Trackball rewrite (#600)

- Implement generic trackball settings
- Refactor T-Deck trackball driver into generic driver at `Drivers/gpio-trackball-module`
- Automatically bind/unbind trackball devices with LVGL
- Automatically load settings for trackball devices on boot

TactilityKernel/include/tactility/drivers/trackball.h

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: Apache-2.0
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <tactility/device.h>
+#include <tactility/error.h>
+
+/**
+ * @brief API for trackball drivers.
+ * Reports raw, unscaled movement: sensitivity and mode (encoder vs. pointer) are UI concerns
+ * layered on top by the consumer (see lvgl/devices/trackball.h), not something this driver knows about.
+ */
+struct TrackballApi {
+    /**
+     * @brief Reads the accumulated movement since the last read, then resets it to zero.
+     * @param[in] device the trackball device
+     * @param[out] out_dx horizontal movement (right positive), in raw pulses
+     * @param[out] out_dy vertical movement (down positive), in raw pulses
+     * @retval ERROR_NONE when the operation was successful
+     */
+    error_t (*read_delta)(struct Device* device, int32_t* out_dx, int32_t* out_dy);
+
+    /**
+     * @brief Gets whether the click button is currently pressed.
+     * @param[in] device the trackball device
+     * @param[out] out_pressed true when pressed
+     * @retval ERROR_NONE when the operation was successful
+     */
+    error_t (*get_button_pressed)(struct Device* device, bool* out_pressed);
+};
+
+/**
+ * @brief Reads the accumulated movement using the specified trackball device.
+ */
+error_t trackball_read_delta(struct Device* device, int32_t* out_dx, int32_t* out_dy);
+
+/**
+ * @brief Gets whether the click button is currently pressed on the specified trackball device.
+ */
+error_t trackball_get_button_pressed(struct Device* device, bool* out_pressed);
+
+extern const struct DeviceType TRACKBALL_TYPE;
+
+#ifdef __cplusplus
+}
+#endif