Early commit to trigger code review due to file limit on upcoming changes

Buildscripts/DevicetreeCompiler/source/generator.py

@@ -135,7 +135,7 @@ def write_device_init(file, device: Device, bindings: list[Binding], verbose: bo
     identifier = get_device_identifier_safe(device)
     device_variable = identifier
     # Write device struct
-    file.write(f"\tif (device_construct_add_start(&{device_variable}, \"{compatible_property.value}\") != ERROR_NONE) return ERROR_RESOURCE;\n")
+    file.write("\t{ " f"&{device_variable}, \"{compatible_property.value}\"" " },\n")
     # Write children
     for child_device in device.devices:
         write_device_init(file, child_device, bindings, verbose)
@@ -145,8 +145,6 @@ def generate_devicetree_c(filename: str, items: list[object], bindings: list[Bin
         file.write(dedent('''\
         // Default headers
         #include <tactility/device.h>
-        #include <tactility/error.h>
-        #include <tactility/log.h>
         // DTS headers
         '''))
 
@@ -161,14 +159,14 @@ def generate_devicetree_c(filename: str, items: list[object], bindings: list[Bin
             if type(item) is Device:
                 write_device_structs(file, item, None, bindings, verbose)
         # Init function body start
-        file.write("error_t devices_builtin_init() {\n")
+        file.write("struct CompatibleDevice devicetree_devices[] = {\n")
         # Init function body logic
         for item in items:
             if type(item) is Device:
                 write_device_init(file, item, bindings, verbose)
-        file.write("\treturn ERROR_NONE;\n")
         # Init function body end
-        file.write("}\n")
+        file.write("\t{ NULL, NULL },\n")
+        file.write("};\n")
 
 def generate_devicetree_h(filename: str):
     with open(filename, "w") as file:
@@ -180,7 +178,7 @@ def generate_devicetree_h(filename: str):
         extern "C" {
         #endif
         
-        extern error_t devices_builtin_init();
+        extern struct CompatibleDevice devicetree_devices[];
         
         #ifdef __cplusplus
         }

Devices/lilygo-tdeck/Source/module.cpp

@@ -0,0 +1,22 @@
+#include <tactility/module.h>
+
+extern "C" {
+
+static error_t start() {
+    // Empty for now
+    return ERROR_NONE;
+}
+
+static error_t stop() {
+    // Empty for now
+    return ERROR_NONE;
+}
+
+/** @warn The variable name must be exactly "platform_module" */
+struct Module device_module = {
+    .name = "LilyGO T-Deck",
+    .start = start,
+    .stop = stop
+};
+
+}

Devices/lilygo-tlora-pager/Source/drivers/Register.cpp

@@ -1,10 +0,0 @@
-#include <tactility/driver.h>
-
-extern "C" {
-
-extern void register_device_drivers() {
-    extern Driver tlora_pager_driver;
-    driver_construct(&tlora_pager_driver);
-}
-
-}

Devices/lilygo-tlora-pager/Source/module.cpp

@@ -0,0 +1,30 @@
+#include <tactility/check.h>
+#include <tactility/driver.h>
+#include <tactility/module.h>
+
+extern "C" {
+
+extern Driver tlora_pager_driver;
+
+static error_t start() {
+    /* We crash when destruct fails, because if a single driver fails to construct,
+     * there is no guarantee that the previously constructed drivers can be destroyed */
+    check(driver_construct(&tlora_pager_driver) == ERROR_NONE);
+    return ERROR_NONE;
+}
+
+static error_t stop() {
+    /* 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_destruct(&tlora_pager_driver) == ERROR_NONE);
+    return ERROR_NONE;
+}
+
+/** @warn The variable name must be exactly "platform_module" */
+struct Module device_module = {
+    .name = "LilyGO T-Lora Pager",
+    .start = start,
+    .stop = stop
+};
+
+}

Firmware/Source/Main.cpp

@@ -3,6 +3,11 @@
 #include <tactility/driver.h>
 #include <devicetree.h>
 
+// From the relevant platform
+extern struct Module platform_module;
+// From the relevant device
+extern struct Module device_module;
+
 #ifdef ESP_PLATFORM
 #include <tt_init.h>
 #else
@@ -14,10 +19,6 @@ extern const tt::hal::Configuration hardwareConfiguration;
 
 extern "C" {
 
-extern void register_kernel_drivers();
-extern void register_platform_drivers();
-extern void register_device_drivers();
-
 void app_main() {
     static const tt::Configuration config = {
         /**
@@ -31,12 +32,7 @@ void app_main() {
     tt_init_tactility_c(); // ELF bindings for side-loading on ESP32
 #endif
 
-    register_kernel_drivers();
-    register_platform_drivers();
-    register_device_drivers();
-
-    devices_builtin_init();
-    tt::run(config);
+    tt::run(config, &platform_module, &device_module, devicetree_devices);
 }
 
