[PATCH v2 1/2] Input: rotary-encoder: Add 'stepped' irq handler

[Ezequiel Garcia]

Some rotary-encoder devices (such as those with detents) are capable
of producing a stable event on each step. This commit adds support
for this case, by implementing a new interruption handler.

The handler needs only detect the direction of the turn and generate
an event according to this detection.

Cc: Daniel Mack <zonque@xxxxxxxxx>
Cc: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>
---
v1->v2:
  * Add DT property handling
  * Replace binary representation by hexa-decimal in the sum encoding

 drivers/input/misc/rotary_encoder.c | 41 +++++++++++++++++++++++++++++++++++++
 include/linux/rotary_encoder.h      |  1 +
 2 files changed, 42 insertions(+)

diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c
index 5b1aff8..6c7a554 100644
--- a/drivers/input/misc/rotary_encoder.c
+++ b/drivers/input/misc/rotary_encoder.c
@@ -117,6 +117,42 @@ static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t rotary_encoder_stepped_irq(int irq, void *dev_id)
+{
+	struct rotary_encoder *encoder = dev_id;
+	int state;
+	unsigned char sum;
+
+	state = rotary_encoder_get_state(encoder->pdata);
+
+	/*
+	 * We encode the previous and the current state using a byte.
+	 * The previous state in the MSB nibble, the current state in the LSB
+	 * nibble. Then use a table to decide the direction of the turn.
+	 */
+	sum = (encoder->last_stable << 4) + state;
+	switch (sum) {
+	case 0x31:
+	case 0x10:
+	case 0x02:
+	case 0x23:
+		encoder->dir = 0; /* clockwise */
+		break;
+	/*
+	 * TODO: Add the other case, and the illegal values should
+	 * say a WARN (it's a BUG, but we won't stop the kernel for it :)
+	 */
+	default:
+		encoder->dir = 1;
+	}
+
+	rotary_encoder_report_event(encoder);
+
+	encoder->last_stable = state;
+
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
 {
 	struct rotary_encoder *encoder = dev_id;
@@ -180,6 +216,8 @@ static struct rotary_encoder_platform_data *rotary_encoder_parse_dt(struct devic
 					"rotary-encoder,rollover", NULL);
 	pdata->half_period = !!of_get_property(np,
 					"rotary-encoder,half-period", NULL);
+	pdata->on_each_step = !!of_get_property(np,
+					"rotary-encoder,on-each-step", NULL);
 
 	return pdata;
 }
@@ -254,6 +292,9 @@ static int rotary_encoder_probe(struct platform_device *pdev)
 	if (pdata->half_period) {
 		handler = &rotary_encoder_half_period_irq;
 		encoder->last_stable = rotary_encoder_get_state(pdata);
+	} else if (pdata->on_each_step) {
+		handler = &rotary_encoder_stepped_irq;
+		encoder->last_stable = rotary_encoder_get_state(pdata);
 	} else {
 		handler = &rotary_encoder_irq;
 	}
diff --git a/include/linux/rotary_encoder.h b/include/linux/rotary_encoder.h
index 3f594dc..499f6f7 100644
--- a/include/linux/rotary_encoder.h
+++ b/include/linux/rotary_encoder.h
@@ -11,6 +11,7 @@ struct rotary_encoder_platform_data {
 	bool relative_axis;
 	bool rollover;
 	bool half_period;
+	bool on_each_step;
 };
 
 #endif /* __ROTARY_ENCODER_H__ */
-- 
1.8.1.5

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