X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=blobdiff_plain;f=Documentation%2Finput%2Frotary-encoder.txt;h=92e68bce13a40ce2042326d287093c3ad41f7ad2;hp=943e8f6f2b15fdcc491441d20e30854fd56f1803;hb=fce637e392a762e4d4f0fc41ac3d3f557187ac21;hpb=4cb1f43ce8c72ee453c00fcb9f6ee9c4ebd03f98

diff --git a/Documentation/input/rotary-encoder.txt b/Documentation/input/rotary-encoder.txt
index 943e8f6f2b15..92e68bce13a4 100644
--- a/Documentation/input/rotary-encoder.txt
+++ b/Documentation/input/rotary-encoder.txt
@@ -9,6 +9,9 @@ peripherals with two wires. The outputs are phase-shifted by 90 degrees
 and by triggering on falling and rising edges, the turn direction can
 be determined.
 
+Some encoders have both outputs low in stable states, whereas others also have
+a stable state with both outputs high (half-period mode).
+
 The phase diagram of these two outputs look like this:
 
                   _____       _____       _____
@@ -26,6 +29,8 @@ The phase diagram of these two outputs look like this:
                 |<-------->|
 	          one step
 
+                |<-->|
+	          one step (half-period mode)
 
 For more information, please see
 	http://en.wikipedia.org/wiki/Rotary_encoder
@@ -34,6 +39,13 @@ For more information, please see
 1. Events / state machine
 -------------------------
 
+In half-period mode, state a) and c) above are used to determine the
+rotational direction based on the last stable state. Events are reported in
+states b) and d) given that the new stable state is different from the last
+(i.e. the rotation was not reversed half-way).
+
+Otherwise, the following apply:
+
 a) Rising edge on channel A, channel B in low state
 	This state is used to recognize a clockwise turn
 
@@ -96,6 +108,7 @@ static struct rotary_encoder_platform_data my_rotary_encoder_info = {
 	.gpio_b		= GPIO_ROTARY_B,
 	.inverted_a	= 0,
 	.inverted_b	= 0,
+	.half_period	= false,
 };
 
 static struct platform_device rotary_encoder_device = {