Linux驱动分析之LCD驱动架构

// include/linux/fb.h
struct fb_info {
  atomic_t count;
  int node;
  int flags;
 
 
  int fbcon_rotate_hint;
  struct mutex lock;    /* open/release/ioctl中使用*/
  struct mutex mm_lock;    /*fb_mmap和smem_*数据域中使用 */
  struct fb_var_screeninfo var;  /* LCD屏可变参数 */
  struct fb_fix_screeninfo fix;  /* LCD屏固定参数 */
  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
  struct backlight_device *bl_dev; //背光设备
 
 
  struct mutex bl_curve_mutex;  
  u8 bl_curve[FB_BACKLIGHT_LEVELS]; //背光水平曲线
#endif
#ifdef CONFIG_FB_DEFERRED_IO
  struct delayed_work deferred_work;
  struct fb_deferred_io *fbdefio;
#endif
 
 
  struct fb_ops *fbops;          /*真正操作硬件寄存器的方法集合*/
  struct device *device;  
  struct device *dev;            /* fb设备*/
  int class_flag;                    /* private sysfs flags */
#ifdef CONFIG_FB_TILEBLITTING
  struct fb_tile_ops *tileops;    /* Tile Blitting */
#endif
  union {
    char __iomem *screen_base;  /* LCD虚拟显存地址 */
    char *screen_buffer;
  };
  unsigned long screen_size;  /* LCD虚拟显存大小 */ 
  void *pseudo_palette;    /* 指向16种颜色的调试板，其实就是一块内存*/ 
#define FBINFO_STATE_RUNNING  0
#define FBINFO_STATE_SUSPENDED  1
  u32 state;      /* Hardware state i.e suspend */
  void *fbcon_par;
 
 
  void *par; //私有数据，用来存放自己的数据的结构地址
  
  struct apertures_struct {
    unsigned int count;
    struct aperture {
      resource_size_t base;
      resource_size_t size;
    } ranges[0];
  } *apertures;
 
 
  bool skip_vt_switch; /* no VT switch on suspend/resume required */
};

struct fb_var_screeninfo {
  __u32 xres;      /* 可见屏幕一行有多少像素点     */
  __u32 yres;                     /*可见屏幕一屏有多少行,也就是列*/
  __u32 xres_virtual;    /* 虚拟屏幕一行有多少像素点*/
  __u32 yres_virtual;             /*虚拟屏幕一屏有多少行*/
 //显存大小并不一定等于实际屏幕显示对应的区域
  __u32 xoffset;      /* 虚拟屏到实际屏的水平偏移量 */
  __u32 yoffset;      /* 虚拟屏到实际屏的垂直偏移量*/
 
 
  __u32 bits_per_pixel;    /* 每个像素的位数即BPP,比如:RGB565则填入16*/
  __u32 grayscale;    /* 0 = 彩色, 1 = 灰度屏*/
          /* >1 = FOURCC      */
  struct fb_bitfield red;    /* 红色的长度和偏移信息  */
  struct fb_bitfield green;  /* 绿色的长度和偏移信息 */
  struct fb_bitfield blue;        /* 蓝色的长度和偏移信息 */
  struct fb_bitfield transp;  /* 透明色的长度和偏移信息*/  
 
 
  __u32 nonstd;      /* 不等于0则为非标准像素格式 */
   //定义修改参数生效时刻，一般马上生效，对应值是0，宏名是 FB_ACTIVATE_NOW
  __u32 activate;      /* see FB_ACTIVATE_*    */
   //存放物理屏的物理尺寸，是外观尺寸，单位是mm，可选择填充的项  非重点
  __u32 height;      /* height of picture in mm    */
  __u32 width;      /* width of picture in mm     */
 
