Input: add SparkFun Qwiic Joystick driver

A simple analog joystick built on Low Power ATtiny85 Microcontroller.
Directional movements are measured with two 10 kΩ potentiometers
connected with a gimbal mechanism that separates the horizontal and
vertical movements. This joystick also has a select button that is actuated
when the joystick is pressed down.

Input events polled over the I2C bus.

Product page:
https://www.sparkfun.com/products/15168
Firmware and hardware sources:
https://github.com/sparkfun/Qwiic_Joystick

Tested on RPi4B and O4-iMX-NANO boards.

Signed-off-by: Oleh Kravchenko <[e-mail]>
Reviewed-by: Jeff LaBundy <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/joystick/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called pxrc.
 
+config JOYSTICK_QWIIC
+	tristate "SparkFun Qwiic Joystick"
+	depends on I2C
+	help
+	  Say Y here if you want to use the SparkFun Qwiic Joystick.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called qwiic-joystick.
+
 config JOYSTICK_FSIA6B
 	tristate "FlySky FS-iA6B RC Receiver"
 	select SERIO

drivers/input/joystick/Makefile

···
 obj-$(CONFIG_JOYSTICK_N64)		+= n64joy.o
 obj-$(CONFIG_JOYSTICK_PSXPAD_SPI)	+= psxpad-spi.o
 obj-$(CONFIG_JOYSTICK_PXRC)		+= pxrc.o
+obj-$(CONFIG_JOYSTICK_QWIIC)		+= qwiic-joystick.o
 obj-$(CONFIG_JOYSTICK_SIDEWINDER)	+= sidewinder.o
 obj-$(CONFIG_JOYSTICK_SPACEBALL)	+= spaceball.o
 obj-$(CONFIG_JOYSTICK_SPACEORB)		+= spaceorb.o

drivers/input/joystick/qwiic-joystick.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Oleh Kravchenko <[e-mail]>
+ *
+ * SparkFun Qwiic Joystick
+ * Product page:https://www.sparkfun.com/products/15168
+ * Firmware and hardware sources:https://github.com/sparkfun/Qwiic_Joystick
+ */
+
+#include <linux/bits.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define DRV_NAME "qwiic-joystick"
+
+#define QWIIC_JSK_REG_VERS	1
+#define QWIIC_JSK_REG_DATA	3
+
+#define QWIIC_JSK_MAX_AXIS	GENMASK(9, 0)
+#define QWIIC_JSK_FUZZ		2
+#define QWIIC_JSK_FLAT		2
+#define QWIIC_JSK_POLL_INTERVAL	16
+#define QWIIC_JSK_POLL_MIN	8
+#define QWIIC_JSK_POLL_MAX	32
+
+struct qwiic_jsk {
+	char phys[32];
+	struct input_dev *dev;
+	struct i2c_client *client;
+};
+
+struct qwiic_ver {
+	u8 major;
+	u8 minor;
+};
+
+struct qwiic_data {
+	__be16 x;
+	__be16 y;
+	u8 thumb;
+};
+
+static void qwiic_poll(struct input_dev *input)
+{
+	struct qwiic_jsk *priv = input_get_drvdata(input);
+	struct qwiic_data data;
+	int err;
+
+	err = i2c_smbus_read_i2c_block_data(priv->client, QWIIC_JSK_REG_DATA,
+					    sizeof(data), (u8 *)&data);
+	if (err != sizeof(data))
+		return;
+
+	input_report_abs(input, ABS_X, be16_to_cpu(data.x) >> 6);
+	input_report_abs(input, ABS_Y, be16_to_cpu(data.y) >> 6);
+	input_report_key(input, BTN_THUMBL, !data.thumb);
+	input_sync(input);
+}
+
+static int qwiic_probe(struct i2c_client *client)
+{
+	struct qwiic_jsk *priv;
+	struct qwiic_ver vers;
+	int err;
+
+	err = i2c_smbus_read_i2c_block_data(client, QWIIC_JSK_REG_VERS,
+					    sizeof(vers), (u8 *)&vers);
+	if (err < 0)
+		return err;
+	if (err != sizeof(vers))
+		return -EIO;
+
+	dev_dbg(&client->dev, "SparkFun Qwiic Joystick, FW: %u.%u\n",
+		vers.major, vers.minor);
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->client = client;
+	snprintf(priv->phys, sizeof(priv->phys),
+		 "i2c/%s", dev_name(&client->dev));
+	i2c_set_clientdata(client, priv);
+
+	priv->dev = devm_input_allocate_device(&client->dev);
+	if (!priv->dev)
+		return -ENOMEM;
+
+	priv->dev->id.bustype = BUS_I2C;
+	priv->dev->name = "SparkFun Qwiic Joystick";
+	priv->dev->phys = priv->phys;
+	input_set_drvdata(priv->dev, priv);
+
+	input_set_abs_params(priv->dev, ABS_X, 0, QWIIC_JSK_MAX_AXIS,
+			     QWIIC_JSK_FUZZ, QWIIC_JSK_FLAT);
+	input_set_abs_params(priv->dev, ABS_Y, 0, QWIIC_JSK_MAX_AXIS,
+			     QWIIC_JSK_FUZZ, QWIIC_JSK_FLAT);
+	input_set_capability(priv->dev, EV_KEY, BTN_THUMBL);
+
+	err = input_setup_polling(priv->dev, qwiic_poll);
+	if (err) {
+		dev_err(&client->dev, "failed to set up polling: %d\n", err);
+		return err;
+	}
+	input_set_poll_interval(priv->dev, QWIIC_JSK_POLL_INTERVAL);
+	input_set_min_poll_interval(priv->dev, QWIIC_JSK_POLL_MIN);
+	input_set_max_poll_interval(priv->dev, QWIIC_JSK_POLL_MAX);
+
+	err = input_register_device(priv->dev);
+	if (err) {
+		dev_err(&client->dev, "failed to register joystick: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_qwiic_match[] = {
+	{ .compatible = "sparkfun,qwiic-joystick", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, of_qwiic_match);
+#endif /* CONFIG_OF */
+
+static const struct i2c_device_id qwiic_id_table[] = {
+	{ KBUILD_MODNAME, 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, qwiic_id_table);
+
+static struct i2c_driver qwiic_driver = {
+	.driver = {
+		.name		= DRV_NAME,
+		.of_match_table	= of_match_ptr(of_qwiic_match),
+	},
+	.id_table	= qwiic_id_table,
+	.probe_new	= qwiic_probe,
+};
+module_i2c_driver(qwiic_driver);
+
+MODULE_AUTHOR("Oleh Kravchenko <[e-mail]>");
+MODULE_DESCRIPTION("SparkFun Qwiic Joystick driver");
+MODULE_LICENSE("GPL v2");