UEFI原理与编程（三）

1 开发UEFI服务

本质Protocol 就是包含属性和函数指针的结构体，功能上来说就是提供者和使用者对服务的一种约定。

2 开发UEFI驱动

一个设备/总线驱动程序在安装时首要找到对应的硬件设备（UEFI中是要找到对应的控制器），然后执行安装操作，将驱动程序安装到硬件设备的控制器上。

一个完整的驱动程序框架需要三个部分:

Findout(): 找出对应的硬件设备
Install()/Start(): 安装驱动到指定的硬件设备。
Uninstall()/Stop(): 从硬件设备中卸载驱动

1 UEFI驱动模型

UEFI驱动模型核心通过 EFI Driver Binding Protocol管理驱动程序。完整的驱动程序包含两个核心部分:EFI Driver Binding Protocol 和驱动服务本身。

//file:  MdePkg\Include\Protocol\DriverBinding.h

typedef struct _EFI_DRIVER_BINDING_PROTOCOL {

///

/// This protocol provides the services required to determine if a driver supports a given controller.

/// If a controller is supported, then it also provides routines to start and stop the controller.

///

struct _EFI_DRIVER_BINDING_PROTOCOL {

  EFI_DRIVER_BINDING_SUPPORTED  Supported;  // 检测一个设备是否支持该驱动

  EFI_DRIVER_BINDING_START      Start;      // 用于将驱动安装到设备上

  EFI_DRIVER_BINDING_STOP       Stop;       // 用于将驱动从设备上卸载

  ///

  /// The version number of the UEFI driver that produced the

  /// EFI_DRIVER_BINDING_PROTOCOL. This field is used by

  /// the EFI boot service ConnectController() to determine

  /// the order that driver's Supported() service will be used when

  /// a controller needs to be started. EFI Driver Binding Protocol

  /// instances with higher Version values will be used before ones

  /// with lower Version values. The Version values of 0x0-

  /// 0x0f and 0xfffffff0-0xffffffff are reserved for

  /// platform/OEM specific drivers. The Version values of 0x10-

  /// 0xffffffef are reserved for IHV-developed drivers.

  ///

  UINT32                        Version;   // EDBP版本号

  ///

  /// The image handle of the UEFI driver that produced this instance

  /// of the EFI_DRIVER_BINDING_PROTOCOL.

  ///

  EFI_HANDLE                    ImageHandle; // ImageHandle是生成EDBP映像文件句柄

  ///

  /// The handle on which this instance of the

  /// EFI_DRIVER_BINDING_PROTOCOL is installed. In most

  /// cases, this is the same handle as ImageHandle. However, for

  /// UEFI drivers that produce more than one instance of the

  /// EFI_DRIVER_BINDING_PROTOCOL, this value may not be

  /// the same as ImageHandle.

  ///

  EFI_HANDLE                    DriverBindingHandle;  // DriverBindingHandle是安装了EDBP的Handle

};

Supported函数

用于检测一个设备是否支持该驱动，支持返回EFI_SUCCESS，否则返回其他。

//@file:   MdePkg\Include\Protocol\DriverBinding.h

/**

  Tests to see if this driver supports a given controller. If a child device is provided,

  it further tests to see if this driver supports creating a handle for the specified child device.

  This function checks to see if the driver specified by This supports the device specified by

  ControllerHandle. Drivers will typically use the device path attached to

  ControllerHandle and/or the services from the bus I/O abstraction attached to

  ControllerHandle to determine if the driver supports ControllerHandle. This function

  may be called many times during platform initialization. In order to reduce boot times, the tests

  performed by this function must be very small, and take as little time as possible to execute. This

  function must not change the state of any hardware devices, and this function must be aware that the

  device specified by ControllerHandle may already be managed by the same driver or a

  different driver. This function must match its calls to AllocatePages() with FreePages(),

  AllocatePool() with FreePool(), and OpenProtocol() with CloseProtocol().

  Because ControllerHandle may have been previously started by the same driver, if a protocol is

  already in the opened state, then it must not be closed with CloseProtocol(). This is required

  to guarantee the state of ControllerHandle is not modified by this function.

  @param[in]  This                 A pointer to the EFI_DRIVER_BINDING_PROTOCOL instance.

  @param[in]  ControllerHandle     The handle of the controller to test. This handle

                                   must support a protocol interface that supplies

                                   an I/O abstraction to the driver.

