Input: cypress-sf - add Cypress StreetFighter touchkey driver

This adds support for Cypress StreetFighter touchkey controllers such
as sf3155. This driver supports managing regulators and generating
input events.

Due to lack of documentation, this driver is entirely based on
information gathered from a driver written for an old Android kernel
fork[1][2].

[1] https://github.com/LineageOS/android_kernel_xiaomi_msm8996/blob/lineage-18.1/drivers/input/touchscreen/cyttsp_button.c
[2] https://github.com/LineageOS/android_kernel_xiaomi_msm8996/blob/lineage-18.1/arch/arm/boot/dts/qcom/a4-msm8996-mtp.dtsi#L291-L314

Signed-off-by: Yassine Oudjana <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

MAINTAINERS

···
 S:	Maintained
 F:	drivers/input/touchscreen/cy8ctma140.c
 
+CYPRESS STREETFIGHTER TOUCHKEYS DRIVER
+M:	Yassine Oudjana <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	drivers/input/keyboard/cypress-sf.c
+
 CYTTSP TOUCHSCREEN DRIVER
 M:	Linus Walleij <[e-mail]>
 L:	[e-mail]

drivers/input/keyboard/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called pmic-keys.
 
+config KEYBOARD_CYPRESS_SF
+	tristate "Cypress StreetFighter touchkey support"
+	depends on I2C
+	help
+	  Say Y here if you want to enable support for Cypress StreetFighter
+	  touchkeys.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called cypress-sf.
+
 endif

drivers/input/keyboard/Makefile

···
 obj-$(CONFIG_KEYBOARD_CAP11XX)		+= cap11xx.o
 obj-$(CONFIG_KEYBOARD_CLPS711X)		+= clps711x-keypad.o
 obj-$(CONFIG_KEYBOARD_CROS_EC)		+= cros_ec_keyb.o
+obj-$(CONFIG_KEYBOARD_CYPRESS_SF)	+= cypress-sf.o
 obj-$(CONFIG_KEYBOARD_DAVINCI)		+= davinci_keyscan.o
 obj-$(CONFIG_KEYBOARD_DLINK_DIR685)	+= dlink-dir685-touchkeys.o
 obj-$(CONFIG_KEYBOARD_EP93XX)		+= ep93xx_keypad.o

