Imbedding virtual device driver calls in a dynamic link library

Abstract: An interface (28) in a dynamic link library (26) is created which communicates with and provides data translation functions from an application program, such as a test tool (12) , to a device driver. A virtual device driver (30) in an operating system of a computing system is accessed by a calling program to perform and verify the operation of the virtual device driver. A request from the calling program (12) to perform an operation supported by the virtual device driver is decoded in the interface of the dynamic link library. An address of the virtual device driver corresponding to the requested operation is acquired in the dynamic link library. A processing module (40, 42, 44, 46, 48) maintained in the dynamic link library for processing the requested operation is invoked, and data from this module is passed to the virtual device driver in response to the requested operation. In addition, data parameters are configured by the processing module of the dynamic link library for passing the requested data from the calling program to the virtual device driver. A return value is received from the virtual device driver indicating the success or failure of the requested operation. The return value is passed from the module of the dynamic link library to the calling program. Also, the processing module of the dynamic link library receives data returned from the virtual device driver in response to the requested operation, processes the data, and passes the processed data to the calling program.

Description: FIELD OF THE INVENTION This invention relates to interfacing between an application program and a device driver in a computing system. More particularly, the invention relates to providing a flexible interface for data translation between an application program and a device driver. DESCRIPTION OF PRIOR ART Many application level software programs are limited in their ability to transmit or receive data from external applications or devices. For example, as shown in FIG. 1, tool 12 used in the development of graphical user interfaces (GUI) 14 is designed to communicate with the GUI through standard Microsoft Windows 1 dynamic link libraries (DLL) 13. One such tool, the QA Partner 2 test tool by Segue Software, tests GUI applications by communicating with standard Windows GUI controls through standard Windows Application Program Interface DLL functions. Among many of the operations that a GUI may perform, a GUI may invoke the device drivers of the operating system, such as Windows virtual device drivers (VxD). However, conventional test tools are not designed to communicate directly with a virtual device driver. Since conventional test tools are used to test GUI's through conventional Windows DLLs, a virtual device driver level call, upon which the GUI is dependent, cannot be independently verified by the test tool. For instance, if the GUI performs operations which invoke and communicate with a device driver or VxD, there are no means for a conventional test tool to verify the proper underlying operation of the device driver. Further, since conventional test tools are designed to test the operation of the GUI and are not designed to communicate with a device driver, these test tools do not support software testing of device drivers. While the test tool permits communications with an external DLL, conventional test tools have limited communications capabilities when receiving or transmitting data with external programs. For instance, while test tools can communicate using message strings, conventional test tools cannot handle complex data structures involving pointers. For instance, the QA Partner test tool cannot pass pointers or dynamically allocate memory. Additionally, conventional test tools do not support high level language structures, such as algorithms written in C or C++. Therefore, conventional test tools do not directly support Microsoft's interface of DeviceIOControl, used by high level programs to communicate with a VxD. EP-A-0,654,735 describes apparatus for analyzing or debugging a system of processes including a dynamically-linked library (DLL) which performs system calls and also sends messages indicating that the system calls have been performed. The messages are displayed in a graphical user interface showing the current state of the system, from which the user may control which system calls result in messages, the rate at which the display system responds to messages, and the execution of processes. However, the apparatus described does not verify a test that is requested to be performed by a process by providing that the process must send a return value indicating the success or failure of the process to complete the test. IBM Technical Disclosure Bulletin Vol. 38, No. 10 October 1995; "Device Driver Test Tool" also describes a test tool in which a DLL implements device-specific interface functions, such as DOSDevIOCtl calls, in a DOS or OS/2 operating system environment. Device driver tests are controlled by test case script files, which are parsed by a generic parser resident in the DLL. Other methods and systems for testing a device driver are described in US-A-5,557,740, US-A-5,691,926, and US-A-5,233,611. US-A-5,696,970 describes an implementation of a PCMCIA Card Services virtual device driver for the Microsoft Windows 3.1 operating system in enhanced mode, including a special Card Services DLL. In Dr. Dobbs Journal on CD ROM November 1995, Don Matthews, pages 1-13, "Porting VxDs from Windows 3.1 to Windows 95", describes a VxD that works with both Microsoft Windows 3.1 and Windows 95 applications and different techniques for calling its services. SUMMARY OF THE INVENTION In accordance with this invention, as defined in the claims, which follow, the above problems have been solved by creating an interface in a dynamic link library which communicates with and provides data translation functions from a calling program, such as a test