  @param[in]  RemainingDevicePath  A pointer to the remaining portion of a device path.  This

                                   parameter is ignored by device drivers, and is optional for bus

                                   drivers. For bus drivers, if this parameter is not NULL, then

                                   the bus driver must determine if the bus controller specified

                                   by ControllerHandle and the child controller specified

                                   by RemainingDevicePath are both supported by this

                                   bus driver.

  @retval EFI_SUCCESS              The device specified by ControllerHandle and

                                   RemainingDevicePath is supported by the driver specified by This.

  @retval EFI_ALREADY_STARTED      The device specified by ControllerHandle and

                                   RemainingDevicePath is already being managed by the driver

                                   specified by This.

  @retval EFI_ACCESS_DENIED        The device specified by ControllerHandle and

                                   RemainingDevicePath is already being managed by a different

                                   driver or an application that requires exclusive access.

                                   Currently not implemented.

  @retval EFI_UNSUPPORTED          The device specified by ControllerHandle and

                                   RemainingDevicePath is not supported by the driver specified by This.

**/

typedef

EFI_STATUS

(EFIAPI *EFI_DRIVER_BINDING_SUPPORTED)(

  IN EFI_DRIVER_BINDING_PROTOCOL            *This,

  IN EFI_HANDLE                             ControllerHandle, //检查这个驱动是否支持这个控制器

  IN EFI_DEVICE_PATH_PROTOCOL               *RemainingDevicePath OPTIONAL

  );

Start函数

Start函数用来将驱动安装到设备上并启动硬件设备，函数最重要的事情是调用 InstallProtocolInterface() 或者 InstallMultipleProtocolInterfaces() 在ControllerHandle 上安装驱动Protocol

//@file:   MdePkg\Include\Protocol\DriverBinding.h

/**

  Starts a device controller or a bus controller.

  The Start() function is designed to be invoked from the EFI boot service ConnectController().

  As a result, much of the error checking on the parameters to Start() has been moved into this

  common boot service. It is legal to call Start() from other locations,

  but the following calling restrictions must be followed, or the system behavior will not be deterministic.

  1. ControllerHandle must be a valid EFI_HANDLE.

  2. If RemainingDevicePath is not NULL, then it must be a pointer to a naturally aligned

     EFI_DEVICE_PATH_PROTOCOL.

  3. Prior to calling Start(), the Supported() function for the driver specified by This must

     have been called with the same calling parameters, and Supported() must have returned EFI_SUCCESS.  

  @param[in]  This                 A pointer to the EFI_DRIVER_BINDING_PROTOCOL instance.

  @param[in]  ControllerHandle     The handle of the controller to start. This handle

                                   must support a protocol interface that supplies

                                   an I/O abstraction to the driver.

  @param[in]  RemainingDevicePath  A pointer to the remaining portion of a device path.  This

                                   parameter is ignored by device drivers, and is optional for bus

                                   drivers. For a bus driver, if this parameter is NULL, then handles

                                   for all the children of Controller are created by this driver.

                                   If this parameter is not NULL and the first Device Path Node is

                                   not the End of Device Path Node, then only the handle for the

                                   child device specified by the first Device Path Node of

                                   RemainingDevicePath is created by this driver.

                                   If the first Device Path Node of RemainingDevicePath is

                                   the End of Device Path Node, no child handle is created by this

                                   driver.

  @retval EFI_SUCCESS              The device was started.

  @retval EFI_DEVICE_ERROR         The device could not be started due to a device error.Currently not implemented.

  @retval EFI_OUT_OF_RESOURCES     The request could not be completed due to a lack of resources.

  @retval Others                   The driver failded to start the device.

**/

typedef

EFI_STATUS

(EFIAPI *EFI_DRIVER_BINDING_START)(

  IN EFI_DRIVER_BINDING_PROTOCOL            *This,

  IN EFI_HANDLE                             ControllerHandle,  //驱动将被安装到这个Handles上

  IN EFI_DEVICE_PATH_PROTOCOL               *RemainingDevicePath OPTIONAL

  );

Stop函数

Stop函数用于停止硬件设备并卸载驱动（调用函数 UninstallProtocolInterface() 或者 UninstallMultipleProtocolInterfaces()从ControllerHandle 卸载驱动协议）

//@file:   MdePkg\Include\Protocol\DriverBinding.h

/**

  Stops a device controller or a bus controller.

  The Stop() function is designed to be invoked from the EFI boot service DisconnectController().

