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. Hardware version 1
      3.1 Registers
      3.2 Native relative mode 4 byte packet format
      3.3 Native absolute mode 4 byte packet format
   4. Hardware version 2
      4.1 Registers
      4.2 Native absolute mode 6 byte packet format
          4.2.1 One finger touch
          4.2.2 Two finger touch
  
  
  
  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.
  
  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.
  
     It is not known yet whether hardware version 2 provides the same parity
     bits. Hence checking is disabled by default. Currently even turning it on
     will do nothing.
  
  
  /////////////////////////////////////////////////////////////////////////////
  
  
  3. Hardware version 1
     ==================
  
  3.1 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?
  
  
  3.2 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
  
  
  3.3 Native absolute mode 4 byte packet format
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  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)
  
  
  /////////////////////////////////////////////////////////////////////////////
  
  
  4. Hardware version 2
     ==================
  
  
  4.1 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)
  
  
  4.2 Native absolute mode 6 byte packet format
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  4.2.1 One finger touch
        ~~~~~~~~~~~~~~~~
  
  byte 0:
  
     bit   7   6   5   4   3   2   1   0
          n1  n0   .   .   .   .   R   L
  
           L, R = 1 when Left, Right mouse button pressed
           n1..n0 = numbers of fingers on touchpad
  
  byte 1:
  
     bit   7   6   5   4   3   2   1   0

           .   .   .   .   .  x10 x9  x8

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

           x10..x0 = absolute x value (horizontal)

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

           .   .   .   .   .   .  y9  y8

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

           y9..y0 = absolute y value (vertical)

  
  
  4.2.2 Two finger touch
        ~~~~~~~~~~~~~~~~
  
  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 = numbers 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 = first 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 = first 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 = second 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 = second finger absolute y value