tool, to a device driver. In a method implementation of the invention, a virtual device driver in an operating system of a computing system is accessed from a calling program in order to verify the operation of the virtual device driver. The method begins by decoding, in a dynamic link library, a request from the calling program to perform an operation supported by the virtual device driver. An address of the virtual device driver to perform the requested operation is acquired in the dynamic link library. A module maintained in the dynamic link library for processing the requested operation is invoked, and data from this module is passed to the virtual device driver in response to the requested operation. As a further feature of the invention, a setup step configures data parameters in the module of the dynamic link library for passing the request data from the calling program to the virtual device driver. A return value is received from the virtual device driver indicating the success or failure of the requested operation. A passing step passes the return value from the module of the dynamic link library to the calling program. In another feature of the invention, the module of the dynamic link library receives data returned from the virtual device driver in response to the requested operation. This module of the dynamic link library processes the data returned from the virtual device driver and passes the data processed by the module to the calling program. The above computer implemented steps in another implementation of the invention are provided as an article of manufacture, i.e., a computer storage medium containing a computer program of instructions for performing the above-described steps. In a machine implementation of the invention, an apparatus for accessing a virtual device driver in an operating system in a computer from a calling program in order to perform and verify requested operations of the virtual device driver. The apparatus has a decoder, an acquisition module, an invoking module, and a call module. The decoder is in a dynamic link library and decodes a request from the calling program to perform an operation supported by the virtual device driver. The acquisition module acquires the address of the virtual device driver corresponding to the requested operation. The invoking module invokes a processing module in the dynamic link library to perform the requested operation. The call module passes data from the processing module of the dynamic link library to the virtual device driver in response to the requested operation. In another feature of the invention a setup module configures data parameters, in the processing module of the dynamic link library, for passing by data from the calling program to the virtual device driver. A receiver receives, from the virtual device driver, a return value indicating the success or failure of the requested operation, and a return module passes the return value from the module of the dynamic link library to the calling program. In another feature of the invention, a receiver in the processing module of the dynamic link library receives data returned from the virtual device driver in response to the requested operation. The processing module of the dynamic link library processes the data returned from the virtual device driver, and a data sending module passes the data processed by the processing module to the calling program. The great advantage and utility of the present invention is that a calling program, such as a conventional test tool program, can be linked to a device driver through the data translating DLL of the present invention. In this manner, a calling program can communicate with the device driver and verify its operations. Still another utility of the present invention is the translation data contained in complex data structures from the device driver to a conventional test tool. Still another utility of the present invention is that it enables a test tool to independently read, write, and modify data of a device driver. Still another utility of the present invention is to permit a software developer to use a conventional test tool in the development of a device driver. The foregoing and other features, utilities, and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 illustrates conventional test tool communication interfaces. FIG. 2 illustrates a computing system to perform the computer implemented steps in accordance with the invention. FIG. 3A is a preferred embodiment of the interface according to the present invention. FIG. 3B is a preferred embodiment of the interface according to the present invention. FIG. 4 shows the logical operations performed by the interface of Fig. 3A. FIG. 5 shows the logical operations performed by a command operation of the interface. FIG. 6 shows the logical operations performed by a write operation of the interface. FIG. 7 shows the logical operations performed by the read operation of the interface. FIG. 8 shows the logical operations performed by the read/post-processing operations of the interface. FIG. 9 shows the logical operations performed by the read/modify/write operations of the interface. FIG. 10 shows an alternative embodiment of the present invention where two dynamic link libraries are used. