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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