understanding Debugfs

[Belisko Marek]

On Mon, Aug 20, 2012 at 10:45 AM, swair shah <swairshah at gmail.com> wrote:
> I'm trying to understand the use of debugfs with the use of this sample
> program.
>
> #include <linux/init.h>
> #include <linux/debugfs.h>
> #include <linux/module.h>
> #include <linux/fs.h>
>
> #define len 200
> u64 intvalue,hexvalue;
> struct dentry *dirret,*fileret,*u64int,*u64hex;
> char ker_buf[len];
> int filevalue;
> /* read file operation */
> static ssize_t myreader(struct file *fp, char __user *user_buffer,
>                                 size_t count, loff_t *position){
>      return simple_read_from_buffer(user_buffer, count, position, ker_buf,
> len);
> }
>
> /* write file operation */
> static ssize_t mywriter(struct file *fp, const char __user *user_buffer,
>                                 size_t count, loff_t *position){
>         if(count > len )
>                 return -EINVAL;
>
>         return simple_write_to_buffer(ker_buf, len, position, user_buffer,
> count);
> }
>
> static const struct file_operations fops_debug = {
>         .read = myreader,
>         .write = mywriter,
> };
>
> static int __init init_debug(void)
> {
>     /* create a directory by the name dell in /sys/kernel/debugfs */
>     dirret = debugfs_create_dir("dell", NULL);
>
>     /* create a file in the above directory
>     This requires read and write file operations */
>     fileret = debugfs_create_file("text", 0644, dirret, &filevalue,
> &fops_debug);
>
>     /* create a file which takes in a int(64) value */
>     u64int = debugfs_create_u64("number", 0644, dirret, &intvalue);
>     if (!u64int) {
>         printk("error creating int file");
>         return (-ENODEV);
>     }
>     /* takes a hex decimal value */
>     u64hex = debugfs_create_x64("hexnum", 0644, dirret, &hexvalue );
>     if (!u64hex) {
>         printk("error creating hex file");
>         return (-ENODEV);
>     }
>
>     return (0);
> }
> module_init(init_debug);
>
> static void __exit exit_debug(void){
>     debugfs_remove_recursive(dirret);
> }
> module_exit(exit_debug);
>
> Shouldn't it create a dir named 'dell' in sys/kernel/debug ?. (debugfs is
> mounted.)
> Can someone explain the use of debugfs or may be point to some good
> resources?
Documentation/filesystems/debugfs.txt
>
> thanks!
> swair
>
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>

cheers,

marek

-- 
as simple and primitive as possible
-------------------------------------------------
Marek Belisko - OPEN-NANDRA
Freelance Developer

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