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diff --git a/Documentation/lib/abi-data-consumption.md b/Documentation/lib/abi-data-consumption.md new file mode 100644 index 000000000000..d162199cab1b --- /dev/null +++ b/Documentation/lib/abi-data-consumption.md @@ -0,0 +1,25 @@ +# ABI data consumption + +This text describes the ABI coreboot presents to downstream users. Such +users are payloads and/or operating systems. Therefore, this text serves +at what can be relied on for downstream consumption. Anything not explicitly +listed as consumable is subject to change without notice. + +## Background and Usage + +coreboot passes information to downstream users using coreboot tables. These +table definitions can be found in +`./src/commonlib/include/commonlib/coreboot_tables.h` and +`./payloads/libpayload/include/coreboot_tables.h` respectively within coreboot +and libpayload. One of the most vital and important pieces of information +found within these tables is the memory map of the system indicating +available and reserved memory. + +In 2009 cbmem was added to coreboot. The "CBMEM high table memory manager" +serves a way for coreboot to bookkeep its own internal data. While some +of this data may be exposed through the coreboot tables the data structures +used to manage the data within the cbmem area is subject to change. + +Provided the above, if one needs a piece of data exposed to the OS +or payload it should reside within the coreboot tables. If it isn't there +then a code change will be required to add it to the coreboot tables. |