Linux FrameBuffer分析之编写基于FrameBuffer接口的应用程序

作者：刘昊昱

博客：http://blog.csdn.net/liuhaoyutz

测试环境：Ubuntu 12.04终端模式

在网上找到一个很不错的介绍FrameBuffer相关知识的帖子，原帖网址如下：http://bbs.chinaunix.net/thread-1932291-1-1.html，现把其中测试FrameBuffer的应用程序代码转帖过来，方便分析学习：

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <linux/kd.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <string.h>
#include <errno.h>struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
char *frameBuffer = 0;//打印fb驱动中fix结构信息，注：在fb驱动加载后，fix结构不可被修改。
void
printFixedInfo ()
{printf ("Fixed screen info:\n""\tid: %s\n""\tsmem_start:0x%lx\n""\tsmem_len:%d\n""\ttype:%d\n""\ttype_aux:%d\n""\tvisual:%d\n""\txpanstep:%d\n""\typanstep:%d\n""\tywrapstep:%d\n""\tline_length: %d\n""\tmmio_start:0x%lx\n""\tmmio_len:%d\n""\taccel:%d\n""\n",finfo.id, finfo.smem_start, finfo.smem_len, finfo.type,finfo.type_aux, finfo.visual, finfo.xpanstep, finfo.ypanstep,finfo.ywrapstep, finfo.line_length, finfo.mmio_start,finfo.mmio_len, finfo.accel);
}//打印fb驱动中var结构信息，注：fb驱动加载后，var结构可根据实际需要被重置
void
printVariableInfo ()
{printf ("Variable screen info:\n""\txres:%d\n""\tyres:%d\n""\txres_virtual:%d\n""\tyres_virtual:%d\n""\tyoffset:%d\n""\txoffset:%d\n""\tbits_per_pixel:%d\n""\tgrayscale:%d\n""\tred: offset:%2d, length: %2d, msb_right: %2d\n""\tgreen: offset:%2d, length: %2d, msb_right: %2d\n""\tblue: offset:%2d, length: %2d, msb_right: %2d\n""\ttransp: offset:%2d, length: %2d, msb_right: %2d\n""\tnonstd:%d\n""\tactivate:%d\n""\theight:%d\n""\twidth:%d\n""\taccel_flags:0x%x\n""\tpixclock:%d\n""\tleft_margin:%d\n""\tright_margin: %d\n""\tupper_margin:%d\n""\tlower_margin:%d\n""\thsync_len:%d\n""\tvsync_len:%d\n""\tsync:%d\n""\tvmode:%d\n""\n",vinfo.xres, vinfo.yres, vinfo.xres_virtual, vinfo.yres_virtual,vinfo.xoffset, vinfo.yoffset, vinfo.bits_per_pixel,vinfo.grayscale, vinfo.red.offset, vinfo.red.length,vinfo.red.msb_right,vinfo.green.offset, vinfo.green.length,vinfo.green.msb_right, vinfo.blue.offset, vinfo.blue.length,vinfo.blue.msb_right, vinfo.transp.offset, vinfo.transp.length,vinfo.transp.msb_right, vinfo.nonstd, vinfo.activate,vinfo.height, vinfo.width, vinfo.accel_flags, vinfo.pixclock,vinfo.left_margin, vinfo.right_margin, vinfo.upper_margin,vinfo.lower_margin, vinfo.hsync_len, vinfo.vsync_len,vinfo.sync, vinfo.vmode);
}//画大小为width*height的同色矩阵，8alpha+8reds+8greens+8blues
void
drawRect_rgb32 (int x0, int y0, int width,int height, int color)
{const int bytesPerPixel = 4;const int stride = finfo.line_length / bytesPerPixel;int *dest = (int *) (frameBuffer)+ (y0 + vinfo.yoffset) * stride + (x0 + vinfo.xoffset);int x, y;for (y = 0; y < height; ++y){for (x = 0; x < width; ++x){dest[x] = color;}dest += stride;}
}//画大小为width*height的同色矩阵，5reds+6greens+5blues
void
drawRect_rgb16 (int x0, int y0, int width,int height, int color)
{const int bytesPerPixel = 2;const int stride = finfo.line_length / bytesPerPixel;const int red = (color & 0xff0000) >> (16 + 3);const int green = (color & 0xff00) >> (8 + 2);const int blue = (color & 0xff) >> 3;const short color16 = blue | (green << 5) | (red << (5 +6));short *dest = (short *) (frameBuffer)+ (y0 + vinfo.yoffset) * stride + (x0 +vinfo.xoffset);int x, y;for (y = 0; y < height; ++y){for (x = 0; x < width; ++x){dest[x] = color16;}dest += stride;}
}//画大小为width*height的同色矩阵，5reds+5greens+5blues
void
drawRect_rgb15 (int x0, int y0, int width,int height, int color)
{const int bytesPerPixel = 2;const int stride = finfo.line_length / bytesPerPixel;const int red = (color & 0xff0000) >> (16 + 3);const int green = (color & 0xff00) >> (8 + 3);const int blue = (color & 0xff) >> 3;const short color15 = blue | (green << 5) | (red << (5 + 5))| 0x8000;short *dest = (short *) (frameBuffer)+ (y0 + vinfo.yoffset) * stride + (x0 + vinfo.xoffset);int x, y;for (y = 0; y < height; ++y){for (x = 0; x < width; ++x){dest[x] = color15;}dest += stride;}
}void
drawRect (int x0, int y0, int width, intheight, int color)
{switch (vinfo.bits_per_pixel){case 32:drawRect_rgb32 (x0, y0, width, height, color);break;case 16:drawRect_rgb16 (x0, y0, width, height, color);break;case 15:drawRect_rgb15 (x0, y0, width, height, color);break;default:printf ("Warning: drawRect() not implemented for color depth%i\n",vinfo.bits_per_pixel);break;}
}#define PERFORMANCE_RUN_COUNT 5
void
performSpeedTest (void *fb, int fbSize)
{int i, j, run;struct timeval startTime, endTime;unsigned long long results[PERFORMANCE_RUN_COUNT];unsigned long long average;unsigned int *testImage;unsigned int randData[17] = {0x3A428472, 0x724B84D3, 0x26B898AB,0x7D980E3C, 0x5345A084,0x6779B66B, 0x791EE4B4, 0x6E8EE3CC, 0x63AF504A, 0x18A21B33,0x0E26EB73, 0x022F708E, 0x1740F3B0, 0x7E2C699D, 0x0E8A570B,0x5F2C22FB, 0x6A742130};printf ("Frame Buffer Performance test...\n");for (run = 0; run < PERFORMANCE_RUN_COUNT; ++run){/* Generate test image with random(ish) data: */testImage = (unsigned int *) malloc (fbSize);j = run;for (i = 0; i < (int) (fbSize / sizeof (int)); ++i){testImage[i] = randData[j];j++;if (j >= 17)j = 0;}gettimeofday (&startTime, NULL);memcpy (fb, testImage, fbSize);gettimeofday (&endTime,NULL);long secsDiff = endTime.tv_sec - startTime.tv_sec;results[run] =secsDiff * 1000000 +(endTime.tv_usec - startTime.tv_usec);free (testImage);}average = 0;for (i = 0; i < PERFORMANCE_RUN_COUNT; ++i)average += results[i];average = average / PERFORMANCE_RUN_COUNT;printf (" Average: %llu usecs\n", average);printf (" Bandwidth: %.03f MByte/Sec\n",(fbSize / 1048576.0) / ((double) average / 1000000.0));printf (" Max. FPS: %.03f fps\n\n",1000000.0 / (double) average);/* Clear the framebuffer back to black again: */memset (fb, 0, fbSize);
}int
main (int argc, char **argv)
{const char *devfile = "/dev/fb0";long int screensize = 0;int fbFd = 0;/* Open the file for reading and writing */fbFd = open (devfile, O_RDWR);if (fbFd == -1){perror ("Error: cannot open framebuffer device");exit (1);}//获取finfo信息并显示if (ioctl (fbFd, FBIOGET_FSCREENINFO, &finfo) == -1){perror ("Error reading fixed information");exit (2);}printFixedInfo ();//获取vinfo信息并显示if (ioctl (fbFd, FBIOGET_VSCREENINFO, &vinfo) == -1){perror ("Error reading variable information");exit (3);}printVariableInfo ();/* Figure out the size of the screen in bytes */screensize = finfo.smem_len;/* Map the device to memory */frameBuffer =(char *) mmap (0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,fbFd, 0);if (frameBuffer == MAP_FAILED){perror ("Error: Failed to map framebuffer device to memory");exit (4);}//测试virt fb的性能performSpeedTest (frameBuffer, screensize);printf ("Will draw 3 rectangles on the screen,\n""they should be coloredred, green and blue (in that order).\n");drawRect (vinfo.xres / 8, vinfo.yres / 8,vinfo.xres / 4, vinfo.yres /4, 0xffff0000);drawRect (vinfo.xres * 3 / 8, vinfo.yres * 3 / 8,vinfo.xres / 4, vinfo.yres / 4,0xff00ff00);drawRect (vinfo.xres * 5 / 8, vinfo.yres * 5 / 8,vinfo.xres / 4, vinfo.yres /4, 0xff0000ff);sleep (5);printf (" Done.\n");munmap (frameBuffer, screensize);   //解除内存映射，与mmap对应close (fbFd);return 0;
}

