Step to UEFI (120）UEFI 下控制USB键盘 LED

本文介绍如何在Shell 下实现控制 USB Keyboard 上面的 LED。
代码流程如下： 首先是找到USB键盘，然后获得它上加载的 USB IO Protocol，通过发送 set report request 的放置通知它当前 LED 应该设置的状态即可。
代码有点长如果你是第一次接触,建议先研究之前的获得 USB VID PID的例子.

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/BaseMemoryLib.h>
#include  <Protocol/UsbIo.h>

#include "EfiKey.h"

extern EFI_BOOT_SERVICES         *gBS;
extern EFI_HANDLE					 gImageHandle;

EFI_GUID  gEfiUsbIoProtocolGuid   = 
	{ 0x2B2F68D6, 0x0CD2, 0x44CF, 
		{ 0x8E, 0x8B, 0xBB, 0xA2, 0x0B, 0x1B, 0x5B, 0x75 }};

EFI_GUID  gEfiSimpleTextInputExProtocolGuid = 
	{0xdd9e7534, 0x7762, 0x4698, 
		{ 0x8c, 0x14, 0xf5, 0x85, 0x17, 0xa6, 0x25, 0xaa }};
		
//C:\UDK2015\MdePkg\Library\UefiUsbLib\Hid.c
/**
  Set the report descriptor of the specified USB HID interface.

  Submit a USB set HID report request for the USB device specified by UsbIo,
  Interface, ReportId, and ReportType, and set the report descriptor using the
  buffer specified by ReportLength and Report.
  If UsbIo is NULL, then ASSERT().
  If Report is NULL, then ASSERT().

  @param  UsbIo         A pointer to the USB I/O Protocol instance for the specific USB target.
  @param  Interface     The index of the report interface on the USB target.
  @param  ReportId      The identifier of the report to retrieve.
  @param  ReportType    The type of report to retrieve.
  @param  ReportLength  The size, in bytes, of Report.
  @param  Report        A pointer to the report descriptor buffer to set.

  @retval  EFI_SUCCESS       The request executed successfully.
  @retval  EFI_TIMEOUT       A timeout occurred executing the request.
  @retval  EFI_DEVICE_ERROR  The request failed due to a device error.

**/
EFI_STATUS
EFIAPI
UsbSetReportRequest (
  IN EFI_USB_IO_PROTOCOL     *UsbIo,
  IN UINT8                   Interface,
  IN UINT8                   ReportId,
  IN UINT8                   ReportType,
  IN UINT16                  ReportLen,
  IN UINT8                   *Report
  )
{
  UINT32                  Status;
  EFI_STATUS              Result;
  EFI_USB_DEVICE_REQUEST  Request;


  //
  // Fill Device request packet
  //
  Request.RequestType = USB_HID_CLASS_SET_REQ_TYPE;
  Request.Request = EFI_USB_SET_REPORT_REQUEST;
  Request.Value   = (UINT16) ((ReportType << 8) | ReportId);
  Request.Index   = Interface;
  Request.Length  = ReportLen;

  Result = UsbIo->UsbControlTransfer (
                    UsbIo,
                    &Request,
                    EfiUsbDataOut,
                    3000, //PcdGet32 (PcdUsbTransferTimeoutValue),
                    Report,
                    ReportLen,
                    &Status
                    );

  return Result;
}

VOID
RunSetKeyLED (
  IN  USB_KB_DEV    *UsbKeyboardDevice
  )
{
  LED_MAP Led;
  UINT8   ReportId;
  UINT8		i;
  
  for (i=0;i<32;i++)	
  {
	  
		  //
		  // Set each field in Led map.
		  //
		  Led.NumLock    = i      % 2;
		  Led.CapsLock   = (i>>1) % 2;
		  Led.ScrollLock = (i>>2) % 2;
		  Led.Resrvd     = 0;

		  ReportId       = 0;
		  //
		  // Call Set_Report Request to lighten the LED.
		  //
		  UsbSetReportRequest (
			UsbKeyboardDevice->UsbIo,
			UsbKeyboardDevice->InterfaceDescriptor.InterfaceNumber,
			ReportId,
			HID_OUTPUT_REPORT,
			1,
			(UINT8 *) &Led
			);
			gBS->Stall(100000);
	}
}
		
