hid-lg3ff.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Force feedback support for Logitech Flight System G940
 *
 *  Copyright (c) 2009 Gary Stein <LordCnidarian@gmail.com>
 */

/*
 */


#include <linux/input.h>
#include <linux/hid.h>

#include "hid-lg.h"

/*
 * G940 Theory of Operation (from experimentation)
 *
 * There are 63 fields (only 3 of them currently used)
 * 0 - seems to be command field
 * 1 - 30 deal with the x axis
 * 31 -60 deal with the y axis
 *
 * Field 1 is x axis constant force
 * Field 31 is y axis constant force
 *
 * other interesting fields 1,2,3,4 on x axis
 * (same for 31,32,33,34 on y axis)
 *
 * 0 0 127 127 makes the joystick autocenter hard
 *
 * 127 0 127 127 makes the joystick loose on the right,
 * but stops all movemnt left
 *
 * -127 0 -127 -127 makes the joystick loose on the left,
 * but stops all movement right
 *
 * 0 0 -127 -127 makes the joystick rattle very hard
 *
 * I'm sure these are effects that I don't know enough about them
 */

struct lg3ff_device {
	struct hid_report *report;
};

static int hid_lg3ff_play(struct input_dev *dev, void *data,
			 struct ff_effect *effect)
{
	struct hid_device *hid = input_get_drvdata(dev);
	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
	int x, y;

/*
 * Available values in the field should always be 63, but we only use up to
 * 35. Instead, clear the entire area, however big it is.
 */
	memset(report->field[0]->value, 0,
	       sizeof(__s32) * report->field[0]->report_count);

	switch (effect->type) {
	case FF_CONSTANT:
/*
 * Already clamped in ff_memless
 * 0 is center (different then other logitech)
 */
		x = effect->u.ramp.start_level;
		y = effect->u.ramp.end_level;

		/* send command byte */
		report->field[0]->value[0] = 0x51;

/*
 * Sign backwards from other Force3d pro
 * which get recast here in two's complement 8 bits
 */
		report->field[0]->value[1] = (unsigned char)(-x);
		report->field[0]->value[31] = (unsigned char)(-y);

		hid_hw_request(hid, report, HID_REQ_SET_REPORT);
		break;
	}
	return 0;
}
static void hid_lg3ff_set_autocenter(struct input_dev *dev, u16 magnitude)
{
	struct hid_device *hid = input_get_drvdata(dev);
	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);

/*
 * Auto Centering probed from device
 * NOTE: deadman's switch on G940 must be covered
 * for effects to work
 */
	report->field[0]->value[0] = 0x51;
	report->field[0]->value[1] = 0x00;
	report->field[0]->value[2] = 0x00;
	report->field[0]->value[3] = 0x7F;
	report->field[0]->value[4] = 0x7F;
	report->field[0]->value[31] = 0x00;
	report->field[0]->value[32] = 0x00;
	report->field[0]->value[33] = 0x7F;
	report->field[0]->value[34] = 0x7F;

	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
}


static const signed short ff3_joystick_ac[] = {
	FF_CONSTANT,
	FF_AUTOCENTER,
	-1
};

int lg3ff_init(struct hid_device *hid)
{
	struct hid_input *hidinput;
	struct input_dev *dev;
	const signed short *ff_bits = ff3_joystick_ac;
	int error;
	int i;

	if (list_empty(&hid->inputs)) {
		hid_err(hid, "no inputs found\n");
		return -ENODEV;
	}
	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
	dev = hidinput->input;

	/* Check that the report looks ok */
	if (!hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 35))
		return -ENODEV;

	/* Assume single fixed device G940 */
	for (i = 0; ff_bits[i] >= 0; i++)
		set_bit(ff_bits[i], dev->ffbit);

	error = input_ff_create_memless(dev, NULL, hid_lg3ff_play);
	if (error)
		return error;

	if (test_bit(FF_AUTOCENTER, dev->ffbit))
		dev->ff->set_autocenter = hid_lg3ff_set_autocenter;

	hid_info(hid, "Force feedback for Logitech Flight System G940 by Gary Stein <LordCnidarian@gmail.com>\n");
	return 0;
}