linux/Documentation/input/alps.txt
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   1ALPS Touchpad Protocol
   2----------------------
   3
   4Introduction
   5------------
   6Currently the ALPS touchpad driver supports five protocol versions in use by
   7ALPS touchpads, called versions 1, 2, 3, 4 and 5.
   8
   9Since roughly mid-2010 several new ALPS touchpads have been released and
  10integrated into a variety of laptops and netbooks.  These new touchpads
  11have enough behavior differences that the alps_model_data definition
  12table, describing the properties of the different versions, is no longer
  13adequate.  The design choices were to re-define the alps_model_data
  14table, with the risk of regression testing existing devices, or isolate
  15the new devices outside of the alps_model_data table.  The latter design
  16choice was made.  The new touchpad signatures are named: "Rushmore",
  17"Pinnacle", and "Dolphin", which you will see in the alps.c code.
  18For the purposes of this document, this group of ALPS touchpads will
  19generically be called "new ALPS touchpads".
  20
  21We experimented with probing the ACPI interface _HID (Hardware ID)/_CID
  22(Compatibility ID) definition as a way to uniquely identify the
  23different ALPS variants but there did not appear to be a 1:1 mapping.
  24In fact, it appeared to be an m:n mapping between the _HID and actual
  25hardware type.
  26
  27Detection
  28---------
  29
  30All ALPS touchpads should respond to the "E6 report" command sequence:
  31E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or
  3200-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s
  33if some buttons are pressed.
  34
  35If the E6 report is successful, the touchpad model is identified using the "E7
  36report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is
  37matched against known models in the alps_model_data_array.
  38
  39For older touchpads supporting protocol versions 3 and 4, the E7 report
  40model signature is always 73-02-64. To differentiate between these
  41versions, the response from the "Enter Command Mode" sequence must be
  42inspected as described below.
  43
  44The new ALPS touchpads have an E7 signature of 73-03-50 or 73-03-0A but
  45seem to be better differentiated by the EC Command Mode response.
  46
  47Command Mode
  48------------
  49
  50Protocol versions 3 and 4 have a command mode that is used to read and write
  51one-byte device registers in a 16-bit address space. The command sequence
  52EC-EC-EC-E9 places the device in command mode, and the device will respond
  53with 88-07 followed by a third byte. This third byte can be used to determine
  54whether the devices uses the version 3 or 4 protocol.
  55
  56To exit command mode, PSMOUSE_CMD_SETSTREAM (EA) is sent to the touchpad.
  57
  58While in command mode, register addresses can be set by first sending a
  59specific command, either EC for v3 devices or F5 for v4 devices. Then the
  60address is sent one nibble at a time, where each nibble is encoded as a
  61command with optional data. This enoding differs slightly between the v3 and
  62v4 protocols.
  63
  64Once an address has been set, the addressed register can be read by sending
  65PSMOUSE_CMD_GETINFO (E9). The first two bytes of the response contains the
  66address of the register being read, and the third contains the value of the
  67register. Registers are written by writing the value one nibble at a time
  68using the same encoding used for addresses.
  69
  70For the new ALPS touchpads, the EC command is used to enter command
  71mode. The response in the new ALPS touchpads is significantly different,
  72and more important in determining the behavior.  This code has been
  73separated from the original alps_model_data table and put in the
  74alps_identify function.  For example, there seem to be two hardware init
  75sequences for the "Dolphin" touchpads as determined by the second byte
  76of the EC response.
  77
  78Packet Format
  79-------------
  80
  81In the following tables, the following notation is used.
  82
  83 CAPITALS = stick, miniscules = touchpad
  84
  85?'s can have different meanings on different models, such as wheel rotation,
  86extra buttons, stick buttons on a dualpoint, etc.
  87
  88PS/2 packet format
  89------------------
  90
  91 byte 0:  0    0 YSGN XSGN    1    M    R    L
  92 byte 1: X7   X6   X5   X4   X3   X2   X1   X0
  93 byte 2: Y7   Y6   Y5   Y4   Y3   Y2   Y1   Y0
  94
  95Note that the device never signals overflow condition.
