In this guest column, two engineers with Intel’s Software and Solutions Group describe the benefits of UEFI pre-boot software to mobile and embedded devices. The Unified Extensible Firmware Interface specifications are meant to facilitate emerging technologies, services, security mechanisms, and user experiences that come into play prior to loading the device’s OS.

 

Designed to allow for cross-functionality between devices, software, and systems, Unified Extensible Firmware Interface (UEFI) specifications encourage innovation, helping to drive the evolution of next-generation technologies, such as the expansion of embedded and non-PC systems. To accomplish this, UEFI provides a plurality of services, including console, storage, and networking services.

Hosted and implemented by the UEFI Forum, this technology enables firmware innovation by promoting a standardized, extensible, and interoperable firmware interface that extends far beyond the PC and into the future of computing and the realm of embedded systems.
 

Embedded systems — from simple-state platforms to 64-bit micros

Decades ago, embedded systems were analog or simple-state, machine-based platforms using SSI, MSI, or PLDs. In 1970, the Intel 4004 introduced the ability for reprogrammable embedded systems, such as traffic lights, controls, and other fixed-function usages.

The microprocessor ushered in a wave of continual evolution, demonstrated by the embedded market shift from 8-bit, to 16-bit, to 32-bit, to 64-bit microprocessors. This reflects the progression from simple cell phones to smartphones, from mechanical brakes to microprocessor-controlled anti-lock units, and from handwritten directions to satellite-based navigation systems. Along with this advancement, in-vehicle infotainment and digital signage emerged, along with many other instances of hidden intelligence in the world around us — providing several new modes of utility for UEFI.

This wave of hardware evolution brought about a nearly insatiable appetite for software.
 

Scaling the PC ecosystem into the embedded space

With the increasing richness of the software ecosystem and the growing complexity of platforms, a layer between the operating system kernel and the platform became a necessity. As UEFI-enabled PC platforms became pervasive, a new challenge emerged: how does one take the evolving PC ecosystem and scale it down for use in the embedded space? Typical PC platforms aren’t scaled to meet the advances in the embedded territory. For various embedded operating systems, user demand drives a vastly different set of requirements, such as instant power-on.

Many of these operating systems require customized firmware with OS-specific hardware interfaces in order to fit into the PC firmware ecosystem model. Ultimately, everyone — from the vendor, to the developer, to the end-user — wants to work smarter, as opposed to harder. The contemporary challenge is to provide the embedded platform firmware with capabilities comparable to the traditional model. The firmware must be OS-agnostic, scalable across different platform hardware, and capable of enhancing the efficiency of developers. With its capability of supporting scalability, UEFI specifications fulfill a unique role.

UEFI specifications provide a consistent set of OS-agnostic software interfaces that abstract the underlying details of the platform. These abstractions can be layered upon SATA, SCSI, iSCSI, USB Bulk Only Transport, or any other block device. By traveling with the system board, UEFI serves as a set of built-in drivers and capabilities upon which operating system loaders and pre-OS applications can depend.

From the software perspective, not only does UEFI work across platforms to help facilitate growth and interoperability, but it serves as a useful tool in the fight against malware in the pre-OS space. Using UEFI standards, independent software vendors (ISVs) serving the pre-OS market can write interoperable applications — such as provisioning agents, diagnostics, and full-disk encryption. Because UEFI standards enable troubleshooting and testing to be completed prior to when the OS loads, efficiency in the development process is enhanced.

From the hardware perspective, UEFI specifications promote innovation and interoperability, working across platforms to sustain technological growth. Independent hardware vendors (IHVs) support UEFI drivers that are designed to function on any UEFI-conformant system board. These driver programs can function under UEFI specifications on multiple processor architectures.
 

UEFI architecture and optimization of extensible boot

From its onset, UEFI firmware was designed to support extreme scalability, as shown in the diagram below. There are no design differences between the normal boot and an optimized boot. Optimizing a platform’s performance does not require violating any of the design specifications. Additionally, a UEFI standards-compliant design need not encompass all aspects of the standard PC architecture; instead, its scope can be limited to the components required for platform initialization.

Architectural boot flow comparison
(click image to enlarge; source Intel)

Designed for scalability, extensibility and interoperability, UEFI is well-positioned to streamline technological evolution in both PC and embedded applications. As the complexity of the platform increases in the embedded sphere, the decoupling of concerns between the hardware and system software constituencies makes way for the flexibility and standardization provided by UEFI.

For more information about UEFI, visit the UEFI Forum website.
 

Michael Rothman is an engineer in the Software and Solutions Group at Intel. During his career, he has had published several technical articles and books, more than 200 US patents issued, and has presented at multiple industry conferences. You can find him on Twitter at @MichaelARothman. Vincent Zimmer is an engineer in the Software and Solutions Group at Intel. Originally from Houston, he has worked at Intel since 1997. During his 20 years working in embedded systems and firmware, he has received more than 250 US patents, presented at several industry conferences and contributed to several book publications.