linux-kernel - Re: [PATCH v8 5/8] Loongson: YeeLoong: add hardware monitoring driver

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Date:	Sun, 6 Dec 2009 09:47:17 +0100
From:	Pavel Machek <pavel@....cz>
To:	Wu Zhangjin <wuzhangjin@...il.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>, akpm@...ux-foundation.org,
	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>, zhangfx@...ote.com,
	linux-laptop@...r.kernel.org,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH v8 5/8] Loongson: YeeLoong: add hardware monitoring
	driver

Hi!

> +static int get_battery_current(void)
> +{
> +	s16 value;
> +
> +	value = (ec_read(REG_BAT_CURRENT_HIGH) << 8) |
> +		(ec_read(REG_BAT_CURRENT_LOW));
> +
> +	if (value < 0)
> +		value = ~value + 1;
> +
> +	return value;
> +}

What is going on here? I thought the value is already in two's
complement... Is the above equivalent of

	      if (value < 0)
	      	 value = -value; 

? If so, why? If not, can you add a comment?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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