How to perform sequential read in procfs? - c

Question

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/jiffies.h>
#include <linux/seq_file.h>
//extern uint64_t interrupt_time;
static struct proc_dir_entry *test_dir;
static int my_proc_show(struct seq_file *m, void *v)
{
seq_printf(m, "%lu\n", jiffies);
//seq_printf(m, "%lu", interrupt_time);
return 0;
}
static int my_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, my_proc_show, NULL);
}
static const struct file_operations tst_fops = {
.open = my_proc_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int __init test_init(void)
{
test_dir = proc_mkdir("myproc", NULL);
if (test_dir)
proc_create("jiffies", 0, test_dir, &tst_fops);
return 0;
}
static void __exit test_exit(void)
{
remove_proc_entry ("jiffies", test_dir);
proc_remove (test_dir);
}
module_init(test_init);
module_exit(test_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Test");
The above code is for procfs driver in which the above code contains the init function, exit function, file operation function but how to create a seq_read() function from kernel to user. What is the API for that?
This is the code I modified in /linuxversion/net/core/dev.c
int netif_rx(struct sk_buff *skb)
{
skb->tstamp = ktime_get_real(); //this will give a timestamp and it will be stored in //skb buffer
//I am calculating a timestamp here. because whenever kernel receive the data then the kernel is
//interrupted and start executing the newly arrived task but I have to read the time when the
//interrupt occurs and get the value of it.
}
My question is: How to copy this time-stamp to procfs?

Answer 1

I'm not sure if your issue is how to create and populate entries in /proc or how to read from an existing one. Regarding the latter:
how to read it to the user application
From the user program open /proc/foo/bar and read from it, as from any other file.