 } // extern

Platforms/PlatformEsp32/Include/tactility/drivers/esp32_i2c.h

@@ -18,8 +18,6 @@ struct Esp32I2cConfig {
 };
 
 error_t esp32_i2c_get_port(struct Device* device, i2c_port_t* port);
-void esp32_i2c_lock(struct Device* device);
-void esp32_i2c_unlock(struct Device* device);
 
 #ifdef __cplusplus
 }

Platforms/PlatformEsp32/Source/drivers/esp32_gpio.cpp

@@ -107,6 +107,8 @@ const static GpioControllerApi esp32_gpio_api  = {
     .get_options = get_options
 };
 
+extern struct Module platform_module;
+
 Driver esp32_gpio_driver = {
     .name = "esp32_gpio",
     .compatible = (const char*[]) { "espressif,esp32-gpio", nullptr },
@@ -114,7 +116,8 @@ Driver esp32_gpio_driver = {
     .stopDevice = stop,
     .api =  (void*)&esp32_gpio_api,
     .deviceType = nullptr,
-    .internal = { 0 }
+    .owner = &platform_module,
+    .internal = nullptr
 };
 
 } // extern "C"

Platforms/PlatformEsp32/Source/drivers/esp32_i2c.cpp

@@ -150,14 +150,6 @@ error_t esp32_i2c_get_port(struct Device* device, i2c_port_t* port) {
     return ERROR_NONE;
 }
 
-void esp32_i2c_lock(struct Device* device) {
-    mutex_lock(&GET_DATA(device)->mutex);
-}
-
-void esp32_i2c_unlock(struct Device* device) {
-    mutex_unlock(&GET_DATA(device)->mutex);
-}
-
 static error_t start(Device* device) {
     ESP_LOGI(TAG, "start %s", device->name);
     auto dts_config = GET_CONFIG(device);
@@ -214,6 +206,8 @@ const static I2cControllerApi esp32_i2c_api = {
     .write_register = write_register
 };
 
+extern struct Module platform_module;
+
 Driver esp32_i2c_driver = {
     .name = "esp32_i2c",
     .compatible = (const char*[]) { "espressif,esp32-i2c", nullptr },
@@ -221,7 +215,8 @@ Driver esp32_i2c_driver = {
     .stopDevice = stop,
     .api = (void*)&esp32_i2c_api,
     .deviceType = &I2C_CONTROLLER_TYPE,
-    .internal = { 0 }
+    .owner = &platform_module,
+    .internal = nullptr
 };
 
 } // extern "C"

Platforms/PlatformEsp32/Source/drivers/register.cpp

@@ -1,13 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0
-#include <tactility/driver.h>
-
-extern "C" {
-
-extern void register_platform_drivers() {
-    extern Driver esp32_gpio_driver;
-    driver_construct(&esp32_gpio_driver);
-    extern Driver esp32_i2c_driver;
-    driver_construct(&esp32_i2c_driver);
-}
-
-}

Platforms/PlatformEsp32/Source/module.cpp

@@ -0,0 +1,33 @@
+#include <tactility/check.h>
+#include <tactility/driver.h>
+#include <tactility/module.h>
+
+extern "C" {
+
+extern Driver esp32_gpio_driver;
+extern Driver esp32_i2c_driver;
+
+static error_t start() {
+    /* We crash when destruct fails, because if a single driver fails to construct,
+     * there is no guarantee that the previously constructed drivers can be destroyed */
+    check(driver_construct(&esp32_gpio_driver) == ERROR_NONE);
+    check(driver_construct(&esp32_i2c_driver) == ERROR_NONE);
+    return ERROR_NONE;
+}
+
+static error_t stop() {
+    /* 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_destruct(&esp32_gpio_driver) == ERROR_NONE);
+    check(driver_destruct(&esp32_i2c_driver) == ERROR_NONE);
+    return ERROR_NONE;
+}
+
+// The name must be exactly "platform_module"
+struct Module platform_module = {
+    .name = "ESP32 Platform",
+    .start = start,
+    .stop = stop
+};
+
+}

Platforms/PlatformPosix/Source/Register.cpp

@@ -1,10 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0
-#include <tactility/driver.h>
-
-extern "C" {
-
-extern void register_platform_drivers() {
-    /* Placeholder */
-}
-
-}

Platforms/PlatformPosix/Source/module.cpp

@@ -0,0 +1,25 @@
+#include <tactility/module.h>
+
+extern "C" {
+
+extern Driver esp32_gpio_driver;
+extern Driver esp32_i2c_driver;
+
+static error_t start() {
+    /* NO-OP for now */
+    return ERROR_NONE;
+}
+
+static error_t stop() {
+    /* NO-OP for now */
+    return ERROR_NONE;
+}
+
+// The name must be exactly "platform_module"
+struct Module platform_module = {
+    .name = "POSIX Platform",
+    .start = start,
+    .stop = stop
+};
+
+}

Tactility/Include/Tactility/Tactility.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "tactility/device.h"
+#include "tactility/module.h"
 #include <Tactility/Dispatcher.h>
 #include <Tactility/app/AppManifest.h>
 #include <Tactility/hal/Configuration.h>
@@ -17,9 +19,8 @@ struct Configuration {
 
 /**
  * Attempts to initialize Tactility and all configured hardware.
- * @param[in] config
  */
-void run(const Configuration& config);
+void run(const Configuration& config, Module* platformModule, Module* deviceModule, CompatibleDevice devicetreeDevices[]);
 
 /**
  * While technically nullable, this instance is always set if tt_init() succeeds.

