drivers/input/serio/ams_delta_serio.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Amstrad E3 (Delta) keyboard port driver
 *
 *  Copyright (c) 2006 Matt Callow
 *  Copyright (c) 2010 Janusz Krzysztofik
 *
 * Thanks to Cliff Lawson for his help
 *
 * The Amstrad Delta keyboard (aka mailboard) uses normal PC-AT style serial
 * transmission.  The keyboard port is formed of two GPIO lines, for clock
 * and data.  Due to strict timing requirements of the interface,
 * the serial data stream is read and processed by a FIQ handler.
 * The resulting words are fetched by this driver from a circular buffer.
 *
 * Standard AT keyboard driver (atkbd) is used for handling the keyboard data.
 * However, when used with the E3 mailboard that producecs non-standard
 * scancodes, a custom key table must be prepared and loaded from userspace.
 */
#include <linux/irq.h>
#include <linux/platform_data/ams-delta-fiq.h>
#include <linux/platform_device.h>
#include <linux/regulator/consumer.h>
#include <linux/serio.h>
#include <linux/slab.h>
#include <linux/module.h>

#define DRIVER_NAME	"ams-delta-serio"

MODULE_AUTHOR("Matt Callow");
MODULE_DESCRIPTION("AMS Delta (E3) keyboard port driver");
MODULE_LICENSE("GPL");

struct ams_delta_serio {
	struct serio *serio;
	struct regulator *vcc;
	unsigned int *fiq_buffer;
};

static int check_data(struct serio *serio, int data)
{
	int i, parity = 0;

	/* check valid stop bit */
	if (!(data & 0x400)) {
		dev_warn(&serio->dev, "invalid stop bit, data=0x%X\n", data);
		return SERIO_FRAME;
	}
	/* calculate the parity */
	for (i = 1; i < 10; i++) {
		if (data & (1 << i))
			parity++;
	}
	/* it should be odd */
	if (!(parity & 0x01)) {
		dev_warn(&serio->dev,
			 "parity check failed, data=0x%X parity=0x%X\n", data,
			 parity);
		return SERIO_PARITY;
	}
	return 0;
}

static irqreturn_t ams_delta_serio_interrupt(int irq, void *dev_id)
{
	struct ams_delta_serio *priv = dev_id;
	int *circ_buff = &priv->fiq_buffer[FIQ_CIRC_BUFF];
	int data, dfl;
	u8 scancode;

	priv->fiq_buffer[FIQ_IRQ_PEND] = 0;

	/*
	 * Read data from the circular buffer, check it
	 * and then pass it on the serio
	 */
	while (priv->fiq_buffer[FIQ_KEYS_CNT] > 0) {

		data = circ_buff[priv->fiq_buffer[FIQ_HEAD_OFFSET]++];
		priv->fiq_buffer[FIQ_KEYS_CNT]--;
		if (priv->fiq_buffer[FIQ_HEAD_OFFSET] ==
		    priv->fiq_buffer[FIQ_BUF_LEN])
			priv->fiq_buffer[FIQ_HEAD_OFFSET] = 0;

		dfl = check_data(priv->serio, data);
		scancode = (u8) (data >> 1) & 0xFF;
		serio_interrupt(priv->serio, scancode, dfl);
	}
	return IRQ_HANDLED;
}

static int ams_delta_serio_open(struct serio *serio)
{
	struct ams_delta_serio *priv = serio->port_data;

	/* enable keyboard */
	return regulator_enable(priv->vcc);
}

static void ams_delta_serio_close(struct serio *serio)
{
	struct ams_delta_serio *priv = serio->port_data;

	/* disable keyboard */
	regulator_disable(priv->vcc);
}

static int ams_delta_serio_init(struct platform_device *pdev)
{
	struct ams_delta_serio *priv;
	struct serio *serio;
	int irq, err;

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	priv->fiq_buffer = pdev->dev.platform_data;
	if (!priv->fiq_buffer)
		return -EINVAL;

	priv->vcc = devm_regulator_get(&pdev->dev, "vcc");
	if (IS_ERR(priv->vcc)) {
		err = PTR_ERR(priv->vcc);
		dev_err(&pdev->dev, "regulator request failed (%d)\n", err);
		/*
		 * When running on a non-dt platform and requested regulator
		 * is not available, devm_regulator_get() never returns
		 * -EPROBE_DEFER as it is not able to justify if the regulator
		 * may still appear later.  On the other hand, the board can
		 * still set full constriants flag at late_initcall in order
		 * to instruct devm_regulator_get() to returnn a dummy one
		 * if sufficient.  Hence, if we get -ENODEV here, let's convert
		 * it to -EPROBE_DEFER and wait for the board to decide or
		 * let Deferred Probe infrastructure handle this error.
		 */
		if (err == -ENODEV)
			err = -EPROBE_DEFER;
		return err;
	}

	irq = platform_get_irq(pdev, 0);
	if (irq < 0)
		return -ENXIO;

	err = devm_request_irq(&pdev->dev, irq, ams_delta_serio_interrupt,
			       IRQ_TYPE_EDGE_RISING, DRIVER_NAME, priv);
	if (err < 0) {
		dev_err(&pdev->dev, "IRQ request failed (%d)\n", err);
		return err;
	}

	serio = kzalloc(sizeof(*serio), GFP_KERNEL);
	if (!serio)
		return -ENOMEM;

	priv->serio = serio;

	serio->id.type = SERIO_8042;
	serio->open = ams_delta_serio_open;
	serio->close = ams_delta_serio_close;
	strscpy(serio->name, "AMS DELTA keyboard adapter", sizeof(serio->name));
	strscpy(serio->phys, dev_name(&pdev->dev), sizeof(serio->phys));
	serio->dev.parent = &pdev->dev;
	serio->port_data = priv;

	serio_register_port(serio);

	platform_set_drvdata(pdev, priv);

	dev_info(&serio->dev, "%s\n", serio->name);

	return 0;
}

static void ams_delta_serio_exit(struct platform_device *pdev)
{
	struct ams_delta_serio *priv = platform_get_drvdata(pdev);

	serio_unregister_port(priv->serio);
}

static struct platform_driver ams_delta_serio_driver = {
	.probe	= ams_delta_serio_init,
	.remove_new = ams_delta_serio_exit,
	.driver	= {
		.name	= DRIVER_NAME
	},
};
module_platform_driver(ams_delta_serio_driver);