xref: /kernel/linux/linux-5.10/Documentation/input/devices/elantech.rst (revision 8c2ecf20)

Elantech Touchpad Driver
========================

	Copyright (C) 2007-2008 Arjan Opmeer <arjan@opmeer.net>

	Extra information for hardware version 1 found and
	provided by Steve Havelka

	Version 2 (EeePC) hardware support based on patches
	received from Woody at Xandros and forwarded to me
	by user StewieGriffin at the eeeuser.com forum

.. Contents

 1. Introduction
 2. Extra knobs
 3. Differentiating hardware versions
 4. Hardware version 1
    4.1 Registers
    4.2 Native relative mode 4 byte packet format
    4.3 Native absolute mode 4 byte packet format
 5. Hardware version 2
    5.1 Registers
    5.2 Native absolute mode 6 byte packet format
        5.2.1 Parity checking and packet re-synchronization
        5.2.2 One/Three finger touch
        5.2.3 Two finger touch
 6. Hardware version 3
    6.1 Registers
    6.2 Native absolute mode 6 byte packet format
        6.2.1 One/Three finger touch
        6.2.2 Two finger touch
 7. Hardware version 4
    7.1 Registers
    7.2 Native absolute mode 6 byte packet format
        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



Introduction
~~~~~~~~~~~~

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?
that can be read from and written to.

Currently only the registers for hardware version 1 are somewhat understood.
Hardware version 2 seems to use some of the same registers but it is not
known whether the bits in the registers represent the same thing or might
have changed their meaning.

On top of that, some register settings have effect only when the touchpad is
in relative mode and not in absolute mode. As the Linux Elantech touchpad
driver always puts the hardware into absolute mode not all information
mentioned below can be used immediately. But because there is no freely
available Elantech documentation the information is provided here anyway for
completeness sake.


Extra knobs
~~~~~~~~~~~

Currently the Linux Elantech touchpad driver provides three extra knobs under
/sys/bus/serio/drivers/psmouse/serio? for the user.

* debug

   Turn different levels of debugging ON or OFF.

   By echoing "0" to this file all debugging will be turned OFF.

   Currently a value of "1" will turn on some basic debugging and a value of
   "2" will turn on packet debugging. For hardware version 1 the default is
   OFF. For version 2 the default is "1".

   Turning packet debugging on will make the driver dump every packet
   received to the syslog before processing it. Be warned that this can
   generate quite a lot of data!

* paritycheck

   Turns parity checking ON or OFF.

   By echoing "0" to this file parity checking will be turned OFF. Any
   non-zero value will turn it ON. For hardware version 1 the default is ON.
   For version 2 the default it is OFF.

   Hardware version 1 provides basic data integrity verification by
   calculating a parity bit for the last 3 bytes of each packet. The driver
   can check these bits and reject any packet that appears corrupted. Using
   this knob you can bypass that check.

   Hardware version 2 does not provide the same parity bits. Only some basic
   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".

Differentiating hardware versions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To detect the hardware version, read the version number as param[0].param[1].param[2]::

 4 bytes version: (after the arrow is the name given in the Dell-provided driver)
 02.00.22 => EF013
 02.06.00 => EF019

In the wild, there appear to be more versions, such as 00.01.64, 01.00.21,
02.00.00, 02.00.04, 02.00.06::

 6 bytes:
 02.00.30 => EF113
 02.08.00 => EF023
 02.08.XX => EF123
 02.0B.00 => EF215
 04.01.XX => Scroll_EF051
 04.02.XX => EF051

In the wild, there appear to be more versions, such as 04.03.01, 04.04.11. There
appears to be almost no difference, except for EF113, which does not report
pressure/width and has different data consistency checks.

Probably all the versions with param[0] <= 01 can be considered as
4 bytes/firmware 1. The versions < 02.08.00, with the exception of 02.00.30, as
4 bytes/firmware 2. Everything >= 02.08.00 can be considered as 6 bytes.


