efivarfs: Add documentation for the EFI variable filesystem

Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/filesystems/efivarfs.txt b/Documentation/filesystems/efivarfs.txt
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index 00000000000..c477af086e6
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+++ b/Documentation/filesystems/efivarfs.txt
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+
+efivarfs - a (U)EFI variable filesystem
+
+The efivarfs filesystem was created to address the shortcomings of
+using entries in sysfs to maintain EFI variables. The old sysfs EFI
+variables code only supported variables of up to 1024 bytes. This
+limitation existed in version 0.99 of the EFI specification, but was
+removed before any full releases. Since variables can now be larger
+than a single page, sysfs isn't the best interface for this.
+
+Variables can be created, deleted and modified with the efivarfs
+filesystem.
+
+efivarfs is typically mounted like this,
+
+        mount -t efivarfs none /sys/firmware/efi/efivars