PCI Bridge Detection Using Class and Subclass Codes
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Solution Overview
Problem
Conventional image forming apparatuses experience delays in startup time due to pseudo bridges, which are incorrectly identified as PCI bridges, leading to inefficiencies in initializing peripheral devices.
Innovation Solution
The processor in the information processing apparatus obtains class codes and subclass codes or vendor IDs and device IDs from PCI nodes to precisely determine if they are bridges, thereby avoiding the detection of pseudo bridges and optimizing the search for actual bridges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the class code register is used to determine whether a PCI node is a bridge, then the determination process is simple, but pseudo bridges are incorrectly identified as bridges causing startup delays
Solution Approach 1:
The patent changes the determination parameters from only class code to a combination of class code and subclass code. This allows more precise identification of PCI bridges by examining additional classification details, thereby avoiding misidentification of pseudo bridges while maintaining a systematic determination process.
2Reliability
If the CPU initializes PCI devices during startup, then all peripheral devices are properly initialized, but startup time increases
Solution Approach 1:
The patent performs preliminary identification of actual bridges versus pseudo bridges using class code and subclass code before initiating the initialization process. By pre-filtering the list of PCI nodes to identify only genuine bridges, the system avoids unnecessary initialization operations on pseudo bridges, thereby reducing startup time while ensuring complete initialization of actual peripheral devices.
3Productivity
If a PCI bridge is searched for ahead of another PCI node, then the search follows the bus tree structure, but pseudo bridges cause the search to continue unnecessarily
Solution Approach 1:
The patent implements a feedback mechanism where the determination result (whether a PCI node is a bridge or pseudo bridge) feeds back into the search process. When a pseudo bridge is identified through class code and subclass code analysis, the search algorithm receives feedback to stop searching ahead of that node, preventing unnecessary continuation of the search and improving overall search efficiency.
Data Source
AI summary
Provided is an information processing apparatus including a processor and a PCI node connected to the processor via a first PCI bus, the processor obtaining a class code and a subclass code from the PCI node connected to the first PCI bus, determining whether or not the PCI node is a bridge based on the obtained class code and subclass code, searching for a PCI node connected to the PCI node via a second PCI bus based on having determined that the PCI node is a bridge, and searching for another PCI node connected to the first PCI bus based on having determined that the PCI node is not a bridge.