Give some rationale behind EBBR so the reader understands what problem the specification is intended to solve.
Signed-off-by: Bill Mills <[email protected]> [glikely: made it more verbose to make the intent clear] Signed-off-by: Grant Likely <[email protected]> --- source/chapter1-about.rst | 94 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) diff --git a/source/chapter1-about.rst b/source/chapter1-about.rst index b667f1b..cb675d9 100644 --- a/source/chapter1-about.rst +++ b/source/chapter1-about.rst @@ -23,6 +23,100 @@ It leverages the prevalent industry standard firmware specification of [UEFI]_. Comments or change requests can be sent to [email protected]. +Guiding Principals +================== + +EBBR as a specification defines requirements on platforms and operating systems, +but requirements alone don't provide insight into why the specification is +written the way it is, or what problems it is intended to solve. +Using the assumption that better understanding of the thought process behind +EBBR will result in better implementations, this section is a discussion of the +goals and guiding principle that shaped EBBR. + +This section should be considered commentary, and not a formal part of the specification. + +EBBR was written as a response to the lack of boot sequence standardization in the embedded system ecosystem. +As embedded systems are becoming more sophisticated and connected, +it is becoming increasingly important for embedded systems to run standard OS +distributions and software stacks, or to have consistent behaviour across a +large deployment of heterogeneous platforms. +However, the lack of consistency between platforms often requires per-platform +customization to get an OS image to boot on multiple platforms. + +A large part of this ecosystem is based on U-Boot and Linux. +Vendors have heavy investments in both projects and are not interested in large +scale changes to their firmware architecture. +The challenge for EBBR is to define a set of boot standards that reduce the +amount of custom engineering required, make it possible for OS distributions to +support embedded platforms, while still preserving the firmware stack product +vendors are comfortable with. +Or in simpler terms, EBBR is designed to solve the embedded boot mess by +migrating existing firmware projects (U-Boot) to a defined standard (UEFI). + +However, EBBR is a specification, not an implementation. +The goal of EBBR is not to mandate U-Boot and Linux. +Rather, it is to mandate interfaces that can be implemented by any firmware or +OS project, while at the same time work with both Tianocore/EDK2 and U-Boot to +ensure that the EBBR requirements are implemented by both projects. +[#EDK2Note]_ + +.. [#EDK2Note] Tianocore/EDK2 and U-Boot are highlighted here because at the + time of writing these are the two most important firmware projects. + Tianocore/EDK2 is a full featured UEFI implementation and so should + automatically be EBBR compliant. U-Boot is the incumbant firmware project + for embedded platforms and has added basic UEFI compliance. + +The following guiding principals of the EBBR specification and its +process: + +- Be agnostic about ACPI and Devicetree. + + EBBR explicitly does not require a specific system description language. + Both Devicetree and ACPI are supported. + While ACPI provides more standardization, Devicetree is preferred in may embedded + platforms for its flexibility. + The Linux kernel supports both equally well, and so EBBR doesn't require one + over the other. + However, it does require the system description to be provided by the + platform, and that it conform to the relevant ACPI or DT specifications. + +- Focus on the UEFI interface, not a specific codebase + + EBBR does not require a specific firmware implementation. + Any firmware project can implement these interfaces. + Neither U-Boot nor Tianocore/EDK2 are required. + +- Design to be implementable and useful today + + The drafting process for EBBR worked closely with U-Boot and Tianocore + developers to ensure that current upstream code will meet the requirements. + +- Design to be OS independent + + This document uses Linux as an example but other OS's are expected. + +- Support multiple architectures + + Any architecture can implement the EBBR requirements. + + .. note:: + At the time of writing this document only addresses AArch64, but AArch32 and others architectures are expected. + +- Design for common embedded hardware + + EBBR support will be implemented on existing developer hardware. + Generally anything that has a near-upstream U-Boot implementation should be + able to implement the EBBR requirements. + EBBR was drafted with readily available hardware in mind, like the + Raspberry Pi and BeagleBone families of boards, and it is applicable for low cost boards (<$10). + +- Plan to evolve over time + + The first release of EBBR is firmly targeting current embedded hardware. + Future versions will add capabilities which may tighten the hardware requirements. + + However, existing compliant boards will remain compliant. + Scope ===== This document defines the boot and runtime services that are expected by an -- 2.13.0 _______________________________________________ boot-architecture mailing list [email protected] https://lists.linaro.org/mailman/listinfo/boot-architecture
