我在 RHEL 6.0 操作系统上使用带有内置图形加速器 GMA-HD 的 i5 内核。 我需要测试图形驱动程序的图形加速功能(我发现它在我的 PC 中是 i915)。 我使用以下代码(我从互联网上获得并进行了一些修改)写入帧缓冲区。
#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;
int count ;
/* 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 */
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
printf("Error reading fixed information.\n");
exit(2);
}
/* Get variable screen information */
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
printf("Error reading variable information.\n");
exit(3);
}
/* Figure out the size of the screen in bytes */
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
printf("\nScreen size is %d",screensize);
printf("\nVinfo.bpp = %d",vinfo.bits_per_pixel);
/* 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");
x = 100; y = 100; /* Where we are going to put the pixel */
/* Figure out where in memory to put the pixel */
location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length;
for(count = 1 ;count < 100 ;count++)
{
*(fbp + location) = 255; /* Some blue */
*(fbp + location + count) = 0; /* A little green */
*(fbp + location + count + 1) = 0; /* A lot of red */
*(fbp + location + count + 2) = 0; /* No transparency */
}
munmap(fbp, screensize);
close(fbfd);
return 0;
}
运行上述代码后,显示没有发现任何变化,但“cat/dev/fb0”显示了一些数据。 有人可以解释为什么屏幕上什么也看不到吗? (我还发现 fb0 对应于帧缓冲区 'inteldrmfb' 。)
提前致谢
Neeraj N.T
最佳答案
您没有增加位置!所以 255 只在第一个像素上,其他所有像素都是 0。试试这个:
location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length;
for(count = 1 ;count < 100 ;count++)
{
*(fbp + location) = 255; /* Some blue */
*(fbp + location + 1) = 0; /* A little green */
*(fbp + location + 2) = 0; /* A lot of red */
*(fbp + location + 3) = 0; /* No transparency */
location += 4;
}
但是,可能正确的测试方法是使用 directfb它来了 一些帧缓冲性能测试
关于c - 写入帧缓冲区,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4722301/