[PATCH v4 1/2] Input: cypress-sf - Add Cypress StreetFighter touchkey driver

[Yassine Oudjana <y.oudjana@protonmail.com>]

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].

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>

[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
---
Changes since v3:
 - Use device_property_read_u32_array to read keycodes.
 - Read status register into integer first to check for errors.
 - Use bitmap_xor and for_each_set_bit to check for key state changes.
 - More code style fixes.
 - Add MAINTAINERS entry.
Changes since v2:
 - Code style fixes.
 - Added copyright statement.
Changes since v1:
 - Changed version variables in probe to int to allow storing error codes.

 MAINTAINERS                         |   6 +
 drivers/input/keyboard/Kconfig      |  10 ++
 drivers/input/keyboard/Makefile     |   1 +
 drivers/input/keyboard/cypress-sf.c | 219 ++++++++++++++++++++++++++++
 4 files changed, 236 insertions(+)
 create mode 100644 drivers/input/keyboard/cypress-sf.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 5a61cb2d0cd4..0e6ce2b71829 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5123,6 +5123,12 @@ L:	linux-input@vger.kernel.org
 S:	Maintained
 F:	drivers/input/touchscreen/cy8ctma140.c
 
+CYPRESS STREETFIGHTER TOUCHKEYS DRIVER
+M:	Yassine Oudjana <y.oudjana@protonmail.com>
+L:	linux-input@vger.kernel.org
+S:	Maintained
+F:	drivers/input/keyboard/cypress-sf.c
+
 CYTTSP TOUCHSCREEN DRIVER
 M:	Linus Walleij <linus.walleij@linaro.org>
 L:	linux-input@vger.kernel.org
diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index e75650e98c9e..0c607da9ee10 100644
--- a/drivers/input/keyboard/Kconfig
+++ b/drivers/input/keyboard/Kconfig
@@ -788,4 +788,14 @@ config KEYBOARD_MTK_PMIC
 	  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
diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
index 1d689fdd5c00..e3c8648f834e 100644
--- a/drivers/input/keyboard/Makefile
+++ b/drivers/input/keyboard/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_KEYBOARD_BCM)		+= bcm-keypad.o
 obj-$(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
diff --git a/drivers/input/keyboard/cypress-sf.c b/drivers/input/keyboard/cypress-sf.c
new file mode 100644
index 000000000000..dbd5d627f863
--- /dev/null
+++ b/drivers/input/keyboard/cypress-sf.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Cypress StreetFighter Touchkey Driver
+ *
+ * Copyright (c) 2021 Yassine Oudjana <y.oudjana@protonmail.com>
+ */
+
+#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,
+				const struct i2c_device_id *id)
+{
+	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_kzalloc(&client->dev,
+				sizeof(u32) * touchkey->num_keys, 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;
+	}
+	dev_dbg(dev, "Suspended device");
+
+	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);
+	dev_dbg(dev, "Resumed device");
+
+	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);
+
+static const struct of_device_id cypress_sf_of_match[] = {
+	{ .compatible = "cypress,sf3155", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, cypress_sf_of_match);
+
+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 = cypress_sf_probe,
+};
+module_i2c_driver(cypress_sf_driver);
+
+MODULE_AUTHOR("Yassine Oudjana <y.oudjana@protonmail.com>");
+MODULE_DESCRIPTION("Cypress StreetFighter Touchkey Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.33.0