Messages in this thread | | | Date | Sun, 18 Jan 2015 17:11:31 -0800 | From | Guenter Roeck <> | Subject | Re: [tip:core/types] bitops: Add sign_extend8(), 16 and 64 functions |
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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@zytor.com <mailto:tipbot@zytor.com>> wrote: > > Commit-ID: 7e9358073d3f0ed0a028c48aa54009b3296dffc9 > Gitweb: http://git.kernel.org/tip/7e9358073d3f0ed0a028c48aa54009b3296dffc9 > Author: Martin Kepplinger <martink@posteo.de <mailto:martink@posteo.de>> > AuthorDate: Mon, 12 Jan 2015 18:22:50 +0100 > Committer: Ingo Molnar <mingo@kernel.org <mailto:mingo@kernel.org>> > 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@theobroma-systems.com <mailto:christoph.muellner@theobroma-systems.com>> > Signed-off-by: Martin Kepplinger <martink@posteo.de <mailto:martink@posteo.de>> > Reviewed-by: Guenter Roeck <linux@roeck-us.net <mailto:linux@roeck-us.net>> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org <mailto:peterz@infradead.org>> > Cc: John Sullivan <jsrhbz@kanargh.force9.co.uk <mailto:jsrhbz@kanargh.force9.co.uk>> > Cc: Linus Torvalds <torvalds@linux-foundation.org <mailto:torvalds@linux-foundation.org>> > Cc: Maxime COQUELIN <maxime.coquelin@st.com <mailto:maxime.coquelin@st.com>> > Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com <mailto:paulmck@linux.vnet.ibm.com>> > Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk <mailto:linux@rasmusvillemoes.dk>> > Cc: Theodore Ts'o <tytso@mit.edu <mailto:tytso@mit.edu>> > Cc: Andrew Morton <akpm@linux-foundation.org <mailto:akpm@linux-foundation.org>> > Link: http://lkml.kernel.org/r/1421083370-24924-1-git-send-email-martink@posteo.de > Signed-off-by <http://lkml.kernel.org/r/1421083370-24924-1-git-send-email-martink@posteo.de Signed-off-by>: Ingo Molnar <mingo@kernel.org <mailto:mingo@kernel.org>> > --- > 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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