drivers: input: Add driver for the Nintendo Nunchuk through I2C.

Add a driver for the Nintendo Nunchuk, accessed through the I2C bus.
This driver only supports the joystick and the buttons, not the
accelerometer.

Signed-off-by: Miguel Gazquez <miguel.gazquez@bootlin.com>

drivers/input/CMakeLists.txt

@@ -22,6 +22,7 @@ zephyr_library_sources_ifdef(CONFIG_INPUT_ITE_IT8801_KBD input_ite_it8801_kbd.c)
 zephyr_library_sources_ifdef(CONFIG_INPUT_ITE_IT8XXX2_KBD input_ite_it8xxx2_kbd.c)
 zephyr_library_sources_ifdef(CONFIG_INPUT_KBD_MATRIX input_kbd_matrix.c)
 zephyr_library_sources_ifdef(CONFIG_INPUT_NPCX_KBD input_npcx_kbd.c)
+zephyr_library_sources_ifdef(CONFIG_INPUT_NUNCHUK input_nunchuk.c)
 zephyr_library_sources_ifdef(CONFIG_INPUT_PAT912X input_pat912x.c)
 zephyr_library_sources_ifdef(CONFIG_INPUT_PAW32XX input_paw32xx.c)
 zephyr_library_sources_ifdef(CONFIG_INPUT_PINNACLE input_pinnacle.c)

drivers/input/Kconfig

@@ -24,6 +24,7 @@ source "drivers/input/Kconfig.it8801"
 source "drivers/input/Kconfig.it8xxx2"
 source "drivers/input/Kconfig.kbd_matrix"
 source "drivers/input/Kconfig.npcx"
+source "drivers/input/Kconfig.nunchuk"
 source "drivers/input/Kconfig.pat912x"
 source "drivers/input/Kconfig.paw32xx"
 source "drivers/input/Kconfig.pinnacle"

drivers/input/Kconfig.nunchuk

@@ -0,0 +1,10 @@
+# Copyright (c) 2024 Bootlin
+# SPDX-License-Identifier: Apache-2.0
+
+config INPUT_NUNCHUK
+	bool "Nintendo Nunchuk joystick"
+	default y
+	depends on DT_HAS_NINTENDO_NUNCHUK_ENABLED
+	select I2C
+	help
+	  This option enable the driver for the Nintendo Nunchuk joystick.

