Unable to make makefiles for maverick

[Pulock2012]

i am new to Ubuntu. i have been trying to port to linux but the region from which i come is still relatively new to computers and hence adheres to windows OSes. i have intermediate level knowledge of the c programming language. i have been trying to develop a driver for an USB device and i am stuck at making makefiles in maverick. my .c file is this:

#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/usb.h>
static int usb_notify_subscriber(struct notifier_block *self,unsigned long action,void *dev)
{
     printk(KERN_INFO "usb_notify_subscriber\n");
     switch(action)
     {
           case USB_DEVICE_ADD: printk(KERN_INFO"usb_notify_subscriber:USB     device added\n");break;
           case USB_DEVICE_REMOVE: printk(KERN_INFO"usb_notify_subscriber:USB device removed\n");break;
           case USB_BUS_ADD: printk(KERN_INFO"usb_notify_subscriber:USB bus added\n");break;
           case USB_BUS_REMOVE: printk(KERN_INFO"usb_notify_subscriber:USB bus removed\n");
     }
     return NOTIFY_OK;
}
int init_module(void)
{
     printk(KERN_INFO"Init USB simple subscriber.\n");
     usb_register_notify(&usb_simple_nb);
     return 0;
}
void cleanup_module(void)
{
     usb_unregister_notify(&usb_simple_nb);
     printk(KERN_INFO"remove USB simple subscriber\n");
}
MODULE_LICENSE("GPL");

and my makefile is this:

obj-m+=simple_usb_subscriber.o
all:
      make -C/lib/modules/$(shell uname -r)/build M=$(PWD)modules
clean:
      make -C/lib/modules/$(shell uname -r)/build M=$(PWD)clean

while trying to run the makefile i get the error message :
make: nothing to be done for 'all'.

please help.