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Commit 4ea6e4ff authored by Nikolai Kondrashov's avatar Nikolai Kondrashov Committed by Jiri Kosina
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HID: add absolute axis resolution calculation 



Add absolute axis resolution calculation to the core HID layer, according to HID
specification v1.11 6.2.2.7 Global Items. Only exponent 1 length units for
X/Y/Z/RX/RY/RZ axis are supported for now.

Signed-off-by: default avatarNikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent b6dc7992

drivers/hid/hid-input.c

+80 −0
Original line number Original line Diff line number Diff line
@@ -149,6 +149,83 @@ static int hidinput_setkeycode(struct input_dev *dev, 
}

}









/**

 * hidinput_calc_abs_res - calculate an absolute axis resolution

 * @field: the HID report field to calculate resolution for

 * @code: axis code

 *

 * The formula is:

 *                         (logical_maximum - logical_minimum)

 * resolution = ----------------------------------------------------------

 *              (physical_maximum - physical_minimum) * 10 ^ unit_exponent

 *

 * as seen in the HID specification v1.11 6.2.2.7 Global Items.

 *

 * Only exponent 1 length units are processed. Centimeters are converted to

 * inches. Degrees are converted to radians.

 */

static __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code)

{

	__s32 unit_exponent = field->unit_exponent;

	__s32 logical_extents = field->logical_maximum -

					field->logical_minimum;

	__s32 physical_extents = field->physical_maximum -

					field->physical_minimum;

	__s32 prev;



	/* Check if the extents are sane */

	if (logical_extents <= 0 || physical_extents <= 0)

		return 0;



	/*

	 * Verify and convert units.

	 * See HID specification v1.11 6.2.2.7 Global Items for unit decoding

	 */

	if (code == ABS_X || code == ABS_Y || code == ABS_Z) {

		if (field->unit == 0x11) {		/* If centimeters */

			/* Convert to inches */

			prev = logical_extents;

			logical_extents *= 254;

			if (logical_extents < prev)

				return 0;

			unit_exponent += 2;

		} else if (field->unit != 0x13) {	/* If not inches */

			return 0;

		}

	} else if (code == ABS_RX || code == ABS_RY || code == ABS_RZ) {

		if (field->unit == 0x14) {		/* If degrees */

			/* Convert to radians */

			prev = logical_extents;

			logical_extents *= 573;

			if (logical_extents < prev)

				return 0;

			unit_exponent += 1;

		} else if (field->unit != 0x12) {	/* If not radians */

			return 0;

		}

	} else {

		return 0;

	}



	/* Apply negative unit exponent */

	for (; unit_exponent < 0; unit_exponent++) {

		prev = logical_extents;

		logical_extents *= 10;

		if (logical_extents < prev)

			return 0;

	}

	/* Apply positive unit exponent */

	for (; unit_exponent > 0; unit_exponent--) {

		prev = physical_extents;

		physical_extents *= 10;

		if (physical_extents < prev)

			return 0;

	}



	/* Calculate resolution */

	return logical_extents / physical_extents;

}



static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_field *field,

static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_field *field,

				     struct hid_usage *usage)

				     struct hid_usage *usage)

{

{
@@ -537,6 +614,9 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel 
			input_set_abs_params(input, usage->code, a, b, (b - a) >> 8, (b - a) >> 4);

			input_set_abs_params(input, usage->code, a, b, (b - a) >> 8, (b - a) >> 4);

		else	input_set_abs_params(input, usage->code, a, b, 0, 0);

		else	input_set_abs_params(input, usage->code, a, b, 0, 0);





		input_abs_set_res(input, usage->code,

				  hidinput_calc_abs_res(field, usage->code));



		/* use a larger default input buffer for MT devices */

		/* use a larger default input buffer for MT devices */

		if (usage->code == ABS_MT_POSITION_X && input->hint_events_per_packet == 0)

		if (usage->code == ABS_MT_POSITION_X && input->hint_events_per_packet == 0)

			input_set_events_per_packet(input, 60);

			input_set_events_per_packet(input, 60);