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The embodiments of the invention described herein are implemented as logical operations in a computing system. The logical operations of the present invention are implemented (1) as a sequence of computing implemented steps running on the computing system and (2) as interconnected machine modules within the computing system. The implementation is a matter of choice dependent on the performance requirements of computing system implementing the invention. Accordingly, the logical operations making up the embodiments of the invention described herein are referred to variously as operations, steps, or modules. The present invention imbeds modules in a DLL which are capable of communicating with device driver, such as a VxD, and a calling program, such as a test tool. The modules process requests from the test tool to formulate calls to the VxD, and process the data returned by the VxD. The modules include a command module, a write module, a read module, a read/post-process module, and a read/modify/write module. Since a DLL is a module capable of being publicly shared by many application programs, the present invention provides calling programs such as a test tool with the ability to control and monitor the operation of a device driver. The operating environment in which the present invention is used encompasses standalone computing systems or a general distributed computing system, wherein general purpose computers, workstations, or personal computers are connected via communication links of various types, in a client-server arrangement, wherein programs and data, many in the form of objects, are made available by various members of the system. Some of the elements of a standalone computing system or a general purpose workstation computer are shown in FIG. 2, wherein a processor 15 is shown, having an input/output (I/O) section 16, a central processing unit (CPU) 17 and a memory section 18. The I/O section 16 is connected to a keyboard 19, a display unit 20, a disk storage unit 21 and a CD-ROM drive unit 22. The CD-ROM unit 22 can read a CD-ROM medium 23 which typically contains programs 24 and data. The computer program products containing mechanisms to effectuate the apparatus and methods of the present invention may reside in the memory section 18, or on a disk storage unit 21, or on the CD-ROM 23 of such a system. Examples of such systems include SPARC systems offered by Sun Microsystems, Inc., personal computers offered by IBM Corporation and by other manufacturers of IBM-compatible personal computers, and systems running the UNIX operating system or Solaris™ operating system. FIG. 3A shows a block diagram a preferred embodiment of the present invention. Data translating DLL 26 provides a communication interface between calling program 12, such as a test tool, and VxD 30. Data translating DLL 26 communicates with VxD 30 through calls to the interface of DeviceIOControl 28. Interface 28 provides a generic link between external programs and device drivers of the operating system, such as VxD 30. However, as previously explained, conventional versions of test tool 12 cannot support communications to and from DeviceIOControl interface 28. Therefore, the data translation DLL has a command module 40, write module 42, read module 44, read/post-process module 46, and read/modify/write module 48, as shown in FIG. 3B. The operation of each of these modules is described below in greater detail. The overall operation of the preferred embodiment is shown in FIG. 4. At operation 50, data translating DLL 26 receives the call from the external calling program or test tool 12. The call from test tool 12 typically involves a function name and data parameters as arguments of the function. The functions and data parameters required by DLL 26 would be known, a priori, to the software developer using test tool 12. A number of functions can be incorporated into the DLL 26 of the present invention. These functions could include operations to access or control the VxD. For example, DLL 26 could support functions to create a cache, delete the cache, get the VxD version, get cache information, get drive statistics, etc. These higher level functions supported by DLL 26 of the present invention would utilize the respective modules 40-48 shown in FIG. 3B. For instance, a function to delete the cache would access command module 40 so that the test tool could instruct the VxD to delete the cache maintained by the device driver. When the test tool seeks to pass data to the VxD, the data translating DLL 26 extracts this data at operation 50 in FIG. 4 from the call made by the test tool. Based on the data passed by the test tool to the DLL 26, operation 52 requests the "handle" from the appropriate VxD. The "handle" is the addressed identifier of the device driver to be accessed, and the handle is maintained by the operating system. Therefore, before the DLL 26 can communicate with a particular VxD, the DLL must first obtain the address of the VxD as maintained by the operating system. Setup operation 54 at DLL 26 configures, establishes or translates any data parameters necessary to access VxD 30 through the DeviceIOControl interface 28. The DeviceIOcontrol interface 28 is described in the above cross-referenced related application. Using the translating interface disclosed in the above cross-referenced related application, the present invention can be used in either a Windows 95 or Windows 3.X environment. The arguments to the DeviceIOcontrol interface 28 include a "handle" (described above), function number, input data pointer, size of input buffer, output data pointer, size of output buffer, pointer to a variable for receiving the output byte count, and a pointer for overlap input or output. The function number governs the operation to be performed by the given device driver, while the various pointers are used to pass data to and from interface 28 and the VxD 30. Having received the desired function to be performed by the test tool and appropriately building the parameters used by DeviceIOControl interface 28, DLL 26 calls DeviceIOcontrol at call operation 56 with the appropriate parameters. DeviceIOControl 28 then communicates with VxD 30, as shown in FIG. 3A, so that the VxD performs the requested function. VxD 30 then returns data to DeviceIOControl interface 28 depending on the requested function. Operation 58 in FIG. 4 processes the data returned to the data translating DLL 26 from the VxD, and data send module 60 passes this data up to the test tool. Return module 61 passes a return value to the test tool indicating the success or failure of the requested operation. In this manner, a developer using test tool 