Hotplug module autoload part 1

When an hardware  device is plug-in to a system running Linux the linux kernel  try to match the device against its devices table entries .

In order to be included in the device entries table  the module should register it self in the following way :

Each device type (USB , PC card etc ) has it own matching structure  used to identify the device in the devices table .The declaration of device types can be found here.  Popular device type can be i2c , pci , usb , of 

examples for device id structure:

struct of_device_id
{
 char    name[32];
 char    type[32];
 char    compatible[128];
 const void *data;
};

The structure for usb devices :

struct usb_device_id {
 /* which fields to match against? */
 __u16           match_flags;

 /* Used for product specific matches; range is inclusive */
 __u16           idVendor;
 __u16           idProduct;
 __u16           bcdDevice_lo;
 __u16           bcdDevice_hi;

 /* Used for device class matches */
 __u8            bDeviceClass;
 __u8            bDeviceSubClass;
 __u8            bDeviceProtocol;

 /* Used for interface class matches */
 __u8            bInterfaceClass;
 __u8            bInterfaceSubClass;
 __u8            bInterfaceProtocol;

 /* Used for vendor-specific interface matches */
 __u8            bInterfaceNumber;

 /* not matched against */
 kernel_ulong_t  driver_info
         __attribute__((aligned(sizeof(kernel_ulong_t))));

Example for declaring id for usb device :
Declare the device it entry:
static const struct usb_device_id rio_table[] = {
{
USB_DEVICE(0x0841, 1) },              /* Rio 500 */
{ }                                     /* Terminating entry */
};
Were the USB_DEVICE macro is used to describe a specific USB device based on the vendor id and the product id.

MODULE_DEVICE_TABLE (usb, rio_table);
The MODULE_DEVICE_TABLE macro is used to declare the id table of a device.

References to the MODULE_DEVICE_TABLE can be found here.
#define MODULE_DEVICE_TABLE(type,name)

Declare the usb_driver structure :
static struct usb_driver rio_driver =
{
name ="rio500",
probe = probe_rio,
disconnect = disconnect_rio,
id_table = rio_table,
};
Name is a unique name among other USB drivers usually the module name.
Probe is called in order to check if this module can handle a particular USB interface if it can the probe callback although register the device 
Disconnect is called when the device is unplugged or shut down.

Call to register the usb device into the device table
module_usb_driver(rio_driver);