Linux – usb kernel module does not load on demand but works fine with insmod and modprobe from the shell

kernelkernel-moduleslinuxusb

I have a USB Linux Kernel module that compiles and builds. Running insmod loads my module and dmseg and tail -f /var/log/debug shows me it works as expected.

Running depmod -a then modprobe from the terminal loads the module and modprobe -r unloads and I see – tail -f /var/log/debug output as expected.

When I plug in my USB keyboard though it does not trigger and load on-demand as expected.

I have investigated /etc/udev/rules.d with no success. Any workarounds or guidance is most welcome. Am running Ubuntu 12.04.4 LTS with a Custom Linux Kernel 3.14.0

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/usb.h>
#include <linux/usb/input.h>
#include <linux/hid.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Aruna Hewapathirane");
MODULE_DESCRIPTION("A USB Keyboard Driver Kernel Module");

static struct usb_device_id usb_kbd_id_table[] = {
    { USB_INTERFACE_INFO(
        USB_INTERFACE_CLASS_HID,
        USB_INTERFACE_SUBCLASS_BOOT,
        USB_INTERFACE_PROTOCOL_KEYBOARD) },
    { } /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, usb_kbd_id_table);

static int __init kbd_init(void)
{
    printk(KERN_DEBUG "USB Keyboard Plugged In.. \n");
    return 0;
}

static void __exit kbd_exit(void)
{
    printk(KERN_DEBUG "USB Keyboard Removed.. \n");
    return ;
}

module_init(kbd_init);
module_exit(kbd_exit);

Best Answer

You are missing with usb_register and probe functions

Here is updated device driver with usb_register and probe functions 

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/usb.h>
#include <linux/usb/input.h>
#include <linux/hid.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Aruna Hewapathirane");
MODULE_DESCRIPTION("A USB Keyboard Driver Kernel Module");

static struct usb_device_id usb_kbd_id_table[] = {
    { USB_INTERFACE_INFO(
        USB_INTERFACE_CLASS_HID,
        USB_INTERFACE_SUBCLASS_BOOT,
    USB_INTERFACE_PROTOCOL_KEYBOARD) },
    { } /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, usb_kbd_id_table);

static int kbd_probe(struct usb_interface *interface,
    const struct usb_device_id *id)
{
    pr_info("USB keyboard probe function called\n");
    return 0;
}

static void kbd_disconnect(struct usb_interface *interface)
{
    pr_info("USB keyboard disconnect function called\n");
}

static struct usb_driver kbd_driver = {
    .name  = "usbkbd",
    .probe = kbd_probe,
    .disconnect = kbd_disconnect,
    .id_table = usb_kbd_id_table,
};

static int __init kbd_init(void)
{
    int res = 0;
    res = usb_register(&kbd_driver);
    if (res)
        pr_err("usb_register failed with error %d", res);
    return res;
}

static void __exit kbd_exit(void)
{
    pr_debug("USB Keyboard Removed..\n");
    usb_deregister(&kbd_driver);
    return;
}

module_init(kbd_init);
module_exit(kbd_exit);

Please refer previous SO question for probe function's use.

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