Here’s a bit more information about UEFI 2.6, from the changelog in the spec. There are 25 2.5 errata changes, and 39 new 2.6 features, ranging from October 2015 to January 2016.
UEFI 2.5 errata:
1209 UEFI networking API chapter 2.6 requirements errors
1363 Short form URI device path
1365 7.4 Virtual Memory Services lists Section 2.3.2 through Section 2.3.4. incorrectly
1381 Remove informative content in 12.6.1
1388 Missed memory type
1398 Errata update to the runtime GetVariable operation documentation
1399 Clarification for EFI_BROWSER_ACTION_REQUEST_RECONNECT
1405 Errata in table 271 in Appendix O
1407 Networking errata – EFI_HTTP_STATUS typos
1410 Clarifications in appendix O
1417 Add HttpMethodMax to EFI_HTTP_METHOD enum
1418 Inconsistent issues in DNS
1419 Supplicant protocol using same GUID as TLS protocol
1420 GetNextHighMonotonicCount clarification
1421 Misc HTTP API typos
1424 Incorrect link in Section 22.1 FMP GetImageInfo()
1426 UEFI 2.5 typo
1441 UEFI2.5 errata – UNDI Protocol Clarification
1451 Memory Map Consistency
1468 Errata on UEFI Supplicant protocol
1469 UNDI Errata – add more statistics
1472 ATA Pass Thru Errata
1476 Update to Indicate that CloseEvent Unregisters Corresponding Protocol Notification Registrations
1477 Allow CloseEvent to be called within the Notification Function
1481 new network config2 protocol data structure has a magic number
UEFI 2.6 new features:
1357 ARM CPER extensions
1402 Add EFI_BROWSER_ACTION_SUBMITTED
1471 SD/eMMC PassThru Protocol update (follow up to mantis 1376)
1376 SD/eMMC PassThru Protocol
1408 EFI HII Font EX protocol and EFI HII Font Glyph Generator protocols
1414 Generalisation of communication method in Appendix O
1467 New API – EFI_WIRELESS_MAC_CONNECTION_II_PROTOCOL
1480 Refine Progress description in EFI_KEYWORD_HANDLER_PROTOCOL
1452 Minor edits to 0001409
1409 EFI HII ImageEX protocol and EFI HII Image Decoder protocols
1466 UEFI Ram disk protocol
1383 Adding an EraseBlocks() function to a new protocol
1479 UEFI Properties Table Clarification
1491 supplicant errata
1492 wireless mac connection protocol II errata
1493 Updates to the SD_MMC_PASS_THRU interface
1494 Errata against UEFI 2.5 Properties Table
1496 Bad table reference in 13.2 EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL.Configuration()
1501 Define the usage of the “Address Space Granularity” field is defined in the PCI Root IO
1502 PCI IO Define how to use the Address Translation Offset for systems that are not mapped 1:1
1507 Insufficient qualification of page attributes for AArch64
1508 Lack of flexibility and realism in exception level choice when calling runtime services
1509 EFI_PLATFORM_TO_DRIVER_CONFIGURATION_PROTOCOL Response to unsupported ParameterTypeGuid
1516 Editorial comments against 2.6 Draft
1518 Comments against 2.6 Draft
1519 Version for the next UEFI spec is…
1521 comment against UEFI.next draft – M1479
1522 AArch64 bindings Alignment bit errata
1523 Comments against 2.6 Draft
1533 Bugs in the HTTP usage example
1534 Editorial comments against 2.6 Final Draft
1536 UEFI 2.6 Errata : IMAGE EX Protocol and EFI HII Image Decoder protocol Errata
1538 UEFI TLS errata
1539 New EFI_HTTP_ERROR Status Code
1542 UEFI 2.6 supplicant errata
1543 ip4/6 config policy errata/2.6 update
1544 DNS lookup API spelling
1547 Clarify requirements for setting the PK variable.
1548 Clarify boot procedure when file name is absent
The numbers mentioned are the Mantis issue tracking number that UEFI Forum uses to track changes in the spec. This mantis database is only available to UEFI Forum members, nonmmembers can ignore these, sometimes you can search for older references to mantis numbers for older UEFI spec features.
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