open and close Subroutines

An open subroutine call is used to create a channel between the caller and a graphic input device driver.

The keyboard supports two such channels. The most recently created channel is considered the active channel. All other graphic input device drivers support only one channel. The open subroutine call is processed normally, except that the OFLAG and MODE parameters are ignored. The keyboard provides support for the fp_open subroutine call; however, only one kernel mode channel can be open at any given time. The fp_open subroutine call returns EACCES for all other graphic input devices.

The close subroutine is used to remove a channel created by the open subroutine call.