Input: rotary-encoder - add support for half-period encoders
Add support for encoders that have two detents per input signal period.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Acked-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/Documentation/input/rotary-encoder.txt b/Documentation/input/rotary-encoder.txt
index 943e8f6..92e68bc 100644
--- a/Documentation/input/rotary-encoder.txt
+++ b/Documentation/input/rotary-encoder.txt
@@ -9,6 +9,9 @@
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 @@
|<-------->|
one step
+ |<-->|
+ one step (half-period mode)
For more information, please see
http://en.wikipedia.org/wiki/Rotary_encoder
@@ -34,6 +39,13 @@
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 @@
.gpio_b = GPIO_ROTARY_B,
.inverted_a = 0,
.inverted_b = 0,
+ .half_period = false,
};
static struct platform_device rotary_encoder_device = {
diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c
index 077b80b..2c8b84d 100644
--- a/drivers/input/misc/rotary_encoder.c
+++ b/drivers/input/misc/rotary_encoder.c
@@ -2,6 +2,7 @@
* rotary_encoder.c
*
* (c) 2009 Daniel Mack <daniel@caiaq.de>
+ * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
*
* state machine code inspired by code from Tim Ruetz
*
@@ -38,6 +39,8 @@
bool armed;
unsigned char dir; /* 0 - clockwise, 1 - CCW */
+
+ char last_stable;
};
static int rotary_encoder_get_state(struct rotary_encoder_platform_data *pdata)
@@ -112,11 +115,37 @@
return IRQ_HANDLED;
}
+static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
+{
+ struct rotary_encoder *encoder = dev_id;
+ int state;
+
+ state = rotary_encoder_get_state(encoder->pdata);
+
+ switch (state) {
+ case 0x00:
+ case 0x03:
+ if (state != encoder->last_stable) {
+ rotary_encoder_report_event(encoder);
+ encoder->last_stable = state;
+ }
+ break;
+
+ case 0x01:
+ case 0x02:
+ encoder->dir = (encoder->last_stable + state) & 0x01;
+ break;
+ }
+
+ return IRQ_HANDLED;
+}
+
static int __devinit rotary_encoder_probe(struct platform_device *pdev)
{
struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
struct rotary_encoder *encoder;
struct input_dev *input;
+ irq_handler_t handler;
int err;
if (!pdata) {
@@ -187,7 +216,14 @@
}
/* request the IRQs */
- err = request_irq(encoder->irq_a, &rotary_encoder_irq,
+ if (pdata->half_period) {
+ handler = &rotary_encoder_half_period_irq;
+ encoder->last_stable = rotary_encoder_get_state(pdata);
+ } else {
+ handler = &rotary_encoder_irq;
+ }
+
+ err = request_irq(encoder->irq_a, handler,
IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
DRV_NAME, encoder);
if (err) {
@@ -196,7 +232,7 @@
goto exit_free_gpio_b;
}
- err = request_irq(encoder->irq_b, &rotary_encoder_irq,
+ err = request_irq(encoder->irq_b, handler,
IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
DRV_NAME, encoder);
if (err) {
@@ -264,5 +300,5 @@
MODULE_ALIAS("platform:" DRV_NAME);
MODULE_DESCRIPTION("GPIO rotary encoder driver");
-MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
+MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
MODULE_LICENSE("GPL v2");
diff --git a/include/linux/rotary_encoder.h b/include/linux/rotary_encoder.h
index 215278b..3f594dc 100644
--- a/include/linux/rotary_encoder.h
+++ b/include/linux/rotary_encoder.h
@@ -10,6 +10,7 @@
unsigned int inverted_b;
bool relative_axis;
bool rollover;
+ bool half_period;
};
#endif /* __ROTARY_ENCODER_H__ */