 
  __u32 accel_flags;    /* (OBSOLETE) see fb_info.flags */
   //下面是LCD屏的工作时序，参数从datasheet来
  __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 colorspace;    /* colorspace for FOURCC-based modes */
  __u32 reserved[4];    /* Reserved for future compatibility */
};

struct fb_fix_screeninfo {
  char id[16];      /* LCD标识名 填写一个16字符以内字符串即可 */
  unsigned long smem_start;  /* 显存的物理起始地址，不是虚拟地址*/
          /* (physical address) */
  __u32 smem_len;      /* 显存的内存长度 */
  __u32 type;      /* 表示像素类型 see FB_TYPE_*  */
  __u32 type_aux;      /* Interleave for interleaved Planes */
  __u32 visual;      /* 表示颜色类型 see FB_VISUAL_*  */ 
  __u16 xpanstep;      /* 如果没有硬件panning就赋值为0  */
  __u16 ypanstep;      /* 如果没有硬件panning就赋值为0  */
  __u16 ywrapstep;    /* 如果没有硬件panning就赋值为0  */
   //一行的字节数 ,例:(RGB565)240*320,那么这里就等于240*16/8  
  __u32 line_length;    /* length of a line in bytes    */
  unsigned long mmio_start;  /* Start of Memory Mapped I/O   */
          /* (physical address) */
     //独立显卡相关的,基本不用
  __u32 mmio_len;      /* Length of Memory Mapped I/O  */
  __u32 accel;      /* Indicate to driver which  */
          /*  specific chip/card we have  */
  __u16 capabilities;    /* see FB_CAP_*      */
  __u16 reserved[2];    /* Reserved for future compatibility */
};

struct fb_ops {
  /* open/release and usage marking */
  struct module *owner;
  int (*fb_open)(struct fb_info *info, int user);
  int (*fb_release)(struct fb_info *info, int user);
 
 
  /* For framebuffers with strange non linear layouts or that do not
   * work with normal memory mapped access
   */
  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);
 
 
  /* checks var and eventually tweaks it to something supported,
   * DO NOT MODIFY PAR */
  int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);
 
 
  /* set the video mode according to info->var */
  int (*fb_set_par)(struct fb_info *info);
 
 
  /* set color register */
  int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
          unsigned blue, unsigned transp, struct fb_info *info);
 
 
  /* set color registers in batch */
  int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);
 
 
  /* blank display */
  int (*fb_blank)(int blank, struct fb_info *info);
 
 
  /* pan display */
  int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
 
 
  /* Draws a rectangle */
  void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
  /* Copy data from area to another */
  void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
  /* Draws a image to the display */
  void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);
 
 
  /* Draws cursor */
  int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);
 
 
  /* wait for blit idle, optional */
  int (*fb_sync)(struct fb_info *info);
 
 
  /* perform fb specific ioctl (optional) */
  int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
      unsigned long arg);
 
 
  /* Handle 32bit compat ioctl (optional) */
  int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
      unsigned long arg);
 
 
  /* perform fb specific mmap */
  int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);
 
 
  /* get capability given var */
  void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
          struct fb_var_screeninfo *var);
 
 
  /* teardown any resources to do with this framebuffer */
  void (*fb_destroy)(struct fb_info *info);
 
 
  /* called at KDB enter and leave time to prepare the console */
  int (*fb_debug_enter)(struct fb_info *info);
  int (*fb_debug_leave)(struct fb_info *info);
};

/*
函数功能：注册fb_info
*/
int register_framebuffer(struct fb_info *fb_info)
 
 
/*
函数功能：注销fb_info
*/
int unregister_framebuffer(struct fb_info *fb_info)
 
 
/*
函数功能：动态分配DMA内存，同时可以得到分配内存的虚拟地址和物理地址 
参数说明： 
    dev：设备指针如果没有赋值NULL 
    size:内存大小 
    dma_handle：作为输出参数使用，存放分配到的内存对应的物理地址 
    flag：内存分配方式 
返回值：分配到的内存的首地址
*/
void *dma_alloc_writecombine(struct device *dev, size_t size,
                       dma_addr_t *dma_handle, gfp_t flag)
 
 
/*
功能：释放由dma_alloc_writecombine分配的dma内存 
参数： 
dev:设备指针如果没有赋值NULL 
size:内存大小 
cpu_addr：dma_alloc_writecombine得到的虚拟地址首地址 
dma_handle：作为输出参数使用，存放分配到的内存对应的物理地址 
*/                       
void dma_free_writecombine(struct device *dev, size_t size,
                     void *cpu_addr, dma_addr_t dma_handle)