内核新的ioctl方式--unlocked_ioctl和compat_ioctl(解决error:unknown field 'ioctl' specified in initializer)

2026-08-18 17:17:39 +08:00 · 2017-05-08 19:25:22 +08:00
parent a9a43202c7
commit c3b0854f0f
1 changed files with 130 additions and 1 deletions
@@ -1,4 +1,4 @@
-内核新的ioctl方式--unlocked_ioctl和compat_ioctl
+内核新的ioctl方式--unlocked_ioctl和compat_ioctl(解决error:unknown field 'ioctl' specified in initializer)
 =======


@@ -18,6 +18,135 @@
 <br>


+#1	问题
+-------
+
+把早期 `2.6.32`之前的驱动移植到新的内核中, 如果驱动中定义了 `ioctl` 接口, 老是会提示如下错误
+
+>error:unknown field 'ioctl' specified in initializer
+
+
+#2	原因
+-------
+
+单从字面上看, 可以看出是目前我们驱动中定义的 `ioctl` 接口与内核中 `file_operations` 结构 `ioctl` 函数的定义接口不同.
+
+那么内核到底中到底经历了什么呢?
+
+
+去查看 `file_operations` 结构体的定义, 可以发现原因是 :
+
+在 `2.6.36` 内核上 `file_operations` 发生了重大的改变 :
+
+原先的, 参见[include/linux/fs.h, version 2.6.17, line 1015](http://elixir.free-electrons.com/linux/v2.6.17.14/source/include/linux/fs.h#L1015)
+
+>int (*ioctl)(struct inode*, struct file*, unsigned int, unsigned long);
+
+被改为了, 参见[include/linux/fs.h, version 4.11, line 1654](http://elixir.free-electrons.com/linux/v4.11/source/include/linux/fs.h#L1654),
+
+>long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
+>
+>long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
+
+
+具体 `file_operations` 的实现可以参见[include/linux/fs.h, version 4.11, line 1654](http://elixir.free-electrons.com/linux/v4.11/source/include/linux/fs.h#L1654), 
+
+邮件列表参见[The new way of ioctl()](https://lwn.net/Articles/119652/)
+
+早期为了保证兼容性, `file_operations` 结构体中仍然包含 `ioctl` 函数指针成员, 但是在 `kernel 3.0` 中已经完全删除了 `struct file_operations` 中的 `ioctl` 函数指针
+
+
+
+#3	解决方案
+-------
+
+
+因而在实际驱动中, 我们需要
+
+*	将原先的写的 `ioctl` 函数声明给改成下面的 `unlocked_ioctl` 或者 `compat_ioctl`, 
+
+*	在 `file_operations` 结构体的初始化中也是一样. 修改为`unlocked_ioctl` 或者 `compat_ioctl`, 
+
+*	注意参数的兼容性问题, 新的`ioctl()` 接口没有 `struct inode*` 参数, 如果`ioctl` 接口中使用了 `inode`, 因此需要通过其他方式获取 `inode`
+
+内核提供了接口 `file_inode` 来通过文件指针 `file` 来获取其 `inode` 信息, 该函数定义在[include/linux/fs.h, version 4.11, line 1213](http://elixir.free-electrons.com/linux/v4.11/source/include/linux/fs.h#L1213), 如下所示
+
+```cpp
+static inline struct inode *file_inode(const struct file *f)
+{
+	return f->f_inode;
+}
+```
+
+因此解决方案如下 :
+
+
+1.	首先是将 `ioctl` 的实现转换为 `unlock_ioctl`
+
+```cpp
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
+static int XXX_ioctl(
+		struct inode *indoe,
+        struct file *file,
+		unsigned int cmd,
+        unsigned long arg)
+{
+#else
+//long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
+//long (*compat_ioctl) (struct file *file, unsigned int cmd, unsigned long arg)
+static long XXX_unlocked_ioctl(
+		struct file *file,
+        unsigned int cmd,
+        unsigned long arg)
+{
+    //struct inode *inode = file->f_dentry->d_inode;
+    //struct inode *inode = file->d_inode;
+    struct inode *inode = inode = file_inode(file);
+#endif
+	/*  此处是ioctl() 函数结构的具体实现  */
+}
+```
+
+`file_operations` 结构体初始化的过程采取同样的操作
+
+```cpp
+static struct file_operations fpga_fops = {
+	.owner 	= THIS_MODULE,
+	.open	= fpga_open,
+	.read	= fpga_read,
+	.write = fpga_write,
+	.llseek = fpga_llseek,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
+    .ioctl = XXX_ioctl,
+#else
+    .compat_ioctl = XXX_unlocked_ioctl,
+#endif
+};
+```
+
+
+#4	参照
+-------
+
+
+[ioctl 变成了 unlocked_ioctl](http://blog.csdn.net/ypist/article/details/6664973)
+
+[ Linux字符设备驱动入门（二）——加入ioctl功能](http://blog.csdn.net/coolkids_2008/article/details/6982305)
+
+[内核新的ioctl方式---- unlocked_ioctl和compat_ioctl](http://www.cnblogs.com/hfww/archive/2012/03/31/2426717.html)
+
+[error: unknown field 'ioctl' specified in initializer](http://www.360doc.com/content/14/0127/14/14450281_348317383.shtml)
+
+[error: unknown field 'ioctl' specified in initializer](http://blog.chinaunix.net/uid-20620288-id-3066368.html)
+
+[error: unknown field ‘ioctl’ specified in initializer](http://blog.csdn.net/zhou1232006/article/details/6867584)
+
+[error:unknown field 'ioctl' specified in initializer](http://www.cnblogs.com/xiaoya901109/archive/2012/07/13/2589623.html)
+
+[error: unknown field 'ioctl' specified in initializer](http://blog.csdn.net/yusiguyuan/article/details/16829299)
+
+[error: unknown field 'ioctl' specified in initializer问题](http://blog.csdn.net/yuhaibin168/article/details/7711994)
+


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