Function rt_device_open

components/drivers/core/device.c:222–282

* @brief This function will open a device. * * @param dev is the pointer of device driver structure. * * @param oflag is the flags for device open. * * @return the result, RT_EOK on successfully. */

 * @return the result, RT_EOK on successfully.
 */
rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflag)
{
    rt_err_t result = RT_EOK;

    /* parameter check */
    RT_ASSERT(dev != RT_NULL);
    RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);

    /* if device is not initialized, initialize it. */
    if (!(dev->flag & RT_DEVICE_FLAG_ACTIVATED))
    {
        if (device_init != RT_NULL)
        {
            result = device_init(dev);
            if (result != RT_EOK)
            {
                LOG_E("To initialize device:%.*s failed. The error code is %d",
                      RT_NAME_MAX, dev->parent.name, result);

                return result;
            }
        }

        dev->flag |= RT_DEVICE_FLAG_ACTIVATED;
    }

    /* device is a stand alone device and opened */
    if ((dev->flag & RT_DEVICE_FLAG_STANDALONE) &&
        (dev->open_flag & RT_DEVICE_OFLAG_OPEN))
    {
        return -RT_EBUSY;
    }

    /* device is not opened or opened by other oflag, call device_open interface */
    if (!(dev->open_flag & RT_DEVICE_OFLAG_OPEN) ||
         ((dev->open_flag & RT_DEVICE_OFLAG_MASK) != ((oflag & RT_DEVICE_OFLAG_MASK) | RT_DEVICE_OFLAG_OPEN)))
    {
        if (device_open != RT_NULL)
        {
            result = device_open(dev, oflag);
        }
        else
        {
            /* set open flag */
            dev->open_flag = (oflag & RT_DEVICE_OFLAG_MASK);
        }
    }

    /* set open flag */
    if (result == RT_EOK || result == -RT_ENOSYS)
    {
        dev->open_flag |= RT_DEVICE_OFLAG_OPEN;

        dev->ref_count++;
        /* don't let bad things happen silently. If you are bitten by this assert,
        * please set the ref_count to a bigger type. */
        RT_ASSERT(dev->ref_count != 0);
    }