linux-kernel - Re: [PATCH] staging: iio: ad2s1200: Fix sign extension

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Message-ID: <54C20CAF.3010901@metafoo.de>
Date:	Fri, 23 Jan 2015 09:56:15 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Jonathan Cameron <jic23@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Hartmut Knaack <knaack.h@....de>,
	Peter Meerwald <pmeerw@...erw.net>, linux-iio@...r.kernel.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: iio: ad2s1200: Fix sign extension

On 01/23/2015 12:09 AM, Rasmus Villemoes wrote:
> The line above makes vel a 12-bit quantity (st->rx[] is u8). The
> intention is to sign-extend vel using bit 11 as the sign bit. But
> because of C's promotion rules "vel = (vel << 4) >> 4;" is actually a
> no-op, since vel is promoted to int before the inner
> shift. sign_extend32 works equally well for 8 and 16 bits types, so
> use that.
>
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>

Acked-by: Lars-Peter Clausen <lars@...afoo.de>
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