  96
  97ALPS Absolute Mode - Protocol Verion 1
  98--------------------------------------
  99
 100 byte 0:  1    0    0    0    1   x9   x8   x7
 101 byte 1:  0   x6   x5   x4   x3   x2   x1   x0
 102 byte 2:  0    ?    ?    l    r    ?  fin  ges
 103 byte 3:  0    ?    ?    ?    ?   y9   y8   y7
 104 byte 4:  0   y6   y5   y4   y3   y2   y1   y0
 105 byte 5:  0   z6   z5   z4   z3   z2   z1   z0
 106
 107ALPS Absolute Mode - Protocol Version 2
 108---------------------------------------
 109
 110 byte 0:  1    ?    ?    ?    1    ?    ?    ?
 111 byte 1:  0   x6   x5   x4   x3   x2   x1   x0
 112 byte 2:  0  x10   x9   x8   x7    ?  fin  ges
 113 byte 3:  0   y9   y8   y7    1    M    R    L
 114 byte 4:  0   y6   y5   y4   y3   y2   y1   y0
 115 byte 5:  0   z6   z5   z4   z3   z2   z1   z0
 116
 117Dualpoint device -- interleaved packet format
 118---------------------------------------------
 119
 120 byte 0:    1    1    0    0    1    1    1    1
 121 byte 1:    0   x6   x5   x4   x3   x2   x1   x0
 122 byte 2:    0  x10   x9   x8   x7    0  fin  ges
 123 byte 3:    0    0 YSGN XSGN    1    1    1    1
 124 byte 4:   X7   X6   X5   X4   X3   X2   X1   X0
 125 byte 5:   Y7   Y6   Y5   Y4   Y3   Y2   Y1   Y0
 126 byte 6:    0   y9   y8   y7    1    m    r    l
 127 byte 7:    0   y6   y5   y4   y3   y2   y1   y0
 128 byte 8:    0   z6   z5   z4   z3   z2   z1   z0
 129
 130ALPS Absolute Mode - Protocol Version 3
 131---------------------------------------
 132
 133ALPS protocol version 3 has three different packet formats. The first two are
 134associated with touchpad events, and the third is associatd with trackstick
 135events.
 136
 137The first type is the touchpad position packet.
 138
 139 byte 0:    1    ?   x1   x0    1    1    1    1
 140 byte 1:    0  x10   x9   x8   x7   x6   x5   x4
 141 byte 2:    0  y10   y9   y8   y7   y6   y5   y4
 142 byte 3:    0    M    R    L    1    m    r    l
 143 byte 4:    0   mt   x3   x2   y3   y2   y1   y0
 144 byte 5:    0   z6   z5   z4   z3   z2   z1   z0
 145
 146Note that for some devices the trackstick buttons are reported in this packet,
 147and on others it is reported in the trackstick packets.
 148
 149The second packet type contains bitmaps representing the x and y axes. In the
 150bitmaps a given bit is set if there is a finger covering that position on the
 151given axis. Thus the bitmap packet can be used for low-resolution multi-touch
 152data, although finger tracking is not possible.  This packet also encodes the
 153number of contacts (f1 and f0 in the table below).
 154
 155 byte 0:    1    1   x1   x0    1    1    1    1
 156 byte 1:    0   x8   x7   x6   x5   x4   x3   x2
 157 byte 2:    0   y7   y6   y5   y4   y3   y2   y1
 158 byte 3:    0  y10   y9   y8    1    1    1    1
 159 byte 4:    0  x14  x13  x12  x11  x10   x9   y0
 160 byte 5:    0    1    ?    ?    ?    ?   f1   f0
 161
 162This packet only appears after a position packet with the mt bit set, and
 163usually only appears when there are two or more contacts (although
 164occasionally it's seen with only a single contact).
 165
 166The final v3 packet type is the trackstick packet.