Tactility/Source/Tactility.cpp

@@ -22,6 +22,8 @@
 #include <Tactility/service/loader/Loader.h>
 #include <Tactility/settings/TimePrivate.h>
 
+#include <tactility/kernel_init.h>
+
 #include <map>
 #include <format>
 
@@ -317,10 +319,17 @@ void registerApps() {
     registerInstalledAppsFromSdCards();
 }
 
-void run(const Configuration& config) {
+void run(const Configuration& config, Module* platformModule, Module* deviceModule, CompatibleDevice devicetreeDevices[]) {
     LOGGER.info("Tactility v{} on {} ({})", TT_VERSION, CONFIG_TT_DEVICE_NAME, CONFIG_TT_DEVICE_ID);
 
     assert(config.hardware);
+
+    LOGGER.info(R"(Calling kernel_init with modules: "{}" and "{}")", platformModule->name, deviceModule->name);
+    if (kernel_init(platformModule, deviceModule, devicetreeDevices) != ERROR_NONE) {
+        LOGGER.error("Failed to initialize kernel");
+        return;
+    }
+
     const hal::Configuration& hardware = *config.hardware;
 
     // Assign early so starting services can use it

TactilityKernel/Include/tactility/concurrent/recursive_mutex.h

@@ -15,6 +15,7 @@ struct RecursiveMutex {
 };
 
 inline static void recursive_mutex_construct(struct RecursiveMutex* mutex) {
+    check(mutex->handle == NULL);
     mutex->handle = xSemaphoreCreateRecursiveMutex();
 }
 

TactilityKernel/Include/tactility/device.h

@@ -50,6 +50,16 @@ struct Device {
     } internal;
 };
 
+/**
+ * Holds a device pointer and a compatible string.
+ * The device must not be constructed, added or started yet.
+ * This is mused by the devicetree code generator and the application init sequence.
+ */
+struct CompatibleDevice {
+    struct Device* device;
+    const char* compatible;
+};
+
 /**
  * Initialize the properties of a device.
  *

TactilityKernel/Include/tactility/driver.h

@@ -25,11 +25,10 @@ struct Driver {
     const void* api;
     /** Which type of devices this driver creates (can be NULL) */
     const struct DeviceType* deviceType;
+    /** The module that owns this driver. When it is NULL, the system owns the driver and it cannot be removed from registration. */
+    const struct Module* owner;
     /** Internal data */
-    struct {
-        /** Contains private data */
-        void* data;
-    } internal;
+    void* internal;
 };
 
 error_t driver_construct(struct Driver* driver);

TactilityKernel/Include/tactility/error.h

@@ -22,6 +22,7 @@ typedef int error_t;
 #define ERROR_TIMEOUT 8
 #define ERROR_OUT_OF_MEMORY 9
 #define ERROR_NOT_SUPPORTED 10
+#define ERROR_NOT_ALLOWED 11
 
 /** Convert an error_t to a human-readable text. Useful for logging. */
 const char* error_to_string(error_t error);

TactilityKernel/Include/tactility/kernel_init.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <tactility/device.h>
+#include <tactility/error.h>
+#include <tactility/module.h>
+
+/**
+ * Initialize the kernel with platform and device modules, and a device tree.
+ * @param platform_module The platform module to start. This module should not be constructed yet.
+ * @param device_module The device module to start. This module should not be constructed yet.
+ * @param devicetree_devices The list of generated devices from the devicetree.
+ * @return ERROR_NONE on success, otherwise an error code
+ */
+error_t kernel_init(struct Module* platform_module, struct Module* device_module, struct CompatibleDevice devicetree_devices[]);
+
+#ifdef __cplusplus
+}
+#endif

