input: gpio_kbd_matrix: add column drive mode

Add an option to drive inactive columns to inactive state rather than
high impedance. This is useful if the matrix has isolation diodes for
every key, as it allows the matrix to stabilize faster and the API for
changing the pin value is more efficient than the one to change the pin
configuration.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

drivers/input/input_gpio_kbd_matrix.c

@@ -24,6 +24,7 @@ struct gpio_kbd_matrix_config {
 	const struct gpio_dt_spec *col_gpio;
 	struct gpio_callback *gpio_cb;
 	gpio_callback_handler_t handler;
+	bool col_drive_inactive;
 };
 
 struct gpio_kbd_matrix_data {
@@ -53,7 +54,9 @@ static void gpio_kbd_matrix_drive_column(const struct device *dev, int col)
 		const struct gpio_dt_spec *gpio = &cfg->col_gpio[i];
 
 		if ((data->last_col_state ^ state) & BIT(i)) {
-			if (state & BIT(i)) {
+			if (cfg->col_drive_inactive) {
+				gpio_pin_set_dt(gpio, state & BIT(i));
+			} else if (state & BIT(i)) {
 				gpio_pin_configure_dt(gpio, GPIO_OUTPUT_ACTIVE);
 			} else {
 				gpio_pin_configure_dt(gpio, GPIO_INPUT);
@@ -114,7 +117,11 @@ static int gpio_kbd_matrix_init(const struct device *dev)
 			return -ENODEV;
 		}
 
-		ret = gpio_pin_configure_dt(gpio, GPIO_INPUT);
+		if (cfg->col_drive_inactive) {
+			ret = gpio_pin_configure_dt(gpio, GPIO_OUTPUT_INACTIVE);
+		} else {
+			ret = gpio_pin_configure_dt(gpio, GPIO_INPUT);
+		}
 		if (ret != 0) {
 			LOG_ERR("Pin %d configuration failed: %d", i, ret);
 			return ret;
@@ -186,6 +193,7 @@ static const struct input_kbd_matrix_api gpio_kbd_matrix_api = {
 		.col_gpio = gpio_kbd_matrix_col_gpio_##n,					\
 		.gpio_cb = gpio_kbd_matrix_gpio_cb_##n,						\
 		.handler = gpio_kbd_matrix_cb_##n,						\
+		.col_drive_inactive = DT_INST_PROP(n, col_drive_inactive),			\
 	};											\
 												\
 	static struct gpio_kbd_matrix_data gpio_kbd_matrix_data_##n;				\

dts/bindings/input/gpio-kbd-matrix.yaml

@@ -39,5 +39,12 @@ properties:
     required: true
     description: |
       GPIO for the keyboard matrix columns, supports up to 32 different GPIOs.
-      The pins will be driven according to the GPIO_ACTIVE_HIGH or
-      GPIO_ACTIVE_LOW flags when selected, high impedance when not selected.
+      When unselected, this pin will be either driven to inactive state or
+      configured to high impedance (input) depending on the col-drive-inactive
+      property.
+
+  col-drive-inactive:
+    type: boolean
+    description: |
+      If enabled, unselected column GPIOs will be driven to inactive state.
+      Default to configure unselected column GPIOs to high impedance.