Android6.0.1 移植:显示系统(一)--测试framebuffer

 

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <string.h>
#include <stdlib.h>

/*
可编程信息
struct fb_var_screeninfo {
  __u32 xres;           //x轴像素点数量
  __u32 yres;            //y轴像素点数量
  __u32 xres_virtual;   //虚拟屏x轴
  __u32 yres_virtual;   //虚拟屏y轴
  __u32 xoffset;        
  __u32 yoffset;
  __u32 bits_per_pixel;    //色深
  __u32 grayscale;
  struct fb_bitfield red;    //fb缓存的R\G\B位域
  struct fb_bitfield green;
  struct fb_bitfield blue;
  struct fb_bitfield transp;
  __u32 nonstd;
  __u32 activate;
  __u32 height;            //屏幕的高度
  __u32 width;            //屏幕的宽度
  __u32 accel_flags;
  __u32 pixclock;
  __u32 left_margin;
  __u32 right_margin;
  __u32 upper_margin;
  __u32 lower_margin;
  __u32 hsync_len;
  __u32 vsync_len;
  __u32 sync;
  __u32 vmode;
  __u32 rotate;
  __u32 colorspace;
  __u32 reserved[4];
};

固定信息
struct fb_fix_screeninfo {
  char id[16];                //标识符
  unsigned long smem_start; //fb缓存的起始位置
  __u32 smem_len;            //fb缓存的大小
  __u32 type;
  __u32 type_aux;
  __u32 visual;
  __u16 xpanstep;
  __u16 ypanstep;
  __u16 ywrapstep;
  __u32 line_length;
  unsigned long mmio_start;    //内存映射I/O的开始位置
  __u32 mmio_len;            //内存映射I/O的长度
  __u32 accel;
  __u16 capabilities;
  __u16 reserved[2];
}
*/

char *fb_addr;
unsigned fb_size;

void print_screen(char *buf,int width,int height);

int main(int argc,char *argv[])
{
    int fd=0;

    struct fb_fix_screeninfo fb_fix;
    struct fb_var_screeninfo fb_var;

    char *env=NULL;

    short *picture;
    int ret;
    env="/dev/graphics/fb0";
    //env="/sys/class/graphics/fb0";
    
    fd=open(env,O_RDWR);
    printf("aplex test v2 \n");
    printf("fd= %s\n",env);

    ioctl(fd,FBIOGET_FSCREENINFO,&fb_fix);

    printf("fb_fix.line_length=%u\n",fb_fix.line_length);
    printf("fb_fix.accel=%u\n",fb_fix.accel);


    ioctl(fd,FBIOGET_VSCREENINFO,&fb_var);

    printf("fb_var.xres=%u\n",fb_var.xres);
    printf("fb_var.yres=%u\n",fb_var.yres);
    printf("fb_var.xres_virtual=%u\n",fb_var.xres_virtual);
    printf("fb_var.yres_virtual=%u\n",fb_var.yres_virtual);
    
    fb_size=fb_var.yres*fb_fix.line_length;
    
    /*fb_addr的获取,是很核心的步骤,表示成功获得了framebuffer设备*/
    fb_addr=(char *)mmap(NULL,fb_size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
            

    picture=(char *)malloc(fb_var.yres*fb_fix.line_length);
    memset(picture,0xFF,fb_var.yres*fb_fix.line_length); 
            /*注意,这里对颜色的赋值只是一次赋一半值,也就是一个字节,8bit*/
            /*而事实上,一个像素的颜色值是16bit*/
            /*0xFFFF就是白色*/
            /*介绍一下16bit的颜色的类型,颜色是由RGB组成,如果是565排列,
            则依次为Red Green Blue
                    11111 111111 11111
                                           */

    print_screen(picture,fb_var.xres,fb_var.yres);

    return 0;
}

void print_screen(char *buf,int width,int height)
{
    short *t_data=(short *)buf;

    short *t_fb_addr=(short *)fb_addr;

    int bytew=width<<1; /*像素数乘以2即是字节数,因为颜色深度是2个字节(16bit)*/

    while(--height>=0)
    {
       memcpy(t_fb_addr,t_data,bytew); /*一行的数据赋值*/
       t_fb_addr += width;
       t_data += width;
    }
}

 

root@sabresd_6dq:/data # ./frameworkTest
aplex test v2
fd= /dev/graphics/fb0
fb_fix.line_length=3200
fb_fix.accel=0
fb_var.xres=800
fb_var.yres=480
fb_var.xres_virtual=800
fb_var.yres_virtual=1440

 

现象:

上半个屏幕显示为全白色

posted on 2018-03-28 10:00  maogefff  阅读(401)  评论(0编辑  收藏  举报

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