Hardware version 1
~~~~~~~~~~~~~~~~~~

Registers
---------

By echoing a hexadecimal value to a register it contents can be altered.

For example::

   echo -n 0x16 > reg_10

* reg_10::

   bit   7   6   5   4   3   2   1   0
         B   C   T   D   L   A   S   E

         E: 1 = enable smart edges unconditionally
         S: 1 = enable smart edges only when dragging
         A: 1 = absolute mode (needs 4 byte packets, see reg_11)
         L: 1 = enable drag lock (see reg_22)
         D: 1 = disable dynamic resolution
         T: 1 = disable tapping
         C: 1 = enable corner tap
         B: 1 = swap left and right button

* reg_11::

   bit   7   6   5   4   3   2   1   0
         1   0   0   H   V   1   F   P

         P: 1 = enable parity checking for relative mode
         F: 1 = enable native 4 byte packet mode
         V: 1 = enable vertical scroll area
         H: 1 = enable horizontal scroll area

* reg_20::

         single finger width?

* reg_21::

         scroll area width (small: 0x40 ... wide: 0xff)

* reg_22::

         drag lock time out (short: 0x14 ... long: 0xfe;
                             0xff = tap again to release)

* reg_23::

         tap make timeout?

* reg_24::

         tap release timeout?

* reg_25::

         smart edge cursor speed (0x02 = slow, 0x03 = medium, 0x04 = fast)

* reg_26::

         smart edge activation area width?


Native relative mode 4 byte packet format
-----------------------------------------

byte 0::

   bit   7   6   5   4   3   2   1   0
         c   c  p2  p1   1   M   R   L

         L, R, M = 1 when Left, Right, Middle mouse button pressed
            some models have M as byte 3 odd parity bit
         when parity checking is enabled (reg_11, P = 1):
            p1..p2 = byte 1 and 2 odd parity bit
         c = 1 when corner tap detected

byte 1::

   bit   7   6   5   4   3   2   1   0
        dx7 dx6 dx5 dx4 dx3 dx2 dx1 dx0

         dx7..dx0 = x movement;   positive = right, negative = left
         byte 1 = 0xf0 when corner tap detected

byte 2::

   bit   7   6   5   4   3   2   1   0
        dy7 dy6 dy5 dy4 dy3 dy2 dy1 dy0

         dy7..dy0 = y movement;   positive = up,    negative = down

byte 3::

   parity checking enabled (reg_11, P = 1):

      bit   7   6   5   4   3   2   1   0
            w   h  n1  n0  ds3 ds2 ds1 ds0

            normally:
               ds3..ds0 = scroll wheel amount and direction
                          positive = down or left
                          negative = up or right
            when corner tap detected:
               ds0 = 1 when top right corner tapped
               ds1 = 1 when bottom right corner tapped
               ds2 = 1 when bottom left corner tapped
               ds3 = 1 when top left corner tapped
            n1..n0 = number of fingers on touchpad
               only models with firmware 2.x report this, models with
               firmware 1.x seem to map one, two and three finger taps
               directly to L, M and R mouse buttons
            h = 1 when horizontal scroll action
            w = 1 when wide finger touch?

   otherwise (reg_11, P = 0):

      bit   7   6   5   4   3   2   1   0
           ds7 ds6 ds5 ds4 ds3 ds2 ds1 ds0

            ds7..ds0 = vertical scroll amount and direction
                       negative = up
                       positive = down


Native absolute mode 4 byte packet format
-----------------------------------------

EF013 and EF019 have a special behaviour (due to a bug in the firmware?), and
when 1 finger is touching, the first 2 position reports must be discarded.
This counting is reset whenever a different number of fingers is reported.

byte 0::

   firmware version 1.x:

      bit   7   6   5   4   3   2   1   0
            D   U  p1  p2   1  p3   R   L

            L, R = 1 when Left, Right mouse button pressed
            p1..p3 = byte 1..3 odd parity bit
            D, U = 1 when rocker switch pressed Up, Down

   firmware version 2.x:

      bit   7   6   5   4   3   2   1   0
           n1  n0  p2  p1   1  p3   R   L

            L, R = 1 when Left, Right mouse button pressed
            p1..p3 = byte 1..3 odd parity bit
            n1..n0 = number of fingers on touchpad

byte 1::

   firmware version 1.x:

      bit   7   6   5   4   3   2   1   0
            f   0  th  tw  x9  x8  y9  y8

            tw = 1 when two finger touch
            th = 1 when three finger touch
            f  = 1 when finger touch

   firmware version 2.x:

      bit   7   6   5   4   3   2   1   0
            .   .   .   .  x9  x8  y9  y8

byte 2::

   bit   7   6   5   4   3   2   1   0
        x7  x6  x5  x4  x3  x2  x1  x0

         x9..x0 = absolute x value (horizontal)

byte 3::

   bit   7   6   5   4   3   2   1   0
        y7  y6  y5  y4  y3  y2  y1  y0

         y9..y0 = absolute y value (vertical)


Hardware version 2
~~~~~~~~~~~~~~~~~~