UINTN GetUSB( )
{
  EFI_STATUS  Status;
  UINTN       HandleIndex, HandleCount;
  EFI_HANDLE  *DevicePathHandleBuffer = NULL;
  EFI_USB_IO_PROTOCOL 				*USBIO;
  EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL	*SimpleEx;
  USB_KB_DEV                     	*UsbKeyboardDevice;
  EFI_USB_DEVICE_DESCRIPTOR     DeviceDescriptor;
  
  //Get all the Handles that have UsbIO Protocol
  Status = gBS->LocateHandleBuffer(
                  ByProtocol,
                  &gEfiUsbIoProtocolGuid,
                  NULL,
                  &HandleCount,
                  &DevicePathHandleBuffer);
  if (EFI_ERROR(Status)) 
  {
    Print(L"ERROR : Get USBIO count fail.\n");
    return 0;
  }   

  for (HandleIndex = 0; HandleIndex < HandleCount; HandleIndex++) 
  { 
    Status = gBS->HandleProtocol(
                      DevicePathHandleBuffer[HandleIndex],
                      &gEfiUsbIoProtocolGuid,
                      (VOID**)&USBIO);
    if (EFI_ERROR(Status))
      {
        Print(L"ERROR : Open USBIO fail.\n");
        gBS->FreePool(DevicePathHandleBuffer);  
        return 0;
      }
	
	//Check if the Handle has SimpleEx Protocol
 	Status = gBS->OpenProtocol(
		DevicePathHandleBuffer[HandleIndex],
		&gEfiSimpleTextInputExProtocolGuid,
		(VOID**)&SimpleEx,
		gImageHandle,
		NULL,
		EFI_OPEN_PROTOCOL_GET_PROTOCOL);
	//If it has the Protocol, it means it's a USB Keyboard
	if (!EFI_ERROR(Status)) {
		
		//Get USB Device Descriptor
		Status = USBIO->UsbGetDeviceDescriptor(USBIO, &DeviceDescriptor);     
		if (EFI_ERROR(Status))
		{
			Print(L"ERROR : Usb Get Device Descriptor fail.\n");
			gBS->FreePool(DevicePathHandleBuffer);  
			return 0;
		}
      
		//Show the PID and VID
		Print(L"Found a USB Keyboard. VendorID = %04X, ProductID = %04X\n", 
                              DeviceDescriptor.IdVendor, 
                              DeviceDescriptor.IdProduct);       
		
		//Get USB_KB_DEV struct by SimpleEx Protocol
		UsbKeyboardDevice = TEXT_INPUT_EX_USB_KB_DEV_FROM_THIS (SimpleEx);
		//Change LED status
		RunSetKeyLED(UsbKeyboardDevice);
	}
  }
  gBS->FreePool(DevicePathHandleBuffer);       
  return HandleCount;
}


int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  GetUSB( );
  return EFI_SUCCESS;
}

我测试的系统接了2个键盘，代码运行结果如下:

首先是第一个键盘的 LED乱闪，之后是第二个键盘乱闪。
在实际使用中，如果系统同时接入了2个以上的键盘你会发现他们的LED状态是同步的。比如，你在一个键盘上按下 Num Lock，那么另外的一块键盘上的 Num Lock LED同样也会发生变化。因为软件层有专门的机制来进行“同步”。在 EDK2 的代码中\MdeModulePkg\Bus\Usb\UsbKbDxe\KeyBoard.c 可以看到SetKeyLED 这个函数（本文使用的 RunSetKeyLED 也是脱胎于这个函数），有兴趣的朋友可以仔细研究一下。

/**
  Sets USB keyboard LED state.

  @param  UsbKeyboardDevice  The USB_KB_DEV instance.

**/
VOID
SetKeyLED (
  IN  USB_KB_DEV    *UsbKeyboardDevice
  )

完整的代码和 X64 Application下载

kbLEDTest