docs/designs/entity-manager-hw-id-vpd-discover-via-device-tree.md

1 # Entity-Manager HW ID: VPD Discovery via Device-Tree Properties
16 gathered from device tree file paths for Entity-Manager consumption.
34 modifications to the device-tree to output properties as one file handle per
86 the flattened device tree, setting the values for ['/model' and
87 '/serial-number,' which both have well-known paths in the device tree
98 detecting supported hardware configurations. The contents of 'device-tree/model'
104 affect how a service would collect data from the device-tree passed to the
105 kernel from u-Boot. One alternative to modifying the flat device-tree would be
106 to have values like 'model' set in the platform's device-tree source at image
109 This document discusses leveraging a 'device-tree -> D-Bus' daemon in
136   CPLD-based memory device, and exposes it in Linux under /proc/device-tree/
139   tree paths, then parses and publishes to D-Bus
148 ### Entity-Manager probes are extended to handle reading data from arbitrary device-tree nodes
156 1. May encourage undesired device-tree exploitation
158 ### A reserved-memory node in device-tree is used for transport of 'serial-number' and 'model' ID d…
167    like device-tree does; makes more sense for keeping arbitrary data instead of
172    'model' instead of the well known device-tree /model handle would add
174 3. Since /model is well described in device-tree documentation, there is
183 1. Is a well-established device-tree node
186 3. Values can be set from u-Boot via modifications to the flattened device tree
187    available to it (applicable to arbitrary device-tree paths)
234 would be better to host this device-tree VPD daemon in Entity-Manager alongside
254 ### Addendum: Rejected D-Bus interfaces for pending device-tree -> D-Bus daemon
294    Rejection: There are ongoing efforts to enable dynamic device-tree
331 If the path(s) in question do not exist (device-tree/model or
332 device-tree/serial-number), no further work will be done, so there is expected
341 have the device-tree VPD parser daemon hosted in the Entity-Manager repo
346 Technical Oversight Forums consensus has been reached that this device-tree VPD
355 Any platform that has a device-tree 'model' or 'serial-number' node populated in
356 Device-Tree (this can be done by hardcoding a value into the DTS file before
358 device-tree/model and/or serial-number node matches the contents of 'model' and
366 `busctl tree  xyz.openbmc_project.EntityManager` shows a listing of objects that