+1 On Fri, Jul 6, 2018, 5:26 PM Grant Likely <grant.lik...@arm.com> wrote:
> Give some rationale behind EBBR so the reader understands what problem > the specification is intended to solve. > > Signed-off-by: Bill Mills <wmi...@ti.com> > [glikely: made it more verbose to make the intent clear] > Signed-off-by: Grant Likely <grant.lik...@arm.com> > --- > 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 arm.ebbr-disc...@arm.com. > > +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 > > _______________________________________________ > Arm.ebbr-discuss mailing list > arm.ebbr-disc...@arm.com > -- David A Rusling CTO, Linaro https://linaro.org _______________________________________________ boot-architecture mailing list boot-architecture@lists.linaro.org https://lists.linaro.org/mailman/listinfo/boot-architecture
