Peripheral device interface for dynamically selecting boot disk device

Abstract

A common peripheral device interface module is disclosed for use with the Unix (Unix is a trademark of AT&T) operating system which is flexible enough to support many types of disk or tape device drivers. A common disk module (CDM) is included. The CDM contains high level disk operation commands which may be used for common reference to each disk driver on the system. Routines within the CDM are accessed by the Unix system call interface through a series of operating system entry points. Additional routines are included with the pre-existing Unix operating system Disk I/O Subsystem to improve interfacing between this subsystem and the CDM. A common tape module (CTM) is used to perform high level tape operation routines. The Unix system call interface communicates with the CTM through a group of operating system entry points. Because there is no Unix operating system tape I/O subsystem, the CTM completely implements a tape I/O subsystem. To provide hardware portability, the CTM is configured to call a group of low level routines which have been incorporated into a device driver. Because of the large number of possible root disk device drives, the root disk device driver can be dynamically selected for the Unix operating system. Each controller which is resident within the system checks in with the operating system. The controller which checks in first with the operating system is used for booting up the system. Each controller which checks in is matched with an appropriate device driver. The matched device drivers are then used for disk I/O functions.