linux framebuffer 例子

　　昨天做的一個極簡單的framebuffer的例子，用來學習怎樣操作fb設備。

　　這段代碼是在picogl的vesafb backend部分的基礎上簡出來的，所以變量名還保留著。

流程如下：

１　打開framebuffer設備；

２　通過ioctl取得fixed screen information；

３　通過ioctl取得variable screen information；

４　通過mmap映射設備內存到進程空間；

５　寫framebuffer；

６　終止。

 
#include?<stdio.h>  
#include?<stdlib.h> 
#include?<string.h>  
#include?<fcntl.h> 
#include?<linux/fb.h>  
#include?<sys/mman.h> 
struct?fb_fix_screeninfo?FixedInfo; 
struct?fb_var_screeninfo?OrigVarInfo; 
static?int?FrameBufferFD?=?-1; 
void?*FrameBuffer?=?(void?*)?-1; 
void?openFBDEV(void)?{ 
????/*?open?the?framebuffer?device?*/ 
????FrameBufferFD?=?open("/dev/fb0",?O_RDWR); 
????if?(FrameBufferFD?<?0)?{ 
????????fprintf(stderr,?"Error?opening?/dev/fb0/n"); 
????????exit(1); 
????} 
????/*?Get?the?fixed?screen?info?*/ 
????if?(ioctl(FrameBufferFD,?FBIOGET_FSCREENINFO,?&FixedInfo))?{ 
????????fprintf(stderr,?"error:?ioctl(FBIOGET_FSCREENINFO)?failed/n"); 
????????exit(1); 
????} 
????/*?get?the?variable?screen?info?*/ 
????if?(ioctl(FrameBufferFD,?FBIOGET_VSCREENINFO,?&OrigVarInfo))?{ 
????????fprintf(stderr,?"error:?ioctl(FBIOGET_VSCREENINFO)?failed/n"); 
????????exit(1); 
????} 
??????? 
????if?(FixedInfo.visual?!=?FB_VISUAL_TRUECOLOR?&&?FixedInfo.visual?!=?FB_VISUAL_DIRECTCOLOR)?{ 
????????fprintf(stderr,?"non-TRUE/DIRECT-COLOR?visuals?(0x%x)?not?supported?by?this?demo./n",?FixedInfo.visual); 
????????exit(1); 
????} 
????/* 
?????*?fbdev?says?the?frame?buffer?is?at?offset?zero,?and?the?mmio?region 
?????*?is?immediately?after. 
?????*/ 
????/*?mmap?the?framebuffer?into?our?address?space?*/ 
????FrameBuffer?=?(void?*)?mmap(0,?/*?start?*/ 
????????FixedInfo.smem_len,?/*?bytes?*/ 
????????PROT_READ?|?PROT_WRITE,?/*?prot?*/ 
????????MAP_SHARED,?/*?flags?*/ 
????????FrameBufferFD,?/*?fd?*/ 
????????0?/*?offset?*/); 
????if?(FrameBuffer?==?(void?*)?-?1)?{ 
????????fprintf(stderr,?"error:?unable?to?mmap?framebuffer/n"); 
????????exit(1); 
????} 
} 
void?closeFBDEV(void)?{ 
????munmap(FrameBuffer,?FixedInfo.smem_len); 
????close(FrameBufferFD); 
} 
int?main()?{ 
????openFBDEV(); 
????fprintf(stderr,?"openFBDEV?finish/n"); 
????memset(FrameBuffer,?128,?FixedInfo.smem_len); 
????sleep(5); 
????closeFBDEV(); 
????fprintf(stderr,?"closeFBDEV?finish/n"); 
????return?0; 
}
 

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