Registers
---------

By echoing a hexadecimal value to a register it contents can be altered.

For example::

   echo -n 0x56 > reg_10

* reg_10::

   bit   7   6   5   4   3   2   1   0
         0   1   0   1   0   1   D   0

         D: 1 = enable drag and drop

* reg_11::

   bit   7   6   5   4   3   2   1   0
         1   0   0   0   S   0   1   0

         S: 1 = enable vertical scroll

* reg_21::

         unknown (0x00)

* reg_22::

         drag and drop release time out (short: 0x70 ... long 0x7e;
                                   0x7f = never i.e. tap again to release)


Native absolute mode 6 byte packet format
-----------------------------------------

Parity checking and packet re-synchronization
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

There is no parity checking, however some consistency checks can be performed.

For instance for EF113::

        SA1= packet[0];
        A1 = packet[1];
        B1 = packet[2];
        SB1= packet[3];
        C1 = packet[4];
        D1 = packet[5];
        if( (((SA1 & 0x3C) != 0x3C) && ((SA1 & 0xC0) != 0x80)) || // check Byte 1
            (((SA1 & 0x0C) != 0x0C) && ((SA1 & 0xC0) == 0x80)) || // check Byte 1 (one finger pressed)
            (((SA1 & 0xC0) != 0x80) && (( A1 & 0xF0) != 0x00)) || // check Byte 2
            (((SB1 & 0x3E) != 0x38) && ((SA1 & 0xC0) != 0x80)) || // check Byte 4
            (((SB1 & 0x0E) != 0x08) && ((SA1 & 0xC0) == 0x80)) || // check Byte 4 (one finger pressed)
            (((SA1 & 0xC0) != 0x80) && (( C1 & 0xF0) != 0x00))  ) // check Byte 5
		// error detected

For all the other ones, there are just a few constant bits::

        if( ((packet[0] & 0x0C) != 0x04) ||
            ((packet[3] & 0x0f) != 0x02) )
		// error detected


In case an error is detected, all the packets are shifted by one (and packet[0] is discarded).

One/Three finger touch
^^^^^^^^^^^^^^^^^^^^^^

byte 0::

   bit   7   6   5   4   3   2   1   0
	 n1  n0  w3  w2   .   .   R   L

         L, R = 1 when Left, Right mouse button pressed
         n1..n0 = number of fingers on touchpad

byte 1::

   bit   7   6   5   4   3   2   1   0
	 p7  p6  p5  p4 x11 x10 x9  x8

byte 2::

   bit   7   6   5   4   3   2   1   0
	 x7  x6  x5  x4  x3  x2  x1  x0

         x11..x0 = absolute x value (horizontal)

byte 3::

   bit   7   6   5   4   3   2   1   0
	 n4  vf  w1  w0   .   .   .  b2

	 n4 = set if more than 3 fingers (only in 3 fingers mode)
	 vf = a kind of flag ? (only on EF123, 0 when finger is over one
	      of the buttons, 1 otherwise)
	 w3..w0 = width of the finger touch (not EF113)
	 b2 (on EF113 only, 0 otherwise), b2.R.L indicates one button pressed:
		0 = none
		1 = Left
		2 = Right
		3 = Middle (Left and Right)
		4 = Forward
		5 = Back
		6 = Another one
		7 = Another one

byte 4::

   bit   7   6   5   4   3   2   1   0
        p3  p1  p2  p0  y11 y10 y9  y8

	 p7..p0 = pressure (not EF113)

byte 5::

   bit   7   6   5   4   3   2   1   0
        y7  y6  y5  y4  y3  y2  y1  y0

         y11..y0 = absolute y value (vertical)


