Method for allowing application program in computer system to access device directly in exclusive mode by bypassing operating system and blocking requests from other programs

• US 5,535,416 A
• Filed: 06/01/1995
• Issued: 07/09/1996
• Est. Priority Date: 02/12/1993
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wilhelm, George W. Jr., Feeney, James W.
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): MEKY, MOUSTAFA M
• Application Number:
  US08/459,014
• Time in Patent Office: 404 Days
• Field of Search: 395/500, 395/700, 395/821, 395/822, 395/823, 395/824, 395/825, 395/834
• US Class Current: 710/14
• CPC Class Codes: G06F 13/102 where the programme performs an interfacing function, e.g. device driver G06F13/105 takes precedence; scheduling within device drivers G06F9/52; contention policies within device drivers G06F9/4881
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms
• CPC Class Codes: G06F 9/545 where tasks reside in different layers, e.g. user- and kernel-space

Abstract

A data processing system gives an application running on the operating system exclusive ownership of a hardware device. The system is operable in two modes. In the first mode the application interacts with the hardware device by making use of the processing system. In this mode many layers of the processing system are involved and the interaction time with the hardware is slow and inconsistent. In the second mode, exclusive ownership of the hardware device is granted to the application by the driver. In this mode the application has direct access to the hardware device thus avoiding the involvement of the processing system layers. The application accesses and uses the driver through a low latency processor interface linked into the application program itself.

Claims

1. A method for operating a device of a computer system, comprising the steps of:

(a) an operating system of the computer system managing operation of any devices of the computer system;

(b) processing by the operating system (kernel) requests from concurrent applications executing programs to access the device in a first (shared, or general user) mode, said operating system preventing conflicts between applications concurrently requesting access in the first mode to the device, said applications'"'"' access to the device controlled by the operating system;

(c) processing by the operating system a request by one of the application programs for access to the device in a second (exclusive) mode, said processing of the request for access in the second mode including the steps of;

(1) distinguishing said request for access to the device in the second mode, generated by said one of the application programs, from a request for access to the device in the first mode;

(2) passing said request for access to the device in the second mode to a device driver;

(3) blocking by the device driver requests from others of the application programs for access to the device in either the first mode or the second mode; and

(4) entirely bypassing the operating system and accessing the device directly by the application program that issued the request for access in the second mode, without interruption for both input and output access, after step (2), by any operating system processes or interfaces between the device and the application program, until the application program completes its direct accessing.

2. The method of claim 1, wherein step (c) further includes the step of the application program invoking a direct (low latency) interface to the device.

3. The method of claim 2 wherein the interface to the device is linked into the application program.

4. The method of claim 1, wherein steps (b) and (c) include respective calls to the device driver.

5. The method of claim 1, wherein step (c) further includes mapping memory addresses of the device into an address space of the application program.

6. The method of claim 5, wherein the application program sends data to the device by moving said data into a portion of the application program'"'"'s address space into which the addresses of the device are mapped.

7. The method of claim 5, wherein step (c) further includes the steps of:

(i) moving data by the device driver from the device into a portion of the application program'"'"'s address space into which the device'"'"'s addresses are mapped, and

(ii) reading said data by the application program from said portion of the application program'"'"'s address space.

8. The method of claim 5, wherein step (c) further includes the steps of:

(i) the device driver transferring the data from the device to a buffer,

(ii) the application program requesting the data,

(iii) the device driver moving the data from the buffer into a portion of the application program'"'"'s address space into which are mapped the device'"'"'s addresses, and

(iv) the application program reading the data from said portion of the application program'"'"'s address space.