usb_device_interface_t interface is implemented
by all USB devices. It is used by the USB host to communicate with
the USB devices. The interface is Simics internal, and may be
changed in future versions of Simics. It should not be used by
user-defined classes.
The submit_transfer() function is used by the USB host controller
to send a new transfer to a USB device. Transfers are the basic means of
communication between the USB host controller and the USB devices. A
transfer contains all information needed to handle control, bulk, interrupt,
and isochronous transfers. A transfer to a USB device simply moves the
control from the USB host to the USB device. The USB device can then
decide when to send back any useful data to the USB host. The USB device
receives a pointer to the transfer to handle. It can either handle the
transfer immediately or send the transfer back later using the
complete_transfer() function in the
usb_interface_t interface, which is implemented by the USB
host.
The USB device must return USB_Transfer_Completed when it
handles the transfer immediately, i.e., it has filled the required fields in
the transfer structure. The USB device must return
USB_Transfer_Not_Ready for unfinished transfers, i.e., the
USB device does not have any interesting data to deliver at this point. The
isochronous and interrupt transfers contain a field indicating how long time
the USB host expects the USB device to wait before returning the
transfer. Note that it is just an indication on how often this transfer is
scheduled in the periodic list and USB devices can complete the transfers at
any time. A value of 0 means that the USB host does have any
expectations about the return time.
The abort_transfer() function tells the USB device to abort a transfer previously issued by the USB host. The USB device should not call the complete_transfer() function for a request that has been aborted.
The reset() function is used by the USB host to reset the USB device.
The USB host expects the device to return the same transfer pointer it received when completing, i.e., the transfer pointer is used to identify uniquely a transfer.
SIM_INTERFACE(usb_device) {
usb_transfer_completion_t (*submit_transfer)(conf_object_t *dev_obj,
usb_transfer_t *transfer);
void (*abort_transfer)(conf_object_t *dev_obj,
usb_transfer_t *transfer);
void (*reset)(conf_object_t *dev_obj);
};
#define USB_DEVICE_INTERFACE "usb_device"