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Date: Wed, 14 Mar 2007 19:11:49 +0800
From: "Cong WANG" <xiyou.wangcong@gmail.com>
To: linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH] Apple SMC driver (hardware monitoring and control)
In-Reply-To: <45F7C083.7090504@boichat.ch>
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I am sorry. I forgot to CC to the list.

2007/3/14, Nicolas Boichat wrote:
> Hello,
>

<snip>

> +static ssize_t applesmc_show_fan_manual(struct device *dev, char *buf,
> +                                                               int offset)
> +{
> +       int ret;
> +       u16 manual = 0;
> +       u8 buffer[2];
> +
> +       down(&applesmc_sem);
> +
> +       ret = applesmc_read_key(FANS_MANUAL, buffer, 2);
> +       manual = ((buffer[0] << 8 | buffer[1]) >> offset) & 0x01;
> +
> +       up(&applesmc_sem);
> +       if (ret)
> +               return ret;
> +       else
> +               return sprintf(buf, "%d\n", manual);
> +}
> +

I doubt about your last 'sprintf'. Your 'buf' just has only two 'u8's,
which maybe only has two bytes, and '\n' already consumes one. So only
one byte is left for the decimal vaule of 'manual'. Even it is just
less than 10, just as what you want, the final '\0' is omitted!

What's more, you can't get such information from the return value of
'sprintf'. So I suggest you to choose 'snprintf' instead.