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Diffstat (limited to 'Documentation/acpi')
| -rw-r--r-- | Documentation/acpi/index.md | 2 | ||||
| -rw-r--r-- | Documentation/acpi/uid.md | 14 |
2 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/acpi/index.md b/Documentation/acpi/index.md index 8add8db38708..c378722018f7 100644 --- a/Documentation/acpi/index.md +++ b/Documentation/acpi/index.md @@ -2,6 +2,8 @@ This section contains documentation about coreboot on ACPI. +- [SSDT UID generation](uid.md) + ## GPIO - [GPIO toggling in ACPI AML](gpio.md) diff --git a/Documentation/acpi/uid.md b/Documentation/acpi/uid.md new file mode 100644 index 000000000000..0354bc52f0c4 --- /dev/null +++ b/Documentation/acpi/uid.md @@ -0,0 +1,14 @@ +# ACPI SSDT \_UID generation + +According to the ACPI spec: + +> The _UID must be unique across all devices with either a common _HID or _CID. + + +When generating SSDTs in coreboot the independent drivers don't know +which \_UID is already in use for a specific \_HID or \_CID. To generate +unique \_UIDs the ACPI device's path is hashed and used as ID. As every ACPI +device has a different path, the hash will be also different for every device. + +Windows 10 verifies all devices with the same \_HID or \_CID and makes +sure that no \_UID is duplicated. If it is it'll BSOD. |