Android P图形架构之FrameBuffer测试Demo

深藏阁楼爱情的钟 2024-04-18 17:29 68阅读 0赞

Android FrameBuffer测试记录。

SurfaceFlinger是一个服务，主要是负责合成各窗口的Surface，然后通过OpenGLES显示到FrameBuffer上。

参考资料：  
https://android.googlesource.com/platform/system/extras/+/donut-release/tests/framebuffer/fb\_test.c

源码：  
framebuffer\_test.c

#include <unistd.h>  
    #include <stdio.h>  
    #include <fcntl.h>  
    #include <linux/fb.h>  
    #include <sys/mman.h>  
    #include <stdlib.h>
    #include "yellow_face.zif"
    int main()  
    {   
        int fbfd = 0;  
        struct fb_var_screeninfo vinfo;  
        struct fb_fix_screeninfo finfo;  
        //struct fb_cmap cmapinfo; 
        long int screensize = 0;  
        char *fbp = 0;  
        int x = 0, y = 0;  
        //long int location = 0; 
        //int b,g,r; 
        // Open the file for reading and writing 
        fbfd = open("/dev/graphics/fb0", O_RDWR,0); // 打开Frame Buffer设备 
        if (fbfd < 0) {   
            printf("Error: cannot open framebuffer device.%x\n",fbfd);  
            exit(1);  
        }  
        printf("The framebuffer device was opened successfully.\n"); 
        // Get fixed screen information 
        if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {  // 获取设备固有信息 
            printf("Error reading fixed information.\n");  
            exit(2);  
        }  
        printf("\ntype:0x%x\n", finfo.type ); // FrameBuffer 类型,如0为象素 
        printf("visual:%d\n", finfo.visual ); // 视觉类型：如真彩2，伪彩3 
        printf("line_length:%d\n", finfo.line_length ); // 每行长度 
        printf("\nsmem_start:0x%lx,smem_len:%u\n", finfo.smem_start, finfo.smem_len ); // 映象RAM的参数 
        printf("mmio_start:0x%lx ,mmio_len:%u\n", finfo.mmio_start, finfo.mmio_len );  
          
        // Get variable screen information 
        if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {  // 获取设备可变信息 
            printf("Error reading variable information.\n");  
            exit(3);  
        }  
        printf("%dx%d, %dbpp,xres_virtual=%d,yres_virtual=%dvinfo.xoffset=%d,vinfo.yoffset=%d\n", 
        vinfo.xres, vinfo.yres, vinfo.bits_per_pixel,
        vinfo.xres_virtual,vinfo.yres_virtual,vinfo.xoffset,vinfo.yoffset);  
    
    	screensize = finfo.line_length * vinfo.yres_virtual;
        // Map the device to memory 通过mmap系统调用将framebuffer内存映射到用户空间,并返回映射后的起始地址 
        fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,fbfd, 0);  
        if ((int)fbp == -1) {   
            printf("Error: failed to map framebuffer device to memory.\n");  
            exit(4);  
        }  
        printf("The framebuffer device was mapped to memory successfully.\n");  
    
        /*****************exampel********************/		
     	unsigned char *pTemp = (unsigned char *)fbp;
    	int i, j;
    	//起始坐标(x,y),终点坐标(right,bottom)
    	x = 0;
    	y = 0;
    	int right = 480;//vinfo.xres;
    	int bottom = 1708;//vinfo.yres;
    	//计算偏移量.例如在（x，y）位置写入颜色 pixel值.
    	//offset = (x + y * screen_width) * 4; // (4个字节) 
    	for(i=y; i< bottom; i++)
    	{ 
    		for(j=x; j<right; j++)
    		{ 
    			unsigned short data = yellow_face_data[(((i-y)  % 128) * 128) + ((j-x) %128)];
    			// *((uint32_t *)(fbp + offset)) = pixel;
    			pTemp[i*finfo.line_length + (j*4) + 2] = (unsigned char)((data & 0xF800) >> 11 << 3);
    			pTemp[i*finfo.line_length + (j*4) + 1] = (unsigned char)((data & 0x7E0) >> 5 << 2);
    			pTemp[i*finfo.line_length + (j*4) + 0] = (unsigned char)((data & 0x1F) << 3);
    		}
    	} 
        /*****************FBIOPAN_DISPLAY********************/	
        //note：vinfo.xoffset =0 vinfo.yoffset =0 否则FBIOPAN_DISPLAY不成功
    	if (ioctl(fbfd, FBIOPAN_DISPLAY, &vinfo)) {     
            printf("Error FBIOPAN_DISPLAY information.\n");  
            exit(5);  
        }  
    	sleep(10);
    	//finfo.smem_len == screensize == finfo.line_length * vinfo.yres_virtual 
    	munmap(fbp,finfo.smem_len);
        close(fbfd);  
        return 0;  
    }

mk编译文件源码：  
Android.mk

LOCAL_PATH:= $(call my-dir)
    include $(CLEAR_VARS)
    LOCAL_MODULE_TAGS := eng
    LOCAL_SRC_FILES:=framebuffer_test.c
    LOCAL_MODULE:=framebuffer_test
    LOCAL_CPPFLAGS += -DANDROID
    LOCAL_SHARED_LIBRARIES:=libc
    LOCAL_C_INCLUDES += $(LOCAL_PATH) $(LOCAL_PATH)/$(KERNEL_DIR)/include
    include $(BUILD_EXECUTABLE)

1、mm编译system\\bin目录下生成framebuffer\_test文件  
2、拷贝到机器system/bin目录下  
3、执行：stop surfaceflinger，关闭surfaceflinger  
4、执行：./framebuffer\_test，运行framebuffer\_test程序  
5、显示图像，执行成功。