Input: add ADC resistor ladder driver (68077264) · Commits · e / devices / android_kernel_fairphone_FP4

Documentation/devicetree/bindings/input/adc-keys.txt

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		ADC attached resistor ladder buttons
		------------------------------------

		Required properties:
		- compatible: "adc-keys"
		- io-channels: Phandle to an ADC channel
		- io-channel-names = "buttons";
		- keyup-threshold-microvolt: Voltage at which all the keys are considered up.

		Optional properties:
		- poll-interval: Poll interval time in milliseconds
		- autorepeat: Boolean, Enable auto repeat feature of Linux input
		subsystem.

		Each button (key) is represented as a sub-node of "adc-keys":

		Required subnode-properties:
		- label: Descriptive name of the key.
		- linux,code: Keycode to emit.
		- press-threshold-microvolt: Voltage ADC input when this key is pressed.

		Example:

		#include <dt-bindings/input/input.h>

		adc-keys {
		compatible = "adc-keys";
		io-channels = <&lradc 0>;
		io-channel-names = "buttons";
		keyup-threshold-microvolt = <2000000>;

		button-up {
		label = "Volume Up";
		linux,code = <KEY_VOLUMEUP>;
		press-threshold-microvolt = <1500000>;
		};

		button-down {
		label = "Volume Down";
		linux,code = <KEY_VOLUMEDOWN>;
		press-threshold-microvolt = <1000000>;
		};

		button-enter {
		label = "Enter";
		linux,code = <KEY_ENTER>;
		press-threshold-microvolt = <500000>;
		};
		};

drivers/input/keyboard/Kconfig

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		@@ -12,6 +12,21 @@ menuconfig INPUT_KEYBOARD

		if INPUT_KEYBOARD

		config KEYBOARD_ADC
		tristate "ADC Ladder Buttons"
		depends on IIO
		select INPUT_POLLDEV
		help
		This driver implements support for buttons connected
		to an ADC using a resistor ladder.

		Say Y here if your device has such buttons connected to an ADC. Your
		board-specific setup logic must also provide a configuration data
		for mapping voltages to buttons.

		To compile this driver as a module, choose M here: the
		module will be called adc_keys.

		config KEYBOARD_ADP5520
		tristate "Keypad Support for ADP5520 PMIC"
		depends on PMIC_ADP5520

drivers/input/keyboard/Makefile

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		@@ -4,6 +4,7 @@

		# Each configuration option enables a list of files.

		obj-$(CONFIG_KEYBOARD_ADC) += adc-keys.o
		obj-$(CONFIG_KEYBOARD_ADP5520) += adp5520-keys.o
		obj-$(CONFIG_KEYBOARD_ADP5588) += adp5588-keys.o
		obj-$(CONFIG_KEYBOARD_ADP5589) += adp5589-keys.o

drivers/input/keyboard/adc-keys.c

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		/*
		* Input driver for resistor ladder connected on ADC
		*
		* Copyright (c) 2016 Alexandre Belloni
		*
		* 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/err.h>
		#include <linux/iio/consumer.h>
		#include <linux/iio/types.h>
		#include <linux/input.h>
		#include <linux/input-polldev.h>
		#include <linux/kernel.h>
		#include <linux/module.h>
		#include <linux/of.h>
		#include <linux/platform_device.h>
		#include <linux/property.h>
		#include <linux/slab.h>

		struct adc_keys_button {
		u32 voltage;
		u32 keycode;
		};

		struct adc_keys_state {
		struct iio_channel *channel;
		u32 num_keys;
		u32 last_key;
		u32 keyup_voltage;
		const struct adc_keys_button *map;
		};

		static void adc_keys_poll(struct input_polled_dev *dev)
		{
		struct adc_keys_state *st = dev->private;
		int i, value, ret;
		u32 diff, closest = 0xffffffff;
		int keycode = 0;

		ret = iio_read_channel_processed(st->channel, &value);
		if (unlikely(ret < 0)) {
		/* Forcibly release key if any was pressed */
		value = st->keyup_voltage;
		} else {
		for (i = 0; i < st->num_keys; i++) {
		diff = abs(st->map[i].voltage - value);
		if (diff < closest) {
		closest = diff;
		keycode = st->map[i].keycode;
		}
		}
		}

