Framebuffer 驱动学习总结（一） ---- 总体架构及关键结构体

struct fb_info {
atomic_t count;
int node; ///次设备号
int flags;
struct mutex lock; //用于open、release、ioctrl功能的锁
struct mutex mm_lock; /* Lock for fb_mmap and smem_* fields */
struct fb_var_screeninfo var; //LCD 可变参数
struct fb_fix_screeninfo fix; //LCD 固定参数
struct fb_monspecs monspecs; /* Current Monitor specs *///LCD 显示器标准
struct work_struct queue; //帧缓冲事件队列
struct fb_pixmap pixmap; ///图像硬件 mapper
struct fb_pixmap sprite; //光标硬件 mapper
struct fb_cmap cmap; //当前颜色表
struct list_head modelist; //模式列表
struct fb_videomode *mode; //当前的显示模式 #ifdef CONFIG_FB_BACKLIGHT
/* assigned backlight device */
/* set before framebuffer registration,
remove after unregister */
struct backlight_device *bl_dev;///对应的背光设备 /* Backlight level curve */
struct mutex bl_curve_mutex;
u8 bl_curve[FB_BACKLIGHT_LEVELS];///背光调整
#endif
#ifdef CONFIG_FB_DEFERRED_IO
struct delayed_work deferred_work;
struct fb_deferred_io *fbdefio;
#endif struct fb_ops *fbops;///---->对底层硬件设备操作的函数指针
struct device *device; /* This is the parent *////父设备节点
struct device *dev; /* This is this fb device *////当前的帧缓冲设备
int class_flag; /* private sysfs flags */
#ifdef CONFIG_FB_TILEBLITTING
struct fb_tile_ops *tileops; /* Tile Blitting *///图块Blitting ?
#endif
char __iomem *screen_base; /* Virtual address *///虚拟地址
unsigned long screen_size; /* Amount of ioremapped VRAM or 0 */ ///LCD IO映射的虚拟内存大小
void *pseudo_palette; /* Fake palette of 16 colors *///伪16色 颜色表
#define FBINFO_STATE_RUNNING 0
#define FBINFO_STATE_SUSPENDED 1
u32 state; /* Hardware state i.e suspend *////LCD 挂起或复位的状态
void *fbcon_par; /* fbcon use-only private area */
/* From here on everything is device dependent */
void *par;
/* we need the PCI or similar aperture base/size not
smem_start/size as smem_start may just be an object
allocated inside the aperture so may not actually overlap */
struct apertures_struct {
unsigned int count;
struct aperture {
resource_size_t base;
resource_size_t size;
} ranges[];
} *apertures; bool skip_vt_switch; /* no VT switch on suspend/resume required */
};

struct fb_fix_screeninfo {
char id[]; //字符串形式的标识符
unsigned long smem_start; /fb 缓存的开始位置
/* (physical address) */
__u32 smem_len; /* Length of frame buffer mem *///fb 缓存的长度
__u32 type; /* see FB_TYPE_* *////看FB_TYPE_* -->
__u32 type_aux; /* Interleave for interleaved Planes *///分界
__u32 visual; ///看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ywrap就赋值为0
__u32 line_length; //一行的字节数
unsigned long mmio_start; //内存映射 IO的开始位置
/* (physical address) */
__u32 mmio_len; //内存映射 IO的长度
__u32 accel; /* Indicate to driver which */
/* specific chip/card we have */
__u16 capabilities; /* see FB_CAP_* *///功能 ---FB_CAP_FOURCC--- Device supports FOURCC-based formats
__u16 reserved[]; //为以后的兼容性保留
};

struct fb_var_screeninfo { ///显示屏信息
__u32 xres; /* visible resolution*//可视区域，一行有多少个像素点
__u32 yres; ///可视区域，一列有多少个像素点
__u32 xres_virtual; /* virtual resolution*//虚拟区域，一行有多少个像素点，简单的意思就是内存中定义的区间是比较大的
__u32 yres_virtual;////虚拟区域，一列有多少个像素点
__u32 xoffset; //虚拟到可见屏幕之间的行偏移
__u32 yoffset; /* resolution *//虚拟到可见屏幕之间的列偏移 __u32 bits_per_pixel; /* guess what*/ 每个像素的 bit 数，这个参数不需要自己配置，而是通过上层在调用 checkvar 函数传递 bpp 的时候赋值的
__u32 grayscale; /* 0 = color, 1 = grayscale,*////等于零就成黑白 (灰度)
/* >1 = FOURCC */
// 通过 pixel per bpp 来设定 red green 和 blue 的位置； pixel per bpp 可以通过 ioctl 设定
struct fb_bitfield red; //fb缓存的R位域
struct fb_bitfield green; /* else only length is significant *//fb缓存的G位域
struct fb_bitfield blue; //fb缓存的B位域
struct fb_bitfield transp; /* transparency *//透明度 __u32 nonstd; /* != 0 Non standard pixel format *///如果nonstd 不等于0，非标准的像素格式 __u32 activate; /* see FB_ACTIVATE_* */ __u32 height; //内存中的图像高度
__u32 width; //内存中的图像宽度 __u32 accel_flags; /* (OBSOLETE) see fb_info.flags *////加速标志 /* Timing: All values in pixclocks, except pixclock (of course) */
///时序，这些部分就是显示器的显示方法了，和具体的液晶显示屏有关，在驱动中一般放在 具体液晶屏的配置文件
__u32 pixclock; /* pixel clock in ps (pico seconds) *///像素时钟
__u32 left_margin; /* time from sync to picture *////行切换，从同步到绘图之间的延迟
__u32 right_margin; /* time from picture to sync *///行切换，从绘图到同步之间的延迟
__u32 upper_margin; /* time from sync to picture *///帧切换，从同步到绘图之间的延迟
__u32 lower_margin; ////帧切换，从绘图到同步之间的延迟
__u32 hsync_len; /* length of horizontal sync */ //水平同步的长度
__u32 vsync_len; /* length of vertical sync */ //垂直同步的长度
__u32 sync; /* see FB_SYNC_* *////---->看 FB_SYNC_*
__u32 vmode; /* see FB_VMODE_* *////---->看 FB_VMODE_*
__u32 rotate; /* angle we rotate counter clockwise */
__u32 colorspace; /* colorspace for FOURCC-based modes */
__u32 reserved[]; /* 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);
/*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);
/* 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);///检查可变参数并进行设置
/* set the video mode according to info->var */
int (*fb_set_par)(struct fb_info *info);///根据设置的值进行更新，使之有效
/* set color register */
int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green, ////设置颜色寄存器
unsigned blue, unsigned transp, struct fb_info *info);
/* set color registers in batch */
int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);

int (*fb_blank)(int blank, struct fb_info *info);///显示空白
/*pan显示*/
int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);///矩形填充
void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);///复制数据
void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);///图形填充
/* 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 */
int (*fb_sync)(struct fb_info *info);
/* fb 特定的 ioctl */
int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
unsigned long arg);
/* 处理32bit compat ioctl (optional) */
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);
/* 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);
};

struct fb_cmap { //颜色映射表
__u32 start; /* First entry *////第一个入口
__u32 len; /* Number of entries *///入口的数字
__u16 *red; /* Red values *///红色
__u16 *green; ///绿色
__u16 *blue; ///蓝色
__u16 *transp; //透明度，允许为空
};