【Linux高级驱动】LCD驱动框架分析

1.framebuffer接口层(fbmem.c)

    功能:给用户提供接口

fbmem_init   //入口函数
  /*1.申请主设备号,注册字符设备*/
 register_chrdev(FB_MAJOR( 29), "fb", &fb_fops)
 
  /*2.创建一个设备类*/
 fb_class = class_create(THIS_MODULE, "graphics");
static const struct file_operations fb_fops = {
 .owner = THIS_MODULE,
 .read =  fb_read,
 .write = fb_write,
 .unlocked_ioctl = fb_ioctl,
# ifdef CONFIG_COMPAT
 .compat_ioctl = fb_compat_ioctl,
# endif
 .mmap =  fb_mmap,
 .open =  fb_open,
 .release = fb_release,
# ifdef HAVE_ARCH_FB_UNMAPPED_AREA
 .get_unmapped_area = get_fb_unmapped_area,
# endif
# ifdef CONFIG_FB_DEFERRED_IO
 .fsync = fb_deferred_io_fsync,
# endif
};

 

2.从应用层往下分析

open

app : open( "/dev/xxx",xxx)
== == == == == == == == == == == == == == == =
vfs : sys_open
  ...
  ...
fbmem.c struct file_operations fb_fops
   .open =  fb_open,
     /*1.获取此设备号*/
     int fbidx = iminor(inode);
     struct fb_info *info;
     /*2.以此设备号为下标,从register_fb数组中取出fb_info结构体*/
    info = registered_fb[fbidx];
    file - >private_data = info;
     if (info - >fbops - >fb_open) {
     res = info - >fbops - >fb_open(info, 1);

ioctl

app : ioctl(fd,FBIOGET_VSCREENINFO,args)
== == == == == == == == == == == == == == == == == == == == == =
vfs : sys_ioctl
  ...
  ...
fbmem.c struct file_operations fb_fops
   .unlocked_ioctl = fb_ioctl,
     /*1.获取此设备号*/
     struct inode *inode = file - >f_path.dentry - >d_inode;
     int fbidx = iminor(inode);
     /*2.以此设备号为下标,从register_fb数组中取出fb_info结构体*/
     struct fb_info *info = registered_fb[fbidx];
    do_fb_ioctl(info, cmd, arg);
      struct fb_var_screeninfo var;   //表示可变参数
      struct fb_fix_screeninfo fix;   //表示固定参数
      switch (cmd) {
       case FBIOGET_VSCREENINFO :
        if ( !lock_fb_info(info))
         return -ENODEV;
       var = info - >var; //取出fb_info中的可变参数
       unlock_fb_info(info);
       ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0;
        break;
     }

    搜索registered_fb数组,看在哪里被设置了?

s3c_fb_probe( struct platform_device *pdev)
 ...
 ...
  for (win = 0; win < S3C_FB_MAX_WIN; win ++) {
   /*设置一个硬件窗口:一个窗口就是一个帧缓冲设备,一个帧缓冲设备用struct fb_info来描述*/
  s3c_fb_probe_win      //drivers\video\s3c-fb.c
    /*构建fb_info:表示一个帧缓冲设备*/
   
    /*设置fb_info*/
    /*设置它的可变参数*/
    /*设置它的固定参数*/
    /*设置它的操作方法*/
    /*注册一个fb_info结构体*/
   register_framebuffer( struct fb_info *fb_info)
     /*将fb_info加入数组项*/
    registered_fb[i] = fb_info;

 

 

  @成鹏致远

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