There are two types of processes involved in software version management and code update:
A simple system design would be to include a single ImageManager and two ItemUpdaters: one for the BMC itself and one for the Host.
The ImageManager would provide interfaces at /xyz/openbmc_project/software to allow additional images to be added to the BMC, such as Object.Add() for REST and DownloadViaTFTP() for TFTP. The standard Object.Delete() interface would also be provided to facilitate removing images which are no longer needed. Images maintained in the file system would be presented as a corresponding /xyz/openbmc_project/software/<id> object. In addition, the xyz.openbmc_project.Common.FilePath interface would be provided to specify the location of the image.
It is assumed that the ImageManager has [at least] a bare minimum amount of parsing knowledge, perhaps due to a common image format, to allow it to populate all of the properties of xyz.openbmc_project.Software.Version. ItemUpdaters will likely listen for standard D-Bus signals to identify new images being created.
The ItemUpdater is responsible for monitoring for new Software.Version elements being created to identify versions that are applicable to the inventory element(s) it is managing. The ItemUpdater should dynamically create an xyz.openbmc_project.Software.Activation interface under /xyz/openbmc_project/software/, an association of type {active_image,software_version} between the Software.Version and Software.Activation under /xyz/openbmc_project/software/, and an association of type {activation,item} between the Inventory.Item and Software.Activation under /xyz/openbmc_project/software/<id>. Application of the software image is then handled through the RequestedActivation property of the Software.Activation interface.
The ItemUpdater should, if possible, also create its own xyz.openbmc_project.Software.Version objects, and appropriate associations for software versions that are currently present on the managed inventory element(s). This provides a mechanism for interrogation of the software versions when the ImageManager no longer contains a copy.
The ImageManager and ItemUpdater should use a common, though perhaps implementation specific, algorithm for the <id> portion of a D-Bus path for each Software.Version. This allows the same software version to be contained in multiple locations but represented by the same object path.
A reasonable algorithm might be: echo <Version.Version> <Version.Purpose> | sha512sum | cut -b 1-8
TODO: May need an issue against the REST server to 'merge' two copies of a single D-Bus object into a single REST object.
xyz.openbmc_project.Software.Activation has a property Activation that can be in the following states:
Software.Version.Purpose suggested the image was valid for a managed element, a detailed analysis by the ItemUpdater showed that it was not. Reasons may include image corruption detected via CRC or security verification failure. An event may be recorded with additional details.Software.Version can be activated.Software.Version is in the process of being activated.Software.Version is active on the managed element. Note that on systems with redundant storage devices a version might be Active but not the primary version.Software.Version or the storage medium on which it is stored has failed. An event may be recorded with additional details.It is sometimes useful to block a system state transition while activations are being performed. For example, we do not want to boot a managed host while its BIOS is being updated. In order to facilitate this, the interface xyz.openbmc_project.Software.ActivationBlocksTransition may be added to any object with Software.Activation to indicate this behavior. See that interface for more details.
It is strongly suggested that any activations are completed prior to a managed BMC reboot. This could be facilitated with systemd service specifiers.
All version identifiers are implementation specific strings. No format should be assumed.
Some software versions are a collection of images, each with their own version identifiers. The xyz.openbmc_project.Software.ExtendedVersion interface can be added to any Software.Version to express the versioning of the aggregation.
The xyz.openbmc_project.Software.ActivationProgress interface is provided to show current progress while a software version is Activating. It is expected that an ItemUpdater will dynamically create this interface while the version is Activating and dynamically remove it when the activation is complete (or failed).
The xyz.openbmc_project.Software.RedundancyPriority interface is provided to express the relationship between two (or more) software versions activated for a single managed element. It is expected that all installed versions are listed as Active and the Priority shows which version is the primary and which are available for redundancy.
List /xyz/openbmc_project/software/. This list can be filtered to just active listing .../software/active/ and following the software_version association to retrieve version information.
List /xyz/openbmc_project/inventory/.../<item>/activation association.
HTTP PUT to /xyz/openbmc_project/software/. ImageManager will assign the <id> when called for Object.Add().
Need additional interfaces defined for alternative upload methods.
Modify RequestedActivation to Active on the desired Activation.
Set Priority to 0 on the desired RedundancyPriority interface.