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    Subject[PATCH 49/50] efivars: Add Documentation
    Date
    From: Mike Waychison <mikew@google.com>

    This patch documents the interface exposed by the 'efivars' module.

    Signed-off-by: Mike Waychison <mikew@google.com>
    Cc: Matt Domsch <Matt_Domsch@dell.com>,
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    Documentation/ABI/stable/sysfs-firmware-efi-vars | 75 ++++++++++++++++++++++
    1 files changed, 75 insertions(+), 0 deletions(-)
    create mode 100644 Documentation/ABI/stable/sysfs-firmware-efi-vars

    diff --git a/Documentation/ABI/stable/sysfs-firmware-efi-vars b/Documentation/ABI/stable/sysfs-firmware-efi-vars
    new file mode 100644
    index 0000000..5def20b
    --- /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.
    --
    1.7.4.1


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