TactilityKernel/Include/tactility/module.h

@@ -0,0 +1,112 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "error.h"
+#include <stdbool.h>
+
+struct ModuleParent;
+
+/**
+ * A module is a collection of drivers or other functionality that can be loaded and unloaded at runtime.
+ */
+struct Module {
+    /**
+     * The name of the module, for logging/debugging purposes
+     * Should never be NULL.
+     */
+    const char* name;
+
+    /**
+     * A function to initialize the module.
+     * Should never be NULL.
+     * This can be used to load drivers, initialize hardware, etc.
+     * @return ERROR_NONE if successful
+     */
+    error_t (*start)(void);
+
+    /**
+     * Deinitializes the module.
+     * Should never be NULL.
+     * @return ERROR_NONE if successful
+     */
+    error_t (*stop)(void);
+
+    struct {
+        bool started;
+        struct ModuleParent* parent;
+    } internal;
+};
+
+/**
+ * A module parent is a collection of modules that can be loaded and unloaded at runtime.
+ */
+struct ModuleParent {
+    /** The name of the parent module, for logging/debugging purposes */
+    const char* name;
+    struct {
+        void* data;
+    } internal;
+};
+
+/**
+ * @brief Initialize the module parent.
+ * @warn This function does no validation on input or state.
+ * @param parent parent module
+ * @return ERROR_NONE if successful, ERROR_OUT_OF_MEMORY if allocation fails
+ */
+error_t module_parent_construct(struct ModuleParent* parent);
+
+/**
+ * @brief Deinitialize the module parent. Must have no children when calling this.
+ * @warn This function does no validation on input.
+ * @param parent parent module
+ * @return ERROR_NONE if successful or ERROR_INVALID_STATE if the parent has children
+ */
+error_t module_parent_destruct(struct ModuleParent* parent);
+
+/**
+ * @brief Set the parent of the module.
+ * @warning must call before module_start()
+ * @param module module
+ * @param parent nullable parent module
+ * @return ERROR_NONE if successful, ERROR_INVALID_STATE if the module is already started
+ */
+error_t module_set_parent(struct Module* module, struct ModuleParent* parent);
+
+/**
+ * @brief Start the module.
+ * @param module module
+ * @return ERROR_NONE if already started, ERROR_INVALID_STATE if the module doesn't have a parent, or otherwise it returns the result of the module's start function
+ */
+error_t module_start(struct Module* module);
+
+/**
+ * @brief Check if the module is started.
+ * @param module module to check
+ * @return true if the module is started, false otherwise
+ */
+bool module_is_started(struct Module* module);
+
+/**
+ * @brief Stop the module.
+ * @param module module
+ * @return ERROR_NONE if successful or if the module wasn't started, or otherwise it returns the result of the module's stop function
+ */
+error_t module_stop(struct Module* module);
+
+error_t kernel_module_parent_construct(void);
+
+error_t kernel_module_parent_destruct(void);
+
+/**
+ * @brief Get the kernel module parent. This parent is the root parent for kernel modules.
+ * @return the kernel module parent
+ */
+struct ModuleParent* get_kernel_module_parent(void);
+
+#ifdef __cplusplus
+}
+#endif

TactilityKernel/Source/driver.cpp

@@ -12,16 +12,16 @@
 
 #define TAG LOG_TAG(driver)
 
-struct DriverInternalData {
+struct DriverInternal {
     Mutex mutex { 0 };
     int use_count = 0;
     bool destroying = false;
 
-    DriverInternalData() {
+    DriverInternal() {
         mutex_construct(&mutex);
     }
 
-    ~DriverInternalData() {
+    ~DriverInternal() {
         mutex_destruct(&mutex);
     }
 };
@@ -54,9 +54,9 @@ static DriverLedger& get_ledger() {
 
 #define ledger get_ledger()
 
-#define driver_internal_data(driver) static_cast<DriverInternalData*>(driver->internal.data)
-#define driver_lock(driver) mutex_lock(&driver_internal_data(driver)->mutex);
-#define driver_unlock(driver) mutex_unlock(&driver_internal_data(driver)->mutex);
+#define get_internal(driver) static_cast<DriverInternal*>(driver->internal)
+#define driver_lock(driver) mutex_lock(&get_internal(driver)->mutex);
+#define driver_unlock(driver) mutex_unlock(&get_internal(driver)->mutex);
 
 static void driver_add(Driver* driver) {
     LOG_I(TAG, "add %s", driver->name);
@@ -83,8 +83,8 @@ static error_t driver_remove(Driver* driver) {
 extern "C" {
 
 error_t driver_construct(Driver* driver) {
-    driver->internal.data = new(std::nothrow) DriverInternalData;
-    if (driver->internal.data == nullptr) {
+    driver->internal = new(std::nothrow) DriverInternal;
+    if (driver->internal == nullptr) {
         return ERROR_OUT_OF_MEMORY;
     }
     driver_add(driver);
@@ -93,19 +93,29 @@ error_t driver_construct(Driver* driver) {
 
 error_t driver_destruct(Driver* driver) {
     driver_lock(driver);
-    if (driver_internal_data(driver)->use_count != 0 || driver_internal_data(driver)->destroying) {
+    // No module means the system owns it and it cannot be destroyed
+    if (driver->owner == nullptr) {
+        driver_unlock(driver);
+        return ERROR_NOT_ALLOWED;
+    }
+    if (get_internal(driver)->use_count != 0 || get_internal(driver)->destroying) {
         driver_unlock(driver);
         return ERROR_INVALID_STATE;
     }
-    driver_internal_data(driver)->destroying = true;
-    driver_unlock(driver);
+    get_internal(driver)->destroying = true;
 
     if (driver_remove(driver) != ERROR_NONE) {
         LOG_W(TAG, "Failed to remove driver from ledger: %s", driver->name);
     }
 
