struct fb_info {  
    int node;/*  序号索引值，/dev/fb0，/dev/fb1  其中0,1 就是从这里获得的*/  
    int flags;  
    struct fb_var_screeninfo var;   /* Current var  可变参数，很重要 */  
    struct fb_fix_screeninfo fix;   /* Current fix  固定参数，很重要 */  
    struct fb_monspecs monspecs;    /* Current Monitor specs */  
    struct work_struct queue;   /* Framebuffer event queue */  
    struct fb_pixmap pixmap;    /* Image hardware mapper */  
    struct fb_pixmap sprite;    /* Cursor hardware mapper */  
    struct fb_cmap cmap;        /* Current cmap */  
    struct list_head modelist;      /* mode list */  
    struct fb_videomode *mode;  /* current mode */  

#ifdef CONFIG_FB_BACKLIGHT  
    /* assigned backlight device */  
    /* set before framebuffer registration,  
       remove after unregister */  
    struct backlight_device *bl_dev;  
    /* Backlight level curve */  
    struct mutex bl_curve_mutex;      
    u8 bl_curve[FB_BACKLIGHT_LEVELS];  
#endif  
#ifdef CONFIG_FB_DEFERRED_IO  
    struct delayed_work deferred_work;  
    struct fb_deferred_io *fbdefio;  
#endif  
    struct fb_ops *fbops;/* fb_ops，各种帧缓冲操作函数,很重要 */  
    struct device *device;      /* This is the parent */  
    struct device *dev;     /* This is this fb device */  
    int class_flag;                    /* private sysfs flags */  
#ifdef CONFIG_FB_TILEBLITTING  
    struct fb_tile_ops *tileops;    /* Tile Blitting */  
#endif  
    char __iomem *screen_base;  /* Virtual address  "显存“的基地址 */  
    unsigned long screen_size;  /* Amount of ioremapped VRAM or 0 ”显存“的大小，重要 */   
    void *pseudo_palette;       /* Fake palette of 16 colors */ /* 16位假的调色板，重要 */   
#define FBINFO_STATE_RUNNING    0  
#define FBINFO_STATE_SUSPENDED  1  
    u32 state;          /* Hardware state i.e suspend */  
    void *fbcon_par;                /* fbcon use-only private area */  
    /* From here on everything is device dependent */  
    void *par;   /* 这个用来存放私有数据 */  
};  

struct fb_var_screeninfo {  
    __u32 xres;         /* visible resolution       */  
    __u32 yres;  
    __u32 xres_virtual;     /* virtual resolution       */  
    __u32 yres_virtual;  
    __u32 xoffset;          /* offset from virtual to visible */  
    __u32 yoffset;          /* resolution           */  

    __u32 bits_per_pixel;       /* guess what           */  
    __u32 grayscale;        /* != 0 Graylevels instead of colors */  

    struct fb_bitfield red;     /* bitfield in fb mem if true color, */  
    struct fb_bitfield green;   /* else only length is significant */  
    struct fb_bitfield blue;  
    struct fb_bitfield transp;  /* transparency         */    

    __u32 nonstd;           /* != 0 Non standard pixel format */  

    __u32 activate;         /* see FB_ACTIVATE_*        */  

    __u32 height;           /* height of picture in mm    */  
    __u32 width;            /* width of picture in mm     */  

    __u32 accel_flags;      /* (OBSOLETE) see fb_info.flags */  

    /* Timing: All values in pixclocks, except pixclock (of course) */  
    __u32 pixclock;         /* pixel clock in ps (pico seconds) */  
    __u32 left_margin;      /* time from sync to picture    */  
    __u32 right_margin;     /* time from picture to sync    */  
    __u32 upper_margin;     /* time from sync to picture    */  
    __u32 lower_margin;  
    __u32 hsync_len;        /* length of horizontal sync    */  
    __u32 vsync_len;        /* length of vertical sync  */  
    __u32 sync;         /* see FB_SYNC_*        */  
    __u32 vmode;            /* see FB_VMODE_*       */  
    __u32 rotate;           /* angle we rotate counter clockwise */  
    __u32 reserved[5];      /* Reserved for future compatibility */  
};  

struct fb_fix_screeninfo {  
    char id[16];            /* identification string eg "TT Builtin" */  
    unsigned long smem_start;   /* Start of frame buffer mem */  
                    /* (physical address) */  
    __u32 smem_len;         /* Length of frame buffer mem */  
    __u32 type;         /* see FB_TYPE_*        */  
    __u32 type_aux;         /* Interleave for interleaved Planes */  
    __u32 visual;           /* see FB_VISUAL_*      */   
    __u16 xpanstep;         /* zero if no hardware panning  */  
    __u16 ypanstep;         /* zero if no hardware panning  */  
    __u16 ywrapstep;        /* zero if no hardware ywrap    */  
    __u32 line_length;      /* length of a line in bytes    */  
    unsigned long mmio_start;   /* Start of Memory Mapped I/O   */  
                    /* (physical address) */  
    __u32 mmio_len;         /* Length of Memory Mapped I/O  */  
    __u32 accel;            /* Indicate to driver which */  
                    /*  specific chip/card we have  */  
    __u16 reserved[3];      /* Reserved for future compatibility */  
};

struct fb_ops {
    struct module *owner;
    /* 打开/释放 */
    int (*fb_open)(struct fb_info *info, int user);
    int (*fb_release)(struct fb_info *info, int user);
    /* 对于非线性布局的/常规内存映射无法工作的帧缓冲设备需要 */
        ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
                   size_t count, loff_t *ppos);
        ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
                    size_t count, loff_t *ppos);
    /* 检测可变参数，并调整到支持的值*/
    int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);
    /* 根据 info->var 设置 video 模式 */
    int (*fb_set_par)(struct fb_info *info);
    /* 设置 color 寄存器 */
    int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
                unsigned blue, unsigned transp, struct fb_info *info);
    /* 批量设置 color 寄存器，设置颜色表 */
    int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);
    /*显示空白 */
    int (*fb_blank)(int blank, struct fb_info *info);
    /* pan 显示 */
    int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
    /* 矩形填充 */
    void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
    /* 数据复制 */
    void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
    /* 图形填充 */
    void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);
    /* 绘制光标 */
    int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);
    /* 旋转显示 */
    void (*fb_rotate)(struct fb_info *info, int angle);
    /* 等待 blit 空闲 (可选) */
    int (*fb_sync)(struct fb_info *info);
    /* fb 特定的 ioctl (可选) */
    int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
            unsigned long arg);
    /* 处理 32 位的 compat ioctl (可选) */
    int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
            unsigned long arg);
     /* fb 特定的 mmap */
    int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);
    /* 保存目前的硬件状态 */
    void (*fb_save_state)(struct fb_info *info);
    /* 恢复被保存的硬件状态 */
    void (*fb_restore_state)(struct fb_info *info);
    /* get capability given var */
    void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
                struct fb_var_screeninfo *var);
};