1# Entity Manager 2 3Entity manager is a design for managing physical system components, and mapping 4them to software resources within the BMC. Said resources are designed to allow 5the flexible adjustment of the system at runtime, as well as the reduction in 6the number of independent system configurations one needs to create. 7 8## Definitions 9 10### Entity 11 12A server component that is physically separate, detectable through some means, 13and can be added or removed from a given OpenBMC system. Said component can, and 14likely does contain multiple sub-components, but the component itself as a whole 15is referred to as an entity. 16 17Note, this term is needed because most other terms that could've been used 18(Component, Field Replaceable Unit, or Assembly) are already overloaded in the 19industry, and have a distinct definition already, which is a subset of what an 20entity encompasses. 21 22### Exposes 23 24A particular feature of an Entity. An Entity generally will have multiple 25Exposes records for the various features that component supports. Some examples 26of features include, LM75 sensors, PID control parameters, or CPU information. 27 28### Probe 29 30A set of rules for detecting a given entity. Said rules generally take the form 31of a D-Bus interface definition. 32 33## Goals 34 35Entity manager has the following goals (unless you can think of better ones): 36 371. Minimize the time and debugging required to "port" OpenBMC to new systems 382. Reduce the amount of code that is different between platforms 393. Create system level maintainability in the long term, across hundreds of 40 platforms and components, such that components interoperate as much as 41 physically possible. 42 43## Implementation 44 45A full BMC setup using Entity Manager consists of a few parts: 46 471. **A detection daemon** This is something that can be used to detect 48 components at runtime. The most common of these, fru-device, is included in 49 the Entity-Manager repo, and scans all available I2C buses for IPMI FRU 50 EEPROM devices. Other examples of detection daemons include: 51 **[peci-pcie](https://github.com/openbmc/peci-pcie):** A daemon that utilizes 52 the CPU bus to read in a list of PCIe devices from the processor. 53 **[smbios-mdr](https://github.com/openbmc/smbios-mdr):** A daemon that 54 utilizes the x86 SMBIOS table specification to detect the available systems 55 dependencies from BIOS. 56 57 In many cases, the existing detection daemons are sufficient for a single 58 system, but in cases where there is a superseding inventory control system in 59 place (such as in a large datacenter) they can be replaced with application 60 specific daemons that speak the protocol information of their controller, and 61 expose the inventory information, such that failing devices can be detected 62 more readily, and system configurations can be "verified" rather than 63 detected. 64 652. **An entity manager configuration file** Entity manager configuration files 66 are located in the ./configurations directory in the entity manager 67 repository, and include one file per device supported. Entities are detected 68 based on the "Probe" key in the json file. The intention is that this folder 69 contains all hardware configurations that OpenBMC supports, to allows an easy 70 answer to "Is X device supported". An EM configuration contains a number of 71 Exposes records that specify the specific features that this Entity supports. 72 Once a component is detected, entity manager will publish these Exposes 73 records to D-Bus. 74 753. **A reactor** The reactors are things that take the entity manager 76 configurations, and use them to execute and enable the features that they 77 describe. One example of this is dbus-sensors, which contains a suite of 78 applications that input the Exposes records for sensor devices, then connect 79 to the filesystem to create the sensors and scan loops to scan sensors for 80 those devices. Other examples of reactors could include: CPU management 81 daemons and Hot swap backplane management daemons, or drive daemons. 82 83**note:** In some cases, a given daemon could be both a detection daemon and a 84reactor when architectures are multi-tiered. An example of this might include a 85hot swap backplane daemon, which both reacts to the hot swap being detected, and 86also creates detection records of what drives are present. 87 88### Associations 89 90Entity Manager will automatically create associations between its entities in 91certain cases. For details see [here](docs/associations.md). 92 93## Requirements 94 951. Entity manager shall support the dynamic discovery of hardware at runtime, 96 using inventory interfaces. The types of devices include, but are not limited 97 to hard drives, hot swap backplanes, baseboards, power supplies, CPUs, and 98 PCIe Add-in-cards. 99 1002. Entity manager shall support the ability to add or remove support for 101 particular devices in a given binary image. By default, entity manager will 102 support all available and known working devices for all platforms. 103 1043. Entity manager shall provide data to D-Bus about a particular device such 105 that other daemons can create instances of the features being exposed. 106 1074. Entity manager shall support multiple detection runs, and shall do the 108 minimal number of changes necessary when new components are detected or no 109 longer detected. Some examples of re-detection events might include host 110 power on, drive plug/unplug, PSU plug/unplug. 111 1125. Entity manager shall have exactly one configuration file per supported device 113 model. In some cases this will cause duplicated information between files, 114 but the ability to list and see all supported device models in a single 115 place, as well as maintenance when devices do differ in the future is 116 determined to be more important than duplication of configuration files. 117 118### Explicitly out of scope 119 1201. Entity manager shall not directly participate in the detection of devices, 121 and instead will rely on other D-Bus applications to publish interfaces that 122 can be detected. 1232. Entity manager shall not directly participate in management of any specific 124 device. This is requirement is intended to intentionally limit the size and 125 feature set of entity manager, to ensure it remains small, and effective to 126 all users. 127 128### Entity Manager Compatible Software 129 130**bmcweb** A webserver implementation that uses the inventory information from 131entity-manager to produce a Redfish compliant REST API. **intel-ipmi-oem** An 132implementation of the IPMI SDR, FRU, and Storage commands that utilize Entity 133Manager as the source of information. 134 135## Additional Documentation 136 1371. **[Entity Manager DBus API](https://github.com/openbmc/entity-manager/blob/master/docs/entity_manager_dbus_api.md)** 1382. **[My First Sensor Example](https://github.com/openbmc/entity-manager/blob/master/docs/my_first_sensors.md)** 1393. **[Configuration File Schema](https://github.com/openbmc/entity-manager/tree/master/schemas)** 140