-    delete driver_internal_data(driver);
-    driver->internal.data = nullptr;
+    // Copy the mutex so we can free the driver's memory and unlock the mutex later
+    struct Mutex mutex_copy;
+    memcpy(&mutex_copy, &get_internal(driver)->mutex, sizeof(Mutex));
+
+    delete get_internal(driver);
+    driver->internal = nullptr;
+
+    mutex_unlock(&mutex_copy);
     return ERROR_NONE;
 }
 
@@ -140,7 +150,7 @@ error_t driver_bind(Driver* driver, Device* device) {
     driver_lock(driver);
 
     error_t error = ERROR_NONE;
-    if (driver_internal_data(driver)->destroying || !device_is_added(device)) {
+    if (get_internal(driver)->destroying || !device_is_added(device)) {
         error = ERROR_INVALID_STATE;
         goto error;
     }
@@ -152,7 +162,7 @@ error_t driver_bind(Driver* driver, Device* device) {
         }
     }
 
-    driver_internal_data(driver)->use_count++;
+    get_internal(driver)->use_count++;
     driver_unlock(driver);
 
     LOG_I(TAG, "bound %s to %s", driver->name, device->name);
@@ -168,7 +178,7 @@ error_t driver_unbind(Driver* driver, Device* device) {
     driver_lock(driver);
 
     error_t error = ERROR_NONE;
-    if (driver_internal_data(driver)->destroying || !device_is_added(device)) {
+    if (get_internal(driver)->destroying || !device_is_added(device)) {
         error = ERROR_INVALID_STATE;
         goto error;
     }
@@ -180,7 +190,7 @@ error_t driver_unbind(Driver* driver, Device* device) {
         }
     }
 
-    driver_internal_data(driver)->use_count--;
+    get_internal(driver)->use_count--;
     driver_unlock(driver);
 
     LOG_I(TAG, "unbound %s from %s", driver->name, device->name);

TactilityKernel/Source/drivers/register.cpp

@@ -1,12 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0
-
-#include <tactility/driver.h>
-
-extern "C" {
-
-extern void register_kernel_drivers() {
-    extern Driver root_driver;
-    driver_construct(&root_driver);
-}
-
-}

TactilityKernel/Source/drivers/root.cpp

@@ -12,7 +12,8 @@ Driver root_driver = {
     .stopDevice = nullptr,
     .api = nullptr,
     .deviceType = nullptr,
-    .internal = { 0 }
+    .owner = nullptr,
+    .internal = nullptr
 };
 
 }

TactilityKernel/Source/kernel_init.cpp

@@ -0,0 +1,58 @@
+#include <tactility/kernel_init.h>
+#include <tactility/log.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define TAG LOG_TAG(kernel)
+
+struct ModuleParent kernel_module_parent;
+
+static error_t init_kernel_drivers() {
+    extern Driver root_driver;
+    if (driver_construct(&root_driver) != ERROR_NONE) return ERROR_RESOURCE;
+    return ERROR_NONE;
+}
+
+error_t kernel_init(struct Module* platform_module, struct Module* device_module, struct CompatibleDevice devicetree_devices[]) {
+    LOG_I(TAG, "init");
+
+    if (module_parent_construct(&kernel_module_parent) != ERROR_NONE) {
+        LOG_E(TAG, "init failed to create kernel module parent");
+        return ERROR_RESOURCE;
+    }
+
+    if (init_kernel_drivers() != ERROR_NONE) {
+        LOG_E(TAG, "init failed to init kernel drivers");
+        return ERROR_RESOURCE;
+    }
+
+    module_set_parent(platform_module, &kernel_module_parent);
+    if (module_start(platform_module) != ERROR_NONE) {
+        LOG_E(TAG, "init failed to start platform module");
+        return ERROR_RESOURCE;
+    }
+
+    module_set_parent(device_module, &kernel_module_parent);
+    if (module_start(device_module) != ERROR_NONE) {
+        LOG_E(TAG, "init failed to start device module");
+        return ERROR_RESOURCE;
+    }
+
+    CompatibleDevice* compatible_device = devicetree_devices;
+    while (compatible_device->device != nullptr) {
+        if (device_construct_add_start(compatible_device->device, compatible_device->compatible) != ERROR_NONE) {
+            LOG_E(TAG, "kernel_init failed to construct device: %s (%s)", compatible_device->device->name, compatible_device->compatible);
+            return ERROR_RESOURCE;
+        }
+        compatible_device++;
+    }
+
+    LOG_I(TAG, "init done");
+    return ERROR_NONE;
+};
+
+#ifdef __cplusplus
+}
+#endif

