[PATCH] Input: gpio-keys - add full support of EV_REL and EV_ABS

[Xiong Nandi <xndchn@gmail.com>]

gpio_keys_gpio_report_event() handled EV_ABS but silently ignored EV_REL,
while the polled driver supports both.  Extend the interrupt-driven driver
to fire an EV_REL event on button press.

For EV_ABS, use a shared atomic counter per (type, code) pair so that
a zero-value reset is sent only when the last active button on an axis
is released, avoiding premature axis resets when multiple buttons share
the same axis code.

Add gpio_keys_set_abs_params() to call input_set_abs_params() at setup
time, deriving the axis min/max from the configured button values.
Without this the input subsystem reports unbounded axis ranges.

Signed-off-by: Xiong Nandi <xndchn@gmail.com>
---
 drivers/input/keyboard/gpio_keys.c | 65 +++++++++++++++++++++++++++++-
 include/linux/gpio_keys.h          |  4 +-
 2 files changed, 65 insertions(+), 4 deletions(-)

diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
index e19617485679..652a6932c52f 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c
@@ -51,8 +51,10 @@ struct gpio_button_data {
 	spinlock_t lock;
 	bool disabled;
 	bool key_pressed;
+	bool axis_active;
 	bool suspended;
 	bool debounce_use_hrtimer;
+	atomic_t *axis_count;
 };
 
 struct gpio_keys_drvdata {
@@ -373,9 +375,16 @@ static void gpio_keys_gpio_report_event(struct gpio_button_data *bdata)
 		return;
 	}
 
-	if (type == EV_ABS) {
-		if (state)
+	if (type == EV_ABS || type == EV_REL) {
+		if (state && !bdata->axis_active) {
+			bdata->axis_active = true;
+			atomic_inc(bdata->axis_count);
 			input_event(input, type, button->code, button->value);
+		} else if (!state && bdata->axis_active) {
+			bdata->axis_active = false;
+			if (atomic_dec_and_test(bdata->axis_count))
+				input_event(input, type, button->code, 0);
+		}
 	} else {
 		input_event(input, type, *bdata->code, state);
 	}
@@ -493,6 +502,27 @@ static irqreturn_t gpio_keys_irq_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static void gpio_keys_set_abs_params(struct input_dev *input,
+				     struct gpio_keys_drvdata *ddata,
+				     unsigned int code)
+{
+	int i, min = 0, max = 0;
+
+	for (i = 0; i < ddata->pdata->nbuttons; i++) {
+		const struct gpio_keys_button *button = &ddata->pdata->buttons[i];
+
+		if (button->type != EV_ABS || button->code != code)
+			continue;
+
+		if (button->value < min)
+			min = button->value;
+		if (button->value > max)
+			max = button->value;
+	}
+
+	input_set_abs_params(input, code, min, max, 0, 0);
+}
+
 static int gpio_keys_setup_key(struct platform_device *pdev,
 				struct input_dev *input,
 				struct gpio_keys_drvdata *ddata,
@@ -651,6 +681,8 @@ static int gpio_keys_setup_key(struct platform_device *pdev,
 	bdata->code = &ddata->keymap[idx];
 	*bdata->code = button->code;
 	input_set_capability(input, button->type ?: EV_KEY, *bdata->code);
+	if ((button->type ?: EV_KEY) == EV_ABS)
+		gpio_keys_set_abs_params(input, ddata, button->code);
 
 	/*
 	 * Install custom action to cancel release timer and
@@ -928,6 +960,35 @@ static int gpio_keys_probe(struct platform_device *pdev)
 
 	fwnode_handle_put(child);
 
+	/* Allocate shared axis counters for EV_ABS/EV_REL buttons */
+	for (i = 0; i < pdata->nbuttons; i++) {
+		struct gpio_button_data *bdata = &ddata->data[i];
+		unsigned int type = bdata->button->type ?: EV_KEY;
+		int j;
+
+		if (type != EV_ABS && type != EV_REL)
+			continue;
+
+		/* Reuse counter from an earlier button with same (type, code) */
+		for (j = 0; j < i; j++) {
+			struct gpio_button_data *prev = &ddata->data[j];
+			unsigned int prev_type = prev->button->type ?: EV_KEY;
+
+			if (prev_type == type &&
+			    prev->button->code == bdata->button->code) {
+				bdata->axis_count = prev->axis_count;
+				break;
+			}
+		}
+
+		if (!bdata->axis_count) {
+			bdata->axis_count = devm_kzalloc(dev,
+					sizeof(*bdata->axis_count), GFP_KERNEL);
+			if (!bdata->axis_count)
+				return -ENOMEM;
+		}
+	}
+
 	error = input_register_device(input);
 	if (error) {
 		dev_err(dev, "Unable to register input device, error: %d\n",
diff --git a/include/linux/gpio_keys.h b/include/linux/gpio_keys.h
index 80fa930b04c6..75a745a32fe1 100644
--- a/include/linux/gpio_keys.h
+++ b/include/linux/gpio_keys.h
@@ -13,13 +13,13 @@ struct device;
  * @active_low:		%true indicates that button is considered
  *			depressed when gpio is low
  * @desc:		label that will be attached to button's gpio
- * @type:		input event type (%EV_KEY, %EV_SW, %EV_ABS)
+ * @type:		input event type (%EV_KEY, %EV_SW, %EV_ABS, %EV_REL)
  * @wakeup:		configure the button as a wake-up source
  * @wakeup_event_action:	event action to trigger wakeup
  * @debounce_interval:	debounce ticks interval in msecs
  * @can_disable:	%true indicates that userspace is allowed to
  *			disable button via sysfs
- * @value:		axis value for %EV_ABS
+ * @value:		axis value for %EV_ABS/%EV_REL
  * @irq:		Irq number in case of interrupt keys
  * @wakeirq:		Optional dedicated wake-up interrupt
  */
-- 
2.25.1