1. 根目录:
2. drivers
3. input
4. touchscreen
5. of_touchscreen.c

/*
 *  Generic DT helper functions for touchscreen devices
 *
 *  Copyright (c) 2014 Sebastian Reichel <sre@kernel.org>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 */

#include <linux/of.h>
#include <linux/input.h>
#include <linux/input/mt.h>
#include <linux/input/touchscreen.h>

static u32 of_get_optional_u32(struct device_node *np,
			       const char *property)
{
	u32 val = 0;

	of_property_read_u32(np, property, &val);

	return val;
}

static void touchscreen_set_params(struct input_dev *dev,
				   unsigned long axis,
				   int max, int fuzz)
{
	struct input_absinfo *absinfo;

	if (!test_bit(axis, dev->absbit)) {
		/*
		 * Emit a warning only if the axis is not a multitouch
		 * axis, which might not be set by the driver.
		 */
		if (!input_is_mt_axis(axis))
			dev_warn(&dev->dev,
				 "DT specifies parameters but the axis is not set up\n");
		return;
	}

	absinfo = &dev->absinfo[axis];
	absinfo->maximum = max;
	absinfo->fuzz = fuzz;
}

/**
 * touchscreen_parse_of_params - parse common touchscreen DT properties
 * @dev: device that should be parsed
 *
 * This function parses common DT properties for touchscreens and setups the
 * input device accordingly. The function keeps previously setuped default
 * values if no value is specified via DT.
 */
void touchscreen_parse_of_params(struct input_dev *dev)
{
	struct device_node *np = dev->dev.parent->of_node;
	u32 maximum, fuzz;

	input_alloc_absinfo(dev);
	if (!dev->absinfo)
		return;

	maximum = of_get_optional_u32(np, "touchscreen-size-x");
	fuzz = of_get_optional_u32(np, "touchscreen-fuzz-x");
	if (maximum || fuzz) {
		touchscreen_set_params(dev, ABS_X, maximum, fuzz);
		touchscreen_set_params(dev, ABS_MT_POSITION_X, maximum, fuzz);
	}

	maximum = of_get_optional_u32(np, "touchscreen-size-y");
	fuzz = of_get_optional_u32(np, "touchscreen-fuzz-y");
	if (maximum || fuzz) {
		touchscreen_set_params(dev, ABS_Y, maximum, fuzz);
		touchscreen_set_params(dev, ABS_MT_POSITION_Y, maximum, fuzz);
	}

	maximum = of_get_optional_u32(np, "touchscreen-max-pressure");
	fuzz = of_get_optional_u32(np, "touchscreen-fuzz-pressure");
	if (maximum || fuzz) {
		touchscreen_set_params(dev, ABS_PRESSURE, maximum, fuzz);
		touchscreen_set_params(dev, ABS_MT_PRESSURE, maximum, fuzz);
	}
}
EXPORT_SYMBOL(touchscreen_parse_of_params);