linux-kernel - [PATCH 05/16] uuid: add the v1 layout to uuid

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Date:   Wed, 10 May 2017 20:02:03 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org
Cc:     Shaohua Li <shli@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        David Howells <dhowells@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        linux-xfs@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: [PATCH 05/16] uuid: add the v1 layout to uuid_t

Turn the content of uuid_t into a union and add the fields for the v1
interpretation to it.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/uapi/linux/uuid.h | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/uuid.h b/include/uapi/linux/uuid.h
index 1a2914d8b225..1039d2f3e114 100644
--- a/include/uapi/linux/uuid.h
+++ b/include/uapi/linux/uuid.h
@@ -25,7 +25,34 @@ typedef struct {
 } guid_t;
 
 typedef struct {
-	__u8 b[16];
+	union {
+		__u8			b[16];
+
+		/*
+		 * V1 (time-based) UUID definition [RFC 4122]:
+		 * - the timestamp is a 60-bit value, split 32/16/12, and goes
+		 *   in 100ns increments since midnight 15th October 1582
+		 *   - add UUID_TO_UNIX_TIME to convert unix time in 100ns
+		 *     units to UUID time
+		 * - the clock sequence is a 14-bit counter to avoid duplicate
+		 *   times
+		 */
+		struct {
+			__be32		time_low;
+			__be16		time_mid;
+			__be16		time_hi_and_version;
+#define UUID_TO_UNIX_TIME	0x01b21dd213814000ULL
+#define UUID_TIMEHI_MASK	0x0fff
+#define UUID_VERSION_TIME	0x1000	/* time-based UUID */
+#define UUID_VERSION_NAME	0x3000	/* name-based UUID */
+#define UUID_VERSION_RANDOM	0x4000	/* (pseudo-)random generated UUID */
+			u8		clock_seq_hi_and_reserved;
+#define UUID_CLOCKHI_MASK	0x3f
+#define UUID_VARIANT_STD	0x80
+			u8		clock_seq_low;
+			u8		node[6];
+		} v1;
+	};
 } uuid_t;
 
 #define GUID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)			\
-- 
2.11.0