Browse Prior Art Database

Multiple Instances of a Device Driver in the Kernel

IP.com Disclosure Number: IPCOM000100266D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Goal, P: AUTHOR [+2]

Abstract

A program is disclosed that allows multiple instances of a device driver in the kernel of a UNIX* operating system. (Image Omitted)

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 63% of the total text.

Multiple Instances of a Device Driver in the Kernel

       A program is disclosed that allows multiple instances of
a device driver in the kernel of a UNIX* operating system.

                            (Image Omitted)

      On traditional UNIX systems, a device driver is usually
designed to support only one instance of the device driver with a
fixed number of  control blocks to accommodate a fixed number of
instances of the supporting device.  The device driver instance is
represented by a major device number, and a device instance is
represented by a minor device number.  Ideally, the number of device
instances that a device driver can support should be an infinite
number, and the system should dynamically allocate resources for a
device instance.

      There are two cases that the system may need to create a new
device driver instance.  First, when there is a need to support a new
device instance.  In this case, the system first attempts to allocate
a minor device number under the current device driver instance.  If
there is no more available minor device number under the current
device driver instance, the system automatically checks to see if
another instance of the device driver can be generated.  If yes, then
the system creates a new instance of the device driver, and assigns a
new major device number for the device driver instance.  Second, when
there is a need to generate a new device driver instance for an
applicat...