VIDEOS 》 Linux Kernel /sysfs Interface

/sysfs is one of the most popular kernel to user-space interface which you can leverage to add an interface to your Kernel code such as Kernel modules, Kernel Device Drivers, etc. Although personally I prefer /proc interface than other alternatives such as /sysfs, ioctl() and so on for my personal Kernel modules/stack.

So here is my detailed multi-episode Youtube video series on /sysfs Interface.

I also conduct sessions/classes on Systems and Network software programming and architecture. If you are interested, click HERE for more details.

Download this episode my entire kernel module sample code, make file, clean script HERE. And here is the same source code for a quick reference.

/* sysfs_example.c
 * Author: Kiran Kankipati
 * Updated: 14-May-2022
 * Release notes: this is the first version of Sample /sysfs read access file.
 * compatible with: 5.13.0-41-generic (Ubuntu 21.10) - as well tested with: 5.15.0-27-generic (Ubuntu 22.04 LTS)
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h> 
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/skbuff.h>  
#include <linux/udp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/proc_fs.h>
#include <linux/netlink.h>
#include <linux/mroute.h>
#include <net/checksum.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/arp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/inetpeer.h>
#include <net/protocol.h>
#include <net/flow.h>
#include <asm/types.h>
#include <asm/string.h>

static struct kobject *register_kobj;
static char *sysfs_buf;
#define SYSFS_BUF_MAX_SIZE 1024

static ssize_t sysfs_read_value(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
{ return sprintf(buf, "%s\n", sysfs_buf); }


static ssize_t __used sysfs_write_value(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count)
{ strcpy(sysfs_buf, buf); return count; }

static struct kobj_attribute sysfs_val_attribute = __ATTR( my_sysfs_file, 0660, sysfs_read_value, sysfs_write_value);

static int sysfs_module_init(void)
{
    sysfs_buf = kzalloc(SYSFS_BUF_MAX_SIZE, GFP_KERNEL); if(sysfs_buf==NULL) { return 0; }

    register_kobj = kobject_create_and_add("my_sysfs", kernel_kobj); { if(!register_kobj) { return -ENOMEM; } }


    if(sysfs_create_file(register_kobj, &sysfs_val_attribute.attr)) { printk("failed to create the my_sysfs_file file in /sys/kernel/my_sysfs/my_sysfs_file \n"); } 

    return 0;
}

static void sysfs_module_exit(void)
{
    kfree(sysfs_buf);
    kobject_put(register_kobj);
}


module_init(sysfs_module_init);
module_exit(sysfs_module_exit);

MODULE_DESCRIPTION("Sample /sysfs read/write access file");
MODULE_AUTHOR("Copyright(c) 2022 - Kiran Kankipati");
MODULE_LICENSE("GPL v2");