Linux Framebuffer编程简介

linux下，framebuffer设备文件名通常是/

dev/fb0,1,2等。
控制framebuffer设备的一般步骤如下：
1） 打开设备，映射framebuffer
2）依照硬件要求，准备好数据
3）把数据复制到framebuffer

例子程序如下：

1）打开设备，映射framebuffer
static void *fbbuf;
int openfb(char *devname)
{
int fd;
fd = open(devname, O_RDWR);
if (ioctl(fd, FBIOGET_VSCREENINFO, &fbvar) < 0)
return -1;
bpp = fbvar.bits_per_pixel;
screen_size = fbvar.xres * fbvar.yres * bpp / 8;
fbbuf = mmap(0, screen_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
return fd;
}

2）数据准备，假设lcd控制器被初始化为565， 16bit格式的
static inline int make_pixel(unsigned int a, unsigned int r, unsigned int g, unsigned int b)
{
return (unsigned int)(((r>>3)<<11)|((g>>2)<<5|( b>>3)));
}

3) 把想要显示的数据复制到framebuffer， 假设把framebuffer填充成一种颜色
static void fill_pixel(unsigned int pixel, int x0, int y0, int w, int h)
{
int i, j;
unsigned short *pbuf = (unsigned short *)fbbuf;
for (i = y0; i < h; i ++) {
for (j = x0; j < w; j ++) {
pbuf[i * screen_width + j] = pixel;
}
}
}

下面程序把lcd屏幕填充成蓝色
fill_pixel(make_pixel(0, 0, 0,0xff), 0, 0, screen_width, screen_height);