fb-test.c

周立功PXA270实验箱的LCD驱动的源代码

#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;
    struct fb_cmap cmapinfo;
    long int screensize = 0;
    char *fbp = 0;
    int x = 0, y = 0;
    long int location = 0;
		int b,g,r;
    // Open the file for reading and writing
    fbfd = open("/dev/fb0", O_RDWR);	// 打开Frame Buffer设备
    if (fbfd < 0) {
	printf("Error: cannot open framebuffer device.%x\n",fbfd);
				exit(1);
    }
    printf("The framebuffer device was opened successfully.\n");

    // Get fixed screen information
    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {	// 获取设备固有信息
	printf("Error reading fixed information.\n");
	exit(2);
    }
		printf(finfo.id);
    printf("\ntype:0x%x\n", finfo.type );							// FrameBuffer 类型,如0为象素
    printf("visual:%d\n", finfo.visual );						// 视觉类型：如真彩2，伪彩3 
    printf("line_length:%d\n", finfo.line_length );	// 每行长度
    printf("\nsmem_start:0x%x,smem_len:%d\n", finfo.smem_start, finfo.smem_len ); // 映象RAM的参数
    printf("mmio_start:0x%x ,mmio_len:%d\n", finfo.mmio_start, finfo.mmio_len );
    
    // Get variable screen information
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {	// 获取设备可变信息
	printf("Error reading variable information.\n");
	exit(3);
    }
    printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );
    // Figure out the size of the screen in bytes
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
    // Map the device to memory
    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");

    vinfo.xoffset = (640-420)/2; 
    vinfo.yoffset = (480-340)/2;       // Where we are going to put the pixel
		 b = 10;
		 g = 100;     // A little green
		 r = 100;    // A lot of red
    // Figure out where in memory to put the pixel
    for ( y = 0; y < 340; y++ )				// 行扫描
	for ( x = 0; x < 420; x++ ) {			// 列扫描

	    location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +	// 定位
		       (y+vinfo.yoffset) * finfo.line_length;
	    if ( vinfo.bits_per_pixel == 32 ) {		//		
		*(fbp + location) = b;          // Some blue
		*(fbp + location + 1) = g; 	// A little green
		*(fbp + location + 2) = r; 	// A lot of red
		*(fbp + location + 3) = 0;     	// No transparency
	    } else  {				//assume 16bpp
		unsigned short int t = r<<11 | g << 5 | b;
		*((unsigned short int*)(fbp + location)) = t;
        }
    }
    munmap(fbp, screensize);
    close(fbfd);

    return 0;
}