linux-kernel - Re: [PATCH] hwmon: (ads1015) Handle negative conversion values correctly

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Message-ID: <56C65027.5010403@lysator.liu.se>
Date:	Fri, 19 Feb 2016 00:13:43 +0100
From:	Peter Rosin <peda@...ator.liu.se>
To:	Dirk Eibach <eibach@...ys.de>
CC:	Peter Rosin <peda@...ntia.se>, Jean Delvare <jdelvare@...e.de>,
	Guenter Roeck <linux@...ck-us.net>, lm-sensors@...sensors.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (ads1015) Handle negative conversion values correctly

Hi!

Sorry for the noise, but...

On 2016-02-18 14:07, Peter Rosin wrote:
> From: Peter Rosin <peda@...ntia.se>
> 
> Make the divisor signed as DIV_ROUND_CLOSEST is undefined for negative
> dividends when the divisor is unsigned.
> 
> Signed-off-by: Peter Rosin <peda@...ntia.se>

...I forgot to add this to the commit message
Cc: stable@...r.kernel.org

I also didn't explicitly mention any example platform where this
bug causes real problems; it was triggered on ARM (atmel sama5d).

Cheers,
Peter

> ---
>  drivers/hwmon/ads1015.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/ads1015.c b/drivers/hwmon/ads1015.c
> index f155b8380481..2b3105c8aed3 100644
> --- a/drivers/hwmon/ads1015.c
> +++ b/drivers/hwmon/ads1015.c
> @@ -126,7 +126,7 @@ static int ads1015_reg_to_mv(struct i2c_client *client, unsigned int channel,
>  	struct ads1015_data *data = i2c_get_clientdata(client);
>  	unsigned int pga = data->channel_data[channel].pga;
>  	int fullscale = fullscale_table[pga];
> -	const unsigned mask = data->id == ads1115 ? 0x7fff : 0x7ff0;
> +	const int mask = data->id == ads1115 ? 0x7fff : 0x7ff0;
>  
>  	return DIV_ROUND_CLOSEST(reg * fullscale, mask);
>  }
>