目录
一、概述
二、struct fb_fix_screeninfo详解
 2.1 struct fb_fix_screeninfo定义
 2.2 struct fb_fix_screeninfo字段说明：
三、struct fb_var_screeninfo详解
 3.1 struct fb_var_screeninfo定义：
 3.2 struct fb_var_screeninfo字段说明：
四、打印 struct fb_fix_screeninfo 和 struct fb_var_screeninfo

一、概述

struct fb_fix_screeninfo 和 struct fb_var_screeninfo 都定义在系统的/usr/include/linux/fb.h文件内。下面分别结构体定义、结构体字段说明两部分来详细解释这两个结构体。

二、struct fb_fix_screeninfo详解

struct fb_fix_screeninfo主要用于获取FrameBuffer的固定信息，这些信息无法在应用层被更改，只能通过ioctl函数使用FBIOGET_FSCREENINFO去获取。

2.1 struct fb_fix_screeninfo定义：

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 capabilities;		/* see FB_CAP_*					*/__u16 reserved[2];		/* Reserved for future compatibility */
};

2.2 struct fb_fix_screeninfo字段说明：

表格中提到的宏如FB_TYPE_PACKED_PIXELS、FB_VISUAL_TRUECOLOR、FB_ACCEL_NONE请查看 /usr/include/linux/fb.h 的相关定义。

三、struct fb_var_screeninfo详解

struct fb_var_screeninfo主要用于获取和设置FrameBuffer的可变屏幕信息，包括分辨率、像素位深、像素格式等。这些信息可以通过ioctl函数使用FBIOGET_VSCREENINFO获取，也可以通过FBIOPUT_VSCREENINFO修改。

3.1 struct fb_var_screeninfo定义：

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 = color, 1 = grayscale,*//* >1 = FOURCC*/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 */
};

3.2 struct fb_var_screeninfo字段说明：

表格中提到的宏和结构体请查看 /usr/include/linux/fb.h 的相关定义。

四、打印 struct fb_fix_screeninfo 和 struct fb_var_screeninfo

复制下面代码保存为printFbInfo.c，编译后，在ubuntu系统上，加上sudo执行，就可以看到FrameBuffer的固定信息和可变信息了，再结合上面的说明，可以更好地理解这两个结构体。

#include 
#include #include 
#include 
#include void print_finfo(struct fb_fix_screeninfo *finfo)
{fprintf(stderr,"Printing fb_fix_screeninfo:\n");fprintf(stderr,"smem_start=%p,smem_len=%d\n",(char *)finfo->smem_start,finfo->smem_len);fprintf(stderr,"type = %d\n", finfo->type);fprintf(stderr,"type_aux = %d\n", finfo->type_aux);fprintf(stderr,"visual = %d\n", finfo->visual);fprintf(stderr,"xpanstep = %d, ypanstep = %d\n", finfo->xpanstep,finfo->ypanstep);fprintf(stderr,"ywrapstep = %d\n", finfo->ywrapstep);fprintf(stderr,"line_length = %d\n", finfo->line_length);fprintf(stderr,"mmio_start=%p, mmio_len=%d\n",(char *)finfo->mmio_start,finfo->mmio_len);fprintf(stderr,"accel = %d\n\n", finfo->accel);
}
void print_vinfo(struct fb_var_screeninfo *vinfo)
{fprintf(stderr, "Printing vinfo:\n");fprintf(stderr, "xres:%d, yres:%d\n", vinfo->xres,vinfo->yres);fprintf(stderr, "xres_virtual:%d, yres_virtual:%d\n", vinfo->xres_virtual,vinfo->yres_virtual);fprintf(stderr, "xoffset:%d, yoffset:%d\n", vinfo->xoffset,vinfo->yoffset);fprintf(stderr, "bits_per_pixel: %d\n", vinfo->bits_per_pixel);fprintf(stderr, "grayscale: %d\n", vinfo->grayscale);fprintf(stderr, "red: %d/%d\n", vinfo->red.length, vinfo->red.offset);fprintf(stderr, "green: %d/%d\n", vinfo->green.length, vinfo->green.offset);fprintf(stderr, "blue: %d/%d\n", vinfo->blue.length, vinfo->blue.offset);fprintf(stderr, "transp: %d/%d\n", vinfo->transp.length, vinfo->transp.offset);fprintf(stderr, "nonstd: %d\n", vinfo->nonstd);fprintf(stderr, "activate: %d\n", vinfo->activate);fprintf(stderr, "height: %d\n", vinfo->height);fprintf(stderr, "width: %d\n", vinfo->width);fprintf(stderr, "accel_flags: %d\n", vinfo->accel_flags);fprintf(stderr, "pixclock: %d\n", vinfo->pixclock);fprintf(stderr, "left_margin: %d\n", vinfo->left_margin);fprintf(stderr, "right_margin: %d\n", vinfo->right_margin);fprintf(stderr, "upper_margin: %d\n", vinfo->upper_margin);fprintf(stderr, "lower_margin: %d\n", vinfo->lower_margin);fprintf(stderr, "hsync_len: %d\n", vinfo->hsync_len);fprintf(stderr, "vsync_len: %d\n", vinfo->vsync_len);fprintf(stderr, "sync: %d\n", vinfo->sync);fprintf(stderr, "vmode: %d\n", vinfo->vmode);fprintf(stderr, "rotate: %d\n\n", vinfo->rotate);
}int main(int argc, char *argv[])
{// 1.打开设备char fbPath[64] = "/dev/fb0";int framebuf_fd = open(fbPath, O_RDWR);if ( framebuf_fd < 0 ) {printf("[%s:%d] open %s error \n", __FILE__,__LINE__,fbPath);return -1;}// 2.获取设备固定参数struct fb_fix_screeninfo finfo;if (ioctl(framebuf_fd, FBIOGET_FSCREENINFO, &finfo) < 0){fprintf(stderr, "ioctl FBIOGET_FSCREENINFO err \r\n");return -1;}print_finfo(&finfo);// 3.1 获取虚拟参数struct fb_var_screeninfo vinfo;if (ioctl(framebuf_fd, FBIOGET_VSCREENINFO, &vinfo) < 0){fprintf(stderr, "ioctl FBIOGET_VSCREENINFO err \r\n");return -1;}print_vinfo(&vinfo);return 0;
}

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