Add a motivation and purpose for this new proposed node.
Signed-off-by: Simon Glass sjg@chromium.org ---
(no changes since v1)
dtschema/schemas/firmware.yaml | 83 ++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 dtschema/schemas/firmware.yaml
diff --git a/dtschema/schemas/firmware.yaml b/dtschema/schemas/firmware.yaml new file mode 100644 index 0000000..4439a70 --- /dev/null +++ b/dtschema/schemas/firmware.yaml @@ -0,0 +1,83 @@ +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-clause +# Copyright 2023 Google LLC +# + +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/firmware.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: /firmware Node + +maintainers: + - Simon Glass sjg@chromium.org + +description: | + The '/firmware' node does not represent a real device, but serves as a place + for recording information about the main firmware used on the device, such as + a map of its contents. This is used by the Operating System (OS), user space + programs and possibly other firmware components. Data in the '/firmware' node + does not itself represent the hardware. + + Properties in this node should be common to (and used by) at least two + firmware projects, such as U-Boot and TF-A. Project-specific subnodes can be + used for properties which are specific to a single project. + + Purpose of '/firmware' node + --------------------------- + + Firmware has traditionally been fairly opaque to the OS, with the OS taking + no interest in its contents, version, layout or how it might be updated. This + is less than ideal, since firmware is an important part of the system and + visibility into its operation is every bit as important as visbility into the + OS and user-space programs within the system. + + The traditional approach has been to let firmware deal with firmware, and the + OS deal with everything else. Updating firmware has been handled by firmware. + For example, the UEFI spec defines a way for the OS to post a 'capsule' which + is discovered next time the system boots, permitting firmware updates. But + firmware updates in firmware are highly problematic. They require a reboot + and a sometimes-lengthy wait with a strange-looking interface unfamiliar + to most users. It seems better to make the update as transparent as possible + to the user. As an example of that, ChromeOS has full knowledge of the + firmware version and layout, updates it in the background from user space and + instantly selects the new firmware when the user reboots or logs out. + + A common objection to considering the system holistically is that some parts + of the system are inaccessible to the OS, such as a secure enclave. However + this does not preclude providing visibility into what is present in that + enclave. Firmware-version information is still useful. Firmware updates are + still needed and can still be initiated from user space. + + Another objection is that firmware should provide an interface to the OS, + while keeping its structure private. This thinking is largely driven by + extrapolating from how firmware has been handled in the 'BIOS' days. + It should be considered a degenerate case rather than the norm. As complexity + increases, it creates an artificial boundary between two pieces of the whole. + Mechanisms then need to be invented to cross this unnecessary chasm. An + example of this is Intel's Dynamic Platform and Thermal Framework (DPTF), + which consists of user-space, OS and firmware components all working towards + a shared goal. We need a standard description of these cross-system pieces. + + In order to 'teach the OS about firmware', we need a place to put this + information. That is the purpose of this node. + + In an Open Source world the entire model of firmware needs to adjust to be + more open, more visible and managed just like any other part of the system. + The major goal is to standardise how firmware is presented to the OS and user + space, so that common utilities can be used to manage the entire system, + including the firmware. For example, fwupd can look in this node for + information on how to update the firmware, similar to how VBE works. [1] + It is likely that other purposes will come to light over time. + + [1] https://github.com/fwupd/fwupd/tree/main/plugins/vbe + +properties: + $nodename: + const: firmware + + "#address-cells": true + "#size-cells": true + +additionalProperties: + type: object