The OpenBMC API provides a global setting for enforcement of minimum ship level. Typically a setting like this would be used to enable the use of hardware configurations in platform development that may not necessarily be supported in a manufacturing or field environment.
If an OpenBMC implementation provides MinimumShipLevelRequired, it must be on /xyz/openbmc_project/control/minimum_ship_level_required. There are no requirements on how the setting is used; implementations are free to react to the value of the setting however they choose.
In anticipation of a common use case of examining hardware assets, determining if they are of a certain revision or part, and taking some action if they are not, the OpenBMC API also provides an inventory decorator called MeetsMinimumShipLevel.
MeetsMinimumShipLevel can be implemented on any object in the inventory namespace. Again, there are no requirements on what an implementation does when a particular inventory object does or does not meet the minimum ship level.
Consider a server platform with an MSL requirement that a fan control card is a certain revision, and if it is not, the server must not be allowed to boot, unless a user explicitly specifies otherwise.
Phosphor OpenBMC provides a basic implementation of MinimumShipLevelRequired. It maintains a setting store and interface for the setting value. This implementation is suitable for the hypothetical platform implementation requirements, allowing a user to toggle the setting back and forth.
To enable verification that MSL has been satisfied, the hypothetical platform implementation would need to write an application that implements MeetsMinimumShipLevel on the inventory assets to be verified. At present Phosphor OpenBMC does not provide any applications that do this. If your application is general purpose and could meet the needs of others, consider contributing it to Phosphor OpenBMC. A possible implementation for the hypothetical fan control card might be an application that validates a number of hwmon sensors exist and then sets the MinimumShipLevelRequired on the fan inventory object accordingly.
Finally, the setting and the inventory assets must be compared and the server prevented from powering on. This could be accomplished with a custom application or for simple logic, with PDM rules.