linux-kernel - bitops.h: improve sign extending API

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Message-Id: <1444925909-6013-1-git-send-email-martink@posteo.de>
Date:	Thu, 15 Oct 2015 18:18:27 +0200
From:	Martin Kepplinger <martink@...teo.de>
To:	mingo@...nel.org, akpm@...ux-foundation.org, linux@...izon.com,
	linux@...musvillemoes.dk, maxime.coquelin@...com,
	dvlasenk@...hat.com, yury.norov@...il.com,
	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: bitops.h: improve sign extending API

PATCH 1/2 improves the doc of sign_extend32()

This should help to avoid different manual approaches to sign extension


PATCH 2/2 adds sign_extend64()

An informal example of what could follow in
arch/sh/kernel/traps_64.c after PATCH 2/2:

@@ -101,7 +102,7 @@ static int generate_and_check_address(struct pt_regs *regs,
                __s64 displacement;
                displacement = (opcode >> 10) & 0x3ff;
-               displacement = ((displacement << 54) >> 54); /* sign extend */
+               displacement = sign_extend64(displacement, 9);
                addr = (__u64)((__s64)base_address + (displacement << width_shift));
        } else {


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