linux-kernel - [PATCH 1/6] bitops.h: add sign

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Message-Id: <1418660317-21750-2-git-send-email-martink@posteo.de>
Date:	Mon, 15 Dec 2014 17:18:32 +0100
From:	Martin Kepplinger <martink@...teo.de>
To:	peterz@...radead.org
Cc:	mingo@...nel.org, tytso@....edu, linux-kernel@...r.kernel.org,
	Martin Kepplinger <martink@...teo.de>
Subject: [PATCH 1/6] bitops.h: add sign_extend8 function

This adds a helper function that extends any signed value smaller than
8 bits to a s8.

Signed-off-by: Martin Kepplinger <martink@...teo.de>
---
 include/linux/bitops.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 5d858e0..3c2a539 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -161,6 +161,17 @@ static inline __u8 ror8(__u8 word, unsigned int shift)
 }
 
 /**
+ * sign_extend8 - sign extend a 8-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<8) to sign bit
+ */
+static inline __s8 sign_extend8(__u8 value, int index)
+{
+	__u8 shift = 7 - index;
+	return (__s8)(value << shift) >> shift;
+}
+
+/**
  * sign_extend32 - sign extend a 32-bit value using specified bit as sign-bit
  * @value: value to sign extend
  * @index: 0 based bit index (0<=index<32) to sign bit
-- 
2.1.3

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