typedef struct hw_module_t {
    /** tag must be initialized to HARDWARE_MODULE_TAG */
    uint32_t tag;

    /**
     * The API version of the implemented module. The module owner is
     * responsible for updating the version when a module interface has
     * changed.
     *
     * The derived modules such as gralloc and audio own and manage this field.
     * The module user must interpret the version field to decide whether or
     * not to inter-operate with the supplied module implementation.
     * For example, SurfaceFlinger is responsible for making sure that
     * it knows how to manage different versions of the gralloc-module API,
     * and AudioFlinger must know how to do the same for audio-module API.
     *
     * The module API version should include a major and a minor component.
     * For example, version 1.0 could be represented as 0x0100. This format
     * implies that versions 0x0100-0x01ff are all API-compatible.
     *
     * In the future, libhardware will expose a hw_get_module_version()
     * (or equivalent) function that will take minimum/maximum supported
     * versions as arguments and would be able to reject modules with
     * versions outside of the supplied range.
     */
    uint16_t module_api_version;
#define version_major module_api_version
    /**
     * version_major/version_minor defines are supplied here for temporary
     * source code compatibility. They will be removed in the next version.
     * ALL clients must convert to the new version format.
     */

    /**
     * The API version of the HAL module interface. This is meant to
     * version the hw_module_t, hw_module_methods_t, and hw_device_t
     * structures and definitions.
     *
     * The HAL interface owns this field. Module users/implementations
     * must NOT rely on this value for version information.
     *
     * Presently, 0 is the only valid value.
     */
    uint16_t hal_api_version;
#define version_minor hal_api_version

    /** Identifier of module */
    const char *id;

    /** Name of this module */
    const char *name;

    /** Author/owner/implementor of the module */
    const char *author;

    /** Modules methods */
    struct hw_module_methods_t* methods;

    /** module's dso */
    void* dso;

    /** padding to 128 bytes, reserved for future use */
    uint32_t reserved[32-7];

} hw_module_t;

typedef struct hw_module_methods_t {
    /** Open a specific device */
    int (*open)(const struct hw_module_t* module, const char* id,
            struct hw_device_t** device);

} hw_module_methods_t;

/**
 * Every device data structure must begin with hw_device_t
 * followed by module specific public methods and attributes.
 */
typedef struct hw_device_t {
    /** tag must be initialized to HARDWARE_DEVICE_TAG */
    uint32_t tag;

    /**
     * Version of the module-specific device API. This value is used by
     * the derived-module user to manage different device implementations.
     *
     * The module user is responsible for checking the module_api_version
     * and device version fields to ensure that the user is capable of
     * communicating with the specific module implementation.
     *
     * One module can support multiple devices with different versions. This
     * can be useful when a device interface changes in an incompatible way
     * but it is still necessary to support older implementations at the same
     * time. One such example is the Camera 2.0 API.
     *
     * This field is interpreted by the module user and is ignored by the
     * HAL interface itself.
     */
    uint32_t version;

    /** reference to the module this device belongs to */
    struct hw_module_t* module;

    /** padding reserved for future use */
    uint32_t reserved[12];

    /** Close this device */
    int (*close)(struct hw_device_t* device);

} hw_device_t;

typedef struct camera_module {
    hw_module_t common;

    /**
     * get_number_of_cameras:
     *
     * Returns the number of camera devices accessible through the camera
     * module.  The camera devices are numbered 0 through N-1, where N is the
     * value returned by this call. The name of the camera device for open() is
     * simply the number converted to a string. That is, "0" for camera ID 0,
     * "1" for camera ID 1.
     *
     * The value here must be static, and cannot change after the first call to
     * this method
     */
    int (*get_number_of_cameras)(void);

    /**
     * get_camera_info:
     *
     * Return the static camera information for a given camera device. This
     * information may not change for a camera device.
     *
     */
    int (*get_camera_info)(int camera_id, struct camera_info *info);

    /**
     * set_callbacks:
     *
     * Provide callback function pointers to the HAL module to inform framework
     * of asynchronous camera module events. The framework will call this
     * function once after initial camera HAL module load, after the
     * get_number_of_cameras() method is called for the first time, and before
     * any other calls to the module.
     *
     * Version information (based on camera_module_t.common.module_api_version):
     *
     *  CAMERA_MODULE_API_VERSION_1_0, CAMERA_MODULE_API_VERSION_2_0:
     *
     *    Not provided by HAL module. Framework may not call this function.
     *
     *  CAMERA_MODULE_API_VERSION_2_1:
     *
     *    Valid to be called by the framework.
     *
     */
    int (*set_callbacks)(const camera_module_callbacks_t *callbacks);

    /**
     * get_vendor_tag_ops:
     *
     * Get methods to query for vendor extension metadata tag information. The
     * HAL should fill in all the vendor tag operation methods, or leave ops
     * unchanged if no vendor tags are defined.
     *
     * Version information (based on camera_module_t.common.module_api_version):
     *
     *  CAMERA_MODULE_API_VERSION_1_x/2_0/2_1:
     *    Not provided by HAL module. Framework may not call this function.
     *
     *  CAMERA_MODULE_API_VERSION_2_2:
     *    Valid to be called by the framework.
     */
    void (*get_vendor_tag_ops)(vendor_tag_ops_t* ops);

    /* reserved for future use */
    void* reserved[8];
} camera_module_t;

camera_module_t HAL_MODULE_INFO_SYM __attribute__ ((visibility("default"))) = {
    common : {
        tag                : HARDWARE_MODULE_TAG,
        module_api_version : CAMERA_MODULE_API_VERSION_2_0,
        hal_api_version    : HARDWARE_HAL_API_VERSION,
        id                 : CAMERA_HARDWARE_MODULE_ID,
        name               : "Default Camera HAL",
        author             : "The Android Open Source Project",
        methods            : &gCameraModuleMethods,
        dso                : NULL,
        reserved           : {0},
    },
    get_number_of_cameras : get_number_of_cameras,
    get_camera_info       : get_camera_info,
    set_callbacks         : set_callbacks
};

int Camera::open(const hw_module_t *module, hw_device_t **device)
{
    ALOGI("%s:%d: Opening camera device", __func__, mId);
    CAMTRACE_CALL();
    pthread_mutex_lock(&mMutex);
    if (mBusy) {
        pthread_mutex_unlock(&mMutex);
        ALOGE("%s:%d: Error! Camera device already opened", __func__, mId);
        return -EBUSY;
    }

    // TODO: open camera dev nodes, etc
    mBusy = true;
    mDevice.common.module = const_cast(module);
    *device = &mDevice.common;

    pthread_mutex_unlock(&mMutex);
    return 0;
}

Camera::Camera(int id)
  : mId(id),
    mStaticInfo(NULL),
    mBusy(false),
    mCallbackOps(NULL),
    mStreams(NULL),
    mNumStreams(0),
    mSettings(NULL)
{
    pthread_mutex_init(&mMutex, NULL);
    pthread_mutex_init(&mStaticInfoMutex, NULL);

    memset(&mDevice, 0, sizeof(mDevice));
    mDevice.common.tag    = HARDWARE_DEVICE_TAG;
    mDevice.common.version = CAMERA_DEVICE_API_VERSION_3_0;
    mDevice.common.close  = close_device;
    mDevice.ops           = const_cast(&sOps);
    mDevice.priv          = this;
}