  As a result, much of the error checking on the parameters to Stop() has been moved

  into this common boot service. It is legal to call Stop() from other locations,

  but the following calling restrictions must be followed, or the system behavior will not be deterministic.

  1. ControllerHandle must be a valid EFI_HANDLE that was used on a previous call to this

     same driver's Start() function.

  2. The first NumberOfChildren handles of ChildHandleBuffer must all be a valid

     EFI_HANDLE. In addition, all of these handles must have been created in this driver's

     Start() function, and the Start() function must have called OpenProtocol() on

     ControllerHandle with an Attribute of EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER.

  @param[in]  This              A pointer to the EFI_DRIVER_BINDING_PROTOCOL instance.

  @param[in]  ControllerHandle  A handle to the device being stopped. The handle must

                                support a bus specific I/O protocol for the driver

                                to use to stop the device.

  @param[in]  NumberOfChildren  The number of child device handles in ChildHandleBuffer.

  @param[in]  ChildHandleBuffer An array of child handles to be freed. May be NULL

                                if NumberOfChildren is 0.

  @retval EFI_SUCCESS           The device was stopped.

  @retval EFI_DEVICE_ERROR      The device could not be stopped due to a device error.

**/

typedef

EFI_STATUS

(EFIAPI *EFI_DRIVER_BINDING_STOP)(

  IN EFI_DRIVER_BINDING_PROTOCOL            *This,

  IN  EFI_HANDLE                            ControllerHandle, //停止对这个控制器上对应的驱动

  IN  UINTN                                 NumberOfChildren, // 子控制器数量

  IN  EFI_HANDLE                            *ChildHandleBuffer OPTIONAL //子控制器数组

  );

对设备驱动来说 NumberOfChildren为0 ， ChildHandleBuffer为NULL ; 对Bus Drive来说如果NumberOfChildren不为0，那么ChildHandleBuffer子节点都要被释放。

根据是否满足UEFI Driver Model来区分：一种是普通的Driver，一种就是满足UEFI Driver Model的驱动

前者是再编写驱动的时候就主动去寻找设备并初始化它，前者的实现一般在驱动运行的时候就直接完成了（DEX阶段）

后者是系统服务自己根据设备来寻到到合适的驱动然后初始化。而后者需要先注册驱动，然后再后续（通常是BDS阶段）通过调用系统服务来完成，这个系统复位就是EFI_BOOT_SERVICES.ConnectController() (第五章启动服务的驱动管理服务）。

2 编写驱动的步骤驱动分为两个部分：

硬件相关部分，用于驱动硬件设备，为用户提供服务，以协议形式出现，如DiskIo BlockIo
框架部分：需要实现Driver Binding Protocol,主要是三个接口（Support,Start, Stop）这部分主要用于驱动的安装卸载。

入口函数: InitializeGigUNDIDriver调用uefi驱动模型库函数： EfiLibInstallDriverBinding这个函数主要用来：安装并完成驱动程序绑定协议实例的初始化（_EFI_DRIVER_BINDING_PROTOCOL的三个属性）。调用函数： InstallMultipleProtocolInterfaces

将新的协议安装到ControllerHandle上。

Support函数(GigUndiDriverSupported):

1 通过gBS服务中OpenProtocol() 打开所有需要Protocol，标准驱动要用EFI_OPEN_PROTOCOL_BY_DRIVER属性打开Protocol, 若OpenProtocol() 返回错误，则调用CloseProtocol()关闭已经打开的Protocol 并返回错误代码。

2 所需所有Protocol成功打开后，测试这个Drive是否支持此Controller. 测试失败则关闭所有打开的Protocol，

返回EFI_UNSUPPORTED，成功则调用 CloseProtocol()关闭所有打开的Protocol，返回EFI_SUCCESS 。

Start函数(GigUndiDriverStart):

1 通过gBS中OpenProtocol（）打开所有需要Protocol，若OpenProtocol() 返回错误，直接返回错误代码。

Stop函数(GigUndiDriverStop):卸载安装的Protocol关闭所有打开的Protocol释放所有申请的资源

将驱动程序（Support();、Start();、Stop();函数）注册到Image Handle上，仅是注册，驱动程序不会执行，即不会操作任何硬件,DXE阶段驱动程序注册完成后，BDS阶段当查询到一个控制器后，会利用ConnectController() 函数为该控制器寻找最好的驱动，通过调用该驱动的Support();函数确认是否支持该控制器，调用Start();函数启动该驱动。