Two finger touch
^^^^^^^^^^^^^^^^

Note that the two pairs of coordinates are not exactly the coordinates of the
two fingers, but only the pair of the lower-left and upper-right coordinates.
So the actual fingers might be situated on the other diagonal of the square
defined by these two points.

byte 0::

   bit   7   6   5   4   3   2   1   0
        n1  n0  ay8 ax8  .   .   R   L

         L, R = 1 when Left, Right mouse button pressed
         n1..n0 = number of fingers on touchpad

byte 1::

   bit   7   6   5   4   3   2   1   0
        ax7 ax6 ax5 ax4 ax3 ax2 ax1 ax0

	 ax8..ax0 = lower-left finger absolute x value

byte 2::

   bit   7   6   5   4   3   2   1   0
        ay7 ay6 ay5 ay4 ay3 ay2 ay1 ay0

	 ay8..ay0 = lower-left finger absolute y value

byte 3::

   bit   7   6   5   4   3   2   1   0
         .   .  by8 bx8  .   .   .   .

byte 4::

   bit   7   6   5   4   3   2   1   0
        bx7 bx6 bx5 bx4 bx3 bx2 bx1 bx0

         bx8..bx0 = upper-right finger absolute x value

byte 5::

   bit   7   6   5   4   3   2   1   0
        by7 by8 by5 by4 by3 by2 by1 by0

         by8..by0 = upper-right finger absolute y value

Hardware version 3
~~~~~~~~~~~~~~~~~~

Registers
---------

* reg_10::

   bit   7   6   5   4   3   2   1   0
         0   0   0   0   R   F   T   A

         A: 1 = enable absolute tracking
         T: 1 = enable two finger mode auto correct
         F: 1 = disable ABS Position Filter
         R: 1 = enable real hardware resolution

Native absolute mode 6 byte packet format
-----------------------------------------

1 and 3 finger touch shares the same 6-byte packet format, except that
3 finger touch only reports the position of the center of all three fingers.

Firmware would send 12 bytes of data for 2 finger touch.

Note on debounce:
In case the box has unstable power supply or other electricity issues, or
when number of finger changes, F/W would send "debounce packet" to inform
driver that the hardware is in debounce status.
The debouce packet has the following signature::

    byte 0: 0xc4
    byte 1: 0xff
    byte 2: 0xff
    byte 3: 0x02
    byte 4: 0xff
    byte 5: 0xff

When we encounter this kind of packet, we just ignore it.

One/Three finger touch
^^^^^^^^^^^^^^^^^^^^^^

byte 0::

   bit   7   6   5   4   3   2   1   0
        n1  n0  w3  w2   0   1   R   L

        L, R = 1 when Left, Right mouse button pressed
        n1..n0 = number of fingers on touchpad

byte 1::

   bit   7   6   5   4   3   2   1   0
        p7  p6  p5  p4 x11 x10  x9  x8

byte 2::

   bit   7   6   5   4   3   2   1   0
        x7  x6  x5  x4  x3  x2  x1  x0

        x11..x0 = absolute x value (horizontal)

byte 3::

   bit   7   6   5   4   3   2   1   0
         0   0  w1  w0   0   0   1   0

         w3..w0 = width of the finger touch

byte 4::

   bit   7   6   5   4   3   2   1   0
        p3  p1  p2  p0  y11 y10 y9  y8

        p7..p0 = pressure

byte 5::

   bit   7   6   5   4   3   2   1   0
        y7  y6  y5  y4  y3  y2  y1  y0

        y11..y0 = absolute y value (vertical)

Two finger touch
^^^^^^^^^^^^^^^^

The packet format is exactly the same for two finger touch, except the hardware
sends two 6 byte packets. The first packet contains data for the first finger,
the second packet has data for the second finger. So for two finger touch a
total of 12 bytes are sent.

Hardware version 4
~~~~~~~~~~~~~~~~~~

Registers
---------

* reg_07::

   bit   7   6   5   4   3   2   1   0
         0   0   0   0   0   0   0   A

         A: 1 = enable absolute tracking

Native absolute mode 6 byte packet format
-----------------------------------------

v4 hardware is a true multitouch touchpad, capable of tracking up to 5 fingers.
Unfortunately, due to PS/2's limited bandwidth, its packet format is rather
complex.

