Method allocate_buffers

rustcv-camera/src/backend/linux/mod.rs:402–424

Allocate mmap buffers from the kernel. 从内核分配 mmap 缓冲区。 Steps: 1. VIDIOC_REQBUFS — ask kernel for N buffers 2. For each buffer: VIDIOC_QUERYBUF → mmap() 步骤： 1. VIDIOC_REQBUFS —— 向内核请求 N 个缓冲区 2. 对每个缓冲区：VIDIOC_QUERYBUF → mmap()

(&mut self, count: u32)

    /// 1. VIDIOC_REQBUFS —— 向内核请求 N 个缓冲区
    /// 2. 对每个缓冲区：VIDIOC_QUERYBUF → mmap()
    fn allocate_buffers(&mut self, count: u32) -> Result<()> {
        let req = v4l2_sys::request_buffers(self.fd, count)?;
        let actual_count = req.count;

        if actual_count < 2 {
            return Err(CameraError::BufferAllocationFailed);
        }

        let mut buffers = Vec::with_capacity(actual_count as usize);

        for i in 0..actual_count {
            let buf = v4l2_sys::query_buffer(self.fd, i)?;
            let length = buf.length as usize;
            let offset = unsafe { buf.m.offset };

            let ptr = v4l2_sys::mmap_buffer(self.fd, length, offset)?;

            buffers.push(MmapBuffer { ptr, length });
        }

        self.buffers = buffers;
        Ok(())
    }
}

impl Drop for V4l2Backend {