framebuffer结构体分析

转载出处  http://blog.chinaunix.net/uid-22666248-id-284148.html
fb_fix_screeninfo fb_var_screeninfo结构体测试 四）2011-05-03 12:45:15

分类： 嵌入式

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

    printf("id %s\n",finfo.id);      s3c2410fb

    printf("smem_start %d\n",finfo.smem_start);//帧缓冲
内存开始地址,物理地址

    printf("smem_len %d\n",finfo.smem_len);//
帧缓冲 内存 长度

    printf("type %d\n",finfo.type);

    printf("type_aux %d\n",finfo.type_aux);//平面交织交替

    printf("visual %d\n",finfo.visual);//记录
色彩模式   2

    printf("xpanstep %d\n",finfo.xpanstep);//如果没有硬件panning，赋0

    printf("ypanstep %d\n",finfo.ypanstep);

    printf("line_length %d\n",finfo.line_length);   640

    printf("mmio_start %d\n",finfo.mmio_start);//内存映射IO开始地址
物理地址

    printf("mmio_len %d\n",finfo.mmio_len);//内存映射IO
长度

    printf("accel %d\n\n",finfo.accel);

    

    ioctl(fdfd,FBIOGET_VSCREENINFO,&vinfo);//获取可变参数

    printf("xres %d\n",vinfo.xres);//可见解析度 
320

    printf("yres %d\n",vinfo.yres);           240

    printf("xres_virturl %d\n",vinfo.xres_virtual);//虚拟解析度 
320

    printf("yres_virtual %d\n",vinfo.yres_virtual);             240

    printf("xoffset %d\n",vinfo.xoffset);//虚拟到可见的偏移       0

    printf("yoffset %d\n",vinfo.yoffset);                        0

    printf("bits_per_pixel %d\n",vinfo.bits_per_pixel);//每像素位数
bpp 16

    printf("grayscale %d\n",vinfo.grayscale);//非零时，指灰度

    

    printf("fb_bitfield red.offset %d\n",vinfo.red.offset);    11 
偏移11位

    printf("fb_bitfield .length %d\n",vinfo.red.length);        5

    printf("fb_bitfield .msb_right %d\n",vinfo.red.msb_right);   
0

    printf("fb_bitfield green.offset %d\n",vinfo.green.offset); 5
偏移5位

    printf("fb_bitfield .length %d\n",vinfo.green.length);       
6

    printf("fb_bitfield .msb_right %d\n",vinfo.green.msb_right); 
0

    printf("fb_bitfield blue.offset %d\n",vinfo.blue.offset);

    printf("fb_bitfield .length %d\n",vinfo.blue.length);

    printf("fb_bitfield .msb_right %d\n",vinfo.blue.msb_right);

    printf("fb_bitfield transp.offset %d\n",vinfo.transp.offset);

    printf("fb_bitfield .length %d\n",vinfo.transp.length);

    printf("fb_bitfield .msb_right %d\n",vinfo.transp.msb_right);

    printf("nonstd %d\n",vinfo.nonstd);//!=0
非标准像素格式

        printf("activate %d\n",vinfo.activate);

    printf("height %d\n",vinfo.height);//高度/ 240

    printf("widht %d\n",vinfo.width);            320

    printf("accel_flags %d\n",vinfo.accel_flags);//看
fb_info.flags

    //定时，除了 pixclock之外，其他的都以像素时钟为单位

    printf("pixclock %d\n",vinfo.pixclock);//像素时钟，皮秒  
80000

    printf("left_margin %d\n",vinfo.left_margin);//行切换：从同步到绘图之间的延迟   
28

    printf("right_margin %d\n",vinfo.right_margin);//行切换：从绘图到同步之间的延迟  
24

    printf("upper_margin %d\n",vinfo.upper_margin);//帧切换：从同步到绘图之间的延迟  
6

    printf("lower_margin %d\n",vinfo.lower_margin);//帧切换：从绘图到同步之间的延迟   
2

    printf("hsync_len %d\n",vinfo.hsync_len);//hor
水平同步的长度         42

    printf("vsync_len %d\n",vinfo.vsync_len);//vir
垂直同步的长度         12

    printf("sync %d\n",vinfo.sync);//

    printf("vmode %d\n",vinfo.vmode);

    printf("rotate %d\n",vinfo.rotate);

测试结果

[root@yuweixian yu]#./framebuff-test

the framebuffer device was opended successfully.

id                          s3c2410fb

smem_start                  864813056

smem_len                    153600

type                        0

type_aux                    0

visual                      2

xpanstep                    0

ypanstep                    0

line_length                 640

mmio_start                  0

mmio_len                    0

accel                       0

xres                        320

yres                        240

xres_virturl                320

yres_virtual                240

xoffset                     0

yoffset                     0

bits_per_pixel              16

grayscale                   0

fb_bitfield red.offset      11

fb_bitfield .length         5

fb_bitfield .msb_right      0

fb_bitfield green.offset    5

fb_bitfield .length         6

fb_bitfield .msb_right      0

fb_bitfield blue.offset     0

fb_bitfield .length         5

fb_bitfield .msb_right      0

fb_bitfield transp.offset   0

fb_bitfield .length         0

fb_bitfield .msb_right      0

nonstd                      0

activate                    0

height                      240

widht                       320

accel_flags                 0

pixclock                    80000

left_margin                 28

right_margin                24

upper_margin                6

lower_margin                2

hsync_len                   42

vsync_len                   12

sync                        0

vmode                       0

rotate                      0

the framebuffer devices was mapped to memory successfully

bye the framebuffer

[root@yuweixian yu]#

分析 1.

    printf("fb_bitfield red.offset %d\n",vinfo.red.offset);
11 偏移11位

    printf("fb_bitfield .length %d\n",vinfo.red.length);
5

    printf("fb_bitfield .msb_right %d\n",vinfo.red.msb_right);
0

    printf("fb_bitfield green.offset %d\n",vinfo.green.offset);
5 偏移5位

 

   这个对应 SC32440 中 RGB565 设置方式

分析 2
http://www.lslnet.com/linux/dosc1/48/linux-328178.htm

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

   从上面知道了 分配的内存是 smem_len=153600字

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。