linux-kernel - Re: [PATCH v3 02/13] HID: hid-input: round return value of hidinput_calc_abs

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Date:	Tue, 13 Nov 2012 08:44:38 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	Stephane Chatty <chatty@...c.fr>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/13] HID: hid-input: round return value of
 hidinput_calc_abs_res

On Wed, 7 Nov 2012, Benjamin Tissoires wrote:

> hidinput_calc_abs_res should return the closest int in the division
> instead of the floor.
> On a device with a logical_max of 3008 and a physical_max of 255mm,
> previous implementation gave a resolution of 11 instead of 12.
> With 11, user-space computes a physical size of 273.5mm and the
> round_closest results gives 250.6mm.
> The old implementation introduced an error of 2cm in this example.
> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...il.com>

Acked-by: Jiri Kosina <jkosina@...e.cz>

> ---
>  drivers/hid/hid-input.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index f5b1d57..67044f3 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -287,7 +287,7 @@ __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
>  	}
>  
>  	/* Calculate resolution */
> -	return logical_extents / physical_extents;
> +	return DIV_ROUND_CLOSEST(logical_extents, physical_extents);
>  }
>  EXPORT_SYMBOL_GPL(hidinput_calc_abs_res);
>  
> -- 
> 1.7.11.7
> 

-- 
Jiri Kosina
SUSE Labs
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