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Based on kernel version 4.0. Page generated on 2015-04-14 21:24 EST.

1	ALPS Touchpad Protocol
2	----------------------
3	
4	Introduction
5	------------
6	Currently the ALPS touchpad driver supports seven protocol versions in use by
7	ALPS touchpads, called versions 1, 2, 3, 4, 5, 6 and 7.
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 Version 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	Protocol Version 2 DualPoint devices send standard PS/2 mouse packets for
118	the DualPoint Stick.
119	
120	Dualpoint device -- interleaved packet format
121	---------------------------------------------
122	
123	 byte 0:    1    1    0    0    1    1    1    1
124	 byte 1:    0   x6   x5   x4   x3   x2   x1   x0
125	 byte 2:    0  x10   x9   x8   x7    0  fin  ges
126	 byte 3:    0    0 YSGN XSGN    1    1    1    1
127	 byte 4:   X7   X6   X5   X4   X3   X2   X1   X0
128	 byte 5:   Y7   Y6   Y5   Y4   Y3   Y2   Y1   Y0
129	 byte 6:    0   y9   y8   y7    1    m    r    l
130	 byte 7:    0   y6   y5   y4   y3   y2   y1   y0
131	 byte 8:    0   z6   z5   z4   z3   z2   z1   z0
132	
133	Devices which use the interleaving format normally send standard PS/2 mouse
134	packets for the DualPoint Stick + ALPS Absolute Mode packets for the
135	touchpad, switching to the interleaved packet format when both the stick and
136	the touchpad are used at the same time.
137	
138	ALPS Absolute Mode - Protocol Version 3
139	---------------------------------------
140	
141	ALPS protocol version 3 has three different packet formats. The first two are
142	associated with touchpad events, and the third is associatd with trackstick
143	events.
144	
145	The first type is the touchpad position packet.
146	
147	 byte 0:    1    ?   x1   x0    1    1    1    1
148	 byte 1:    0  x10   x9   x8   x7   x6   x5   x4
149	 byte 2:    0  y10   y9   y8   y7   y6   y5   y4
150	 byte 3:    0    M    R    L    1    m    r    l
151	 byte 4:    0   mt   x3   x2   y3   y2   y1   y0
152	 byte 5:    0   z6   z5   z4   z3   z2   z1   z0
153	
154	Note that for some devices the trackstick buttons are reported in this packet,
155	and on others it is reported in the trackstick packets.
156	
157	The second packet type contains bitmaps representing the x and y axes. In the
158	bitmaps a given bit is set if there is a finger covering that position on the
159	given axis. Thus the bitmap packet can be used for low-resolution multi-touch
160	data, although finger tracking is not possible.  This packet also encodes the
161	number of contacts (f1 and f0 in the table below).
162	
163	 byte 0:    1    1   x1   x0    1    1    1    1
164	 byte 1:    0   x8   x7   x6   x5   x4   x3   x2
165	 byte 2:    0   y7   y6   y5   y4   y3   y2   y1
166	 byte 3:    0  y10   y9   y8    1    1    1    1
167	 byte 4:    0  x14  x13  x12  x11  x10   x9   y0
168	 byte 5:    0    1    ?    ?    ?    ?   f1   f0
169	
170	This packet only appears after a position packet with the mt bit set, and
171	usually only appears when there are two or more contacts (although
172	occasionally it's seen with only a single contact).
173	
174	The final v3 packet type is the trackstick packet.
175	
176	 byte 0:    1    1   x7   y7    1    1    1    1
177	 byte 1:    0   x6   x5   x4   x3   x2   x1   x0
178	 byte 2:    0   y6   y5   y4   y3   y2   y1   y0
179	 byte 3:    0    1    0    0    1    0    0    0
180	 byte 4:    0   z4   z3   z2   z1   z0    ?    ?
181	 byte 5:    0    0    1    1    1    1    1    1
182	
183	ALPS Absolute Mode - Protocol Version 4
184	---------------------------------------
185	
186	Protocol version 4 has an 8-byte packet format.
187	
188	 byte 0:    1    ?   x1   x0    1    1    1    1
189	 byte 1:    0  x10   x9   x8   x7   x6   x5   x4
190	 byte 2:    0  y10   y9   y8   y7   y6   y5   y4
191	 byte 3:    0    1   x3   x2   y3   y2   y1   y0
192	 byte 4:    0    ?    ?    ?    1    ?    r    l
193	 byte 5:    0   z6   z5   z4   z3   z2   z1   z0
194	 byte 6:    bitmap data (described below)
195	 byte 7:    bitmap data (described below)
196	
197	The last two bytes represent a partial bitmap packet, with 3 full packets
198	required to construct a complete bitmap packet.  Once assembled, the 6-byte
199	bitmap packet has the following format:
200	
201	 byte 0:    0    1   x7   x6   x5   x4   x3   x2
202	 byte 1:    0   x1   x0   y4   y3   y2   y1   y0
203	 byte 2:    0    0    ?  x14  x13  x12  x11  x10
204	 byte 3:    0   x9   x8   y9   y8   y7   y6   y5
205	 byte 4:    0    0    0    0    0    0    0    0
206	 byte 5:    0    0    0    0    0    0    0  y10
207	
208	There are several things worth noting here.
209	
210	 1) In the bitmap data, bit 6 of byte 0 serves as a sync byte to
211	    identify the first fragment of a bitmap packet.
212	
213	 2) The bitmaps represent the same data as in the v3 bitmap packets, although
214	    the packet layout is different.
215	
216	 3) There doesn't seem to be a count of the contact points anywhere in the v4
217	    protocol packets. Deriving a count of contact points must be done by
218	    analyzing the bitmaps.