TactilityKernel/Source/module.cpp

@@ -0,0 +1,120 @@
+#include <vector>
+#include <algorithm>
+#include <tactility/concurrent/mutex.h>
+#include <tactility/module.h>
+
+struct ModuleParentInternal {
+    std::vector<struct Module*> modules;
+    struct Mutex mutex = { 0 };
+};
+
+extern "C" {
+
+#pragma region module_parent
+
+error_t module_parent_construct(struct ModuleParent* parent) {
+    parent->internal.data = new (std::nothrow) ModuleParentInternal();
+    if (!parent->internal.data) return ERROR_OUT_OF_MEMORY;
+
+    auto* data = static_cast<ModuleParentInternal*>(parent->internal.data);
+    mutex_construct(&data->mutex);
+
+    return ERROR_NONE;
+}
+
+error_t module_parent_destruct(struct ModuleParent* parent) {
+    auto* data = static_cast<ModuleParentInternal*>(parent->internal.data);
+    if (data == nullptr) return ERROR_NONE;
+
+    mutex_lock(&data->mutex);
+    if (!data->modules.empty()) {
+        mutex_unlock(&data->mutex);
+        return ERROR_INVALID_STATE;
+    }
+    mutex_unlock(&data->mutex);
+
+    mutex_destruct(&data->mutex);
+    delete data;
+    parent->internal.data = nullptr;
+    return ERROR_NONE;
+}
+
+#pragma endregion
+
+#pragma region module
+
+error_t module_set_parent(struct Module* module, struct ModuleParent* parent) {
+    if (module->internal.started) return ERROR_INVALID_STATE;
+    if (module->internal.parent == parent) return ERROR_NONE;
+
+    // Remove from old parent
+    if (module->internal.parent && module->internal.parent->internal.data) {
+        auto* old_data = static_cast<ModuleParentInternal*>(module->internal.parent->internal.data);
+        mutex_lock(&old_data->mutex);
+        auto it = std::find(old_data->modules.begin(), old_data->modules.end(), module);
+        if (it != old_data->modules.end()) {
+            old_data->modules.erase(it);
+        }
+        mutex_unlock(&old_data->mutex);
+    }
+
+    module->internal.parent = parent;
+
+    // Add to new parent
+    if (parent && parent->internal.data) {
+        auto* new_data = static_cast<ModuleParentInternal*>(parent->internal.data);
+        mutex_lock(&new_data->mutex);
+        new_data->modules.push_back(module);
+        mutex_unlock(&new_data->mutex);
+    }
+
+    return ERROR_NONE;
+}
+
+error_t module_start(struct Module* module) {
+    if (module->internal.started) return ERROR_NONE;
+    if (!module->internal.parent) return ERROR_INVALID_STATE;
+
+    error_t error = module->start();
+    module->internal.started = (error == ERROR_NONE);
+    return error;
+}
+
+bool module_is_started(struct Module* module) {
+    return module->internal.started;
+}
+
+error_t module_stop(struct Module* module) {
+    if (!module->internal.started) return ERROR_NONE;
+
+    error_t error = module->stop();
+    if (error != ERROR_NONE) {
+        return error;
+    }
+
+    module->internal.started = false;
+    return error;
+}
+
+#pragma endregion
+
+#pragma region kernel_module_parent;
+
+static struct ModuleParent kernel_module_parent = { "kernel", { nullptr } };
+
+error_t kernel_module_parent_construct(void) {
+    return module_parent_construct(&kernel_module_parent);
+}
+
+error_t kernel_module_parent_destruct(void) {
+    return module_parent_destruct(&kernel_module_parent);
+}
+
+struct ModuleParent* get_kernel_module_parent(void) {
+    return &kernel_module_parent;
+}
+
+#pragma endregion
+
+}
+

Tests/TactilityKernel/DeviceTest.cpp

@@ -4,6 +4,13 @@
 #include <vector>
 
 #include <tactility/device.h>
+#include <tactility/module.h>
+
+static Module module = {
+    .name = "test_module",
+    .start = nullptr,
+    .stop = nullptr
+};
 
 TEST_CASE("device_construct and device_destruct should set and unset the correct fields") {
     Device device = { 0 };
@@ -164,7 +171,8 @@ TEST_CASE("device_is_ready should return true only when it is started") {
         .stopDevice = nullptr,
         .api = nullptr,
         .deviceType = nullptr,
-        .internal = { 0 }
+        .owner = &module,
+        .internal = nullptr
     };
 
     Device device = { 0 };

