在fb_var_screeninfo中设置yres_virtual时无效的参数错误

我正在尝试为Linux创建一个直接写入帧缓冲区/ dev / fb0的应用程序.为了使其具有双缓冲,我尝试使虚拟屏幕的大小是屏幕大小的两倍.这是我写的程序：

struct fb_var_screeninfo screeninfo_var;
struct fb_fix_screeninfo screeninfo_fixed;
unsigned int* screenbuffer;

void gfx_init()
{
    fb0 = open("/dev/fb0", O_RDWR);
    if(fb0 == 0)
        error("Could not open framebuffer located in /dev/fb0!");

    if (ioctl(fb0, FBIOGET_FSCREENINFO, &screeninfo_fixed) == -1)
        error("Could not retrive fixed screen info!");

    if (ioctl(fb0, FBIOGET_VSCREENINFO, &screeninfo_var) == -1)
        error("Could not retrive variable screen info!");

    screeninfo_var.xres_virtual = screeninfo_var.xres;
    screeninfo_var.yres_virtual = screeninfo_var.yres * 2;
    screeninfo_var.width = screeninfo_var.xres;
    screeninfo_var.height = screeninfo_var.yres;
    screeninfo_var.xoffset = 0;
    screeninfo_var.yoffset = 0;

    if (ioctl(fb0, FBIOPUT_VSCREENINFO, &screeninfo_var) == -1)
        error("Could not set variable screen info!");

    info("Detected monitor of %ix%i pixels using %i bit colors.",screeninfo_var.xres, screeninfo_var.yres, screeninfo_var.bits_per_pixel);

    screenbuffersize = screeninfo_var.xres_virtual * screeninfo_var.yres_virtual * screeninfo_var.bits_per_pixel/8;
    screenbuffer = (unsigned int *)mmap(0, screenbuffersize, PROT_READ | PROT_WRITE, MAP_SHARED, fb0, 0);
    if( (long)screenbuffer == 0 || (long)screenbuffer == -1 )
        error("Failed to map framebuffer to device memory!");
}

程序在ioctl(fb0,FBIOPUT_VSCREENINFO和& screeninfo_var)上失败,报告错误无效参数.当删除行screeninfo_var.yres_virtual = screeninfo_var.yres * 2;它运行正常(但没有双重缓冲).

有人在这里看到我做错了吗？

解决方法:

这是一个常见问题,它是由视频驱动程序的限制引起的.例如,英特尔的810芯片组仅允许640×480分辨率,而Broadcom将宽度限制为不超过1200(http://www.raspberrypi.org/phpBB3/viewtopic.php?f=66&t=29968).

除非您更改驱动程序或视频卡本身(如果可能),否则您在这里不能做很多事情.

编辑：如果您在PC上,请尝试使用vesafb,而不是intel的驱动程序.

这里有个提示：http://www.mail-archive.com/debian-russian@lists.debian.org/msg27725.html

标签：c-3,framebuffer,linux,doublebuffered
来源： https://codeday.me/bug/20191010/1888790.html