Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) =======================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) efivarfs - a (U)EFI variable filesystem
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) =======================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) The efivarfs filesystem was created to address the shortcomings of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) using entries in sysfs to maintain EFI variables. The old sysfs EFI
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) variables code only supported variables of up to 1024 bytes. This
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) limitation existed in version 0.99 of the EFI specification, but was
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) removed before any full releases. Since variables can now be larger
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) than a single page, sysfs isn't the best interface for this.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) Variables can be created, deleted and modified with the efivarfs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) filesystem.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) efivarfs is typically mounted like this::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) 	mount -t efivarfs none /sys/firmware/efi/efivars
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) Due to the presence of numerous firmware bugs where removing non-standard
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) UEFI variables causes the system firmware to fail to POST, efivarfs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) files that are not well-known standardized variables are created
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) as immutable files.  This doesn't prevent removal - "chattr -i" will work -
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) but it does prevent this kind of failure from being accomplished
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) accidentally.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) .. warning ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29)       When a content of an UEFI variable in /sys/firmware/efi/efivars is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30)       displayed, for example using "hexdump", pay attention that the first
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)       4 bytes of the output represent the UEFI variable attributes,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)       in little-endian format.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34)       Practically the output of each efivar is composed of:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36)           +-----------------------------------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)           |4_bytes_of_attributes + efivar_data|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)           +-----------------------------------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) *See also:*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) - Documentation/admin-guide/acpi/ssdt-overlays.rst
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) - Documentation/ABI/stable/sysfs-firmware-efi-vars