EBBR only requires a subset of UEFI. Provide a replacement for the UEFI section that lists base requirements.
Fixes: #60 Fixes: #61 Fixes: #64 --- source/chapter2-uefi.rst | 164 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 162 insertions(+), 2 deletions(-)
diff --git a/source/chapter2-uefi.rst b/source/chapter2-uefi.rst index 9906fd9..f47a98d 100644 --- a/source/chapter2-uefi.rst +++ b/source/chapter2-uefi.rst @@ -14,8 +14,168 @@ This document uses version 2.8 Errata A of the UEFI specification [UEFI]_. UEFI Compliance ===============
-EBBR compliant platforms shall conform to the requirements in [UEFI]_ § 2.6, -except where explicit exemptions are provided by this document. +EBBR compliant platform shall conform to a subset of the [UEFI]_ spec as listed +in this section. +Normally, UEFI compliance would require full compliance with all items listed +in UEFI § 2.6. +However, the EBBR target market has a reduced set of requirements, +and so some UEFI features are omitted as unnecessary. + +Required Elements +----------------- + +This section replaces the list of required elements in [UEFI]_ § 2.6.1. +All of the following UEFI elements are required for EBBR compliance. + +.. list-table:: UEFI Required Elements + :widths: 50 50 + :header-rows: 1 + + * - Element + - Requirement + * - `EFI_SYSTEM_TABLE` + - The system table is required to provide required to access UEFI Boot Services, + UEFI Runtime Services, consoles, and other firmware, vendor and platform + information. + * - `EFI_BOOT_SERVICES` + - All functions defined as boot services must exist. + Methods for unsupported or unimplemented behaviour must return + an appropriate error code. + * - `EFI_RUNTIME_SERVICES` + - All functions defined as runtime services must exist. + Methods for unsupported or unimplemented behaviour must return + an appropriate error code. + * - `EFI_LOADED_IMAGE_PROTOCOL` + - Must be installed for each loaded image + * - `EFI_LOADED_IMAGE_DEVICE_PATH_PROTOCOL` + - Must be installed for each loaded image + * - `EFI_DEVICE_PATH_PROTOCOL` + - An `EFI_DEVICE_PATH_PROTOCOL` must be installed onto all device + handles provided by the firmware. + * - `EFI_DEVICE_PATH_UTILITIES_PROTOCOL` + - Interface for creating and manipulating UEFI device paths + +.. list-table:: Notable omissions from UEFI § 2.6.1 + :header-rows: 1 + + * - Element + - Note + * - `EFI_DECOMPRESS_PROTOCOL` + - Native EFI decompression is rarely used and therefore not required. + +Required Platform Specific Elements +----------------------------------- + +This section replaces the list of required elements in [UEFI]_ § 2.6.2. +All of the following UEFI elements are required for EBBR compliance. + +.. list-table:: UEFI Platform-Specific Required Elements + :widths: 50 50 + :header-rows: 1 + + * - Element + - Description + * - Console devices + - The platform must have at least one console device + * - `EFI_SIMPLE_TEXT_INPUT_PROTOCOL` + - Needed for console input + * - `EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL` + - Needed for console input + * - `EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL` + - Needed for console output + * - `EFI_DEVICE_PATH_TO_TEXT_PROTOCOL` + - Needed for console output + * - `EFI_HII_STRING_PROTOCOL` + - Required by EFI shell and for compliance testing + * - `EFI_HII_DATABASE_PROTOCOL` + - Required by EFI shell and for compliance testing + * - `EFI_UNICODE_COLLATION2_PROTOCOL` + - Required by EFI shell and for compliance testing + * - `EFI_BLOCK_IO_PROTOCOL` + - Required for block device access + * - `EFI_SIMPLE_FILE_SYSTEM_PROTOCOL` + - Required if booting from block device is supported + * - `EFI_RNG_PROTOCOL` + - Required if the platform has a hardware entropy source + * - `EFI_SIMPLE_NETWORK_PROTOCOL` + - Required if the platform has a network device. + * - HTTP Boot (UEFI § 24.7) + - Required if the platform supports network booting + +The following table is a list of notable deviations from UEFI § 2.6.2. +Many of these deviations are because the EBBR use cases do not require +interface specific UEFI protocols, and so they have been made optional. + +.. list-table:: Notable Deviations from UEFI § 2.6.2 + :widths: 50 50 + :header-rows: 1 + + * - Element + - Description of deviation + * - `EFI_HII_CONFIG_ACCESS_PROTOCOL` + - UEFI requires this for console devices, but it is rarely necessary in practice. + Therefore this protocol is not required. + * - `EFI_HII_CONFIG_ROUTING_PROTOCOL` + - UEFI requires this for console devices, but it is rarely necessary in practice. + Therefore this protocol is not required. + * - Graphical console + - Platforms with a graphical device are not required to expose it as a graphical console. + * - `EFI_DISK_IO_PROTOCOL` + - Rarely used interface that isn't required for EBBR use cases + * - `EFI_PXE_BASE_CODE_PROTOCOL` + - Booting via the Preboot Execution Environment (PXE) is insecure. + Loading via PXE is typically executed before launching the first UEFI application. + * - Network protocols + - A full implementation of the UEFI general purpose networking ABIs is not required, + including `EFI_NETWORK_INTERFACE_IDENTIFIER_PROTOCOL`, `EFI_MANAGED_NETWORK_PROTOCOL`, + `EFI_*_SERVICE_BINDING_PROTOCOL`, or any of the IPv4 or IPv6 protocols. + * - Byte stream device support (UART) + - UEFI protocols not required + * - PCI bus support + - UEFI protocols not required + * - USB bus support + - UEFI protocols not required + * - NVMe pass through support + - UEFI protocols not required + * - SCSI pass through support + - UEFI protocols not required + * - SCSI pass through support + - UEFI protocols not required + * - `EFI_DRIVER_FAMILY_OVERRIDE_PROTOCOL` + - Not required + * - Option ROM support + - In many EBBR use cases there is no requirement to generically support + any PCIe add in card at the firmware level. + When PCIe devices are used, drivers for the device are often built into + the firmware itself rather than loaded as option ROMs. + For this reason EBBR implementations are not required to support option + ROM loading. + +Required Global Variables +------------------------- + +EBBR compliant platforms are required to support the following Global +Variables as found in [UEFI]_ § 3.3. + +.. list-table:: Required UEFI Variables + :widths: 25 75 + :header-rows: 1 + + * - Variable Name + - Description + * - `Boot####` + - A boot load option. #### is a numerical hex value + * - `BootCurrent` + - The boot option that was selected for the current boot + * - `BootNext` + - The boot option that will be used for the next boot only + * - `BootOrder` + - An ordered list of boot options. + Firmware will attempt each Boot#### entry in this order + * - `OsIndications` + - Method for OS to request features from firmware + * - `OsIndicationsSupported` + - Variable for firmware to indicate which features can be enabled
Block device partitioning -------------------------