Input: add Raspberry Pi Sense HAT joystick driver

This patch adds the driver for the Sense HAT joystick. It outputs BTN_DPAD
key events when moved in any of the four directions and the BTN_SELECT
event when depressed.

Co-developed-by: Daniel Bauman <[e-mail]>
Signed-off-by: Daniel Bauman <[e-mail]>
Co-developed-by: Mwesigwa Guma <[e-mail]>
Signed-off-by: Mwesigwa Guma <[e-mail]>
Co-developed-by: Joel Savitz <[e-mail]>
Signed-off-by: Joel Savitz <[e-mail]>
Signed-off-by: Charles Mirabile <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/joystick/Kconfig

···
 	  Say Y here if you want enable support for the four
 	  built-in controller ports on the Nintendo 64 console.
 
+config JOYSTICK_SENSEHAT
+	tristate "Raspberry Pi Sense HAT joystick"
+	depends on INPUT && I2C
+	select MFD_SIMPLE_MFD_I2C
+	help
+	  Say Y here if you want to enable the driver for the
+	  the Raspberry Pi Sense HAT.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called sensehat_joystick.
+
 endif

drivers/input/joystick/Makefile

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

drivers/input/joystick/sensehat-joystick.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Raspberry Pi Sense HAT joystick driver
+ * http://raspberrypi.org
+ *
+ * Copyright (C) 2015 Raspberry Pi
+ * Copyright (C) 2021 Charles Mirabile, Mwesigwa Guma, Joel Savitz
+ *
+ * Original Author: Serge Schneider
+ * Revised for upstream Linux by: Charles Mirabile, Mwesigwa Guma, Joel Savitz
+ */
+
+#include <linux/module.h>
+#include <linux/input.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/property.h>
+
+#define JOYSTICK_SMB_REG 0xf2
+
+struct sensehat_joystick {
+	struct platform_device *pdev;
+	struct input_dev *keys_dev;
+	unsigned long prev_states;
+	struct regmap *regmap;
+};
+
+static const unsigned int keymap[] = {
+	BTN_DPAD_DOWN, BTN_DPAD_RIGHT, BTN_DPAD_UP, BTN_SELECT, BTN_DPAD_LEFT,
+};
+
+static irqreturn_t sensehat_joystick_report(int irq, void *cookie)
+{
+	struct sensehat_joystick *sensehat_joystick = cookie;
+	unsigned long curr_states, changes;
+	unsigned int keys;
+	int error;
+	int i;
+
+	error = regmap_read(sensehat_joystick->regmap, JOYSTICK_SMB_REG, &keys);
+	if (error < 0) {
+		dev_err(&sensehat_joystick->pdev->dev,
+			"Failed to read joystick state: %d", error);
+		return IRQ_NONE;
+	}
+	curr_states = keys;
+	bitmap_xor(&changes, &curr_states, &sensehat_joystick->prev_states,
+		   ARRAY_SIZE(keymap));
+
+	for_each_set_bit(i, &changes, ARRAY_SIZE(keymap))
+		input_report_key(sensehat_joystick->keys_dev, keymap[i],
+				 curr_states & BIT(i));
+
+	input_sync(sensehat_joystick->keys_dev);
+	sensehat_joystick->prev_states = keys;
+	return IRQ_HANDLED;
+}
+
+static int sensehat_joystick_probe(struct platform_device *pdev)
+{
+	struct sensehat_joystick *sensehat_joystick;
+	int error, i, irq;
+
+	sensehat_joystick = devm_kzalloc(&pdev->dev, sizeof(*sensehat_joystick),
+					 GFP_KERNEL);
+	if (!sensehat_joystick)
+		return -ENOMEM;
+
+	sensehat_joystick->pdev = pdev;
+
+	sensehat_joystick->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!sensehat_joystick->regmap) {
+		dev_err(&pdev->dev, "unable to get sensehat regmap");
+		return -ENODEV;
+	}
+
+	sensehat_joystick->keys_dev = devm_input_allocate_device(&pdev->dev);
+	if (!sensehat_joystick->keys_dev) {
+		dev_err(&pdev->dev, "Could not allocate input device");
+		return -ENOMEM;
+	}
+
+	sensehat_joystick->keys_dev->name = "Raspberry Pi Sense HAT Joystick";
+	sensehat_joystick->keys_dev->phys = "sensehat-joystick/input0";
+	sensehat_joystick->keys_dev->id.bustype = BUS_I2C;
+
+	__set_bit(EV_KEY, sensehat_joystick->keys_dev->evbit);
+	__set_bit(EV_REP, sensehat_joystick->keys_dev->evbit);
+	for (i = 0; i < ARRAY_SIZE(keymap); i++)
+		__set_bit(keymap[i], sensehat_joystick->keys_dev->keybit);
+
+	error = input_register_device(sensehat_joystick->keys_dev);
+	if (error) {
+		dev_err(&pdev->dev, "Could not register input device");
+		return error;
+	}
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "Could not retrieve interrupt request");
+		return irq;
+	}
+
+	error = devm_request_threaded_irq(&pdev->dev, irq,
+					  NULL, sensehat_joystick_report,
+					  IRQF_ONESHOT, "keys",
+					  sensehat_joystick);
+	if (error) {
+		dev_err(&pdev->dev, "IRQ request failed");
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id sensehat_joystick_device_id[] = {
+	{ .compatible = "raspberrypi,sensehat-joystick" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sensehat_joystick_device_id);
+
+static struct platform_driver sensehat_joystick_driver = {
+	.probe = sensehat_joystick_probe,
+	.driver = {
+		.name = "sensehat-joystick",
+		.of_match_table = sensehat_joystick_device_id,
+	},
+};
+
+module_platform_driver(sensehat_joystick_driver);
+
+MODULE_DESCRIPTION("Raspberry Pi Sense HAT joystick driver");
+MODULE_AUTHOR("Charles Mirabile <[e-mail]>");
+MODULE_AUTHOR("Serge Schneider <[e-mail]>");
+MODULE_LICENSE("GPL");