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[4/4] efivarfs: Add documentation for the EFI variable filesystem

Message ID 1349782020-18070-5-git-send-email-apw@canonical.com
State New
Headers show

Commit Message

Andy Whitcroft Oct. 9, 2012, 11:27 a.m. UTC 
From: Matt Fleming <matt.fleming@intel.com>

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

(cherry-picked from commit 91a8a3052685c61d6061c0b11376edfee9d74f61 efi.git)
BugLink: http://bugs.launchpad.net/bugs/1063061
Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
 Documentation/filesystems/00-INDEX     |    2 ++
 Documentation/filesystems/efivarfs.txt |   16 ++++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 Documentation/filesystems/efivarfs.txt
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Patch

diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index 8c624a1..7b52ba7 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -38,6 +38,8 @@  dnotify_test.c
 	- example program for dnotify
 ecryptfs.txt
 	- docs on eCryptfs: stacked cryptographic filesystem for Linux.
+efivarfs.txt
+	- info for the efivarfs filesystem.
 exofs.txt
 	- info, usage, mount options, design about EXOFS.
 ext2.txt
diff --git a/Documentation/filesystems/efivarfs.txt b/Documentation/filesystems/efivarfs.txt
new file mode 100644
index 0000000..c477af0
--- /dev/null
+++ b/Documentation/filesystems/efivarfs.txt
@@ -0,0 +1,16 @@ 
+
+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