On 01/18/2015 11:54 AM, Linus Torvalds wrote:
Why?
Probably because some of us are, unfortunately, sometimes clueless :-(. Guenter
The 8- and 16- bit versions are the same as the 32-bit one. This seems pointless. If you want something where the sign is in bit 3, they all return the same value, just the return type differs, but that's really a *caller* thing, no?
Linus
On Jan 19, 2015 7:07 AM, "tip-bot for Martin Kepplinger" <tipbot@xxxxxxxxx <mailto:tipbot@xxxxxxxxx>> wrote:
Commit-ID: 7e9358073d3f0ed0a028c48aa54009b3296dffc9
Gitweb: http://git.kernel.org/tip/7e9358073d3f0ed0a028c48aa54009b3296dffc9
Author: Martin Kepplinger <martink@xxxxxxxxx <mailto:martink@xxxxxxxxx>>
AuthorDate: Mon, 12 Jan 2015 18:22:50 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx <mailto:mingo@xxxxxxxxxx>>
CommitDate: Sun, 18 Jan 2015 20:03:51 +0100
bitops: Add sign_extend8(), 16 and 64 functions
This adds helper functions for sign-extending signed values of any
lower (hardware-)given size to s8, s16 or s64 respectively, just like
sign_extend32() for s32.
This completes the sign_extend*() API family to work on all bit sizes
like most other bitops APIs do.
Suggested-by: Christoph Muellner <christoph.muellner@xxxxxxxxxxxxxxxxxxxxx <mailto:christoph.muellner@xxxxxxxxxxxxxxxxxxxxx>>
Signed-off-by: Martin Kepplinger <martink@xxxxxxxxx <mailto:martink@xxxxxxxxx>>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx <mailto:linux@xxxxxxxxxxxx>>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx <mailto:peterz@xxxxxxxxxxxxx>>
Cc: John Sullivan <jsrhbz@xxxxxxxxxxxxxxxxxxxx <mailto:jsrhbz@xxxxxxxxxxxxxxxxxxxx>>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx <mailto:torvalds@xxxxxxxxxxxxxxxxxxxx>>
Cc: Maxime COQUELIN <maxime.coquelin@xxxxxx <mailto:maxime.coquelin@xxxxxx>>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx <mailto:paulmck@xxxxxxxxxxxxxxxxxx>>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx <mailto:linux@xxxxxxxxxxxxxxxxxx>>
Cc: Theodore Ts'o <tytso@xxxxxxx <mailto:tytso@xxxxxxx>>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx <mailto:akpm@xxxxxxxxxxxxxxxxxxxx>>
Link: http://lkml.kernel.org/r/1421083370-24924-1-git-send-email-martink@xxxxxxxxx
Signed-off-by <http://lkml.kernel.org/r/1421083370-24924-1-git-send-email-martink@xxxxxxxxx Signed-off-by>: Ingo Molnar <mingo@xxxxxxxxxx <mailto:mingo@xxxxxxxxxx>>
---
include/linux/bitops.h | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 5d858e0..9c31680 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -161,6 +161,28 @@ 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_extend16 - sign extend a 16-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<16) to sign bit
+ */
+static inline __s16 sign_extend16(__u16 value, int index)
+{
+ __u8 shift = 15 - index;
+ return (__s16)(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
@@ -171,6 +193,17 @@ static inline __s32 sign_extend32(__u32 value, int index)
return (__s32)(value << shift) >> shift;
}
+/**
+ * sign_extend64 - sign extend a 64-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<64) to sign bit
+ */
+static inline __s64 sign_extend64(__u64 value, int index)
+{
+ __u8 shift = 63 - index;
+ return (__s64)(value << shift) >> shift;
+}
+
static inline unsigned fls_long(unsigned long l)
{
if (sizeof(l) == 4)
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