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

  
  
  
  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.

  
  The driver tries to support both hardware versions and should be compatible
  with the Xorg Synaptics touchpad driver and its graphical configuration
  utilities.
  
  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.
  
  
  /////////////////////////////////////////////////////////////////////////////
  
  
  2. Extra knobs
     ~~~~~~~~~~~
  
  Currently the Linux Elantech touchpad driver provides two 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.

  
  /////////////////////////////////////////////////////////////////////////////

  3. 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.
  
  /////////////////////////////////////////////////////////////////////////////

  4. Hardware version 1

     ==================

  4.1 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?

  4.2 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

  4.3 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)
  
  
  /////////////////////////////////////////////////////////////////////////////

  5. Hardware version 2

     ==================

  5.1 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)

  5.2 Native absolute mode 6 byte packet format

      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  5.2.1 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).

  5.2.2 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)

  5.2.3 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

  
  /////////////////////////////////////////////////////////////////////////////
  
  6. Hardware version 3
     ==================
  
  6.1 Registers
      ~~~~~~~~~
  * reg_10
  
     bit   7   6   5   4   3   2   1   0
           0   0   0   0   0   0   0   A
  
           A: 1 = enable absolute tracking
  
  6.2 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.
  
  6.2.1 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)
  
  6.2.2 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.

  
  /////////////////////////////////////////////////////////////////////////////
  
  7. Hardware version 4
     ==================
  
  7.1 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
  
  7.2 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.
  
  7.2.1 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
  
  7.2.2 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)
  
  7.2.3 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