12 can control and observe the operations of VxD 30. FIG. 5 shows the logical operations of the command module 40 of Fig. 3B. As previously described, command module 40 is resident in data translating DLL 26 of the present invention. The command module 40 permits test tool 12 to issue commands to the VxD 30. For example, these commands could include a delete cache, flush cache, or reset statistics command. As shown in FIG. 5, operation 62 of command module 40 receives the calling function and arguments from the test tool. Operation 64 gets the handle of the appropriate VxD to perform the desired function to be controlled by the test tool. Then step 66 calls DeviceIOControl using the handle and the appropriate function number derived from the desired function requested by the test tool. No further data pointers are required in formulating the calls of module 40 to DeviceIOControl. The VxD would then perform the requested function. Upon completing the requested function, the VxD would provide a return value to the calling routine. This return value could indicate, among other things, the success or failure of the requested operation. At operation 68, command module 40 receives the return value from the VxD and passes this return value to the test tool at operation 70. In this manner, test tool 12 has issued a given command to the VxD through the DLL interface 26 of the present invention, and the test tool is provided with information regarding the success or failure of the requested command. FIG. 6 illustrates the logical operations of the write module 42 of Fig. 3B. Write module 42 provides test tool 12 with the ability to transmit data to a particular device driver or VxD 30. The write module 42 at operation 72 receives the call and parameters from the test tool. Operation 74 obtains the handle of the appropriate VxD to be affected by the requested operation. Based on information received from the test tool call, operation 76 configures data structures to be passed to the VxD through DeviceIOControl interface 28. In particular, write module 42 establishes pointers to memory locations which contain the data provided by the test tool. Operation 78 passes these pointers to the VxD, and the VxD reads the values contained in these memory locations and acts appropriately based thereon. The VxD then generates a return value passed through DeviceIOControl interface 28. Operation 80 receives the return value from the VxD, and operation 82 passes this value up to the test tool. In this manner, write module 42 enables a developer using test tool 12 to write data into the VxD. For instance, a create cache function could include information sent from the test tool to the VxD relating to the drive to be used as a cache and the size of the cache. The write module 42 is used to pass this data from the test tool 12 to the VxD 30. The logical operations of read module 44 are illustrated in FIG. 7. Read module 44 enables the calling program or test tool 12 to retrieve data from the VxD. For instance, functions could be implemented to provide information about the state of a disk cache, or the version number of a particular device driver. Operation 84 of read module 44 receives the call from the test tool, and operation 86 retrieves the handle of the appropriate VxD. Then operation 88 configures memory buffers to receive data from the VxD. In making the call to the data translating DLL 26, test tool 12 can provide a pointer to a memory location where the information from the VxD should be placed. This pointer is used by operation 92 of read module 44 to pass the requested data up to the test tool after operation 90 has invoked DeviceIOControl. At operation 92, the read module passes this data to the test tool as well as passing the return value, at operation 93, indicating the success or failure of the operation. Read module 44 permits test tool 12 to access data maintained in simple structures (i.e., single integer values). For more complicated data structures (i.e., arrays of data), read/post-processing module 46 of the present invention must be utilized. FIG. 8 illustrates logical operations of read/post-processing module 46 of Fig. 3B. Depending upon the implementation of a particular VxD device driver, some VxDs will respond to a request for information by providing an entire arrayed data structure. For instance, one VxD function may provide an array of information about the hits and misses of all of the drives in the computing system. A developer using a conventional test tool, however, would need information relating solely to one of the drives of the system. Hence, read/post-processing module 46 is designed to receive all of the data provided by the VxD and report only the requested data to the test tool. Operation 94 of the read/post-processing module 46 receives the call from the test tool requesting information from a particular VxD device driver. Step 96 retrieves the handle of the appropriate VxD. Then operation 98 configures a memory location for storage of the array of information to be obtained from the VxD. Operation 100 of the read/post-processing module 46 calls the VxD through DeviceIOControl interface 28 and instructs the VxD to place the array of information at the specified memory location. In response to this message, the VxD fills the specified memory location with the array of data. Operation 102, read/post-processing module 46 indexes through the array of data to locate the desired information requested by the test tool. After locating this information, operation 104 then passes this data to the test tool. Operation 105 passes the success/failure return value to the test tool. In this manner, module 46 breaks down a complex data structure and passes only the needed elements of the data structure to the external calling program or test tool 12. While the initial operations of module 46 are similar to the operations of read module 44, because of the complexity of the array of data generated by the VxD, the post-processing