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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 EST.

1	ALPS Touchpad Protocol
2	----------------------
3	
4	Introduction
5	------------
6	Currently the ALPS touchpad driver supports five protocol versions in use by
7	ALPS touchpads, called versions 1, 2, 3, 4 and 5.
8	
9	Since roughly mid-2010 several new ALPS touchpads have been released and
10	integrated into a variety of laptops and netbooks.  These new touchpads
11	have enough behavior differences that the alps_model_data definition
12	table, describing the properties of the different versions, is no longer
13	adequate.  The design choices were to re-define the alps_model_data
14	table, with the risk of regression testing existing devices, or isolate
15	the new devices outside of the alps_model_data table.  The latter design
16	choice was made.  The new touchpad signatures are named: "Rushmore",
17	"Pinnacle", and "Dolphin", which you will see in the alps.c code.
18	For the purposes of this document, this group of ALPS touchpads will
19	generically be called "new ALPS touchpads".
20	
21	We experimented with probing the ACPI interface _HID (Hardware ID)/_CID
22	(Compatibility ID) definition as a way to uniquely identify the
23	different ALPS variants but there did not appear to be a 1:1 mapping.
24	In fact, it appeared to be an m:n mapping between the _HID and actual
25	hardware type.
26	
27	Detection
28	---------
29	
30	All ALPS touchpads should respond to the "E6 report" command sequence:
31	E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or
32	00-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s
33	if some buttons are pressed.
34	
35	If the E6 report is successful, the touchpad model is identified using the "E7
36	report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is
37	matched against known models in the alps_model_data_array.
38	
39	For older touchpads supporting protocol versions 3 and 4, the E7 report
40	model signature is always 73-02-64. To differentiate between these
41	versions, the response from the "Enter Command Mode" sequence must be
42	inspected as described below.
43	
44	The new ALPS touchpads have an E7 signature of 73-03-50 or 73-03-0A but
45	seem to be better differentiated by the EC Command Mode response.
46	
47	Command Mode
48	------------
49	
50	Protocol versions 3 and 4 have a command mode that is used to read and write
51	one-byte device registers in a 16-bit address space. The command sequence
52	EC-EC-EC-E9 places the device in command mode, and the device will respond
53	with 88-07 followed by a third byte. This third byte can be used to determine
54	whether the devices uses the version 3 or 4 protocol.
55	
56	To exit command mode, PSMOUSE_CMD_SETSTREAM (EA) is sent to the touchpad.
57	
58	While in command mode, register addresses can be set by first sending a
59	specific command, either EC for v3 devices or F5 for v4 devices. Then the
60	address is sent one nibble at a time, where each nibble is encoded as a
61	command with optional data. This enoding differs slightly between the v3 and
62	v4 protocols.
63	
64	Once an address has been set, the addressed register can be read by sending
65	PSMOUSE_CMD_GETINFO (E9). The first two bytes of the response contains the
66	address of the register being read, and the third contains the value of the
67	register. Registers are written by writing the value one nibble at a time
68	using the same encoding used for addresses.
69	
70	For the new ALPS touchpads, the EC command is used to enter command
71	mode. The response in the new ALPS touchpads is significantly different,
72	and more important in determining the behavior.  This code has been
73	separated from the original alps_model_data table and put in the
74	alps_identify function.  For example, there seem to be two hardware init
75	sequences for the "Dolphin" touchpads as determined by the second byte
76	of the EC response.
77	
78	Packet Format
79	-------------
80	
81	In 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,
86	extra buttons, stick buttons on a dualpoint, etc.
87	
88	PS/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	
95	Note that the device never signals overflow condition.
96	
97	ALPS 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	
107	ALPS 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	
117	Dualpoint 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	
130	ALPS Absolute Mode - Protocol Version 3
131	---------------------------------------
132	
133	ALPS protocol version 3 has three different packet formats. The first two are
134	associated with touchpad events, and the third is associatd with trackstick
135	events.
136	
137	The 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	
146	Note that for some devices the trackstick buttons are reported in this packet,
147	and on others it is reported in the trackstick packets.
148	
149	The second packet type contains bitmaps representing the x and y axes. In the
150	bitmaps a given bit is set if there is a finger covering that position on the
151	given axis. Thus the bitmap packet can be used for low-resolution multi-touch
152	data, although finger tracking is not possible.  This packet also encodes the
153	number 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	
162	This packet only appears after a position packet with the mt bit set, and
163	usually only appears when there are two or more contacts (although
164	occasionally it's seen with only a single contact).
165	
166	The 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	
175	ALPS Absolute Mode - Protocol Version 4
176	---------------------------------------
177	
178	Protocol 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	
189	The last two bytes represent a partial bitmap packet, with 3 full packets
190	required to construct a complete bitmap packet.  Once assembled, the 6-byte
191	bitmap 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	
200	There 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	
217	So far no v4 devices with tracksticks have been encountered.
218	
219	ALPS Absolute Mode - Protocol Version 5
220	---------------------------------------
221	This is basically Protocol Version 3 but with different logic for packet
222	decode.  It uses the same alps_process_touchpad_packet_v3 call with a
223	specialized decode_fields function pointer to correctly interpret the
224	packets.  This appears to only be used by the Dolphin devices.
225	
226	For 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	
235	For 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
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