lcd驱动分析文档

嵌入式linux中的lcd驅動分析作者：傑洲村的木棉學校：廣東工業大學QQ：568109894在嵌入式linux中，lcd和觸控式螢幕驅動都是字元驅動，採用“檔層-驅動層”的介面方式,本文檔中分析的lcd驅動是針對linux2.6.13內核的，本人用的開發板是qq2440,lcd是三星的LTV3500V(帶觸控式螢幕的),具體分析的文件:是"include/linux/fb.h","drivers/video/s3c2410fb.h","drivers/video/s3c2410fb.c","drivers/video/fbmem.c","/include/asm/arch- s3c2410.fb.h(些標頭檔是針對s3c2440或s3c2410晶片的)",“/home/linux/5/kernel-2.6.13/arch/arm/mach-s3c2410/mach-smdk2410.c"(驅動移植主要就是要修改這個檔，配置一些參數)。

詳細看一下LCD的驅動,實際上，幾乎lcd設備驅動所要做的所有事情就是填充fb_info結構然後向系統註冊或登出它(1)fb.h包含了framebuffer所用到的結構(2)fbmem.c處於Framebuffer設備驅動技術的中心位置.它為上層應用程式提供系統調用也為下一層的特定硬體驅動提供介面；那些底層硬體驅動需要用到這兒的介面來向系統內核註冊它們自己. fbmem.c 為所有支援FrameBuffer的設備驅動提供了通用的介面，避免重復工作.(3)s3c2410fb.c就是特定硬體驅動(針對s3c2410晶片的),fbmem.c就是溝通應用層跟s3c2410fb.c的橋樑FrameBuffer設備驅動基於如下幾個檔：1)include/linux/fb.h2)drivers/video/fbmem.c3)drivers/video/s3c2410fb.c4)drivers/video/s3c2410fb.h5)include/asm/arch-s3c2410/fb.h現在先來分析這兩個檔：1.fb.h 包含了framebuffer 所用到的結構1)fb_fix_screeninfo 描述顯示卡的屬性，並且系統運行時不能被修改 structfb_fix_screeninfo {char id[16];unsigned long smem_start;/* identification string eg "TT Builtin" */ /* Start of frame buffer mem *//* (physical address) */__u32 smem_len;/* Length of frame buffer mem */__u32 type;__u32 type_aux;/* see FB_TYPE_* *//* Interleave for interleaved Planes */__u32 visual;/* see FB_VISUAL_* */ __u16 xpanstep;/* zero if no hardware panning */__u16 ypanstep;__u16 ywrapstep; __u32 line_length;/* zero if no hardware panning */ /* zero if no hardware ywrap */ /* length of a line in bytes */unsigned long mmio_start;/* Start of Memory Mapped I/O *//* (physical address) */__u32 mmio_len; __u32 accel;/* Length of Memory Mapped I/O *//* Indicate to driver which */ /* specific chip/card we have */};__u16 reserved[3];/* Reserved for future compatibility */2)fb_var_screeninfo 這個結構描述了顯示卡的特性struct fb_var_screeninfo {__u32 xres;__u32 yres;__u32 xres_virtual;/* visible resolution/* virtual resolution*/*/__u32 yres_virtual;__u32 xoffset; /* offset from virtual to visible */ __u32 yoffset;/* resolution*/__u32 bits_per_pixel; __u32 grayscale;/* guess what/* != 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; __u32 width;/* height of picture in mm/* 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 */};3)fb_cmap描述設備無關的顏色映射資訊。

可以通過FBIOGETCMAP 和 FBIOPUTCMAP 對應的ioctl操作設定或獲取顏色映射資訊struct fb_cmap {__u32 start; /* First entry */__u32 len; /* Number of entries */__u16 *red; /* Red values */__u16 *green;__u16 *blue;__u16 *transp; /* transparency, can be NULL */};4)fb_info(1)定義當顯卡的當前狀態；fb_info結構僅在內核中可見，在這個結構中有一個fb_ops指標，指向驅動設備工作所需的函數集。

struct fb_info{ int node;int flags;struct fb_var_screeninfo var; /* Current var */struct fb_fix_screeninfo fix; /* Current fix */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 */struct fb_ops *fbops; //(注意這個結構)struct device *device;struct class_device *class_device; /* sysfs per device attrs */#ifdef CONFIG_FB_TILEBLITTINGstruct fb_tile_ops *tileops; /* Tile Blitting */#endifchar __iomem *screen_base; /* Virtual address */unsigned long screen_size; /* Amount of ioremapped VRAM or 0 */void *pseudo_palette; /* Fake palette of 16 colors */#define FBINFO_STATE_RUNNING 0#define FBINFO_STATE_SUSPENDED 1u32 state; /* Hardware state i.e suspend */void *fbcon_par; /* fbcon use-only private area *//* From here on everything is device dependent */void *par;};(2)fb_info 中紀錄了幀緩衝設備的全部資訊，包括設備的設置參數，狀態以及操作函數指標。