diff options
author | Jean Delvare <jdelvare@suse.de> | 2019-01-29 14:11:42 +0100 |
---|---|---|
committer | Jean Delvare <jdelvare@suse.de> | 2019-01-29 14:11:42 +0100 |
commit | 72fa3909cfabe8822e2b8709e5d324008f55022a (patch) | |
tree | 33a6a741026c21130eaab87f00b732ceb57887a6 | |
parent | 91d6ce2d1d2fa6fcedf8e5685bafdb0515317605 (diff) | |
download | dmidecode-git-72fa3909cfabe8822e2b8709e5d324008f55022a.tar.gz |
dmidecode: Document how the UUID fields are interpreted
There has always been a lot of confusion about the byte order of UUID
fields. While dmidecode is doing "the right thing", documenting it
can't hurt.
This should address bug #55510:
https://savannah.nongnu.org/bugs/index.php?55510
Signed-off-by: Jean Delvare <jdelvare@suse.de>
-rw-r--r-- | man/dmidecode.8 | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/man/dmidecode.8 b/man/dmidecode.8 index 33f7d33..52100a8 100644 --- a/man/dmidecode.8 +++ b/man/dmidecode.8 @@ -256,6 +256,20 @@ It is crafted to hard-code the table address at offset 0x20. .IP \(bu "\w'\(bu'u+1n" The DMI table is located at offset 0x20. +.SH UUID FORMAT +There is some ambiguity about how to interpret the UUID fields prior to SMBIOS +specification version 2.6. There was no mention of byte swapping, and RFC 4122 +says that no byte swapping should be applied by default. However, SMBIOS +specification version 2.6 (and later) explicitly states that the first 3 fields +of the UUID should be read as little-endian numbers (byte-swapped). +Furthermore, it implies that the same was already true for older versions of +the specification, even though it was not mentioned. In practice, many hardware +vendors were not byte-swapping the UUID. So, in order to preserve +compatibility, it was decided to interpret the UUID fields according to RFC +4122 (no byte swapping) when the SMBIOS version is older than 2.6, and to +interpret the first 3 fields as little-endian (byte-swapped) when the SMBIOS +version is 2.6 or later. The Linux kernel follows the same logic. + .SH FILES .I /dev/mem .br |