219	
220	 4) There is a 3 to 1 ratio of position packets to bitmap packets. Therefore
221	    MT position can only be updated for every third ST position update, and
222	    the count of contact points can only be updated every third packet as
223	    well.
224	
225	So far no v4 devices with tracksticks have been encountered.
226	
227	ALPS Absolute Mode - Protocol Version 5
228	---------------------------------------
229	This is basically Protocol Version 3 but with different logic for packet
230	decode.  It uses the same alps_process_touchpad_packet_v3 call with a
231	specialized decode_fields function pointer to correctly interpret the
232	packets.  This appears to only be used by the Dolphin devices.
233	
234	For single-touch, the 6-byte packet format is:
235	
236	 byte 0:    1    1    0    0    1    0    0    0
237	 byte 1:    0   x6   x5   x4   x3   x2   x1   x0
238	 byte 2:    0   y6   y5   y4   y3   y2   y1   y0
239	 byte 3:    0    M    R    L    1    m    r    l
240	 byte 4:   y10  y9   y8   y7  x10   x9   x8   x7
241	 byte 5:    0   z6   z5   z4   z3   z2   z1   z0
242	
243	For mt, the format is:
244	
245	 byte 0:    1    1    1    n3   1   n2   n1   x24
246	 byte 1:    1   y7   y6    y5  y4   y3   y2    y1
247	 byte 2:    ?   x2   x1   y12 y11  y10   y9    y8
248	 byte 3:    0  x23  x22   x21 x20  x19  x18   x17
249	 byte 4:    0   x9   x8    x7  x6   x5   x4    x3
250	 byte 5:    0  x16  x15   x14 x13  x12  x11   x10
251	
252	ALPS Absolute Mode - Protocol Version 6
253	---------------------------------------
254	
255	For trackstick packet, the format is:
256	
257	 byte 0:    1    1    1    1    1    1    1    1
258	 byte 1:    0   X6   X5   X4   X3   X2   X1   X0
259	 byte 2:    0   Y6   Y5   Y4   Y3   Y2   Y1   Y0
260	 byte 3:    ?   Y7   X7    ?    ?    M    R    L
261	 byte 4:   Z7   Z6   Z5   Z4   Z3   Z2   Z1   Z0
262	 byte 5:    0    1    1    1    1    1    1    1
263	
264	For touchpad packet, the format is:
265	
266	 byte 0:    1    1    1    1    1    1    1    1
267	 byte 1:    0    0    0    0   x3   x2   x1   x0
268	 byte 2:    0    0    0    0   y3   y2   y1   y0
269	 byte 3:    ?   x7   x6   x5   x4    ?    r    l
270	 byte 4:    ?   y7   y6   y5   y4    ?    ?    ?
271	 byte 5:   z7   z6   z5   z4   z3   z2   z1   z0
272	
273	(v6 touchpad does not have middle button)
274	
275	ALPS Absolute Mode - Protocol Version 7
276	---------------------------------------
277	
278	For trackstick packet, the format is:
279	
280	 byte 0:    0    1    0    0    1    0    0    0
281	 byte 1:    1    1    *    *    1    M    R    L
282	 byte 2:   X7    1   X5   X4   X3   X2   X1   X0
283	 byte 3:   Z6    1   Y6   X6    1   Y2   Y1   Y0
284	 byte 4:   Y7    0   Y5   Y4   Y3    1    1    0
285	 byte 5:  T&P    0   Z5   Z4   Z3   Z2   Z1   Z0
286	
287	For touchpad packet, the format is:
288	
289	         packet-fmt     b7     b6     b5     b4     b3     b2     b1     b0
290	 byte 0: TWO & MULTI     L      1      R      M      1   Y0-2   Y0-1   Y0-0
291	 byte 0: NEW             L      1   X1-5      1      1   Y0-2   Y0-1   Y0-0
292	 byte 1:             Y0-10   Y0-9   Y0-8   Y0-7   Y0-6   Y0-5   Y0-4   Y0-3
293	 byte 2:             X0-11      1  X0-10   X0-9   X0-8   X0-7   X0-6   X0-5
294	 byte 3:             X1-11      1   X0-4   X0-3      1   X0-2   X0-1   X0-0
295	 byte 4: TWO         X1-10    TWO   X1-9   X1-8   X1-7   X1-6   X1-5   X1-4
296	 byte 4: MULTI       X1-10    TWO   X1-9   X1-8   X1-7   X1-6   Y1-5      1
297	 byte 4: NEW         X1-10    TWO   X1-9   X1-8   X1-7   X1-6      0      0
298	 byte 5: TWO & NEW   Y1-10      0   Y1-9   Y1-8   Y1-7   Y1-6   Y1-5   Y1-4
299	 byte 5: MULTI       Y1-10      0   Y1-9   Y1-8   Y1-7   Y1-6    F-1    F-0
300	
301	 L:         Left button
302	 R / M:     Non-clickpads: Right / Middle button
303	            Clickpads: When > 2 fingers are down, and some fingers
304	            are in the button area, then the 2 coordinates reported
305	            are for fingers outside the button area and these report
306	            extra fingers being present in the right / left button
307	            area. Note these fingers are not added to the F field!
308	            so if a TWO packet is received and R = 1 then there are
309	            3 fingers down, etc.
310	 TWO:       1: Two touches present, byte 0/4/5 are in TWO fmt
311	            0: If byte 4 bit 0 is 1, then byte 0/4/5 are in MULTI fmt
312	               otherwise byte 0 bit 4 must be set and byte 0/4/5 are
313	               in NEW fmt
314	 F:         Number of fingers - 3, 0 means 3 fingers, 1 means 4 ...
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