Tests/TactilityKernel/DriverIntegrationTest.cpp

@@ -1,6 +1,13 @@
 #include "doctest.h"
 #include <tactility/driver.h>
 #include <tactility/device.h>
+#include <tactility/module.h>
+
+static Module module = {
+    .name = "test_module",
+    .start = nullptr,
+    .stop = nullptr
+};
 
 struct IntegrationDriverConfig {
     int startResult;
@@ -30,7 +37,8 @@ static Driver integration_driver = {
     .stopDevice = stop,
     .api = nullptr,
     .deviceType = nullptr,
-    .internal = { 0 }
+    .owner = &module,
+    .internal = nullptr,
 };
 
 TEST_CASE("driver with with start success and stop success should start and stop a device") {

Tests/TactilityKernel/DriverTest.cpp

@@ -1,13 +1,31 @@
 #include "doctest.h"
+
 #include <tactility/driver.h>
+#include <tactility/module.h>
+
+static Module module = {
+    .name = "test_module",
+    .start = nullptr,
+    .stop = nullptr
+};
 
 TEST_CASE("driver_construct and driver_destruct should set and unset the correct fields") {
     Driver driver = { 0 };
+    driver.owner = &module;
 
     CHECK_EQ(driver_construct(&driver), ERROR_NONE);
-    CHECK_NE(driver.internal.data, nullptr);
+    CHECK_NE(driver.internal, nullptr);
+    CHECK_EQ(driver_destruct(&driver), ERROR_NONE);
+    CHECK_EQ(driver.internal, nullptr);
+}
+
+TEST_CASE("a driver without a module should not be destrucable") {
+    Driver driver = { 0 };
+
+    CHECK_EQ(driver_construct(&driver), ERROR_NONE);
+    CHECK_EQ(driver_destruct(&driver), ERROR_NOT_ALLOWED);
+    driver.owner = &module;
     CHECK_EQ(driver_destruct(&driver), ERROR_NONE);
-    CHECK_EQ(driver.internal.data, nullptr);
 }
 
 TEST_CASE("driver_is_compatible should return true if a compatible value is found") {
@@ -19,7 +37,8 @@ TEST_CASE("driver_is_compatible should return true if a compatible value is foun
         .stopDevice = nullptr,
         .api = nullptr,
         .deviceType = nullptr,
-        .internal = { 0 }
+        .owner = &module,
+        .internal = nullptr
     };
     CHECK_EQ(driver_is_compatible(&driver, "test_compatible"), true);
     CHECK_EQ(driver_is_compatible(&driver, "nope"), false);
@@ -35,7 +54,8 @@ TEST_CASE("driver_find should only find a compatible driver when the driver was
         .stopDevice = nullptr,
         .api = nullptr,
         .deviceType = nullptr,
-        .internal = { 0 }
+        .owner = &module,
+        .internal = nullptr
     };
 
     Driver* found_driver = driver_find_compatible("test_compatible");

