sensor read函数咋直接把data_len=0了

发布于 2024-09-03 21:09:23 浏览：176 订阅该版

```c
static rt_ssize_t rt_sensor_read(rt_device_t dev, rt_off_t pos, void *buf, rt_size_t len)
{
    rt_sensor_t sensor = (rt_sensor_t)dev;
    rt_size_t result = 0;
    RT_ASSERT(dev != RT_NULL);
    if (buf == NULL || len == 0)
    {
        return 0;
    }

if (sensor->module)
    {
        rt_mutex_take(sensor->module->lock, RT_WAITING_FOREVER);
    }

/* The buffer is not empty. Read the data in the buffer first */
    if (sensor->data_len > 0)
    {
        if (len > sensor->data_len / sizeof(struct rt_sensor_data))
        {
            len = sensor->data_len / sizeof(struct rt_sensor_data);
        }

rt_memcpy(buf, sensor->data_buf, len * sizeof(struct rt_sensor_data));

/* Clear the buffer */
        sensor->data_len = 0;
        result = len;
    }
    else
    {
        /* If the buffer is empty read the data */
        if (sensor->ops->fetch_data !=  RT_NULL)
        {
            result = sensor->ops->fetch_data(sensor, buf, len);
        }
    }

if (sensor->module)
    {
        rt_mutex_release(sensor->module->lock);
    }

return result;
}
```
如果想把传感器做成fifo应该是会用到这个sensor->data_len,万一len是小于data_len的，没理解为啥这个地方27行直接等于0了。不知道我的理解对不对