drivers/input/input_nunchuk.c

@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2024 Bootlin
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT nintendo_nunchuk
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/i2c.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/input/input.h>
+#include <zephyr/kernel.h>
+#include <zephyr/timing/timing.h>
+
+LOG_MODULE_REGISTER(input_nunchuk, CONFIG_INPUT_LOG_LEVEL);
+
+#define NUNCHUK_DELAY_MS     10
+#define NUNCHUK_READ_SIZE 6
+
+struct nunchuk_config {
+	struct i2c_dt_spec i2c_bus;
+	int polling_interval_ms;
+};
+
+struct nunchuk_data {
+	const struct device *dev;
+	uint8_t joystick_x;
+	uint8_t joystick_y;
+	bool button_c;
+	bool button_z;
+	struct k_work_delayable work;
+	k_timeout_t interval_ms;
+};
+
+static int nunchuk_read_registers(const struct device *dev, uint8_t *buffer)
+{
+	const struct nunchuk_config *cfg = dev->config;
+	int ret;
+	uint8_t value = 0;
+
+	ret = i2c_write_dt(&cfg->i2c_bus, &value, sizeof(value));
+	if (ret < 0) {
+		return ret;
+	}
+
+	k_msleep(NUNCHUK_DELAY_MS);
+	ret = i2c_read_dt(&cfg->i2c_bus, buffer, NUNCHUK_READ_SIZE);
+	if (ret < 0) {
+		return ret;
+	}
+
+	return 0;
+}
+
+static void nunchuk_poll(struct k_work *work)
+{
+	struct k_work_delayable *dwork = k_work_delayable_from_work(work);
+	struct nunchuk_data *data = CONTAINER_OF(dwork, struct nunchuk_data, work);
+	const struct device *dev = data->dev;
+	uint8_t buffer[NUNCHUK_READ_SIZE];
+	uint8_t joystick_x, joystick_y;
+	bool button_c, button_z;
+	bool y_changed;
+	bool sync_flag;
+	int ret;
+
+	nunchuk_read_registers(dev, buffer);
+
+	joystick_x = buffer[0];
+	joystick_y = buffer[1];
+	y_changed = (joystick_y != data->joystick_y);
+
+	if (joystick_x != data->joystick_x) {
+		data->joystick_x = joystick_x;
+		sync_flag = !y_changed;
+		ret = input_report_abs(dev, INPUT_ABS_X, data->joystick_x, sync_flag, K_FOREVER);
+	}
+
+	if (y_changed) {
+		data->joystick_y = joystick_y;
+		ret = input_report_abs(dev, INPUT_ABS_Y, data->joystick_y, true, K_FOREVER);
+	}
+
+	button_z = buffer[5] & BIT(0);
+	if (button_z != data->button_z) {
+		data->button_z = button_z;
+		ret = input_report_key(dev, INPUT_KEY_Z, !data->button_z, true, K_FOREVER);
+	}
+
+	button_c = buffer[5] & BIT(1);
+	if (button_c != data->button_c) {
+		data->button_c = button_c;
+		ret = input_report_key(dev, INPUT_KEY_C, !data->button_c, true, K_FOREVER);
+	}
+
+	k_work_reschedule(dwork, data->interval_ms);
+}
+
+static int nunchuk_init(const struct device *dev)
+{
+	const struct nunchuk_config *cfg = dev->config;
+	struct nunchuk_data *data = dev->data;
+	int ret;
+
+	uint8_t init_seq_1[2] = {0xf0, 0x55};
+	uint8_t init_seq_2[2] = {0xfb, 0x00};
+	uint8_t buffer[NUNCHUK_READ_SIZE];
+
+	data->dev = dev;
+	data->interval_ms = K_MSEC(cfg->polling_interval_ms - 11);
+
+	if (!i2c_is_ready_dt(&cfg->i2c_bus)) {
+		LOG_ERR("Bus device is not ready");
+		return -ENODEV;
+	}
+
+	/* Send the unencrypted init sequence */
+	ret = i2c_write_dt(&cfg->i2c_bus, init_seq_1, sizeof(init_seq_1));
+	if (ret < 0) {
+		LOG_ERR("I2C write failed (%d).", ret);
+		return ret;
+	}
+
+	k_msleep(1);
+	ret = i2c_write_dt(&cfg->i2c_bus, init_seq_2, sizeof(init_seq_2));
+	if (ret < 0) {
+		return ret;
+	}
+
+	k_msleep(1);
+	ret = nunchuk_read_registers(dev, buffer);
+	if (ret < 0) {
+		return ret;
+	}
+
+	/* Sometimes, the first read gives unexpected results, so we make another one. */
+	k_msleep(1);
+	ret = nunchuk_read_registers(dev, buffer);
+	if (ret < 0) {
+		return ret;
+	}
+
+	data->joystick_x = buffer[0];
+	data->joystick_y = buffer[1];
+	data->button_z = buffer[5] & BIT(0);
+	data->button_c = buffer[5] & BIT(1);
+
+	k_work_init_delayable(&data->work, nunchuk_poll);
+	ret = k_work_reschedule(&data->work, data->interval_ms);
+
+	return ret;
+}
+
+#define NUNCHUK_INIT(inst)                                                                         \
+	static const struct nunchuk_config nunchuk_config_##inst = {                               \
+		.i2c_bus = I2C_DT_SPEC_INST_GET(inst),                                             \
+		.polling_interval_ms = DT_INST_PROP(inst, polling_interval_ms),                    \
+	};                                                                                         \
+	BUILD_ASSERT(DT_INST_PROP(inst, polling_interval_ms) > 20);                                \
+                                                                                                   \
+	static struct nunchuk_data nunchuk_data_##inst;                                            \
+                                                                                                   \
+	DEVICE_DT_INST_DEFINE(inst, &nunchuk_init, NULL, &nunchuk_data_##inst,                     \
+			      &nunchuk_config_##inst, POST_KERNEL, CONFIG_INPUT_INIT_PRIORITY,     \
+			      NULL);
+
+DT_INST_FOREACH_STATUS_OKAY(NUNCHUK_INIT)

tests/drivers/build_all/input/app.overlay

@@ -293,6 +293,11 @@
 					};
 				};
 			};
+
+			nunchuk@a {
+				reg = <0xa>;
+				compatible= "nintendo,nunchuk";
+			};
 		};
 
 		spi@2 {