Re: [PATCH V5 2/6] drivers/input/joystick: sensehat: Raspberry Pi Sense HAT joystick driver

Hi Charles,

On Fri, Dec 10, 2021 at 05:10:29PM -0500, Charles Mirabile wrote:

This patch implements support for the joystick.
It supports left/right/up/down/enter and is
attached via i2c and a gpio pin for irq.

This is not really a joystick, at least not in current incarnation, but
rather a set of keys. I'd also question whether the selected set is
right for the application, I'd look into BTN_DPAD_* maybe? 

Or, if you want it to be a joystick, map ABS_X/ABS_Y.

I do not see I2C accessed directly in this driver, nor GPIO interface.
You also do not need to depend on INPUT explicitly here.

Don't think you need this.

+#include <linux/interrupt.h>
+#include <linux/gpio/consumer.h>

Not needed.

+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/mfd/sensehat.h>
+
+#define SENSEHAT_KEYS 0xF2
+
+static int sensehat_get_joystick_state(struct sensehat *sensehat);
+
+static unsigned char keymap[] = {
+	KEY_DOWN, KEY_RIGHT, KEY_UP, KEY_ENTER, KEY_LEFT,
+};

Because you allowing manipulating keymap from userspace you need to make
a copy of it when setting up input device so that changes do would not
persist across bind/unbind.

This array needs to be marked const.

+
+static irqreturn_t sensehat_joystick_report(int n, void *cookie)
+{
+	int i;
+	static s32 prev_keys;
+	struct sensehat *sensehat = cookie;
+	struct sensehat_joystick *sensehat_joystick = &sensehat->joystick;
+	s32 keys = sensehat_get_joystick_state(sensehat);
+	s32 changes = keys ^ prev_keys;
+
+	prev_keys = keys;
+	for (i = 0; i < ARRAY_SIZE(keymap); ++i) {
+		if (changes & (1 << i)) {
+			input_report_key(sensehat_joystick->keys_dev, keymap[i],
+					 keys & (1 << i));
+		}
+	}

If you go with keys/buttons approach, then use
bitmap_xor()/for_each_set_bit() - see
drivers/input/keyboard/cypress-sf.c::cypress_sf_irq_handler() for
example of use.

+	input_sync(sensehat_joystick->keys_dev);
+	return IRQ_HANDLED;
+}
+
+static int sensehat_joystick_probe(struct platform_device *pdev)
+{
+	int ret;

Please call it "error";

+	int i;
+	struct sensehat *sensehat = dev_get_drvdata(&pdev->dev);
+	struct sensehat_joystick *sensehat_joystick = &sensehat->joystick;

This structure (struct sensehat_joystick) should probably be private to
this driver.

+
+	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 = "rpi-sense-joy/input0";
+	sensehat_joystick->keys_dev->id.bustype = BUS_I2C;
+	sensehat_joystick->keys_dev->evbit[0] =
+		BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
+	sensehat_joystick->keys_dev->keycode = keymap;
+	sensehat_joystick->keys_dev->keycodesize = sizeof(unsigned char);
+	sensehat_joystick->keys_dev->keycodemax = ARRAY_SIZE(keymap);
+
+	ret = input_register_device(sensehat_joystick->keys_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not register input device.\n");
+		return ret;
+	}
+
+	ret = devm_request_threaded_irq(&pdev->dev, sensehat->i2c_client->irq,
+					NULL, sensehat_joystick_report,
+					IRQF_TRIGGER_RISING | IRQF_ONESHOT,

Do not specify trigger type, whoever set up client's interrupt should
have set up appropriate trigger.

+					"keys", sensehat);
+
+	if (ret) {
+		dev_err(&pdev->dev, "IRQ request failed.\n");
+		return ret;
+	}
+	return 0;
+}
+
+int sensehat_get_joystick_state(struct sensehat *sensehat)
+{
+	unsigned int reg;
+	int ret = regmap_read(sensehat->regmap, SENSEHAT_KEYS, &reg);
+
+	return ret < 0 ? ret : reg;

I do not see the point in having this wrapper.

+}
+
+static struct platform_device_id sensehat_joystick_device_id[] = {
+	{ .name = "sensehat-joystick" },
+	{},
+};
+MODULE_DEVICE_TABLE(platform, sensehat_joystick_device_id);
+
+static struct platform_driver sensehat_joystick_driver = {
+	.probe = sensehat_joystick_probe,
+	.driver = {
+		.name = "sensehat-joystick",
+	},
+};
+
+module_platform_driver(sensehat_joystick_driver);
+
+MODULE_DESCRIPTION("Raspberry Pi Sense HAT joystick driver");
+MODULE_AUTHOR("Serge Schneider [off-list ref]");
+MODULE_LICENSE("GPL");
-- 
2.31.1

Thanks.

-- 
Dmitry