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Input: ALPS - update documentation for recent touchpad driver mods

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Updated documentation for the new ALPS touchpad support submitted in two
patchsets by Kevin Cernekee.  My understanding is the most recent
patchset '"Dolphin V2" touchpad support' may still need some work but
Future work on the ALPS driver should not impact these documentation changes.

See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/606238

Signed-off-by: David Turvene <dturvene@dahetral.com>
Acked-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
dave turvene 2013-02-23 20:06:34 -08:00 committed by Dmitry Torokhov
parent 75af9e56c1
commit 171fb58da0
1 changed files with 59 additions and 6 deletions
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65
Documentation/input/alps.txt
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@ -3,10 +3,26 @@ ALPS Touchpad Protocol
Introduction
------------
Currently the ALPS touchpad driver supports five protocol versions in use by
ALPS touchpads, called versions 1, 2, 3, 4 and 5.
Currently the ALPS touchpad driver supports four protocol versions in use by
ALPS touchpads, called versions 1, 2, 3, and 4. Information about the various
protocol versions is contained in the following sections.
Since roughly mid-2010 several new ALPS touchpads have been released and
integrated into a variety of laptops and netbooks. These new touchpads
have enough behavior differences that the alps_model_data definition
table, describing the properties of the different versions, is no longer
adequate. The design choices were to re-define the alps_model_data
table, with the risk of regression testing existing devices, or isolate
the new devices outside of the alps_model_data table. The latter design
choice was made. The new touchpad signatures are named: "Rushmore",
"Pinnacle", and "Dolphin", which you will see in the alps.c code.
For the purposes of this document, this group of ALPS touchpads will
generically be called "new ALPS touchpads".
We experimented with probing the ACPI interface _HID (Hardware ID)/_CID
(Compatibility ID) definition as a way to uniquely identify the
different ALPS variants but there did not appear to be a 1:1 mapping.
In fact, it appeared to be an m:n mapping between the _HID and actual
hardware type.
Detection
---------
@ -20,9 +36,13 @@ If the E6 report is successful, the touchpad model is identified using the "E7
report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is
matched against known models in the alps_model_data_array.
With protocol versions 3 and 4, the E7 report model signature is always
73-02-64. To differentiate between these versions, the response from the
"Enter Command Mode" sequence must be inspected as described below.
For older touchpads supporting protocol versions 3 and 4, the E7 report
model signature is always 73-02-64. To differentiate between these
versions, the response from the "Enter Command Mode" sequence must be
inspected as described below.
The new ALPS touchpads have an E7 signature of 73-03-50 or 73-03-0A but
seem to be better differentiated by the EC Command Mode response.
Command Mode
------------
@ -47,6 +67,14 @@ address of the register being read, and the third contains the value of the
register. Registers are written by writing the value one nibble at a time
using the same encoding used for addresses.
For the new ALPS touchpads, the EC command is used to enter command
mode. The response in the new ALPS touchpads is significantly different,
and more important in determining the behavior. This code has been
separated from the original alps_model_data table and put in the
alps_identify function. For example, there seem to be two hardware init
sequences for the "Dolphin" touchpads as determined by the second byte
of the EC response.
Packet Format
-------------
@ -187,3 +215,28 @@ There are several things worth noting here.
well.
So far no v4 devices with tracksticks have been encountered.
ALPS Absolute Mode - Protocol Version 5
---------------------------------------
This is basically Protocol Version 3 but with different logic for packet
decode. It uses the same alps_process_touchpad_packet_v3 call with a
specialized decode_fields function pointer to correctly interpret the
packets. This appears to only be used by the Dolphin devices.
For single-touch, the 6-byte packet format is:
byte 0: 1 1 0 0 1 0 0 0
byte 1: 0 x6 x5 x4 x3 x2 x1 x0
byte 2: 0 y6 y5 y4 y3 y2 y1 y0
byte 3: 0 M R L 1 m r l
byte 4: y10 y9 y8 y7 x10 x9 x8 x7
byte 5: 0 z6 z5 z4 z3 z2 z1 z0
For mt, the format is:
byte 0: 1 1 1 n3 1 n2 n1 x24
byte 1: 1 y7 y6 y5 y4 y3 y2 y1
byte 2: ? x2 x1 y12 y11 y10 y9 y8
byte 3: 0 x23 x22 x21 x20 x19 x18 x17
byte 4: 0 x9 x8 x7 x6 x5 x4 x3
byte 5: 0 x16 x15 x14 x13 x12 x11 x10