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Input: elantech - update the documentation

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A chapter is added to describe the trackpoint packets.

A section is added to describe the behaviour of the knob crc_enabled in
sysfs.

The introduction of the documentation only mentioned v1/v2, but in the
last part it already contains explanation of v3 and v4. The introduction
is updated.

Signed-off-by: Ulrik De Bie <ulrik.debie-os@e2big.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
Ulrik De Bie 2014-11-13 17:48:06 -08:00 committed by Dmitry Torokhov
parent 2d9eb81fdb
commit c6c748ef85
1 changed files with 75 additions and 6 deletions
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81
Documentation/input/elantech.txt
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@ -38,22 +38,38 @@ Contents
7.2.1 Status packet
7.2.2 Head packet
7.2.3 Motion packet
8. Trackpoint (for Hardware version 3 and 4)
8.1 Registers
8.2 Native relative mode 6 byte packet format
8.2.1 Status Packet
1. Introduction
~~~~~~~~~~~~
Currently the Linux Elantech touchpad driver is aware of two different
hardware versions unimaginatively called version 1 and version 2. Version 1
is found in "older" laptops and uses 4 bytes per packet. Version 2 seems to
be introduced with the EeePC and uses 6 bytes per packet, and provides
additional features such as position of two fingers, and width of the touch.
Currently the Linux Elantech touchpad driver is aware of four different
hardware versions unimaginatively called version 1,version 2, version 3
and version 4. Version 1 is found in "older" laptops and uses 4 bytes per
packet. Version 2 seems to be introduced with the EeePC and uses 6 bytes
per packet, and provides additional features such as position of two fingers,
and width of the touch. Hardware version 3 uses 6 bytes per packet (and
for 2 fingers the concatenation of two 6 bytes packets) and allows tracking
of up to 3 fingers. Hardware version 4 uses 6 bytes per packet, and can
combine a status packet with multiple head or motion packets. Hardware version
4 allows tracking up to 5 fingers.
Some Hardware version 3 and version 4 also have a trackpoint which uses a
separate packet format. It is also 6 bytes per packet.
The driver tries to support both hardware versions and should be compatible
with the Xorg Synaptics touchpad driver and its graphical configuration
utilities.
Note that a mouse button is also associated with either the touchpad or the
trackpoint when a trackpoint is available. Disabling the Touchpad in xorg
(TouchPadOff=0) will also disable the buttons associated with the touchpad.
Additionally the operation of the touchpad can be altered by adjusting the
contents of some of its internal registers. These registers are represented
by the driver as sysfs entries under /sys/bus/serio/drivers/psmouse/serio?
@ -78,7 +94,7 @@ completeness sake.
2. Extra knobs
~~~~~~~~~~~
Currently the Linux Elantech touchpad driver provides two extra knobs under
Currently the Linux Elantech touchpad driver provides three extra knobs under
/sys/bus/serio/drivers/psmouse/serio? for the user.
* debug
@ -112,6 +128,20 @@ Currently the Linux Elantech touchpad driver provides two extra knobs under
data consistency checking can be done. For now checking is disabled by
default. Currently even turning it on will do nothing.
* crc_enabled
Sets crc_enabled to 0/1. The name "crc_enabled" is the official name of
this integrity check, even though it is not an actual cyclic redundancy
check.
Depending on the state of crc_enabled, certain basic data integrity
verification is done by the driver on hardware version 3 and 4. The
driver will reject any packet that appears corrupted. Using this knob,
The state of crc_enabled can be altered with this knob.
Reading the crc_enabled value will show the active value. Echoing
"0" or "1" to this file will set the state to "0" or "1".
/////////////////////////////////////////////////////////////////////////////
3. Differentiating hardware versions
@ -746,3 +776,42 @@ byte 5:
byte 0 ~ 2 for one finger
byte 3 ~ 5 for another
8. Trackpoint (for Hardware version 3 and 4)
=========================================
8.1 Registers
~~~~~~~~~
No special registers have been identified.
8.2 Native relative mode 6 byte packet format
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
8.2.1 Status Packet
~~~~~~~~~~~~~
byte 0:
bit 7 6 5 4 3 2 1 0
0 0 sx sy 0 M R L
byte 1:
bit 7 6 5 4 3 2 1 0
~sx 0 0 0 0 0 0 0
byte 2:
bit 7 6 5 4 3 2 1 0
~sy 0 0 0 0 0 0 0
byte 3:
bit 7 6 5 4 3 2 1 0
0 0 ~sy ~sx 0 1 1 0
byte 4:
bit 7 6 5 4 3 2 1 0
x7 x6 x5 x4 x3 x2 x1 x0
byte 5:
bit 7 6 5 4 3 2 1 0
y7 y6 y5 y4 y3 y2 y1 y0
x and y are written in two's complement spread
over 9 bits with sx/sy the relative top bit and
x7..x0 and y7..y0 the lower bits.
~sx is the inverse of sx, ~sy is the inverse of sy.
The sign of y is opposite to what the input driver
expects for a relative movement