设备树中设备的禁用和启用

谁践踏了优雅 2022-06-04 07:16 383阅读 0赞

# 简介 #

device tree中的status标识了设备的状态，使用status可以去禁止设备或者启用设备，看下设备树规范中的status可选值

![这里写图片描述][SouthEast]

默认情况下不设置status属性设备是使能的，下面看两具体的例子  
![这里写图片描述][SouthEast 1]  
![这里写图片描述][SouthEast 2]

下面是设备树中节点属性status的处理代码，位于内核的drivers/of/base.c中

static bool __of_device_is_available(const struct device_node *device)
    {
        const char *status;
        int statlen;
    
        if (!device)
            return false;
    
        status = __of_get_property(device, "status", &statlen);
        if (status == NULL)
            return true; //默认为使能
    
        if (statlen > 0) {
            if (!strcmp(status, "okay") || !strcmp(status, "ok")) //ok和okay都可以
                return true;
        }
        //表中的fail和fail-sss没做具体处理
        return false;
    }
    
    /** * of_device_is_available - check if a device is available for use * * @device: Node to check for availability * * Returns true if the status property is absent or set to "okay" or "ok", * false otherwise */
    bool of_device_is_available(const struct device_node *device)
    {
        unsigned long flags;
        bool res;
    
        raw_spin_lock_irqsave(&devtree_lock, flags);
        res = __of_device_is_available(device);
        raw_spin_unlock_irqrestore(&devtree_lock, flags);
        return res;
    
    }
    EXPORT_SYMBOL(of_device_is_available);

设备数规范下载地址：  
[http://download.csdn.net/download/x356982611/10149254][http_download.csdn.net_download_x356982611_10149254]

# 引用 #

> [http://blog.csdn.net/x356982611/article/details/78740011][http_blog.csdn.net_x356982611_article_details_78740011]  
> [https://www.devicetree.org/][https_www.devicetree.org]

[SouthEast]: /images/20220604/4f7fe81581b04b21a0c34dd8afcc61ce.png
[SouthEast 1]: /images/20220604/9103272e019041dc8b8ce7c7d07c3137.png
[SouthEast 2]: /images/20220604/b2f921fc3fe047cc96bfd2d6be23d2af.png
[http_download.csdn.net_download_x356982611_10149254]: http://download.csdn.net/download/x356982611/10149254
[http_blog.csdn.net_x356982611_article_details_78740011]: http://blog.csdn.net/x356982611/article/details/78740011
[https_www.devicetree.org]: https://www.devicetree.org/