelVersion:	2.6.25

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The file remote_node_defrag_ratio specifies the percentage of

		times SLUB will attempt to refill the cpu slab with a partial

		slab from a remote node as opposed to allocating a new slab on

		the local node.  This reduces the amount of wasted memory over

		the entire system but can be expensive.

		Available when CONFIG_NUMA is enabled.



What:		/sys/kernel/slab/cache/sanity_checks

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The sanity_checks file specifies whether expensive checks

		should be performed on free and, at minimum, enables double free

		checks.  Caches that enable sanity_checks cannot be merged with

		caches that do not.



What:		/sys/kernel/slab/cache/shrink

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The shrink file is written when memory should be reclaimed from

		a cache.  Empty partial slabs are freed and the partial list is

		sorted so the slabs with the fewest available objects are used

		first.



What:		/sys/kernel/slab/cache/slab_size

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The slab_size file is read-only and specifies the object size

		with metadata (debugging information and alignment) in bytes.



What:		/sys/kernel/slab/cache/slabs

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The slabs file is read-only and displays how long many slabs

		there are (both cpu and partial) and from which nodes they are

		from.



What:		/sys/kernel/slab/cache/store_user

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The store_user file specifies whether the location of

		allocation or free should be tracked for a cache.



What:		/sys/kernel/slab/cache/total_objects

Date:		April 2008

KernelVersion:	2.6.26

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The total_objects file is read-only and displays how many total

		objects a cache has and from which nodes they are from.



What:		/sys/kernel/slab/cache/trace

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		The trace file specifies whether object allocations and frees

		should be traced.



What:		/sys/kernel/slab/cache/validate

Date:		May 2007

KernelVersion:	2.6.22

Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,

		Christoph Lameter <cl@linux-foundation.org>

Description:

		Writing to the validate file causes SLUB to traverse all of its

		cache's objects and check the validity of metadata.

Documentation/filesystems/tmpfs.txt

+1 −1
Original line number Diff line number Diff line
@@ -133,4 +133,4 @@ RAM/SWAP in 10240 inodes and it is only accessible by root. 
Author:

   Christoph Rohland <cr@sap.com>, 1.12.01

Updated:

   Hugh Dickins <hugh@veritas.com>, 4 June 2007
 
   Hugh Dickins, 4 June 2007

Documentation/input/multi-touch-protocol.txt

+79 −24
Original line number Diff line number Diff line
@@ -18,8 +18,12 @@ Usage 
Anonymous finger details are sent sequentially as separate packets of ABS

events. Only the ABS_MT events are recognized as part of a finger

packet. The end of a packet is marked by calling the input_mt_sync()

function, which generates a SYN_MT_REPORT event. The end of multi-touch

transfer is marked by calling the usual input_sync() function.

function, which generates a SYN_MT_REPORT event. This instructs the

receiver to accept the data for the current finger and prepare to receive

another. The end of a multi-touch transfer is marked by calling the usual

input_sync() function. This instructs the receiver to act upon events

accumulated since last EV_SYN/SYN_REPORT and prepare to receive a new

set of events/packets.



A set of ABS_MT events with the desired properties is defined. The events

are divided into categories, to allow for partial implementation.  The
@@ -27,11 +31,26 @@ minimum set consists of ABS_MT_TOUCH_MAJOR, ABS_MT_POSITION_X and 
ABS_MT_POSITION_Y, which allows for multiple fingers to be tracked.  If the

device supports it, the ABS_MT_WIDTH_MAJOR may be used to provide the size

of the approaching finger. Anisotropy and direction may be specified with

ABS_MT_TOUCH_MINOR, ABS_MT_WIDTH_MINOR and ABS_MT_ORIENTATION. Devices with

more granular information may specify general shapes as blobs, i.e., as a

sequence of rectangular shapes grouped together by an

ABS_MT_BLOB_ID. Finally, the ABS_MT_TOOL_TYPE may be used to specify

whether the touching tool is a finger or a pen or something else.

ABS_MT_TOUCH_MINOR, ABS_MT_WIDTH_MINOR and ABS_MT_ORIENTATION.  The

ABS_MT_TOOL_TYPE may be used to specify whether the touching tool is a

finger or a pen or something else.  Devices with more granular information

may specify general shapes as blobs, i.e., as a sequence of rectangular

shapes grouped together by an ABS_MT_BLOB_ID. Finally, for the few devices

that currently support it, the ABS_MT_TRACKING_ID event may be used to

report finger tracking from hardware [5].



Here is what a minimal event sequence for a two-finger touch would look

like:



   ABS_MT_TOUCH_MAJOR

   ABS_MT_POSITION_X

   ABS_MT_POSITION_Y

   SYN_MT_REPORT

   ABS_MT_TOUCH_MAJOR

   ABS_MT_POSITION_X

   ABS_MT_POSITION_Y

   SYN_MT_REPORT

   SYN_REPORT





Event Semantics
@@ -44,24 +63,24 @@ ABS_MT_TOUCH_MAJOR 


The length of the major axis of the contact. The length should be given in

surface units. If the surface has an X times Y resolution, the largest

possible value of ABS_MT_TOUCH_MAJOR is sqrt(X^2 + Y^2), the diagonal.

possible value of ABS_MT_TOUCH_MAJOR is sqrt(X^2 + Y^2), the diagonal [4].



