USB device driver under Linux

This paper explains USB device driver with USB mouse.

When calling the Usb_register (struct Usb_driver *) function in the driver, first determine if the USB bus driver supports id_table defined in the Usb_driver, and if so, Usb_driver probe function is called.

So the first thing to do is to define and initialize the USB_DRIVER structure:

Static struct usb_driver usbmouse_as_key_driver = {     "usbmouse_as_key" ,      = Usbmouse_as_key_probe,     = Usbmouse_as_key_disconnect,     = usbmouse_as_key_id_ Table,};

Construction Id_table:

Static struct usb_device_id usbmouse_as_key_id_table[] = {     {usb_interface_info (Usb_interface_class_hid, Usb_interface_subclass, Usb_interface_protocol_mouse)},     {},};

Constructs the probe and disconnect functions: the USB transport needs to use the URB, the definition urb:

Static structURB *uk_urb;Static intUsbmouse_as_key_probe (structUsb_interface *intf,Const structUSB_DEVICE_ID *ID) {     structUsb_device *dev = Interface_to_usbdev (intf);/*device acquired by interface*/     structUsb_host_interface *Interface;/*Setting Descriptor*/     structUsb_endpoint_descripter *endpoint;/*Endpoint Descriptor*/     intpipe; Interface= intf->cur_alterseting;/*Get Set Descriptor*/Endpoint= &Interface->endpoint[0].desc;/*get the endpoint descriptor*/          /*Assigning Settings Input_dev*/Uk_dev=Input_allocate_device (); Set_bit (Ev_key, Uk_dev-evbit); Set_bit (Ev_rep, Uk_dev-evbit); Set_bit (key_l, Uk_dev-keybit); Set_bit (key_s, Uk_dev-keybit); Set_bit (Key_enter, Uk_dev-keybit);          Input_register_device (Uk_dev); /*Structuring data transfer 3 features*/     /*Source*/Pipe= Usb_rcvintpipe (dev, endpoint->bendpointaddress);//generates an interrupt pipeline and assigns the resulting pipe to the URB     /*length*/Len= endpoint->wmaxpacketsize; /*Purpose*/Uk_buf= Usb_buffer_alloc (0, Gfp_kernel); /*URB fill interrupts with three-factor settings Urb*/usb_fill_int_urb (uk_urb, Dev, pipe, usb_buf, Len, USBMOUSE_AS_KEY_IRQ, NULL, endpoint-binterval); Uk_urb-&GT;TRANSER_DMA =Usb_buf_phys; Uk_urb->transfer_flags |=Urb_no_transfer_dma_rep; Usb_submit_urb (Uk_urb, gfp_kernel);/*submit the URB to the USB core*/     return 0;}Static voidUsbmouse_as_key_disconnect (structUsb_interface *intf) {     structUsb_device *dev =Interface_to_usbdev (intf); //printk ("Disconnect usbmouse!\n");usb_kill_urb (UK_URB);     Usb_free_urb (UK_URB);     Usb_buffer_free (Dev, Len, usb_buf, Usb_buf_phys);     Input_unregister_device (Uk_dev); Input_free_device (Uk_dev);}Static voidUSBMOUSE_AS_KEY_IRQ (structURB *URB) {     StaticUnsignedCharPre_val; /*USB mouse Data meaning * Data[0]: bit0-left button, 1-Press, 0-release * bit1-right, 1-Press, 0-release * bit2-Middle Key, 1-Press, 0-release *     */     if((Pre_val & (1<<0)! = (usb_buf[0] & (1<<0))) {          /*the left button has changed.*/input_event (Uk_dev, Ev_key, key_l, (usb_buf[0] & (1<<0)) ?1:0);     Input_sync (Uk_dev); }     if((Pre_val & (1<<1)! = (usb_buf[0] & (1<<1))) {          /*the right button has changed*/input_event (Uk_dev, Ev_key, key_s, (usb_buf[0] & (1<<1)) ?1:0);     Input_sync (Uk_dev); }     if((Pre_val & (1<<2)! = (usb_buf[0] & (1<<2))) {          /*the middle key has changed*/input_event (Uk_dev, Ev_key, Key_enter, (usb_buf[0] & (1<<2)) ?1:0);     Input_sync (Uk_dev); } pre_val= usb_buf[0]; Usb_submit_urb (Uk_urb, gfp_kernel);/*Resubmit Urb*/}