linux-kernel - Re: [lm-sensors] hwmon/f75375s.c: buggy if()

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Message-ID: <20071019143754.0aa4483b@hyperion.delvare>
Date:	Fri, 19 Oct 2007 14:37:54 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	"Mark M. Hoffman" <mhoffman@...htlink.com>
Cc:	Riku Voipio <riku.voipio@....fi>, Adrian Bunk <bunk@...nel.org>,
	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Subject: Re: [lm-sensors] hwmon/f75375s.c: buggy if()

Hi Mark, hi Riku,

On Thu, 18 Oct 2007 09:37:44 -0400, Mark M. Hoffman wrote:
> That patch doesn't apply here, so I applied this:
> 
> commit 805763cd743f2aed41dc61a55569fa43cf1f240c
> Author: Riku Voipio <riku.voipio@....fi>
> Date:   Thu Oct 18 09:29:53 2007 -0400
> 
>     hwmon: (f75375s) fix pwm mode setting
>     
>     Spotted by the Coverity checker. (Thanks Adrian Bunk)
>     
>     Signed-off-by: Riku Voipio <riku.voipio@....fi>
>     Signed-off-by: Mark M. Hoffman <mhoffman@...htlink.com>
> 
> diff --git a/drivers/hwmon/f75375s.c b/drivers/hwmon/f75375s.c
> index 13a0413..59a3470 100644
> --- a/drivers/hwmon/f75375s.c
> +++ b/drivers/hwmon/f75375s.c
> @@ -323,7 +323,7 @@ static ssize_t set_pwm_mode(struct device *dev, struct device_attribute *attr,
>  	int val = simple_strtoul(buf, NULL, 10);
>  	u8 conf = 0;
>  
> -	if (val != 0 || val != 1 || data->kind == f75373)
> +	if (!(val == 0 || val == 1) || data->kind == f75373)
>  		return -EINVAL;
>  
>  	mutex_lock(&data->update_lock);

BTW, that's the wrong way to do it. If the F75373S doesn't support
changing the PWM mode, then the sysfs attribute in question should be
read-only for this chip type. Making it writable and returning an error
on write is confusing.

Riku, can you please submit a patch fixing this? The attribute should
be declared read-only, and then you can use sysfs_chmod_file() to
change it to read-write where supported. Take a look at the w83781d
driver for an example.

Thanks,
-- 
Jean Delvare
-
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