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PSM 

Overview

• PSM (Persistent Storage Manager) component is responsible for the storage of default/system configurations.
• Provides software interfaces and abstractions to read/write variables stored in persistent storage and read factory config variables.
• PSM holds mainly parameters related to hardware configuration.
• In dual processor architecture a process running in peer processor can access PSM DB over DBUS.
• All defaults/system configuration which are not modified during runtime are part of PSM.
• PSM should be up and running for normal configuration of RDKB unit.
• For WiFi initialization, PSM holds all default values of OEM specific custom parameters which is fetched through PSM HAL.

Architecture

Figure 1 - Architectural view of PSM sub-system

Initialization

Figure 2 - Initialization of PSM sub-system

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• First copy the current system file into the backup file
• Then flush the configuration into the current file

Reading configuration

Figure 3 - Reading Configuration

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Restore configuration is tried first from the current system file. If it passes the verification, read is done otherwise restore configuration is tried from the backup system file. If it passes the verification, read is done otherwise restores the factory default configuration. This step has to succeed since there is no any other plan to back it up.

Get values from PSM

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Figure 4 - Retrieving Parameter

Using CLI utility:
psmcli get <parameter name as in bbhm file>
Eg: psmcli get eRT.com.cisco.spvtg.ccsp.Device.WiFi.NotifyWiFiChanges

Set values for PSM

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Figure 5 - Setting Parameter

Using CLI utility:
psmcli set <parameter name as in bbhm file>
Eg: psmcli set eRT.com.cisco.spvtg.ccsp.Device.WiFi.NotifyWiFiChanges true

User and default configuration initialization

Syscfg_create.exe executable creates shared memory with user configuration data (/nvram/syscfg.db). This is present in the code base at the location /ccsp/utopia/source/syscfg

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