		if (abs(st->keyup_voltage - value) < closest)
		keycode = 0;

		if (st->last_key && st->last_key != keycode)
		input_report_key(dev->input, st->last_key, 0);

		if (keycode)
		input_report_key(dev->input, keycode, 1);

		input_sync(dev->input);
		st->last_key = keycode;
		}

		static int adc_keys_load_keymap(struct device dev, struct adc_keys_state st)
		{
		struct adc_keys_button *map;
		struct fwnode_handle *child;
		int i;

		st->num_keys = device_get_child_node_count(dev);
		if (st->num_keys == 0) {
		dev_err(dev, "keymap is missing\n");
		return -EINVAL;
		}

		map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
		if (!map)
		return -ENOMEM;

		i = 0;
		device_for_each_child_node(dev, child) {
		if (fwnode_property_read_u32(child, "press-threshold-microvolt",
		&map[i].voltage)) {
		dev_err(dev, "Key with invalid or missing voltage\n");
		fwnode_handle_put(child);
		return -EINVAL;
		}
		map[i].voltage /= 1000;

		if (fwnode_property_read_u32(child, "linux,code",
		&map[i].keycode)) {
		dev_err(dev, "Key with invalid or missing linux,code\n");
		fwnode_handle_put(child);
		return -EINVAL;
		}

		i++;
		}

		st->map = map;
		return 0;
		}

		static int adc_keys_probe(struct platform_device *pdev)
		{
		struct device *dev = &pdev->dev;
		struct adc_keys_state *st;
		struct input_polled_dev *poll_dev;
		struct input_dev *input;
		enum iio_chan_type type;
		int i, value;
		int error;

		st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
		if (!st)
		return -ENOMEM;

		st->channel = devm_iio_channel_get(dev, "buttons");
		if (IS_ERR(st->channel))
		return PTR_ERR(st->channel);

		if (!st->channel->indio_dev)
		return -ENXIO;

		error = iio_get_channel_type(st->channel, &type);
		if (error < 0)
		return error;

		if (type != IIO_VOLTAGE) {
		dev_err(dev, "Incompatible channel type %d\n", type);
		return -EINVAL;
		}

		if (device_property_read_u32(dev, "keyup-threshold-microvolt",
		&st->keyup_voltage)) {
		dev_err(dev, "Invalid or missing keyup voltage\n");
		return -EINVAL;
		}
		st->keyup_voltage /= 1000;

		error = adc_keys_load_keymap(dev, st);
		if (error)
		return error;

		platform_set_drvdata(pdev, st);

		poll_dev = devm_input_allocate_polled_device(dev);
		if (!poll_dev) {
		dev_err(dev, "failed to allocate input device\n");
		return -ENOMEM;
		}

		if (!device_property_read_u32(dev, "poll-interval", &value))
		poll_dev->poll_interval = value;

		poll_dev->poll = adc_keys_poll;
		poll_dev->private = st;

		input = poll_dev->input;

		input->name = pdev->name;
		input->phys = "adc-keys/input0";

		input->id.bustype = BUS_HOST;
		input->id.vendor = 0x0001;
		input->id.product = 0x0001;
		input->id.version = 0x0100;

		__set_bit(EV_KEY, input->evbit);
		for (i = 0; i < st->num_keys; i++)
		__set_bit(st->map[i].keycode, input->keybit);

		if (device_property_read_bool(dev, "autorepeat"))
		__set_bit(EV_REP, input->evbit);

		error = input_register_polled_device(poll_dev);
		if (error) {
		dev_err(dev, "Unable to register input device: %d\n", error);
		return error;
		}

		return 0;
		}

		#ifdef CONFIG_OF
		static const struct of_device_id adc_keys_of_match[] = {
		{ .compatible = "adc-keys", },
		{ }
		};
		MODULE_DEVICE_TABLE(of, adc_keys_of_match);
		#endif

		static struct platform_driver __refdata adc_keys_driver = {
		.driver = {
		.name = "adc_keys",
		.of_match_table = of_match_ptr(adc_keys_of_match),
		},
		.probe = adc_keys_probe,
		};
		module_platform_driver(adc_keys_driver);

		MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
		MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
		MODULE_LICENSE("GPL v2");