Re: [PATCH 2/6] drivers/input/joystick: sensehat: Raspberry Pi Sense HAT joystick driver

[Nicolas Saenz Julienne <nsaenzju@redhat.com>]

On Wed, 2022-02-02 at 19:25 -0500, Charles Mirabile wrote:
> 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: Mwesigwa Guma <mguma@redhat.com>
> Signed-off-by: Mwesigwa Guma <mguma@redhat.com>
> Co-developed-by: Joel Savitz <jsavitz@redhat.com>
> Signed-off-by: Joel Savitz <jsavitz@redhat.com>
> Signed-off-by: Charles Mirabile <cmirabil@redhat.com>
> ---
>  drivers/input/joystick/Kconfig             |  11 ++
>  drivers/input/joystick/Makefile            |   1 +
>  drivers/input/joystick/sensehat-joystick.c | 128 +++++++++++++++++++++
>  3 files changed, 140 insertions(+)
>  create mode 100644 drivers/input/joystick/sensehat-joystick.c
> 
> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
> index 3b23078bc7b5..505a032e2786 100644
> --- a/drivers/input/joystick/Kconfig
> +++ b/drivers/input/joystick/Kconfig
> @@ -399,4 +399,15 @@ config JOYSTICK_N64
>  	  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
> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
> index 5174b8aba2dd..39c8b5c6e5ae 100644
> --- a/drivers/input/joystick/Makefile
> +++ b/drivers/input/joystick/Makefile
> @@ -28,6 +28,7 @@ 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-$(CONFIG_JOYSTICK_SENSEHAT)         += sensehat-joystick.o
>  obj-$(CONFIG_JOYSTICK_SIDEWINDER)	+= sidewinder.o
>  obj-$(CONFIG_JOYSTICK_SPACEBALL)	+= spaceball.o
>  obj-$(CONFIG_JOYSTICK_SPACEORB)		+= spaceorb.o
> diff --git a/drivers/input/joystick/sensehat-joystick.c b/drivers/input/joystick/sensehat-joystick.c
> new file mode 100644
> index 000000000000..a688cc8fbde3
> --- /dev/null
> +++ b/drivers/input/joystick/sensehat-joystick.c
> @@ -0,0 +1,128 @@
> +// 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/of_irq.h>
> +#include <linux/property.h>
> +
> +struct sensehat_joystick {
> +	struct platform_device *pdev;
> +	struct input_dev *keys_dev;
> +	unsigned long prev_states;
> +	u32 joystick_register;
> +};
> +
> +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 n, void *cookie)
> +{
> +	int i, error, keys;
> +	struct sensehat_joystick *sensehat_joystick = cookie;
> +	struct regmap *regmap =
> +		dev_get_regmap(sensehat_joystick->pdev->dev.parent, NULL);

I think it's better to get this during probe and save it in 'struct
sensehat_joystick'. You'll avoid having to search for it everytime.

> +	unsigned long curr_states, changes;
> +
> +	error = regmap_read(regmap, sensehat_joystick->joystick_register,
> +			    &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)
> +{
> +	int error, i;
> +	struct sensehat_joystick *sensehat_joystick = devm_kzalloc(
> +		&pdev->dev, sizeof(*sensehat_joystick), GFP_KERNEL);
> +
> +	sensehat_joystick->pdev = pdev;
> +	sensehat_joystick->keys_dev = devm_input_allocate_device(&pdev->dev);
> +	if (!sensehat_joystick->keys_dev) {
> +		dev_err(&pdev->dev, "Could not allocate input device.\n");
> +		return -ENOMEM;
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(keymap); i++)
> +		set_bit(keymap[i], sensehat_joystick->keys_dev->keybit);
> +
> +	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;
> +	sensehat_joystick->keys_dev->evbit[0] =
> +		BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
> +
> +	error = input_register_device(sensehat_joystick->keys_dev);
> +	if (error) {
> +		dev_err(&pdev->dev, "Could not register input device.\n");
> +		return error;
> +	}
> +
> +	error = device_property_read_u32(&pdev->dev, "reg",
> +					 &sensehat_joystick->joystick_register);
> +	if (error) {
> +		dev_err(&pdev->dev, "Could not read register property.\n");
> +		return error;
> +	}

I don't think you really need to pass this information through the devicetree.
It's just the address to a register, not a HW design detail (i.e. how the board
is layout). Using a define is good enough.

> +
> +	error = devm_request_threaded_irq(&pdev->dev,
> +					  of_irq_get(pdev->dev.of_node, 0),

Use platform_get_irq() and remember the function may fail, both unrecoverable
errors and EPROBE_DEFER when the irqchip isn't ready yet.

> +					  NULL, sensehat_joystick_report,
> +					  IRQF_ONESHOT, "keys",
> +					  sensehat_joystick);
> +
> +	if (error) {
> +		dev_err(&pdev->dev, "IRQ request failed.\n");
> +		return error;
> +	}

nit: space here

> +	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("Serge Schneider <serge@raspberrypi.org>");
> +MODULE_LICENSE("GPL");

-- 
Nicolás Sáenz