Function open_device

rustcv-camera/src/backend/linux/sys.rs:376–385

Open a V4L2 device node (e.g., "/dev/video0"). 打开 V4L2 设备节点（如 "/dev/video0"）。 Opens with `O_RDWR` (read/write) without `O_NONBLOCK`. Without `O_NONBLOCK`, `DQBUF` will block until a frame is ready, which is the desired behavior for maximum throughput. 以 `O_RDWR`（读写）模式打开，不加 `O_NONBLOCK`。 不加 `O_NONBLOCK` 时，`DQBUF` 会阻塞直到帧就绪， 这是取得最大吞吐量的期望行为。

(path: &str)

/// 不加 `O_NONBLOCK` 时，`DQBUF` 会阻塞直到帧就绪，
/// 这是取得最大吞吐量的期望行为。
pub fn open_device(path: &str) -> io::Result<RawFd> {
    let c_path =
        std::ffi::CString::new(path).map_err(|_| io::Error::other("invalid device path"))?;
    let fd = unsafe { libc::open(c_path.as_ptr(), libc::O_RDWR) };
    if fd == -1 {
        Err(io::Error::last_os_error())
    } else {
        Ok(fd)
    }
}

/// Close a V4L2 device file descriptor.
/// 关闭 V4L2 设备文件描述符。