Whenever the numbers or identities of the fingers changes, the hardware sends a
status packet to indicate how many and which fingers is on touchpad, followed by
head packets or motion packets. A head packet contains data of finger id, finger
position (absolute x, y values), width, and pressure. A motion packet contains
two fingers' position delta.

For example, when status packet tells there are 2 fingers on touchpad, then we
can expect two following head packets. If the finger status doesn't change,
the following packets would be motion packets, only sending delta of finger
position, until we receive a status packet.

One exception is one finger touch. when a status packet tells us there is only
one finger, the hardware would just send head packets afterwards.

Status packet
^^^^^^^^^^^^^

byte 0::

   bit   7   6   5   4   3   2   1   0
         .   .   .   .   0   1   R   L

         L, R = 1 when Left, Right mouse button pressed

byte 1::

   bit   7   6   5   4   3   2   1   0
         .   .   . ft4 ft3 ft2 ft1 ft0

         ft4 ft3 ft2 ft1 ft0 ftn = 1 when finger n is on touchpad

byte 2::

   not used

byte 3::

   bit   7   6   5   4   3   2   1   0
         .   .   .   1   0   0   0   0

         constant bits

byte 4::

   bit   7   6   5   4   3   2   1   0
         p   .   .   .   .   .   .   .

         p = 1 for palm

byte 5::

   not used

Head packet
^^^^^^^^^^^

byte 0::

   bit   7   6   5   4   3   2   1   0
        w3  w2  w1  w0   0   1   R   L

        L, R = 1 when Left, Right mouse button pressed
        w3..w0 = finger width (spans how many trace lines)

byte 1::

   bit   7   6   5   4   3   2   1   0
        p7  p6  p5  p4 x11 x10  x9  x8

byte 2::

   bit   7   6   5   4   3   2   1   0
        x7  x6  x5  x4  x3  x2  x1  x0

        x11..x0 = absolute x value (horizontal)

byte 3::

   bit   7   6   5   4   3   2   1   0
       id2 id1 id0   1   0   0   0   1

       id2..id0 = finger id

byte 4::

   bit   7   6   5   4   3   2   1   0
        p3  p1  p2  p0  y11 y10 y9  y8

        p7..p0 = pressure

byte 5::

   bit   7   6   5   4   3   2   1   0
        y7  y6  y5  y4  y3  y2  y1  y0

        y11..y0 = absolute y value (vertical)

Motion packet
^^^^^^^^^^^^^

byte 0::

   bit   7   6   5   4   3   2   1   0
       id2 id1 id0   w   0   1   R   L

       L, R = 1 when Left, Right mouse button pressed
       id2..id0 = finger id
       w = 1 when delta overflows (> 127 or < -128), in this case
       firmware sends us (delta x / 5) and (delta y  / 5)

byte 1::

   bit   7   6   5   4   3   2   1   0
        x7  x6  x5  x4  x3  x2  x1  x0

        x7..x0 = delta x (two's complement)

byte 2::

   bit   7   6   5   4   3   2   1   0
        y7  y6  y5  y4  y3  y2  y1  y0

        y7..y0 = delta y (two's complement)

byte 3::

   bit   7   6   5   4   3   2   1   0
       id2 id1 id0   1   0   0   1   0

       id2..id0 = finger id

byte 4::

   bit   7   6   5   4   3   2   1   0
        x7  x6  x5  x4  x3  x2  x1  x0

        x7..x0 = delta x (two's complement)

byte 5::

   bit   7   6   5   4   3   2   1   0
        y7  y6  y5  y4  y3  y2  y1  y0

        y7..y0 = delta y (two's complement)

        byte 0 ~ 2 for one finger
        byte 3 ~ 5 for another


Trackpoint (for Hardware version 3 and 4)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Registers
---------

No special registers have been identified.

Native relative mode 6 byte packet format
-----------------------------------------

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