drivers/input/keyboard/cypress-sf.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Cypress StreetFighter Touchkey Driver
+ *
+ * Copyright (c) 2021 Yassine Oudjana <[e-mail]>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
+
+#define CYPRESS_SF_DEV_NAME "cypress-sf"
+
+#define CYPRESS_SF_REG_BUTTON_STATUS	0x4a
+
+struct cypress_sf_data {
+	struct i2c_client *client;
+	struct input_dev *input_dev;
+	struct regulator_bulk_data regulators[2];
+	u32 *keycodes;
+	unsigned long keystates;
+	int num_keys;
+};
+
+static irqreturn_t cypress_sf_irq_handler(int irq, void *devid)
+{
+	struct cypress_sf_data *touchkey = devid;
+	unsigned long keystates, changed;
+	bool new_state;
+	int val, key;
+
+	val = i2c_smbus_read_byte_data(touchkey->client,
+				       CYPRESS_SF_REG_BUTTON_STATUS);
+	if (val < 0) {
+		dev_err(&touchkey->client->dev,
+			"Failed to read button status: %d", val);
+		return IRQ_NONE;
+	}
+	keystates = val;
+
+	bitmap_xor(&changed, &keystates, &touchkey->keystates,
+		   touchkey->num_keys);
+
+	for_each_set_bit(key, &changed, touchkey->num_keys) {
+		new_state = keystates & BIT(key);
+		dev_dbg(&touchkey->client->dev,
+			"Key %d changed to %d", key, new_state);
+		input_report_key(touchkey->input_dev,
+				 touchkey->keycodes[key], new_state);
+	}
+
+	input_sync(touchkey->input_dev);
+	touchkey->keystates = keystates;
+
+	return IRQ_HANDLED;
+}
+
+static int cypress_sf_probe(struct i2c_client *client)
+{
+	struct cypress_sf_data *touchkey;
+	int key, error;
+
+	touchkey = devm_kzalloc(&client->dev, sizeof(*touchkey), GFP_KERNEL);
+	if (!touchkey)
+		return -ENOMEM;
+
+	touchkey->client = client;
+	i2c_set_clientdata(client, touchkey);
+
+	touchkey->regulators[0].supply = "vdd";
+	touchkey->regulators[1].supply = "avdd";
+
+	error = devm_regulator_bulk_get(&client->dev,
+					ARRAY_SIZE(touchkey->regulators),
+					touchkey->regulators);
+	if (error) {
+		dev_err(&client->dev, "Failed to get regulators: %d\n", error);
+		return error;
+	}
+
+	touchkey->num_keys = device_property_read_u32_array(&client->dev,
+							    "linux,keycodes",
+							    NULL, 0);
+	if (touchkey->num_keys < 0) {
+		/* Default key count */
+		touchkey->num_keys = 2;
+	}
+
+	touchkey->keycodes = devm_kcalloc(&client->dev,
+					  touchkey->num_keys,
+					  sizeof(*touchkey->keycodes),
+					  GFP_KERNEL);
+	if (!touchkey->keycodes)
+		return -ENOMEM;
+
+	error = device_property_read_u32_array(&client->dev, "linux,keycodes",
+					       touchkey->keycodes,
+					       touchkey->num_keys);
+
+	if (error) {
+		dev_warn(&client->dev,
+			 "Failed to read keycodes: %d, using defaults\n",
+			 error);
+
+		/* Default keycodes */
+		touchkey->keycodes[0] = KEY_BACK;
+		touchkey->keycodes[1] = KEY_MENU;
+	}
+
+	error = regulator_bulk_enable(ARRAY_SIZE(touchkey->regulators),
+				      touchkey->regulators);
+	if (error) {
+		dev_err(&client->dev,
+			"Failed to enable regulators: %d\n", error);
+		return error;
+	}
+
+	touchkey->input_dev = devm_input_allocate_device(&client->dev);
+	if (!touchkey->input_dev) {
+		dev_err(&client->dev, "Failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	touchkey->input_dev->name = CYPRESS_SF_DEV_NAME;
+	touchkey->input_dev->id.bustype = BUS_I2C;
+
+	for (key = 0; key < touchkey->num_keys; ++key)
+		input_set_capability(touchkey->input_dev,
+				     EV_KEY, touchkey->keycodes[key]);
+
+	error = input_register_device(touchkey->input_dev);
+	if (error) {
+		dev_err(&client->dev,
+			"Failed to register input device: %d\n", error);
+		return error;
+	}
+
+	error = devm_request_threaded_irq(&client->dev, client->irq,
+					  NULL, cypress_sf_irq_handler,
+					  IRQF_ONESHOT,
+					  CYPRESS_SF_DEV_NAME, touchkey);
+	if (error) {
+		dev_err(&client->dev,
+			"Failed to register threaded irq: %d", error);
+		return error;
+	}
+
+	return 0;
+};
+
+static int __maybe_unused cypress_sf_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct cypress_sf_data *touchkey = i2c_get_clientdata(client);
+	int error;
+
+	disable_irq(client->irq);
+
+	error = regulator_bulk_disable(ARRAY_SIZE(touchkey->regulators),
+				       touchkey->regulators);
+	if (error) {
+		dev_err(dev, "Failed to disable regulators: %d", error);
+		enable_irq(client->irq);
+		return error;
+	}
+
+	return 0;
+}
+
+static int __maybe_unused cypress_sf_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct cypress_sf_data *touchkey = i2c_get_clientdata(client);
+	int error;
+
+	error = regulator_bulk_enable(ARRAY_SIZE(touchkey->regulators),
+				      touchkey->regulators);
+	if (error) {
+		dev_err(dev, "Failed to enable regulators: %d", error);
+		return error;
+	}
+
+	enable_irq(client->irq);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(cypress_sf_pm_ops,
+			 cypress_sf_suspend, cypress_sf_resume);
+
+static struct i2c_device_id cypress_sf_id_table[] = {
+	{ CYPRESS_SF_DEV_NAME, 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, cypress_sf_id_table);
+
+#ifdef CONFIG_OF
+static const struct of_device_id cypress_sf_of_match[] = {
+	{ .compatible = "cypress,sf3155", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, cypress_sf_of_match);
+#endif
+
+static struct i2c_driver cypress_sf_driver = {
+	.driver = {
+		.name = CYPRESS_SF_DEV_NAME,
+		.pm = &cypress_sf_pm_ops,
+		.of_match_table = of_match_ptr(cypress_sf_of_match),
+	},
+	.id_table = cypress_sf_id_table,
+	.probe_new = cypress_sf_probe,
+};
+module_i2c_driver(cypress_sf_driver);
+
+MODULE_AUTHOR("Yassine Oudjana <[e-mail]>");
+MODULE_DESCRIPTION("Cypress StreetFighter Touchkey Driver");
+MODULE_LICENSE("GPL v2");