/*
 * v4l2loopback.c  --  video4linux2 loopback driver
 *
 * Copyright (C) 2014 Nicolas Dufresne
 */

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/videodev2.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <stdlib.h>

#define COUNT 4
#define sysfail(msg)                                               \
	{                                                          \
		printf("%s failed: %s\n", (msg), strerror(errno)); \
		return -1;                                         \
	}

void usage(const char *progname)
{
	printf("usage: %s <videodevice>\n", progname);
	exit(1);
}

int main(int argc, char **argv)
{
	struct v4l2_format fmt = { 0 };
	struct v4l2_requestbuffers breq = { 0 };
	struct v4l2_buffer bufs[COUNT];
	void *data[COUNT] = { 0 };
	int fd;
	int i;

	if (argc < 2)
		usage(argv[0]);

	fd = open(argv[1], O_RDWR);
	if (fd < 0)
		sysfail("open");

	fmt.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
	fmt.fmt.pix.width = 320;
	fmt.fmt.pix.height = 240;
	fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB32;

	if (ioctl(fd, VIDIOC_S_FMT, &fmt) < 0)
		sysfail("S_FMT");

	breq.count = COUNT;
	breq.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
	breq.memory = V4L2_MEMORY_MMAP;

	if (ioctl(fd, VIDIOC_REQBUFS, &breq) < 0)
		sysfail("REQBUFS");

	assert(breq.count == COUNT);

	memset(bufs, 0, sizeof(bufs));

	for (i = 0; i < COUNT; i++) {
		int p;

		bufs[i].index = i;
		bufs[i].type = breq.type;
		bufs[i].memory = breq.memory;

		if (ioctl(fd, VIDIOC_QUERYBUF, &bufs[i]) < 0)
			sysfail("QUERYBUF");

		data[i] = mmap(NULL, bufs[i].length, PROT_WRITE, MAP_SHARED, fd,
			       bufs[i].m.offset);
		if (data[i] == MAP_FAILED)
			sysfail("mmap");

		for (p = 0; p < (bufs[i].bytesused >> 2); p++)
			((unsigned int *)data[i])[p] = 0xFF00FF00;
	}

	if (ioctl(fd, VIDIOC_QBUF, &bufs[0]) < 0)
		sysfail("QBUF");

	if ((bufs[0].flags & V4L2_BUF_FLAG_QUEUED) == 0) {
		printf("BUG #1: Driver should set the QUEUED flag before returning from QBUF\n");
		bufs[0].flags |= V4L2_BUF_FLAG_QUEUED;
	}

	if (ioctl(fd, VIDIOC_STREAMON, &fmt.type) < 0)
		sysfail("STREAMON");

	i = 1;
	while (1) {
		struct v4l2_buffer buf = { 0 };

		if (ioctl(fd, VIDIOC_QBUF, &bufs[i]) < 0)
			sysfail("QBUF");

		printf("\tQUEUED=%d\tDONE=%d\n",
		       bufs[i].flags & V4L2_BUF_FLAG_QUEUED,
		       bufs[i].flags & V4L2_BUF_FLAG_DONE);

		if ((bufs[i].flags & V4L2_BUF_FLAG_QUEUED) == 0) {
			printf("BUG #1: Driver should set the QUEUED flag before returning from QBUF\n");
			bufs[i].flags |= V4L2_BUF_FLAG_QUEUED;
		}

		buf.type = breq.type;
		buf.memory = breq.memory;

		if (ioctl(fd, VIDIOC_DQBUF, &buf) < 0)
			sysfail("DBBUF");

		i = buf.index;

		if ((bufs[i].flags & V4L2_BUF_FLAG_QUEUED) == 0) {
			printf("BUG #2: Driver should not dequeue a buffer that was not initially queued\n");
		}

#if 0
    assert (bufs[i].flags & V4L2_BUF_FLAG_QUEUED);
    assert (!(buf.flags & (V4L2_BUF_FLAG_QUEUED | V4L2_BUF_FLAG_DONE)));
#endif
		bufs[i] = buf;
	}

	return 0;
}