I would like to control various ov5640 camera parameters by using ioctl and VIDIOC_S_CTRL from V4L2 in the following manner:
#include <string>
#include <iostream>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <malloc.h>
#include <cstring>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#define IOCTL_TRIES 3
#define CLEAR(x) memset (&(x), 0, sizeof (x))
static int xioctl(int fd, int request, void *arg)
{
int r;
int tries = IOCTL_TRIES;
do {
r = ioctl(fd, request, arg);
} while (--tries > 0 && r == -1 && EINTR == errno);
return r;
}
bool v4l2_ctrl_set(int fd, uint32_t id, int val)
{
struct v4l2_control ctrl;
CLEAR(ctrl);
ctrl.id = id;
ctrl.value = val;
if (xioctl(fd, VIDIOC_S_CTRL, &ctrl) == -1) {
std::cout << "Failed to set ctrl with id "
<< id << " to value " << val
<< "\nerror (" << errno << "): " << strerror(errno) << std::endl;
return false;
}
return true;
}
int main()
{
int fd = open("/dev/video0", O_RDWR | O_NONBLOCK);
if (fd == -1) {
std::cout << "Failed to open the camera" << std::endl;
return -1;
}
v4l2_ctrl_set(fd, V4L2_CID_SATURATION, 100);
return 0;
}
Unfortunately ioctl fails and I get error (25): Inappropriate ioctl for device. I’m using Intrinsyc Open-Q 820 µSOM with linaro 4.14. I’ve managed to add some debugs prints to ov5640 driver file in ov5640_s_ctrl function before if (sensor->power_count == 0) { (in case there were problems with power save mode) and recompile the kernel. I ran the code, but looking through dmesg my printk message doesn’t get printed, so that means that ov5640_s_ctrl doesn’t get called even though the callback is set:
static const struct v4l2_ctrl_ops ov5640_ctrl_ops = {
.g_volatile_ctrl = ov5640_g_volatile_ctrl,
.s_ctrl = ov5640_s_ctrl,
};
Am I using V4L2 wrong? Should I enable something before setting the controls? It’s even more confusing since I manage to get an image from the camera with v4l2, but I can’t set/get any controls.