Tests/TactilityKernel/ModuleTest.cpp

@@ -0,0 +1,174 @@
+#include "doctest.h"
+#include <tactility/module.h>
+
+static error_t test_start_result = ERROR_NONE;
+static bool start_called = false;
+static error_t test_start() {
+    start_called = true;
+    return test_start_result;
+}
+
+static error_t test_stop_result = ERROR_NONE;
+static bool stop_called = false;
+static error_t test_stop() {
+    stop_called = true;
+    return test_stop_result;
+}
+
+TEST_CASE("ModuleParent construction and destruction") {
+    struct ModuleParent parent = { "test_parent", { nullptr } };
+
+    // Test successful construction
+    CHECK_EQ(module_parent_construct(&parent), ERROR_NONE);
+    CHECK_NE(parent.internal.data, nullptr);
+
+    // Test successful destruction
+    CHECK_EQ(module_parent_destruct(&parent), ERROR_NONE);
+    CHECK_EQ(parent.internal.data, nullptr);
+}
+
+TEST_CASE("ModuleParent destruction with children") {
+    struct ModuleParent parent = { "parent", { nullptr } };
+    REQUIRE_EQ(module_parent_construct(&parent), ERROR_NONE);
+
+    struct Module module = {
+        .name = "test",
+        .start = test_start,
+        .stop = test_stop,
+        .internal = {.started = false, .parent = nullptr}
+    };
+
+    REQUIRE_EQ(module_set_parent(&module, &parent), ERROR_NONE);
+
+    // Should fail to destruct because it has a child
+    CHECK_EQ(module_parent_destruct(&parent), ERROR_INVALID_STATE);
+    CHECK_NE(parent.internal.data, nullptr);
+
+    // Remove child
+    REQUIRE_EQ(module_set_parent(&module, nullptr), ERROR_NONE);
+
+    // Now it should succeed
+    CHECK_EQ(module_parent_destruct(&parent), ERROR_NONE);
+    CHECK_EQ(parent.internal.data, nullptr);
+}
+
+TEST_CASE("Module parent management") {
+    struct ModuleParent parent1 = { "parent1", { nullptr } };
+    struct ModuleParent parent2 = { "parent2", { nullptr } };
+    REQUIRE_EQ(module_parent_construct(&parent1), ERROR_NONE);
+    REQUIRE_EQ(module_parent_construct(&parent2), ERROR_NONE);
+
+    struct Module module = {
+        .name = "test",
+        .start = test_start,
+        .stop = test_stop,
+        .internal = {.started = false, .parent = nullptr}
+    };
+
+    // Set parent
+    CHECK_EQ(module_set_parent(&module, &parent1), ERROR_NONE);
+    CHECK_EQ(module.internal.parent, &parent1);
+
+    // Change parent
+    CHECK_EQ(module_set_parent(&module, &parent2), ERROR_NONE);
+    CHECK_EQ(module.internal.parent, &parent2);
+
+    // Clear parent
+    CHECK_EQ(module_set_parent(&module, nullptr), ERROR_NONE);
+    CHECK_EQ(module.internal.parent, nullptr);
+
+    // Set same parent (should be NOOP and return ERROR_NONE)
+    CHECK_EQ(module_set_parent(&module, &parent1), ERROR_NONE);
+    CHECK_EQ(module_set_parent(&module, &parent1), ERROR_NONE);
+    CHECK_EQ(module.internal.parent, &parent1);
+
+    module_parent_destruct(&parent1);
+    module_parent_destruct(&parent2);
+}
+
+TEST_CASE("Module lifecycle") {
+    struct ModuleParent parent = { "parent", { nullptr } };
+    REQUIRE_EQ(module_parent_construct(&parent), ERROR_NONE);
+
+    start_called = false;
+    stop_called = false;
+    test_start_result = ERROR_NONE;
+    test_stop_result = ERROR_NONE;
+
+    struct Module module = {
+        .name = "test",
+        .start = test_start,
+        .stop = test_stop,
+        .internal = {.started = false, .parent = nullptr}
+    };
+
+    // 1. Cannot start without parent
+    CHECK_EQ(module_start(&module), ERROR_INVALID_STATE);
+    CHECK_EQ(module_is_started(&module), false);
+    CHECK_EQ(start_called, false);
+
+    CHECK_EQ(module_set_parent(&module, &parent), ERROR_NONE);
+
+    // 2. Successful start
+    CHECK_EQ(module_start(&module), ERROR_NONE);
+    CHECK_EQ(module_is_started(&module), true);
+    CHECK_EQ(start_called, true);
+
+    // 3. Start when already started (should return ERROR_NONE)
+    start_called = false;
+    CHECK_EQ(module_start(&module), ERROR_NONE);
+    CHECK_EQ(start_called, false); // start() function should NOT be called again
+
+    // 4. Cannot change parent while started
+    CHECK_EQ(module_set_parent(&module, nullptr), ERROR_INVALID_STATE);
+
+    // 5. Successful stop
+    CHECK_EQ(module_stop(&module), ERROR_NONE);
+    CHECK_EQ(module_is_started(&module), false);
+    CHECK_EQ(stop_called, true);
+
+    // 6. Stop when already stopped (should return ERROR_NONE)
+    stop_called = false;
+    CHECK_EQ(module_stop(&module), ERROR_NONE);
+    CHECK_EQ(stop_called, false); // stop() function should NOT be called again
+
+    // 7. Test failed start
+    test_start_result = ERROR_NOT_FOUND;
+    start_called = false;
+    CHECK_EQ(module_start(&module), ERROR_NOT_FOUND);
+    CHECK_EQ(module_is_started(&module), false);
+    CHECK_EQ(start_called, true);
+
+    // 8. Test failed stop
+    CHECK_EQ(module_set_parent(&module, &parent), ERROR_NONE);
+    test_start_result = ERROR_NONE;
+    CHECK_EQ(module_start(&module), ERROR_NONE);
+
+    test_stop_result = ERROR_NOT_SUPPORTED;
+    stop_called = false;
+    CHECK_EQ(module_stop(&module), ERROR_NOT_SUPPORTED);
+    CHECK_EQ(module_is_started(&module), true); // Should still be started if stop failed
+    CHECK_EQ(stop_called, true);
+
+    // Clean up: fix stop result so we can stop it
+    test_stop_result = ERROR_NONE;
+    CHECK_EQ(module_stop(&module), ERROR_NONE);
+
+    module_parent_destruct(&parent);
+}
+
+TEST_CASE("Kernel module parent") {
+    // Ensure it's constructed
+    REQUIRE_EQ(kernel_module_parent_construct(), ERROR_NONE);
+
+    struct ModuleParent* kernel_parent = get_kernel_module_parent();
+    CHECK_NE(kernel_parent, nullptr);
+    CHECK_NE(kernel_parent->internal.data, nullptr);
+
+    // Multiple calls return the same
+    CHECK_EQ(get_kernel_module_parent(), kernel_parent);
+
+    // Test destruction
+    CHECK_EQ(kernel_module_parent_destruct(), ERROR_NONE);
+    CHECK_EQ(kernel_parent->internal.data, nullptr);
+}