linux-kernel - Re: [PATCH v2 01/11] HID: hid-input: export hidinput_calc_abs

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Message-ID: <20121029185750.GA12640@polaris.bitmath.org>
Date:	Mon, 29 Oct 2012 19:57:50 +0100
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Stephane Chatty <chatty@...c.fr>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/11] HID: hid-input: export hidinput_calc_abs_res

Hi Benjamin,

> Exporting this function allows us to calculate the resolution in third
> party drivers like hid-multitouch.
> This patch also complete the function with additional valid axes.
> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...il.com>
> ---

Nice, but please see comment below.

>  drivers/hid/hid-input.c      | 11 +++++++++--
>  drivers/hid/hid-multitouch.c |  1 +
>  include/linux/hid.h          |  1 +
>  3 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index d917c0d..1b0adc3 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -208,7 +208,7 @@ static int hidinput_setkeycode(struct input_dev *dev,
>   * Only exponent 1 length units are processed. Centimeters and inches are
>   * converted to millimeters. Degrees are converted to radians.
>   */
> -static __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
> +__s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
>  {
>  	__s32 unit_exponent = field->unit_exponent;
>  	__s32 logical_extents = field->logical_maximum -
> @@ -229,6 +229,12 @@ static __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)
>  	case ABS_X:
>  	case ABS_Y:
>  	case ABS_Z:
> +	case ABS_MT_POSITION_X:
> +	case ABS_MT_POSITION_Y:
> +	case ABS_MT_TOOL_X:
> +	case ABS_MT_TOOL_Y:
> +	case ABS_MT_TOUCH_MAJOR:
> +	case ABS_MT_TOUCH_MINOR:
>  		if (field->unit == 0x11) {		/* If centimeters */
>  			/* Convert to millimeters */
>  			unit_exponent += 1;
> @@ -281,8 +287,9 @@ static __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);

This line might be best left alone; if the round-off matters, you now
risk regressing a carefully tuned userland.

>  }
> +EXPORT_SYMBOL_GPL(hidinput_calc_abs_res);
>  
>  #ifdef CONFIG_HID_BATTERY_STRENGTH
>  static enum power_supply_property hidinput_battery_props[] = {
> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> index c97011c..375a38d 100644
> --- a/drivers/hid/hid-multitouch.c
> +++ b/drivers/hid/hid-multitouch.c
> @@ -298,6 +298,7 @@ static void set_abs(struct input_dev *input, unsigned int code,
>  	int fmax = field->logical_maximum;
>  	int fuzz = snratio ? (fmax - fmin) / snratio : 0;
>  	input_set_abs_params(input, code, fmin, fmax, fuzz, 0);
> +	input_abs_set_res(input, code, hidinput_calc_abs_res(field, code));
>  }
>  
>  static void mt_store_field(struct hid_usage *usage, struct mt_device *td,
> diff --git a/include/linux/hid.h b/include/linux/hid.h
> index 7e1f37d..9edb06c 100644
> --- a/include/linux/hid.h
> +++ b/include/linux/hid.h
> @@ -743,6 +743,7 @@ int hid_input_report(struct hid_device *, int type, u8 *, int, int);
>  int hidinput_find_field(struct hid_device *hid, unsigned int type, unsigned int code, struct hid_field **field);
>  struct hid_field *hidinput_get_led_field(struct hid_device *hid);
>  unsigned int hidinput_count_leds(struct hid_device *hid);
> +__s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code);
>  void hid_output_report(struct hid_report *report, __u8 *data);
>  struct hid_device *hid_allocate_device(void);
>  struct hid_report *hid_register_report(struct hid_device *device, unsigned type, unsigned id);
> -- 
> 1.7.11.7
> 

Thanks,
Henrik
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