9. Elantech Touchpad Driver¶
Copyright (C) 2007-2008 Arjan Opmeer <arjan@opmeer.net>
Extra information for hardware version 1 found andprovided by Steve Havelka
Version 2 (EeePC) hardware support based on patchesreceived from Woody at Xandros and forwarded to meby user StewieGriffin at the eeeuser.com forum
9.1. Introduction¶
Currently the Linux Elantech touchpad driver is aware of four differenthardware versions unimaginatively called version 1,version 2, version 3and version 4. Version 1 is found in “older” laptops and uses 4 bytes perpacket. Version 2 seems to be introduced with the EeePC and uses 6 bytesper packet, and provides additional features such as position of two fingers,and width of the touch. Hardware version 3 uses 6 bytes per packet (andfor 2 fingers the concatenation of two 6 bytes packets) and allows trackingof up to 3 fingers. Hardware version 4 uses 6 bytes per packet, and cancombine a status packet with multiple head or motion packets. Hardware version4 allows tracking up to 5 fingers.
Some Hardware version 3 and version 4 also have a trackpoint which uses aseparate packet format. It is also 6 bytes per packet.
The driver tries to support both hardware versions and should be compatiblewith the Xorg Synaptics touchpad driver and its graphical configurationutilities.
Note that a mouse button is also associated with either the touchpad or thetrackpoint 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 thecontents of some of its internal registers. These registers are representedby 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 notknown whether the bits in the registers represent the same thing or mighthave changed their meaning.
On top of that, some register settings have effect only when the touchpad isin relative mode and not in absolute mode. As the Linux Elantech touchpaddriver always puts the hardware into absolute mode not all informationmentioned below can be used immediately. But because there is no freelyavailable Elantech documentation the information is provided here anyway forcompleteness sake.
9.2. 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 isOFF. For version 2 the default is “1”.
Turning packet debugging on will make the driver dump every packetreceived to the syslog before processing it. Be warned that this cangenerate quite a lot of data!
paritycheck
Turns parity checking ON or OFF.
By echoing “0” to this file parity checking will be turned OFF. Anynon-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 bycalculating a parity bit for the last 3 bytes of each packet. The drivercan check these bits and reject any packet that appears corrupted. Usingthis knob you can bypass that check.
Hardware version 2 does not provide the same parity bits. Only some basicdata consistency checking can be done. For now checking is disabled bydefault. Currently even turning it on will do nothing.
crc_enabled
Sets crc_enabled to 0/1. The name “crc_enabled” is the official name ofthis integrity check, even though it is not an actual cyclic redundancycheck.
Depending on the state of crc_enabled, certain basic data integrityverification is done by the driver on hardware version 3 and 4. Thedriver 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”.
9.3. 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 => EF01302.06.00 => 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 => EF11302.08.00 => EF02302.08.XX => EF12302.0B.00 => EF21504.01.XX => Scroll_EF05104.02.XX => EF051
In the wild, there appear to be more versions, such as 04.03.01, 04.04.11. Thereappears to be almost no difference, except for EF113, which does not reportpressure/width and has different data consistency checks.
Probably all the versions with param[0] <= 01 can be considered as4 bytes/firmware 1. The versions < 02.08.00, with the exception of 02.00.30, as4 bytes/firmware 2. Everything >= 02.08.00 can be considered as 6 bytes.
9.4. Hardware version 1¶
9.4.1. 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?
9.4.2. 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
9.4.3. Native absolute mode 4 byte packet format¶
EF013 and EF019 have a special behaviour (due to a bug in the firmware?), andwhen 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, Downfirmware 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 touchfirmware 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)
9.5. Hardware version 2¶
9.5.1. 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)
9.5.2. Native absolute mode 6 byte packet format¶
9.5.2.1. 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).
9.5.2.2. 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)
9.5.2.3. Two finger touch¶
Note that the two pairs of coordinates are not exactly the coordinates of thetwo 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 squaredefined 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
9.6. Hardware version 3¶
9.6.1. 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
9.6.2. Native absolute mode 6 byte packet format¶
1 and 3 finger touch shares the same 6-byte packet format, except that3 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, orwhen number of finger changes, F/W would send “debounce packet” to informdriver that the hardware is in debounce status.The debouce packet has the following signature:
byte 0: 0xc4byte 1: 0xffbyte 2: 0xffbyte 3: 0x02byte 4: 0xffbyte 5: 0xff
When we encounter this kind of packet, we just ignore it.
9.6.2.1. 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)
9.6.2.2. Two finger touch¶
The packet format is exactly the same for two finger touch, except the hardwaresends 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 atotal of 12 bytes are sent.
9.7. Hardware version 4¶
9.7.1. 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
9.7.2. 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 rathercomplex.
Whenever the numbers or identities of the fingers changes, the hardware sends astatus packet to indicate how many and which fingers is on touchpad, followed byhead packets or motion packets. A head packet contains data of finger id, fingerposition (absolute x, y values), width, and pressure. A motion packet containstwo fingers’ position delta.
For example, when status packet tells there are 2 fingers on touchpad, then wecan expect two following head packets. If the finger status doesn’t change,the following packets would be motion packets, only sending delta of fingerposition, until we receive a status packet.
One exception is one finger touch. when a status packet tells us there is onlyone finger, the hardware would just send head packets afterwards.
9.7.2.1. 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
9.7.2.2. 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)
9.7.2.3. 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
9.8. Trackpoint (for Hardware version 3 and 4)¶
9.8.1. Registers¶
No special registers have been identified.
9.8.2. Native relative mode 6 byte packet format¶
9.8.2.1. 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