LDD3中提到驱动代码返回ERESTARTSYS和EINTR时如何选择：
Note the check on the return value of down_interruptible; if it returns nonzero, the operation was interrupted. The usual thing to do in this situation is to return -ERESTARTSYS。 Upon seeing this return code, the higher layers of the kernel will either restart the call from the beginning or return the error to the user. If you return -ERESTARTSYS , you must first undo any user-visible changes that might have been made, so that the right thing happens when the system call is retried. If you cannot undo things in this manner, you should return -EINTR instead.
即如果可以把用户看到的设备状态完全回滚到执行驱动代码之前，则返回ERESTARTSYS，否则返回EINTR。因为EINTR错误可以使系统调用失败，并且返回错误码为EINTR给应用程序。而ERESTARTSYS有可能会让kernel重新发起操作，而不会惊动应用程序。可以参考这篇帖子。