linux 模块编译错误

旧城等待， 2022-06-12 02:50 424阅读 0赞

在为android kernel编写模块的时候，将之前另一个工程的ko包驱动移植到新系统工程下，配置kernledir 等参数后，编译出现

warning: initialization from incompatible pointer type \[enabled by default\]

error, forbidden warning:

错误，因为在之前工程中编译没有问题，（因为之前的工程没有开始warning 停止选项)。

其中报警与错误信息解释如下

warning: initialization from incompatible pointer type \[enabled by default\]

表示编写的函数与系统中默认的函数参数不全相同。

error, forbidden warning:

表示开启了编译出现warning时退出报错选项，在这里是因为之前报了函数参数类型不相同的警告，所以编译停止报错。

查找了出错代码行 内容如下：

static const struct file\_operations mytest\_proc\_fops = \{  
.owner = THIS\_MODULE,  
.read=xxx\_proc\_read,  
.write=xxx\_proc\_write,  
  
  
\};

代码中实现的函数命名为

static ssize\_t xxx\_proc\_write(struct file\* filp,char \_\_user \*buf,size\_t count,loff\_t\* f\_pos)

而查找file\_operations  中对于.write的命名为：

struct file_operations {
     struct module *owner;
      loff_t(*llseek) (struct file *, loff_t, int);
      ssize_t(*read) (struct file *, char __user *, size_t, loff_t *);
      ssize_t(*aio_read) (struct kiocb *, char __user *, size_t, loff_t);
      ssize_t(*write) (struct file *, const char __user *, size_t, loff_t *);
      ssize_t(*aio_write) (struct kiocb *, const char __user *, size_t,
             loff_t);
     int (*readdir) (struct file *, void *, filldir_t);
     unsigned int (*poll) (struct file *, struct poll_table_struct *);
     int (*ioctl) (struct inode *, struct file *, unsigned int,
            unsigned long);
     int (*mmap) (struct file *, struct vm_area_struct *);
     int (*open) (struct inode *, struct file *);
     int (*flush) (struct file *);
     int (*release) (struct inode *, struct file *);
     int (*fsync) (struct file *, struct dentry *, int datasync);
     int (*aio_fsync) (struct kiocb *, int datasync);
     int (*fasync) (int, struct file *, int);
     int (*lock) (struct file *, int, struct file_lock *);
      ssize_t(*readv) (struct file *, const struct iovec *, unsigned long,
         loff_t *);
      ssize_t(*writev) (struct file *, const struct iovec *, unsigned long,
          loff_t *);
      ssize_t(*sendfile) (struct file *, loff_t *, size_t, read_actor_t,
            void __user *);
      ssize_t(*sendpage) (struct file *, struct page *, int, size_t,
            loff_t *, int);
     unsigned long (*get_unmapped_area) (struct file *, unsigned long,
             unsigned long, unsigned long,
             unsigned long);
    };

其中 ssize_t(*write) (struct file *, const char __user *, size_t, loff_t *); static ssize_t xxx_proc_write(struct file* filp,char __user *buf,size_t count,loff_t* f_pos)
     对比，第二个参数缺少了一个const 添加上后，编译警告去除，并编译通过。 
     总结： 在编写linux 驱动代码时，对于系统中定义的结构体中的函数，每个参数需要对应正确，否则会出现警告。不要凭印象，直接从相应结构体 头文件中获取函数参数为佳。