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| -rw-r--r-- | Documentation/ABI/stable/sysfs-firmware-efi-vars | 75 |
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diff --git a/Documentation/ABI/stable/sysfs-firmware-efi-vars b/Documentation/ABI/stable/sysfs-firmware-efi-vars new file mode 100644 index 000000000000..5def20b9019e --- /dev/null +++ b/Documentation/ABI/stable/sysfs-firmware-efi-vars @@ -0,0 +1,75 @@ +What: /sys/firmware/efi/vars +Date: April 2004 +Contact: Matt Domsch <Matt_Domsch@dell.com> +Description: + This directory exposes interfaces for interactive with + EFI variables. For more information on EFI variables, + see 'Variable Services' in the UEFI specification + (section 7.2 in specification version 2.3 Errata D). + + In summary, EFI variables are named, and are classified + into separate namespaces through the use of a vendor + GUID. They also have an arbitrary binary value + associated with them. + + The efivars module enumerates these variables and + creates a separate directory for each one found. Each + directory has a name of the form "<key>-<vendor guid>" + and contains the following files: + + attributes: A read-only text file enumerating the + EFI variable flags. Potential values + include: + + EFI_VARIABLE_NON_VOLATILE + EFI_VARIABLE_BOOTSERVICE_ACCESS + EFI_VARIABLE_RUNTIME_ACCESS + EFI_VARIABLE_HARDWARE_ERROR_RECORD + EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS + + See the EFI documentation for an + explanation of each of these variables. + + data: A read-only binary file that can be read + to attain the value of the EFI variable + + guid: The vendor GUID of the variable. This + should always match the GUID in the + variable's name. + + raw_var: A binary file that can be read to obtain + a structure that contains everything + there is to know about the variable. + For structure definition see "struct + efi_variable" in the kernel sources. + + This file can also be written to in + order to update the value of a variable. + For this to work however, all fields of + the "struct efi_variable" passed must + match byte for byte with the structure + read out of the file, save for the value + portion. + + **Note** the efi_variable structure + read/written with this file contains a + 'long' type that may change widths + depending on your underlying + architecture. + + size: As ASCII representation of the size of + the variable's value. + + + In addition, two other magic binary files are provided + in the top-level directory and are used for adding and + removing variables: + + new_var: Takes a "struct efi_variable" and + instructs the EFI firmware to create a + new variable. + + del_var: Takes a "struct efi_variable" and + instructs the EFI firmware to remove any + variable that has a matching vendor GUID + and variable key name. |