当前位置:Linux教程 - Linux资讯 - Linux下FrameBuffer直接写屏

Linux下FrameBuffer直接写屏

  作者:hotfire [文章出自: www.PHPx.com] 因为Linux是工作在保护模式下,所以用户态进程是无法象DOS那样使用显卡BIOS里 提供的中断调用来实现直接写屏,故Linux抽象出FrameBuffer这个设备来供用户态 进程实现直接写屏。 在继续下面的之前,先说明几个背景知识: 1、FrameBuffer主要是根据VESA标准的实现的,所以只能实现最简单的功能。 2、由于涉及内核的问题,FrameBuffer是不允许在系统起来后修改显示模式等一系 列操作。(好象很多人都想要这样干,这是不被允许的,当然如果你自己与驱动 的话,是可以实现的) 3、对FrameBuffer的操作,会直接影响到本机的所有控制台的输出,包括XWIN的图 形界面。 好,现在可以让我们开始实现直接写屏: 1、打开一个FrameBuffer设备 2、通过mmap调用把显卡的物理内存空间映射到用户空间 3、直接写内存。 好象很简单哦~ fBTools.h 代码: #ifndef _FBTOOLS_H_ #define _FBTOOLS_H_ #include <linux/fb.h> //a framebuffer device strUCture; typedef struct fbdev{ int fb; unsigned long fb_mem_offset; unsigned long fb_mem; struct fb_fix_screeninfo fb_fix; struct fb_var_screeninfo fb_var; char dev[20]; } FBDEV, *PFBDEV; //open & init a frame buffer //to use this function, //you must set FBDEV.dev="/dev/fb0" //or "/dev/fbX" //it's your frame buffer. int fb_open(PFBDEV pFbdev); //close a frame buffer int fb_close(PFBDEV pFbdev); //get display depth int get_display_depth(PFBDEV pFbdev); //full screen clear void fb_memset(void *addr, int c, size_t len); #endif fbtools.c 代码: #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <string.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <asm/page.h> #include "fbtools.h" #define TRUE 1 #define FALSE 0 #define MAX(x,y) ((x)>(y)?(x):(y)) #define MIN(x,y) ((x)<(y)?(x):(y)) //open & init a frame buffer int fb_open(PFBDEV pFbdev) { pFbdev->fb = open(pFbdev->dev, O_RDWR); if(pFbdev->fb < 0) { printf("Error opening %s: %m. Check kernel config\\n", pFbdev->dev); return FALSE; } if (-1 == ioctl(pFbdev->fb,FBIOGET_VSCREENINFO,&(pFbdev->fb_var))) { printf("ioctl FBIOGET_VSCREENINFO\\n");
[1] [2] 下一页 

return FALSE; } if (-1 == ioctl(pFbdev->fb,FBIOGET_FSCREENINFO,&(pFbdev->fb_fix))) { printf("ioctl FBIOGET_FSCREENINFO\\n"); return FALSE; } //map physics address to virtual address pFbdev->fb_mem_offset = (unsigned long)(pFbdev->fb_fix.smem_start) & (~PAGE_MASK); pFbdev->fb_mem = (unsigned long int)mmap(NULL, pFbdev->fb_fix.smem_len + pFbdev->fb_mem_offset, PROT_READ PROT_WRITE, MAP_SHARED, pFbdev->fb, 0); if (-1L == (long) pFbdev->fb_mem) { printf("mmap error! mem:%d offset:%d\\n", pFbdev->fb_mem, pFbdev->fb_mem_offset); return FALSE; } return TRUE; } //close frame buffer int fb_close(PFBDEV pFbdev) { close(pFbdev->fb); pFbdev->fb=-1; } //get display depth int get_display_depth(PFBDEV pFbdev); { if(pFbdev->fb<=0) { printf("fb device not open, open it first\\n"); return FALSE; } return pFbdev->fb_var.bits_per_pixel; } //full screen clear void fb_memset (void *addr, int c, size_t len) { memset(addr, c, len); } //use by test #define DEBUG #ifdef DEBUG main() { FBDEV fbdev; memset(&fbdev, 0, sizeof(FBDEV)); strcpy(fbdev.dev, "/dev/fb0"); if(fb_open(&fbdev)==FALSE) { printf("open frame buffer error\\n"); return; } fb_memset(fbdev.fb_mem + fbdev.fb_mem_offset, 0, fbdev.fb_fix.smem_len); fb_close(&fbdev); }

(出处:http://www.sheup.com)


上一页 [1] [2] 

return FALSE; } return pFbdev->fb_var.bits_per_pixel; } //full screen clear void fb_memset (void *addr, int c, size_t len) { memset(addr, c, len); } //use by test #define DEBUG #ifdef DEBUG main() { FBDEV fbdev; memset(&fbdev, 0, sizeof(FBDEV)); strcpy(fbdev.dev, "/dev/fb0"); if(fb_open(&fbdev)==FALSE) { printf("open frame buffer error\\n"); return; } fb_memset(fbdev.fb_mem + fbdev.fb_mem_offset, 0, fbdev.fb_fix.smem_len); fb_close(&fbdev); }

(出处:http://www.sheup.com/)


上一页 [1] [2] [3]