Tomasz Myrta 
I lost some time trying to make this camera working using v4l2. Either
Samsung driver is broken or I didn't provide some important ioctl's. I
performed my tests on 2.6.28 kernel with fimc driver as .c sources and
2.6.38 kernel with already compiled binary drivers.
1. Capture mode
Enumerating capabilities returned: V4L2_CAP_VIDEO_CAPTURE and
V4L2_CAP_VIDEO_OVERLAY. There are 4 possible formats:
- YU12: 4:2:0, planar, Y-Cb-Cr
- 422P: 4:2:2, planar, Y-Cb-Cr
- YUYV: 4:2:2, packed, YCBYCR
- UYVY: 4:2:2, packed
They don't work. ioctl(VIDIOC_S_FMT) doesn't return error, but it also
doesn't fill properly v4l_fmt.fmt.pix.bytesperline and
v4l_fmt.fmt.pix.sizeimage. Overriding these values doesn't help. Reading
frames in "mmap" mode ends with "QUERYBUF for mmap failed 22: Invalid
argument". read(fd,...) doesn't work either.
2. Overlay mode
Enumerating capabilities returned the same values as in capture mode.
VIDIOC_G_FMT failed, but fimc sourcecode gave a hint that two formats are
possible:
- RGB565
- RGB24
If FriendlyARM/qtopia can show image from the camera, then there must be
some way to get these frames. Tracking cmos-camera application (it's closed
source) ioctls helped a lot. I would never guess that:
- overlay mode is used to capture frames
- there is V4L2_CAP_VIDEO_CAPTURE capability, but mmap doesn't work
- there is no support for V4L2_CAP_READWRITE capability, but you have to
use read(fd,...)
- RGB24 format gives you really RGB32 frames
I still don't know how to get better resolution than 640x512.
Anyway, if you want to capture some frames you have to:
int fd=open("/dev/video0", O_RDWR);
struct v4l2_framebuffer fb;
bzero(&fb,sizeof(fb));
fb.fmt.width=640;
fb.fmt.height=480;
fb.fmt.pixelformat=V4L2_PIX_FMT_RGB24;
ioctl(fd,VIDIOC_S_FBUF,&fb);
int some_int_1=1;
ioctl(fd, VIDIOC_OVERLAY, &some_int_1);
read(fd, buf, 640*480*3);
int some_int_0;
ioctl(fd, VIDIOC_OVERLAY, &some_int_0);
I hope this little tutorial will help you.
