New kernel drivers and device migrations (#563)

Devices/unphone/source/module.cpp

@@ -0,0 +1,66 @@
+#include <tactility/check.h>
+#include <tactility/device.h>
+#include <tactility/device_listener.h>
+#include <tactility/driver.h>
+#include <tactility/error.h>
+#include <tactility/module.h>
+
+#include <cstring>
+
+bool init_boot();
+
+extern "C" {
+
+extern Driver unphone_power_switch_driver;
+extern Driver unphone_nav_buttons_driver;
+
+// The root device (the only device with no parent) reaching DEVICE_EVENT_STARTED means the
+// whole devicetree has finished constructing/starting, so it's now safe to power on the
+// unPhone-specific peripherals that initBoot() depends on (e.g. the bq24295 fuel gauge).
+static void on_device_event(Device* device, DeviceEvent event, void* context) {
+    (void)context;
+
+    static bool has_power_switch = false;
+    static bool has_bq24295 = false;
+    static bool has_backlight = false;
+    static bool did_init = false;
+
+    if (event == DEVICE_EVENT_STARTED) {
+        if (strcmp(device->name, "power_switch") == 0) { has_power_switch = true; }
+        if (strcmp(device->name, "bq24295") == 0) { has_bq24295 = true; }
+        if (strcmp(device->name, "display_backlight") == 0) { has_backlight = true; }
+    }
+
+    if (!did_init && has_power_switch && has_bq24295 && has_backlight) {
+        check(init_boot(), "unPhone initBoot failed");
+        did_init = true;
+    }
+}
+
+static error_t start() {
+    /* We crash when construct fails, because if a single driver fails to construct,
+     * there is no guarantee that the previously constructed drivers can be destroyed */
+    check(driver_construct_add(&unphone_power_switch_driver) == ERROR_NONE);
+    check(driver_construct_add(&unphone_nav_buttons_driver) == ERROR_NONE);
+    device_listener_add(on_device_event, nullptr);
+    return ERROR_NONE;
+}
+
+static error_t stop() {
+    device_listener_remove(&on_device_event);
+    /* We crash when destruct fails, because if a single driver fails to destruct,
+     * there is no guarantee that the previously destroyed drivers can be recovered */
+    check(driver_remove_destruct(&unphone_nav_buttons_driver) == ERROR_NONE);
+    check(driver_remove_destruct(&unphone_power_switch_driver) == ERROR_NONE);
+    return ERROR_NONE;
+}
+
+struct Module unphone_module = {
+    .name = "unphone",
+    .start = start,
+    .stop = stop,
+    .symbols = nullptr,
+    .internal = nullptr
+};
+
+}