operation 102 is needed prior to passing data back to the test tool. FIG. 9 illustrates the operations of read/modify/write module 48 of Fig. 3B incorporated into data translating DLL 26. Module 48 permits the external calling program or test tool 12 to change the parameters maintained by the VxD in a large data structure. For example, if a VxD maintains a large table containing alterable parameters of the drives in a computing system, then the VxD may require that the entire table be written in order to modify a single parameter. Such a VxD requirement would imply that a calling program seeking to write or change a single element of the array must first read the entire array, alter the desired element of the array, and then write the entire array to the VxD. Module 48 of the present invention can be used in this capacity. At operation 106 of FIG. 9, module 48 receives the call from the test tool. Operation 108 fetches the handle of the appropriate VxD to be operated upon. Then operation 110 configures the address of the memory to store information to be retrieved from the VxD, in a manner similar to operation 98 of FIG. 8. Operation 112 calls DeviceIOControl to pass to the VxD the location wherein the array of data should be placed. Decision operation 114 tests the return value from the VxD for successful operation and reports an unsuccessful result at operation 116 if module 48 was unable to read the array from the VxD. If, however, operation 112 was successful, then operation 118 indexes through the received array of data to the location of the desired element. Operation 118 overwrites the value contained in this memory location of the array. Step 120 calls DeviceIOControl to write the contents of the entire array back into the VxD. At operation 122, module 48 passes the return value up to the test tool indicating the success or failure of the write operation 120. Hence, data translating DLL 26, comprised of modules 40-48, enables an external calling program, such as a test tool, to communicate with a VxD device driver of the operating system. FIG. 10 illustrates an alternative embodiment of the present invention, wherein two separate DLLs are created which perform the operations described herein. The first data translating DLL 130 contains modules to manipulate data structures so that application program 128 and VxD 30 transmit compatible information. DeviceIOControl DLL 132 contains all of the appropriate calls described above to DeviceIOControl interface 28 (not shown). By separating the functions contained in modules 130 and 132 and placing them in DLLs, these modules become publicly accessible and sharable by application software used in the computing system. Although a preferred embodiment of the present invention has been described in the environment of Windows 95, it will be apparent to one skilled in the art that the invention will be applicable to other environments such as Windows 3.1, Windows 3.11, or Windows NT. While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made therein without departing from the scope of the invention.

Claims: Apparatus for accessing a virtual device driver (30) in an operating system in a computer from a calling program (12) to perform and verify requested operations of the virtual device driver, the computer having a processor (17), an input/output device (19, 20), and a data storage device (21, 22), said apparatus comprising: a decoder decoding in a dynamic link library (26) a request from the calling program (12) to perform a requested operation supported by the virtual device driver (30), said request having request data identifying the requested operation; an acquisition module acquiring in the dynamic link library an address of the virtual device driver, maintained by the operating system, corresponding to the requested operation; an invoking module invoking a processing module (40, 42, 44, 46, 48) maintained in the dynamic link library to perform the requested operation; a call module passing data from the processing module of the dynamic link library to the virtual device driver in response to the requested operation; a setup module configuring data parameters in the processing module of the dynamic link library (26) for passing by the call module the request data from the calling program to the virtual device driver (30); a receiver receiving from the virtual device driver a return value indicating the success or failure of the requested operation; and a return module passing said return value from the module of the dynamic link library to the calling program. The apparatus of claim 1, further comprises: a receiver in the processing module of the dynamic link library receiving data returned from the virtual device driver in response to said requested operation; said processing module of the dynamic link library processing the data returned from the virtual device driver; and data sending module passing the data processed by the processing module to the calling program. A method for accessing a virtual device driver (30) in an operating system of a computing system from a calling program (12) to perform and verify the requested operationsof the virtual device driver, said method comprising the computer-implemented steps of: decoding in a dynamic link library (26) a request from the calling program to perform a requested operation supported by the virtual device driver, said request having request data identifying the requested operation; acquiring in the dynamic link library an address of the virtual device driver, maintained by the operating system, corresponding to the requested operation; invoking a module (40, 42, 44, 46, 48) maintained in the dynamic link library for processing the requested operation; passing data from the module of the dynamic link library to the virtual device driver responsive to the requested operation; configuring data parameters in the module of the dynamic link library for passing the request data from the calling program to the virtual device