Simple Kernel Module for USB

I am trying to get familiar with Linux Kernel Module. So I have written this simplest module which works on usb. I am not sure what I am missing. The module is being loaded. Also on dmesg I can see this :

   [27245.911387] usbcore: registered new interface driver testusb
   [27245.911392] testusb: driver registered successfully

but when I insert a usb stick my testusb_probe function is not getting called. Any idea where I am going wrong. here is the code of the module:

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


   static int testusb_probe(struct usb_interface *interface, const struct usb_device_id *id)
   {
    printk("testusb: probe module\n");
    return 0;
   }


   static void testusb_disconnect(struct usb_interface *interface)
   {
    printk("testusb: disconnect module\n");
   }


   static struct usb_driver testusb_driver = {
           name: "testusb",
        probe: testusb_probe,
           disconnect: testusb_disconnect,
   };

   static int __init testusb_init(void)
   {
           int result;

      开发者_运维知识库     result = usb_register(&testusb_driver);
           if (result) {
                   printk("testusb: registering driver failed");
           } else {
                   printk("testusb: driver registered successfully");
           }

           return result;
   }


   static void __exit testusb_exit(void)
   {
           usb_deregister(&testusb_driver);
           printk("testusb: module deregistered");
   }

   module_init(testusb_init);
   module_exit(testusb_exit);

   MODULE_AUTHOR("Dal Chand");
   MODULE_LICENSE("GPL");

Your test driver is not enabled the USB hotplug.

http://www.linuxjournal.com/node/4786/print

/* Define these values to match your devices */
#define USB_VENDOR_ID      0xfff0
#define USB_PRODUCT_ID     0xfff0

/* table of devices that work with this driver */
static struct usb_device_id test_table [] = {
        { USB_DEVICE(USB_VENDOR_ID, USB_PRODUCT_ID) },
        { }                                     /* Terminating entry */
};
MODULE_DEVICE_TABLE (usb, test_table);

USB_VENDOR_ID and USB_PRODUCT_ID is your usb stick's IDs. If you don't know IDs, check dmesg message when you insert the stick.

According to a comment in the kernel source code above struct usb_driver in linux/usb.h:

USB interface drivers must provide a name, probe() and disconnect()
methods, and an id_table.  Other driver fields are optional.

The id_table is used in hotplugging.  It holds a set of descriptors,
and specialized data may be associated with each entry.  That table
is used by both user and kernel mode hotplugging support.

Your testusb_driver struct is incorrect. You need to set the id_table field.

This requires creating an array of struct usb_device_id which will be used by the USB subsystem to match the device. This array needs to be exported with MODULE_DEVICE_TABLE(usb, ...). The answer given by Wataru is an excellent example.

You have to register driver for notifications from usbcore. Following code should work:

static int usb_notify(struct notifier_block *self, unsigned long action, void *dev) { 
    printk(KERN_INFO “USB device added \n”); 
    switch (action) { 
    case USB_DEVICE_ADD: 
        printk(KERN_INFO “USB device added \n”);
        break;
    case USB_DEVICE_REMOVE: 
        printk(KERN_INFO “USB device removed \n”); 
        break; 
    case USB_BUS_ADD: 
        printk(KERN_INFO “USB Bus added \n”); 
        break; 
    case USB_BUS_REMOVE: 
        printk(KERN_INFO “USB Bus removed \n”); 
    } 
    return NOTIFY_OK; 
} 

static struct notifier_block usb_nb = { 
    .notifier_call = usb_notify, 
}; 

int init_module(void) { 
    printk(KERN_INFO “Init USB hook.\n”); 
    /* 
    * Hook to the USB core to get notification on any addition or removal of USB devices */ 
    usb_register_notify(&usb_nb); 
    return 0; 
}

void cleanup_module(void) { 
    /* 
    * Remove the hook */ 
    usb_unregister_notify(&usb_nb); 
    printk(KERN_INFO “Remove USB hook\n”);
}