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| author | Patrick Rudolph <patrick.rudolph@9elements.com> | 2019-12-13 12:16:06 +0100 |
|---|---|---|
| committer | Felix Held <felix-coreboot@felixheld.de> | 2020-01-09 14:22:51 +0000 |
| commit | c83bab62b3657d97299c8368b6c610e4cbf994b6 (patch) | |
| tree | f568d7f66b4a3491c6292040db29905111771de4 /Documentation/acpi | |
| parent | 5c8ff794a8dcb0760c137d3b2dff1879a4a8dad6 (diff) | |
| download | coreboot-c83bab62b3657d97299c8368b6c610e4cbf994b6.tar.xz | |
acpi: Be more ACPI compliant when generating _UID
* Add function to generate unique _UID using CRC32
* Add function to write the _UID based on a device's ACPI path
ACPI devices that have the same _HID must use different _UID.
Linux doesn't care about _UID if it's not used.
Windows 10 verifies the ACPI code on boot and BSODs if two devices
with the same _HID share the same _UID.
Fixes BSOD seen on Windows 10.
Change-Id: I47cd5396060d325f9ce338afced6af021e7ff2b4
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37695
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
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 8add8db387..c378722018 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 0000000000..0354bc52f0 --- /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. |