我敲写了一遍 程序，然后补充了 fb_fix_screeninfo 和 fb_var_screeninfo 结构体元素的内容测试
完整的代码：
framebuff-myself-press.rar 其中一部分的代码：
- ioctl(fdfd,FBIOGET_FSCREENINFO,&finfo); //获取 固定参数
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printf("id %s\n",finfo.id); s3c2410fb
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printf("smem_start %d\n",finfo.smem_start); //帧缓冲 内存开始地址,物理地址
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printf("smem_len %d\n",finfo.smem_len); // 帧缓冲 内存 长度
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printf("type %d\n",finfo.type);
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printf("type_aux %d\n",finfo.type_aux);//平面交织交替
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printf("visual %d\n",finfo.visual); //记录 色彩模式 2
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printf("xpanstep %d\n",finfo.xpanstep);//如果没有硬件panning，赋0
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printf("ypanstep %d\n",finfo.ypanstep);
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printf("line_length %d\n",finfo.line_length); 640
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printf("mmio_start %d\n",finfo.mmio_start);//内存映射IO开始地址 物理地址
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printf("mmio_len %d\n",finfo.mmio_len);//内存映射IO 长度
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printf("accel %d\n\n",finfo.accel);
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ioctl(fdfd,FBIOGET_VSCREENINFO,&vinfo); //获取可变参数
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printf("xres %d\n",vinfo.xres); //可见解析度 320
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printf("yres %d\n",vinfo.yres); 240
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printf("xres_virturl %d\n",vinfo.xres_virtual); //虚拟解析度 320
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printf("yres_virtual %d\n",vinfo.yres_virtual); 240
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printf("xoffset %d\n",vinfo.xoffset); //虚拟到可见的偏移 0
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printf("yoffset %d\n",vinfo.yoffset); 0
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printf("bits_per_pixel %d\n",vinfo.bits_per_pixel); //每像素位数 bpp 16
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printf("grayscale %d\n",vinfo.grayscale);//非零时，指灰度
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printf("fb_bitfield red.offset %d\n",vinfo.red.offset); 11 偏移11位
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printf("fb_bitfield .length %d\n",vinfo.red.length); 5
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printf("fb_bitfield .msb_right %d\n",vinfo.red.msb_right); 0
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printf("fb_bitfield green.offset %d\n",vinfo.green.offset); 5 偏移5位
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printf("fb_bitfield .length %d\n",vinfo.green.length); 6
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printf("fb_bitfield .msb_right %d\n",vinfo.green.msb_right); 0
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printf("fb_bitfield blue.offset %d\n",vinfo.blue.offset);
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printf("fb_bitfield .length %d\n",vinfo.blue.length);
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printf("fb_bitfield .msb_right %d\n",vinfo.blue.msb_right);
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printf("fb_bitfield transp.offset %d\n",vinfo.transp.offset);
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printf("fb_bitfield .length %d\n",vinfo.transp.length);
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printf("fb_bitfield .msb_right %d\n",vinfo.transp.msb_right);
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printf("nonstd %d\n",vinfo.nonstd); //!=0 非标准像素格式
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printf("activate %d\n",vinfo.activate);
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printf("height %d\n",vinfo.height); //高度/ 240
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printf("widht %d\n",vinfo.width); 320
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printf("accel_flags %d\n",vinfo.accel_flags); //看 fb_info.flags
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//定时，除了 pixclock之外，其他的都以像素时钟为单位
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printf("pixclock %d\n",vinfo.pixclock);//像素时钟，皮秒 80000
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printf("left_margin %d\n",vinfo.left_margin);//行切换：从同步到绘图之间的延迟 28
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printf("right_margin %d\n",vinfo.right_margin);//行切换：从绘图到同步之间的延迟 24
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printf("upper_margin %d\n",vinfo.upper_margin);//帧切换：从同步到绘图之间的延迟 6
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printf("lower_margin %d\n",vinfo.lower_margin);//帧切换：从绘图到同步之间的延迟 2
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printf("hsync_len %d\n",vinfo.hsync_len); //hor 水平同步的长度 42
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printf("vsync_len %d\n",vinfo.vsync_len); //vir 垂直同步的长度 12
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printf("sync %d\n",vinfo.sync); //
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printf("vmode %d\n",vinfo.vmode);
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printf("rotate %d\n",vinfo.rotate);
测试结果
- [root@yuweixian yu]# ./framebuff-test
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the framebuffer device was opended successfully.
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id s3c2410fb
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smem_start 864813056
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smem_len 153600
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type 0
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type_aux 0
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visual 2
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xpanstep 0
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ypanstep 0
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line_length 640
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mmio_start 0
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mmio_len 0
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accel 0
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xres 320
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yres 240
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xres_virturl 320
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yres_virtual 240
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xoffset 0
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yoffset 0
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bits_per_pixel 16
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grayscale 0
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fb_bitfield red.offset 11
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fb_bitfield .length 5
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fb_bitfield .msb_right 0
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fb_bitfield green.offset 5
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fb_bitfield .length 6
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fb_bitfield .msb_right 0
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fb_bitfield blue.offset 0
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fb_bitfield .length 5
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fb_bitfield .msb_right 0
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fb_bitfield transp.offset 0
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fb_bitfield .length 0
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fb_bitfield .msb_right 0
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nonstd 0
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activate 0
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height 240
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widht 320
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accel_flags 0
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pixclock 80000
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left_margin 28
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right_margin 24
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upper_margin 6
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lower_margin 2
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hsync_len 42
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vsync_len 12
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sync 0
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vmode 0
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rotate 0
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the framebuffer devices was mapped to memory successfully
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bye the framebuffer
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[root@yuweixian yu]#
- printf("fb_bitfield red.offset %d\n",vinfo.red.offset); 11 偏移11位
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printf("fb_bitfield .length %d\n",vinfo.red.length); 5
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printf("fb_bitfield .msb_right %d\n",vinfo.red.msb_right); 0
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printf("fb_bitfield green.offset %d\n",vinfo.green.offset); 5 偏移5位
- printf("smem_len %d\n",finfo.smem_len); 153600
printf("line_length %d\n",finfo.line_length); 640
printf("xres %d\n",vinfo.xres); 320
printf("yres %d\n",vinfo.yres); 240
printf("bits_per_pixel %d\n",vinfo.bits_per_pixel); 16- 1.smem_len=153600 是这个 /dev/fb0 d的大小，也就是内存大小
2. line_length =640 是屏幕上一行的点在内存中占有的空间，不是一行上的点数 320*2 因为是 16bpp 一个像素 占有2个字节大小，一行有320个点，所以line_length=640 字节大小 3. xres =320 yres=240 就是 x y 方向的分辨率，就是两个方向上的 像素点 个数4. bits_per_pixel=16bpp 每一个像素点 占用内存空间 2 字节
节=150KB，屏幕每一行占用内存640字节，153600/640=240，
我们发现，240 就是屏幕的高度。
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