Filter Driver USB Power State Error Prevention
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Solution Overview
Problem
Accessing a suspended USB device can result in errors due to the need for careful management of its power state, which is not effectively handled by existing technologies, leading to conflicts between power management and data transfer requests.
Innovation Solution
An information processing device with a filter driver that includes a power state management function and a transfer state management function, which coordinate to ensure that data transfers are only initiated when the USB hub is in a normal operating state, preventing errors by holding transfer requests until the power state is restored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Selective Suspend is implemented to save power by putting USB devices into low-power state, then energy consumption is reduced, but accessing the suspended device results in errors
Solution Approach 1:
A filter driver is introduced as an intermediary layer between the application program and the class driver. This filter driver monitors power state changes, intercepts access requests, and coordinates between power management operations and data transfer operations. The filter driver holds access requests when the device is suspended and releases them when the device returns to normal state, preventing errors while maintaining power savings.
2Reliability
If the filter driver intercepts control requests from application programs, then access errors are prevented, but control processing time increases
Solution Approach 1:
The filter driver performs preliminary actions by monitoring power state changes in advance and proactively holding access requests before they reach the class driver. When a power state change is detected, the filter driver preemptively intercepts and queues access requests, so they are processed only when appropriate. This prevents errors while minimizing delays by only holding requests when necessary.
3Reliability
If access requests are held until power state returns to normal, then error-free access is ensured, but data transfer latency increases
Solution Approach 1:
The filter driver dynamically adjusts its behavior based on the current power state of the USB device. When the device is in normal state, access requests are processed immediately without interruption. When the device transitions to low-power state, the filter driver dynamically holds requests and releases them when the device returns to normal state. This dynamic adaptation ensures reliability while minimizing latency by only delaying transfers when the device is actually suspended.
Data Source
AI summary
In an information processing device, if the power state of a peripheral device changed by a class driver is the low-power state, in which the peripheral device consumes less power than in its normal state but its operation is limited, a filter driver below the class driver suspends controlling the peripheral device in accordance with a control request from an application program without passing through the class driver until the power state of the peripheral device returns to the normal state.