Dynamic function replacement for streams framework
First Claim
1. A data structure implemented in a computer system that provides a bidirectional data path between a user process, a module which is an intermediate processing element that can be dynamically added to, or removed from, said data path, and a device driver, said device driver being resident in a system kernel and controlling a peripheral device to transfer data between said kernel and said device, where data written by said user process travel downstream toward said driver, and where data received by said driver from said device travel upstream to be retrieved by a user, the data structure comprising:
- a normal function that implements a specific module or driver instance;
at least one alternative function that implements an optional module or driver instance; and
a controller for generating a control command that remaps addresses of said normal function and said at least one alternative function to define new function addresses that dynamically replace said normal function with said at least one alternative function, thereby implementing said optional module or driver or instance to dynamically change the execution behavior of said data structure, while either still executing an original execution path or executing a new execution path, and without requiring any modification to said module and said driver.
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Abstract
An extension to the STREAMS framework, referred to as dynamic function replacement, uses data structures that contain function pointers which allow STREAMS to execute various module or driver functions without requiring framework modification, or understanding what these functions actually do beyond their rudimentary classifications. This provides a simple, yet elegant, mechanism for replacing these function definitions and, hence, changing the execution behavior of STREAMS modules and drivers without requiring the modules or drivers to be rewritten or modified.
114 Citations
29 Claims
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1. A data structure implemented in a computer system that provides a bidirectional data path between a user process, a module which is an intermediate processing element that can be dynamically added to, or removed from, said data path, and a device driver, said device driver being resident in a system kernel and controlling a peripheral device to transfer data between said kernel and said device, where data written by said user process travel downstream toward said driver, and where data received by said driver from said device travel upstream to be retrieved by a user, the data structure comprising:
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a normal function that implements a specific module or driver instance; at least one alternative function that implements an optional module or driver instance; and a controller for generating a control command that remaps addresses of said normal function and said at least one alternative function to define new function addresses that dynamically replace said normal function with said at least one alternative function, thereby implementing said optional module or driver or instance to dynamically change the execution behavior of said data structure, while either still executing an original execution path or executing a new execution path, and without requiring any modification to said module and said driver. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A data structure implemented in a computer system that provides a bidirectional data path between a user process, a module which is an intermediate processing element that can be dynamically added to, or removed from, said data path, and a device driver, said device driver being resident in a system kernel and controlling a peripheral device to transfer data between said kernel and said device, where data written by said user process travel downstream toward said driver, and where data received by said driver from said device travel upstream to be retrieved by a user, said system being implemented in a STREAMS framework in which each module or driver defines a streamtab structure that contains pointers to qinit structures, the data structure, comprising:
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a normal function that implements a specific module or driver instance; at least one alternative function that implements an optional module or driver instance; and a controller for generating a control command that remaps addresses of said normal function and said at least one alternative function to define new function addresses that dynamically replace said normal function with said at least one alternative function, thereby implementing said optional module or driver or instance to dynamically change the execution behavior of said data structure, while either still executing an original execution path or executing a new execution path, and without requiring any modification to said module and said driver. - View Dependent Claims (17, 18, 19, 20, 21)
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22. A method for implementing a data structure in a computer system that provides a bidirectional data path between a user process, a module which is an intermediate processing element that can be dynamically added to, or removed from, said data path, and a device driver, said device driver being resident in a system kernel and controlling a peripheral device to transfer data between said kernel and said device, where data written by said user process travel downstream toward said driver, and where data received by said driver from said device travel upstream to be retrieved by a user, said system being implemented in a STREAMS framework in which each module or driver defines a streamtab structure that contains pointers to qinit structures, the method comprising the steps of:
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providing a normal function that implements a specific module or driver instance; providing at least one alternative function that implements an optional module or driver instance; and generating, with a controller, a control command that remaps addresses of said normal function and said at least one alternative function to define new function addresses that dynamically replace said normal function with said at least one alternative function, thereby implementing said optional module or driver or instance to dynamically change the execution behavior of said data structure, while either still executing an original execution path or executing a new execution path, and without requiring any modification to said module and said driver. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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Specification