该程序需要在打开FrameBuffer的终端模式下运行，我使用的Ubuntu 12.04，直接按Ctrl + Alt + F1，切换到终端1下，即可运行该程序。程序运行效果如下图所示：

说明一下，在终端模式下，截图软件我用的是fbgrab。

在我的电脑上，该程序在终端打印的信息如下：

Fixed screen info:id: inteldrmfbsmem_start: 0xd0064000smem_len: 8294400type: 0type_aux: 0visual: 2xpanstep: 1ypanstep: 1ywrapstep: 0line_length: 7680mmio_start: 0x0mmio_len: 0accel: 0Variable screen info:xres: 1920yres: 1080xres_virtual: 1920yres_virtual: 1080yoffset: 0xoffset: 0bits_per_pixel: 32grayscale: 0red: offset: 16, length:  8,msb_right:  0green: offset:  8, length:  8, msb_right: 0blue: offset:  0, length:  8, msb_right: 0transp: offset:  0, length:  0, msb_right: 0nonstd: 0activate: 0height: -1width: -1accel_flags: 0x1pixclock: 0left_margin: 0right_margin: 0upper_margin: 0lower_margin: 0hsync_len: 0vsync_len: 0sync: 0vmode: 0Frame Buffer Performance test...Average: 1489 usecsBandwidth: 5312.395 MByte/SecMax.FPS: 671.592 fpsWill draw 3 rectangles on the screen,
they should be colored red, green and blue(in that order).Done.

通过这个测试程序，我们就能理解怎样在Linux用户空间，基于FrameBuffer接口，绘制想要的图形。

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