implement a read operation list in debugfs

i’m implementing a kernel module. using several techniques. 1 of them is to give read/write to different module variables. i was able to read/write all variables except the list i have in my module. the linked list:

    static struct node {
        struct list_head list;
        unsigned int x;
        struct tm time;
    };

i would like to have a corresponding file in debugfs that will print the full list. i tried all the ‘simple’ read functions , but none of them actually work.. 🙁

Answer

You can read list using function similar to this one:

struct k_list {                                                                 
        struct list_head links;                                                     
        int data;                                                                   
};                                                                              

struct k_list my_list;

static ssize_t pop_queue(struct file * file,                                       
                                char *buf,                                         
                                size_t count,                                      
                                loff_t *ppos)                                      
{                                                                                  
        struct list_head *pos, *q;                                                 
        struct k_list *tmp;                                                        

        printk(KERN_INFO "--Listing inserted numbers--");                          
        list_for_each_safe(pos, q, &my_list.links) {                               
                tmp = list_entry(pos, struct k_list, links);                       
                printk(KERN_INFO "object: %d ", tmp->data);                        
        }                                                                          
        printk(KERN_INFO "--End of list--");                                       

        return count;                                                              
}