driver; receiving from the virtual device driver a return value indicating the success or failure of the requested operation; and passing said return value from the module of the dynamic link library to the calling program. The method of claim 3, further comprising the steps of: receiving in the module of the dynamic link library data returned from the virtual device driver responsive to said requested operation; processing in the module of the dynamic link library the data returned from the virtual device driver; and passing the data processed by the module to the calling program. The method of claim 3, wherein the module of the dynamic link library invoked is a COMMAND module (40) for sending commands from the calling program (12) to the virtual device driver (30). The method of claim 3, wherein the module of the dynamic link library invoked is a WRITE module (42) for writing data from the calling program (12) to the virtual device driver (30). The method of claim 3, wherein the module of the dynamic link library invoked is a READ module (44) for reading device data from the virtual device driver (30). The method of claim 7, further comprising the steps of: configuring (88) memory buffers in the dynamic link library for receiving the device data from the virtual device driver (30); receiving in the READ module (44) of the dynamic link library device data returned from the virtual device driver responsive to said requested operation; and passing (92) the device data received by the READ module to the calling program. The method of claim 3, wherein the module of the dynamic link library invoked is a READ/POST-PROCESSING module (46) for reading and processing an array of device data from the virtual device driver. The method of claim 9, further comprising the steps of: configuring (98) memory buffers in the dynamic link library (26) for receiving the device data from the virtual device driver; receiving in the READ/POST-PROCESSING module (46) of the dynamic link library device data returned from the virtual device driver responsive to said requested operation; processing in the READ/POST-PROCESSING module (46) of the dynamic link library the array of device data returned from the virtual device driver, said processing including indexing through the array (102) of device data to locate an element of the device data responsive to the requested operation of the calling program; and passing (104) the element of device data located by the READ/POST-PROCESSING module (46) to the calling program. The method of claim 3, wherein the module of the dynamic link library invoked is a READ/MODIFY/WRITE module (48) for reading a data structure from the virtual device driver (30), modifying an element of the data structure, and writing the data structure as modified to the virtual device driver. The method of claim 11, further comprising the steps of: configuring (110) memory buffers in the dynamic link library for receiving the data structure from the virtual device driver; receiving in the READ/MODIFY/WRITE module (48) of the dynamic link library the data structure returned from the virtual device driver responsive to said requested operation; receiving from the virtual device driver a return value indicating the success or failure of the requested operation; if the return value indicates (114) that the requested operation was successful, then processing in the READ/MODIFY/WRITE module (48) of the dynamic link library the array of data returned from the virtual device driver, said processing including indexing through the array of data (118) to locate an element of the data to be modified responsive to the requested operation of the calling program; and modifying the element of data located by the READ/MODIFY/WRITE module (48); writing the array of data to the virtual device driver; receiving from the virtual device driver a return value indicating the success or failure of the requested operation; and passing (116) said return value from the module of the dynamic link library to the calling program. A computer program storage medium readable by a computing system and encoding a computer program of instructions for executing a computer process for accessing a virtual device driver in an operating system from a calling program in order to perform and verify the requested operations of the virtual device driver, said computer process comprising the steps of: decoding in a dynamic link library a request from the calling program to perform a requested operation supported by the virtual device driver, said request having request data identifying the requested operation; acquiring in the dynamic link library an address of the virtual device driver, maintained by an operating system in the computing system, corresponding to the requested operation; invoking a module maintained in the dynamic link library for processing the requested operation; passing data from the module of the dynamic link library to the virtual device driver responsive to the requested operation; configuring data parameters in the module of the dynamic link library in order to pass the request data from the calling program to the virtual device driver; receiving from the virtual device driver a return value indicating the success or failure of the requested operation; and passing said return value from the module of the dynamic link library to the calling program. The computer program storage medium of claim 13 where said computer process in the computer program further comprises the steps of: receiving in the module of the dynamic link library data returned from the virtual device driver responsive to said requested operation; processing in the module of the dynamic link library the data returned from the virtual device driver; and passing the data processed by the module to the calling program.

Inventors: SCHAFFER DANIEL H, SCHAFFER, DANIEL H.
Applicants: SUN MICROSYSTEMS INC, SUN MICROSYSTEMS, INC.
Application year: 1997
Main classification: G06F11
IPC codes: G06F11, G06F9