ABS_MT_TOUCH_MINOR



The length, in surface units, of the minor axis of the contact. If the

contact is circular, this event can be omitted.

contact is circular, this event can be omitted [4].



ABS_MT_WIDTH_MAJOR



The length, in surface units, of the major axis of the approaching

tool. This should be understood as the size of the tool itself. The

orientation of the contact and the approaching tool are assumed to be the

same.

same [4].



ABS_MT_WIDTH_MINOR



The length, in surface units, of the minor axis of the approaching

tool. Omit if circular.

tool. Omit if circular [4].



The above four values can be used to derive additional information about

the contact. The ratio ABS_MT_TOUCH_MAJOR / ABS_MT_WIDTH_MAJOR approximates
@@ -70,14 +89,17 @@ different characteristic widths [1]. 


ABS_MT_ORIENTATION



The orientation of the ellipse. The value should describe half a revolution

clockwise around the touch center. The scale of the value is arbitrary, but

zero should be returned for an ellipse aligned along the Y axis of the

surface. As an example, an index finger placed straight onto the axis could

return zero orientation, something negative when twisted to the left, and

something positive when twisted to the right. This value can be omitted if

the touching object is circular, or if the information is not available in

the kernel driver.

The orientation of the ellipse. The value should describe a signed quarter

of a revolution clockwise around the touch center. The signed value range

is arbitrary, but zero should be returned for a finger aligned along the Y

axis of the surface, a negative value when finger is turned to the left, and

a positive value when finger turned to the right. When completely aligned with

the X axis, the range max should be returned.  Orientation can be omitted

if the touching object is circular, or if the information is not available

in the kernel driver. Partial orientation support is possible if the device

can distinguish between the two axis, but not (uniquely) any values in

between. In such cases, the range of ABS_MT_ORIENTATION should be [0, 1]

[4].



ABS_MT_POSITION_X
@@ -98,8 +120,35 @@ ABS_MT_BLOB_ID 


The BLOB_ID groups several packets together into one arbitrarily shaped

contact. This is a low-level anonymous grouping, and should not be confused

with the high-level contactID, explained below. Most kernel drivers will

not have this capability, and can safely omit the event.

with the high-level trackingID [5]. Most kernel drivers will not have blob

capability, and can safely omit the event.



ABS_MT_TRACKING_ID



The TRACKING_ID identifies an initiated contact throughout its life cycle

[5]. There are currently only a few devices that support it, so this event

should normally be omitted.





Event Computation

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



The flora of different hardware unavoidably leads to some devices fitting

better to the MT protocol than others. To simplify and unify the mapping,

this section gives recipes for how to compute certain events.



For devices reporting contacts as rectangular shapes, signed orientation

cannot be obtained. Assuming X and Y are the lengths of the sides of the

touching rectangle, here is a simple formula that retains the most

information possible:



   ABS_MT_TOUCH_MAJOR := max(X, Y)

   ABS_MT_TOUCH_MINOR := min(X, Y)

   ABS_MT_ORIENTATION := bool(X > Y)



The range of ABS_MT_ORIENTATION should be set to [0, 1], to indicate that

the device can distinguish between a finger along the Y axis (0) and a

finger along the X axis (1).





Finger Tracking
@@ -109,14 +158,18 @@ The kernel driver should generate an arbitrary enumeration of the set of 
anonymous contacts currently on the surface. The order in which the packets

appear in the event stream is not important.



The process of finger tracking, i.e., to assign a unique contactID to each

The process of finger tracking, i.e., to assign a unique trackingID to each

initiated contact on the surface, is left to user space; preferably the

multi-touch X driver [3]. In that driver, the contactID stays the same and

multi-touch X driver [3]. In that driver, the trackingID stays the same and

unique until the contact vanishes (when the finger leaves the surface). The

problem of assigning a set of anonymous fingers to a set of identified

fingers is a euclidian bipartite matching problem at each event update, and

relies on a sufficiently rapid update rate.



There are a few devices that support trackingID in hardware. User space can

make use of these native identifiers to reduce bandwidth and cpu usage.





Notes

-----
@@ -136,5 +189,7 @@ could be used to derive tilt. 
time of writing (April 2009), the MT protocol is not yet merged, and the

prototype implements finger matching, basic mouse support and two-finger

scrolling. The project aims at improving the quality of current multi-touch

functionality available in the synaptics X driver, and in addition

functionality available in the Synaptics X driver, and in addition

implement more advanced gestures.

[4] See the section on event computation.

[5] See the section on finger tracking.

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -1535,6 +1535,10 @@ and is between 256 and 4096 characters. It is defined in the file 
			register save and restore. The kernel will only save

			legacy floating-point registers on task switch.



	noxsave		[BUGS=X86] Disables x86 extended register state save

			and restore using xsave. The kernel will fallback to

			enabling legacy floating-point and sse state.



	nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or

			wfi(ARM) instruction doesn't work correctly and not to

			use it. This is also useful when using JTAG debugger.

Documentation/networking/ip-sysctl.txt

+12 −3

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