举一个详细的板级支持包代码的例子,列出代码内容
时间: 2023-04-05 19:03:19 浏览: 73
以下是一个简单的板级支持包代码的例子:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/fb.h>
int main(int argc, char **argv)
{
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 framebuffer device file for reading and writing
fbfd = open("/dev/fb0", O_RDWR);
if (fbfd == -1) {
perror("Error: cannot open framebuffer device");
exit(1);
}
// Get fixed screen information
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {
perror("Error reading fixed information");
exit(2);
}
// Get variable screen information
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
perror("Error reading variable information");
exit(3);
}
// Calculate the size to mmap
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
// Map the framebuffer into memory
fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
if ((int)fbp == -1) {
perror("Error: failed to map framebuffer device to memory");
exit(4);
}
// Draw some pixels
for (y = 0; y < vinfo.yres; y++) {
for (x = 0; x < vinfo.xres; x++) {
location = (x + vinfo.xoffset) * (vinfo.bits_per_pixel / 8) +
(y + vinfo.yoffset) * finfo.line_length;
if (vinfo.bits_per_pixel == 32) {
*(fbp + location) = 100; // Some blue
*(fbp + location + 1) = 15 + x / 2; // A little green
*(fbp + location + 2) = 200 - y / 5; // A lot of red
*(fbp + location + 3) = 0; // No transparency
} else { // Assume 16bpp
int b = 10;
int g = (x % 64) * 4;
int r = (y % 32) * 8;
unsigned short int t = r << 11 | g << 5 | b;
*((unsigned short int *)(fbp + location)) = t;
}
}
}
// Unmap framebuffer
munmap(fbp, screensize);
// Close framebuffer device
close(fbfd);
return 0;
}
这个代码片段演示了如何使用 Linux 的帧缓冲设备来绘制一些像素。它打开了 /dev/fb0 设备文件,获取了固定和可变的屏幕信息,然后将帧缓冲映射到内存中。接下来,它使用两个嵌套的循环来遍历屏幕上的每个像素,并根据像素的位置和颜色值来设置帧缓冲中的相应字节。最后,它取消映射帧缓冲并关闭设备文件。