From: Martin Kepplinger <martink@posteo.de>
Date: Wed, 21 Oct 2015 22:03:51 +0000 (+1100)
Subject: bitops.h: improve sign_extend32()'s documentation
X-Git-Tag: KARO-TX6UL-2015-11-03~14^2~56
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9228cba6ca06ead7a6c299659f56eaeeb1ae0055;p=karo-tx-linux.git

bitops.h: improve sign_extend32()'s documentation

It is often overlooked that sign_extend32(), despite its name, is safe to
use for 16 and 8 bit types as well.  This should help prevent sign
extension being done manually some other way.

Signed-off-by: Martin Kepplinger <martin.kepplinger@theobroma-systems.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: George Spelvin <linux@horizon.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Maxime Coquelin <maxime.coquelin@st.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Yury Norov <yury.norov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index e63553386ae7..5629923a8701 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -164,6 +164,8 @@ static inline __u8 ror8(__u8 word, unsigned int 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
+ *
+ * This is safe to use for 16- and 8-bit types as well.
  */
 static inline __s32 sign_extend32(__u32 value, int index)
 {