#include <linux/module.h>
#include <linux/version.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/seq_file.h>

MODULE_LICENSE("GPL");

static void *IteratorStart(struct seq_file *m, loff_t *Index)
{
   int i;
   struct task_struct *tptr = current;

   for( i = (int)*Index; i && tptr != tptr->parent; i-- )
	tptr = tptr->parent;
   if( tptr == tptr->parent )
	return NULL;
   return (void *)tptr;
}

static void IteratorStop(struct seq_file *m, void *ObjectIdent)
{
   return;
}

static void *IteratorNext(struct seq_file *m, void *ObjectIdent, loff_t *pos)
{
   struct task_struct *tptr = ( struct task_struct * )ObjectIdent;

   if( tptr == tptr->parent ) {
		return NULL;
   }
   (*pos)++;
   return (void *)tptr->parent;
}

static int SFShow(struct seq_file *m, void *ObjectIdent)
{
   struct task_struct *tptr = ( struct task_struct * )ObjectIdent;

   seq_printf( m, "Prozess PID: %d\n", tptr->pid );
   seq_printf( m, "     Eltern: %p\n", tptr->parent );
   return 0;
}

static struct seq_operations sops = {
   .start = IteratorStart,
   .next  = IteratorNext,
   .stop  = IteratorStop,
   .show  = SFShow,
};

static int call_seq_open( struct inode *GeraeteDatei, struct file *Instanz )
{
   return seq_open( Instanz, &sops );
}

static struct file_operations fops = {
   .open    = call_seq_open,
   .read    = seq_read,
   .llseek  = seq_lseek,
   .release = seq_release,
};

static int __init ProcInit(void)
{
   static struct proc_dir_entry *procdirentry;

   procdirentry=create_proc_entry( "SequenceFileTest", 0, NULL );
   if( procdirentry ) {
	procdirentry->proc_fops = &fops;
   }
   return 0;
}

static void __exit ProcExit(void)
{
   remove_proc_entry( "SequenceFileTest", NULL );
}

module_init( ProcInit );
module_exit( ProcExit );