// gcc -std=gnu99 -ggdb -L /home/gjasny/src/libv4l-0.3.7/libv4l2 -L /home/gjasny/src/libv4l-0.3.7/libv4lconvert -I/home/gjasny/src/libv4l-0.3.7/include -lv4l2 -lv4lconvert -o reqbufs reqbufs.c

#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/ioctl.h>
#include <linux/videodev2.h>

#if 1
# include <libv4l2.h>
# define my_ioctl       v4l2_ioctl
# define my_open        v4l2_open
# define my_close       v4l2_close
# define my_mmap        v4l2_mmap
#else
# define my_ioctl       ioctl
# define my_open        open
# define my_close       close
# define my_mmap        mmap
#endif

#define NBUFFERS        2
#define WIDTH           352
#define HEIGHT          288

struct buffer {
    void   *start;
    size_t length;
} g_buffers[NBUFFERS];

static int xioctl( int fd, unsigned long int request, void *arg )
{
    int r;

    do r = my_ioctl (fd, request, arg);
    while (r == -1 && errno == EINTR);

    return r;
}

int main(int argc, char *argv[])
{
    const char *device = "/dev/video0";

    int fd = my_open (device, O_RDWR);
    if (!fd) {
        perror ("open");
        return -1;
    }
    
    struct v4l2_format format;
    memset( &format, 0, sizeof(struct v4l2_format));
    format.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    format.fmt.pix.width       = WIDTH;
    format.fmt.pix.height      = HEIGHT;
    format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    format.fmt.pix.field       = V4L2_FIELD_ANY;

    if (xioctl (fd, VIDIOC_S_FMT, &format) == -1) {
        perror("ioctl (VIDIOC_S_FMT)");
        return -1;
    }

    // init mmap
    struct v4l2_requestbuffers m_req;
    memset( &m_req, 0, sizeof(struct v4l2_requestbuffers) );

    m_req.count   = NBUFFERS;
    m_req.type    = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    m_req.memory  = V4L2_MEMORY_MMAP;

    if (xioctl (fd, VIDIOC_REQBUFS, &m_req) == -1) {
        if (EINVAL == errno) {
            fprintf (stderr, "device does not support memory mapping.\n");
        } else {
            perror ("ioctl (VIDIOC_REQBUFS)");
        }
        return -1;
    }

    if (m_req.count < NBUFFERS) {
        fprintf (stderr, "Insufficient buffer memory.\n");
        return -1;
    }

    for (unsigned i = 0; i < m_req.count; ++i) {

        struct v4l2_buffer buf;
        memset( &buf, 0, sizeof(buf) );

        buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory      = V4L2_MEMORY_MMAP;
        buf.index       = i;

        if (xioctl (fd, VIDIOC_QUERYBUF, &buf) == -1) {
            perror("ioctl (VIDIOC_QUERYBUF)");
            return -1;
        }

        g_buffers[i].length = buf.length;
        g_buffers[i].start  = my_mmap (NULL /* start anywhere */,
                                       buf.length,
                                       PROT_READ | PROT_WRITE /* required */,
                                       MAP_SHARED /* recommended */,
                                       fd, buf.m.offset);

        if (g_buffers[i].start == MAP_FAILED) {
            perror("mmap");
            return -1;
        }
    }

    for (unsigned i = 0; i < NBUFFERS; ++i) {
        struct v4l2_buffer buf;
        memset( &buf, 0, sizeof(buf) );

        buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory      = V4L2_MEMORY_MMAP;
        buf.index       = i;

        if (xioctl (fd, VIDIOC_QBUF, &buf) == -1) {
            perror ("ioctl (VIDIOC_QBUF)");
            return -1;
        }
    }

    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (xioctl (fd, VIDIOC_STREAMON, &type) == -1) {
        perror("ioctl (VIDIOC_STREAMON)");
        return -1;
    }

    my_close (fd);

    return -1;
}