简介 在前面我们已经完成了myvivi这个虚拟的v4l2摄像头驱动程序的编写。这里继续编写一个该驱动的应用测试程序来加深一下该驱动的工作原理。具体代码
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <getopt.h>#include <fcntl.h>#include <unistd.h> #include <errno.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/time.h> #include <sys/mman.h> #include <sys/ioctl.h> #include <asm/types.h> #include <linux/videodev2.h> #include <linux/fb.h> #define CLEAR(x) memset (&(x), 0, sizeof (x))#define SET_WIDTH 320#define SET_HEIGHT 240 struct buffer { void * start; size_t length; };static char * dev_name = NULL; static int fd = -1; struct buffer * buffers = NULL; static unsigned int n_buffers = 0; static int time_in_sec_capture=5; static int fbfd = -1; static struct fb_var_screeninfo vinfo; static struct fb_fix_screeninfo finfo; static char *fbp=NULL; static long screensize=0;static void errno_exit (const char * s) { fprintf (stderr, "%s error %d, %s/n",s, errno, strerror (errno)); exit (EXIT_FAILURE); }static int xioctl (int fd,int request,void * arg) { int r; do r = ioctl (fd, request, arg); while (-1 == r && EINTR == errno); return r; }inline int clip(int value, int min, int max) { return (value > max ? max : value < min ? min : value); }static void process_image (const void * p){ unsigned char* in=(char*)p; int width=SET_WIDTH; int height=SET_HEIGHT; int istride=SET_WIDTH * 2; int x,y,j; int y0,u,y1,v,r,g,b; long location=0;for ( y = 100; y < height + 100; ++y) {for (j = 0, x=100; j < width * 2 ; j += 4,x +=2) {location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +(y+vinfo.yoffset) * finfo.line_length;y0 = in[j];u = in[j + 1] – 128;y1 = in[j + 2];v = in[j + 3] – 128;r = (298 * y0 + 409 * v + 128) >> 8;g = (298 * y0 – 100 * u – 208 * v + 128) >> 8;b = (298 * y0 + 516 * u + 128) >> 8;fbp[ location + 0] = clip(b, 0, 255);fbp[ location + 1] = clip(g, 0, 255);fbp[ location + 2] = clip(r, 0, 255);fbp[ location + 3] = 255;r = (298 * y1 + 409 * v + 128) >> 8;g = (298 * y1 – 100 * u – 208 * v + 128) >> 8;b = (298 * y1 + 516 * u + 128) >> 8;fbp[ location + 4] = clip(b, 0, 255);fbp[ location + 5] = clip(g, 0, 255);fbp[ location + 6] = clip(r, 0, 255);fbp[ location + 7] = 255;}in +=istride; } }static int read_frame (void) { struct v4l2_buffer buf; unsigned int i;CLEAR (buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP;if (-1 == xioctl (fd, VIDIOC_DQBUF, &buf)) {switch (errno) {case EAGAIN:return 0;case EIO:default:errno_exit ("VIDIOC_DQBUF");} }assert (buf.index < n_buffers); process_image(buffers[buf.index].start); if (-1 == xioctl (fd, VIDIOC_QBUF, &buf))errno_exit ("VIDIOC_QBUF");return 1; }static void run (void) { unsigned int count; int frames; frames = 30 * time_in_sec_capture;while (frames– > 0) {for (;;) {fd_set fds;struct timeval tv;int r;FD_ZERO (&fds);FD_SET (fd, &fds);tv.tv_sec = 2;tv.tv_usec = 0;r = select (fd + 1, &fds, NULL, NULL, &tv);if (-1 == r) {if (EINTR == errno)continue;errno_exit ("select");}else if (0 == r) {fprintf (stderr, "select timeout/n");exit (EXIT_FAILURE);}if(read_frame())break;} } }static void stop_capturing (void) { enum v4l2_buf_type type;type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (-1 == xioctl (fd, VIDIOC_STREAMOFF, &type))errno_exit ("VIDIOC_STREAMOFF"); }static void start_capturing (void) { unsigned int i; enum v4l2_buf_type type;for (i = 0; i < n_buffers; ++i) {struct v4l2_buffer buf;CLEAR (buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = i;if (-1 == xioctl (fd, VIDIOC_QBUF, &buf))errno_exit ("VIDIOC_QBUF"); }type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if (-1 == xioctl (fd, VIDIOC_STREAMON, &type))errno_exit ("VIDIOC_STREAMON"); }static void uninit_device (void) { unsigned int i;for (i = 0; i < n_buffers; ++i)if (-1 == munmap (buffers[i].start, buffers[i].length))errno_exit ("munmap");if (-1 == munmap(fbp, screensize)) {printf(" Error: framebuffer device munmap() failed./n");exit (EXIT_FAILURE) ; }free (buffers); }static void init_mmap (void) { struct v4l2_requestbuffers req;//mmap framebuffer fbp = (char *)mmap(NULL,screensize,PROT_READ | PROT_WRITE,MAP_SHARED ,fbfd, 0); if ((int)fbp == -1) {printf("Error: failed to map framebuffer device to memory./n");exit (EXIT_FAILURE) ; } memset(fbp, 0, screensize); CLEAR (req);req.count = 4; req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; req.memory = V4L2_MEMORY_MMAP;if (-1 == xioctl (fd, VIDIOC_REQBUFS, &req)) {if (EINVAL == errno) {fprintf (stderr, "%s does not support memory mapping/n", dev_name);exit (EXIT_FAILURE);} else {errno_exit ("VIDIOC_REQBUFS");} }if (req.count < 4) { //if (req.count < 2)fprintf (stderr, "Insufficient buffer memory on %s/n",dev_name);exit (EXIT_FAILURE); }buffers = calloc (req.count, sizeof (*buffers));if (!buffers) {fprintf (stderr, "Out of memory/n");exit (EXIT_FAILURE); }for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {struct v4l2_buffer buf;CLEAR (buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = n_buffers;if (-1 == xioctl (fd, VIDIOC_QUERYBUF, &buf))errno_exit ("VIDIOC_QUERYBUF");buffers[n_buffers].length = buf.length;buffers[n_buffers].start =mmap (NULL,buf.length,PROT_READ | PROT_WRITE ,MAP_SHARED,fd, buf.m.offset);if (MAP_FAILED == buffers[n_buffers].start)errno_exit ("mmap"); }}static void init_device (void) { struct v4l2_capability cap; struct v4l2_cropcap cropcap; struct v4l2_crop crop; struct v4l2_format fmt; unsigned int min;// Get fixed screen information if (-1==xioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {printf("Error reading fixed information.\n");exit (EXIT_FAILURE); }// Get variable screen information if (-1==xioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {printf("Error reading variable information.\n");exit (EXIT_FAILURE); } screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;if (-1 == xioctl (fd, VIDIOC_QUERYCAP, &cap)) {if (EINVAL == errno) {fprintf (stderr, "%s is no V4L2 device\n",dev_name);exit (EXIT_FAILURE);} else {errno_exit ("VIDIOC_QUERYCAP");} }if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {fprintf (stderr, "%s is no video capture device\n",dev_name);exit (EXIT_FAILURE); }if (!(cap.capabilities & V4L2_CAP_STREAMING)) {fprintf (stderr, "%s does not support streaming i/o\n",dev_name);exit (EXIT_FAILURE); }CLEAR (fmt);fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; fmt.fmt.pix.width = SET_WIDTH;fmt.fmt.pix.height = SET_HEIGHT; fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;if (-1 == xioctl (fd, VIDIOC_S_FMT, &fmt))errno_exit ("VIDIOC_S_FMT");init_mmap(); }static void close_device (void) { if (-1 == close(fd))errno_exit ("close"); fd = -1; close(fbfd); }static void open_device (void) { //open framebuffer fbfd = open("/dev/fb0", O_RDWR); if (fbfd==-1) {printf("Error: cannot open framebuffer device./n");exit (EXIT_FAILURE); }//open camera fd = open (dev_name, O_RDWR| O_NONBLOCK, 0); if (-1 == fd) {fprintf (stderr, "Cannot open '%s': %d, %s/n",dev_name, errno, strerror (errno));exit (EXIT_FAILURE); } }int main (int argc,char ** argv){ dev_name = "/dev/video0";open_device(); init_device(); start_capturing();run(); stop_capturing(); uninit_device(); close_device(); exit (EXIT_SUCCESS);return 0; }
效果演示 用gcc编译好这个应用程序之后，使用ctrl+Alt+F1切换控制台，然后在运行这个应用程序，才能看到效果。。当然，运行这个程序之前，需要保证myvivi.ko这个驱动正常加载成功了。最后演示效果如下：
代码分析open_device从起点，到尽头，也许快乐，或有时孤独，
