Function rt_device_read

components/drivers/core/device.c:337–362

* @brief This function will read some data from a device. * * @param dev is the pointer of device driver structure. * * @param pos is the position when reading. * * @param buffer is a data buffer to save the read data. * * @param size is the size of buffer. * * @return the actually read size on successful, otherwise 0 will be returned. * * @note the unit of size/pos is a block for bloc

 * @note the unit of size/pos is a block for block device.
 */
rt_ssize_t rt_device_read(rt_device_t dev,
                         rt_off_t    pos,
                         void       *buffer,
                         rt_size_t   size)
{
    /* parameter check */
    RT_ASSERT(dev != RT_NULL);
    RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);

    if (dev->ref_count == 0)
    {
        rt_set_errno(-RT_ERROR);
        return 0;
    }

    /* call device_read interface */
    if (device_read != RT_NULL)
    {
        return device_read(dev, pos, buffer, size);
    }

    /* set error code */
    rt_set_errno(-RT_ENOSYS);

    return 0;
}
RTM_EXPORT(rt_device_read);

/**