 167
 168 byte 0:    1    1   x7   y7    1    1    1    1
 169 byte 1:    0   x6   x5   x4   x3   x2   x1   x0
 170 byte 2:    0   y6   y5   y4   y3   y2   y1   y0
 171 byte 3:    0    1    0    0    1    0    0    0
 172 byte 4:    0   z4   z3   z2   z1   z0    ?    ?
 173 byte 5:    0    0    1    1    1    1    1    1
 174
 175ALPS Absolute Mode - Protocol Version 4
 176---------------------------------------
 177
 178Protocol version 4 has an 8-byte packet format.
 179
 180 byte 0:    1    ?   x1   x0    1    1    1    1
 181 byte 1:    0  x10   x9   x8   x7   x6   x5   x4
 182 byte 2:    0  y10   y9   y8   y7   y6   y5   y4
 183 byte 3:    0    1   x3   x2   y3   y2   y1   y0
 184 byte 4:    0    ?    ?    ?    1    ?    r    l
 185 byte 5:    0   z6   z5   z4   z3   z2   z1   z0
 186 byte 6:    bitmap data (described below)
 187 byte 7:    bitmap data (described below)
 188
 189The last two bytes represent a partial bitmap packet, with 3 full packets
 190required to construct a complete bitmap packet.  Once assembled, the 6-byte
 191bitmap packet has the following format:
 192
 193 byte 0:    0    1   x7   x6   x5   x4   x3   x2
 194 byte 1:    0   x1   x0   y4   y3   y2   y1   y0
 195 byte 2:    0    0    ?  x14  x13  x12  x11  x10
 196 byte 3:    0   x9   x8   y9   y8   y7   y6   y5
 197 byte 4:    0    0    0    0    0    0    0    0
 198 byte 5:    0    0    0    0    0    0    0  y10
 199
 200There are several things worth noting here.
 201
 202 1) In the bitmap data, bit 6 of byte 0 serves as a sync byte to
 203    identify the first fragment of a bitmap packet.
 204
 205 2) The bitmaps represent the same data as in the v3 bitmap packets, although
 206    the packet layout is different.
 207
 208 3) There doesn't seem to be a count of the contact points anywhere in the v4
 209    protocol packets. Deriving a count of contact points must be done by
 210    analyzing the bitmaps.
 211
 212 4) There is a 3 to 1 ratio of position packets to bitmap packets. Therefore
 213    MT position can only be updated for every third ST position update, and
 214    the count of contact points can only be updated every third packet as
 215    well.
 216
 217So far no v4 devices with tracksticks have been encountered.
 218
 219ALPS Absolute Mode - Protocol Version 5
 220---------------------------------------
 221This is basically Protocol Version 3 but with different logic for packet
 222decode.  It uses the same alps_process_touchpad_packet_v3 call with a
 223specialized decode_fields function pointer to correctly interpret the
 224packets.  This appears to only be used by the Dolphin devices.
 225
 226For single-touch, the 6-byte packet format is:
 227
 228 byte 0:    1    1    0    0    1    0    0    0
 229 byte 1:    0   x6   x5   x4   x3   x2   x1   x0
 230 byte 2:    0   y6   y5   y4   y3   y2   y1   y0
 231 byte 3:    0    M    R    L    1    m    r    l
 232 byte 4:   y10  y9   y8   y7  x10   x9   x8   x7
 233 byte 5:    0   z6   z5   z4   z3   z2   z1   z0
 234
 235For mt, the format is:
 236
 237 byte 0:    1    1    1    n3   1   n2   n1   x24
 238 byte 1:    1   y7   y6    y5  y4   y3   y2    y1
 239 byte 2:    ?   x2   x1   y12 y11  y10   y9    y8
 240 byte 3:    0  x23  x22   x21 x20  x19  x18   x17
 241 byte 4:    0   x9   x8    x7  x6   x5   x4    x3
 242 byte 5:    0  x16  x15   x14 x13  x12  x11   x10
 243