LCD应用程序（转载）

#include unistd.h>
#include stdio.h>
#include fcntl.h>
#include linux/fb.h>
#include sys/mman.h>
int main()
{
    int fbfd = 0;
    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;
    long int screensize = 0;
    char *fbp = 0;
    int x = 0, y = 0;
    long int location = 0;
    // Open the file for reading and writing
    fbfd = open("/dev/fb0", O_RDWR);
    if (!fbfd) {
        printf("Error: cannot open framebuffer device.\n");
        exit(1);
    }
    printf("The framebuffer device was opened successfully.\n");
    // Get fixed screen information
    //FBIOGET_FSCREENINFO获得固定的屏幕参数设置
    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
        printf("Error reading fixed information.\n");
        exit(2);
    }
    printf("%d, %d, %d, %d\n", finfo.smem_start, finfo.smem_len, finfo.mmio_start,finfo.mmio_len);
    //869007360, 153600, 0, 0
    // Get variable screen information
    //FBIOGET_VSCREENINFO 获得可变的屏幕参数
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
        printf("Error reading variable information.\n");
        exit(3);
    }
    printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
    //320X240,16bpp bpp 每像素位数 每个点用多少个字节表示
    // Figure out the size of the screen in bytes
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
    //2^16=64K TFT 320*240*16/8=153600byte
    // Map the device to memory
    /*void *mmap(void *start, size_t length, int prot, int flags,
　　int fd, off_t offset);mmap函数是unix/linux下的系统调用
    fbmem.c是内核的，应用程序调用了mmap进入内核空间就是执行的fb_mmap了，
    应用程序是统一的接口，但是在内核空间，不同的驱动使用的实现函数是不一样的*/
    //#include  and #include  /usr/include/sys/mman.h
    fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
                       fbfd, 0);
    if ((int)fbp == -1) {
        printf("Error: failed to map framebuffer device to memory.\n");
        exit(4);
    }
    printf("The framebuffer device was mapped to memory successfully.\n");
#if 1
    x = 10; y = 10; // Where we are going to put the pixel
    // Figure out where in memory to put the pixel
    for (y = 10; y  20; y++)
        for (x = 10; x  30; x++) 
        {
            location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
                       (y+vinfo.yoffset) * finfo.line_length;
            if (vinfo.bits_per_pixel == 32) 
            {
                *(fbp + location) = 10; // Some blue
                *(fbp + location + 1) = 15+(x-10)/2; // A little green
                *(fbp + location + 2) = 20-(y-10)/5; // A lot of red
                *(fbp + location + 3) = 0; // No transparency
            } 
            else 
            { //assume 16bpp
                unsigned short b = 10;
                unsigned short g = (x-10)/6; // A little green
                unsigned short r = 31-(y-10)/16; // A lot of red
                unsigned short t = r11 | g  5 | b;
                *((unsigned short *)(fbp + location)) = t;
    //    printf("x=%d,%d\n",x,y);
            }
        }
#endif
    munmap(fbp, screensize);//删除特定地址区域的对象映射 int munmap(void *start, size_t length); 
    printf("The framebuffer device was munmapped to memory successfully.\n");
    close(fbfd);
    printf("The framebuffer device was closed successfully.\n");
    return 0;
}