EFI GOP Driver

GOP (Graphic Output Protocol) driver 是 EFI架構下取代傳統VBIOS 黑箱的 EFI Driver, 另外for embedded system bootloader 上的graphic driver叫EPOG(embedded Pre-OS Graphic).

GOP Driver 的共有GUID

#define EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID \
  {0x9042a9de,0x23dc,0x4a38, \
  0x96,0xfb,0x7a,0xde,0xd0,0x80,0x51,0x6a}

Protocol 主要包含3個function 及 1個data structure

typedef struct EFI_GRAPHICS_OUTPUT_PROTCOL {
  EFI_GRAPHICS_OUTPUT_PROTOCOL_QUERY_MODE QueryMode;
  EFI_GRAPHICS_OUTPUT_PROTOCOL_SET_MODE   SetMode;
  EFI_GRAPHICS_OUTPUT_PROTOCOL_BLT        Blt;
  EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE       *Mode;
} EFI_GRAPHICS_OUTPUT_PROTOCOL;

1. QueryMode: Returns information for an available graphics mode that the graphics device and the set of active video output devices supports.(是詢問graphic controller 和 系統所有接上的顯示器所支援的顯示模式)
2. SetMode:Set the video device into the specified mode and clears the visible portions of the output display to black. 則是設定顯示裝置一個特定的顯示模式
3. Blt:Software abstraction to draw on the video device’s frame buffer.則是直接透過寫入framebuffer  畫矩形圖片

取材UEFI spec 2.3 chap. 11.9