Message-ID: <fb4c668518ac342f21f4c2eabd7db236@dk-develop.de>
Date:   Tue, 01 Aug 2017 20:51:40 +0200
From:   danilokrummrich@...develop.de
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linus.walleij@...aro.org, rdunlap@...radead.org
Subject: Re: [PATCH v3] serio: PS/2 gpio bit banging driver for the serio bus

Hi Dmitry,

thank you for reviewing and giving your comments.

On 2017-08-01 19:32, Dmitry Torokhov wrote:
> Hi Danilo,
> 
> On Tue, Aug 01, 2017 at 06:26:14AM +0200, Danilo Krummrich wrote:
>> This driver provides PS/2 serio bus support by implementing bit 
>> banging
>> with the GPIO API. The GPIO pins, data and clock, can be configured 
>> with
>> a node in the device tree or by static platform data.
>> 
>> Writing to a device is supported as well, though it is not recommended 
>> as
>> the timings to be halt given by libps2 are very tough and difficult to
>> reach with bit banging. Therefore it can be configured (also in DT and
>> pdata) whether the serio write function should be available for 
>> clients.
>> 
>> This driver is for development purposes and not for productive use.
>> However, this driver can be useful e.g. when no USB port is available 
>> or
>> using old peripherals is desired as PS/2 controller chips getting 
>> rare.
>> 
>> This driver was tested on a RPI1 and on Hikey960 and it worked well
>> together with the atkbd driver.
>> 
>> Signed-off-by: Danilo Krummrich <danilokrummrich@...develop.de>
>> ---
>> v2: Removed one verbose print statement, changed another one to 
>> dev_dbg.
>> v3: - fixed compiler warning on blackfin
>>     - depends on GPIOLIB
>>     - clarify documentation
>> ---
>>  .../devicetree/bindings/serio/ps2-gpio.txt         |  20 +
>>  Documentation/gpio/drivers-on-gpio.txt             |   5 +
>>  drivers/input/serio/Kconfig                        |  11 +
>>  drivers/input/serio/Makefile                       |   1 +
>>  drivers/input/serio/ps2-gpio.c                     | 439 
>> +++++++++++++++++++++
>>  include/linux/ps2-gpio.h                           |  27 ++
>>  6 files changed, 503 insertions(+)
>>  create mode 100644 
>> Documentation/devicetree/bindings/serio/ps2-gpio.txt
>>  create mode 100644 drivers/input/serio/ps2-gpio.c
>>  create mode 100644 include/linux/ps2-gpio.h
>> 
>> diff --git a/Documentation/devicetree/bindings/serio/ps2-gpio.txt 
>> b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
>> new file mode 100644
>> index 0000000..828a5b6
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
>> @@ -0,0 +1,20 @@
>> +Device-Tree bindings for ps2 gpio driver
>> +
>> +Required properties:
>> +	- compatible = "ps2-gpio";
>> +	- gpios: data and clock gpio
>> +
>> +Optional properties:
>> +	- ps2-gpio,write-enable: Indicates whether write function is 
>> provided
>> +	to serio device. Most probably providing the write fn will not work,
>> +	because of the tough timing libps2 requires.
>> +
>> +Example nodes:
>> +
>> +ps2@0 {
>> +	compatible = "ps2-gpio";
>> +	gpios = <&gpio 24 0 /* data */
>> +		 &gpio 23 0 /* clock */
>> +		>;
>> +	i2c-gpio,write-enable = <0>;
>> +};
>> diff --git a/Documentation/gpio/drivers-on-gpio.txt 
>> b/Documentation/gpio/drivers-on-gpio.txt
>> index 3065132..97c8716 100644
>> --- a/Documentation/gpio/drivers-on-gpio.txt
>> +++ b/Documentation/gpio/drivers-on-gpio.txt
>> @@ -84,6 +84,11 @@ hardware descriptions such as device tree or ACPI:
>>    NAND flash MTD subsystem and provides chip access and partition 
>> parsing like
>>    any other NAND driving hardware.
>> 
>> +- ps2-gpio: drivers/input/serio/ps2-gpio.c is used to drive an PS/2 
>> (IBM) serio
>> +  bus, data and clock line, by bit banging two GPIO lines. It will 
>> appear as
>> +  any other serio bus to the system and makes it possible to connect 
>> drivers
>> +  for e.g. keyboards and other PS/2 protocol based devices.
>> +
>>  Apart from this there are special GPIO drivers in subsystems like 
>> MMC/SD to
>>  read card detect and write protect GPIO lines, and in the TTY serial 
>> subsystem
>>  to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO 
>> lines. The
>> diff --git a/drivers/input/serio/Kconfig b/drivers/input/serio/Kconfig
>> index c3d05b4..292d6e2 100644
>> --- a/drivers/input/serio/Kconfig
>> +++ b/drivers/input/serio/Kconfig
>> @@ -292,6 +292,17 @@ config SERIO_SUN4I_PS2
>>  	  To compile this driver as a module, choose M here: the
>>  	  module will be called sun4i-ps2.
>> 
>> +config SERIO_GPIO_PS2
>> +	tristate "GPIO PS/2 bit banging driver"
>> +	depends on GPIOLIB
>> +	help
>> +	  Say Y here if you want PS/2 bit banging support via GPIO.
>> +
>> +	  To compile this driver as a module, choose M here: the
>> +	  module will be called gpio-ps2.
>> +
>> +	  If you are unsure, say N.
>> +
>>  config USERIO
>>  	tristate "User space serio port driver support"
>>  	help
>> diff --git a/drivers/input/serio/Makefile 
>> b/drivers/input/serio/Makefile
>> index 2374ef9..767bd9b 100644
>> --- a/drivers/input/serio/Makefile
>> +++ b/drivers/input/serio/Makefile
>> @@ -30,4 +30,5 @@ obj-$(CONFIG_SERIO_APBPS2)	+= apbps2.o
>>  obj-$(CONFIG_SERIO_OLPC_APSP)	+= olpc_apsp.o
>>  obj-$(CONFIG_HYPERV_KEYBOARD)	+= hyperv-keyboard.o
>>  obj-$(CONFIG_SERIO_SUN4I_PS2)	+= sun4i-ps2.o
>> +obj-$(CONFIG_SERIO_GPIO_PS2)	+= ps2-gpio.o
>>  obj-$(CONFIG_USERIO)		+= userio.o
>> diff --git a/drivers/input/serio/ps2-gpio.c 
>> b/drivers/input/serio/ps2-gpio.c
>> new file mode 100644
>> index 0000000..fc5368b
>> --- /dev/null
>> +++ b/drivers/input/serio/ps2-gpio.c
>> @@ -0,0 +1,439 @@
>> +/*
>> + * GPIO based serio bus driver for bit banging the PS/2 protocol
>> + *
>> + * Author: Danilo Krummrich <danilokrummrich@...develop.de>
>> + *
>> + * This program is free software; you can redistribute it and/or 
>> modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +
>> +#include <linux/gpio.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/module.h>
>> +#include <linux/serio.h>
>> +#include <linux/slab.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/workqueue.h>
>> +#include <linux/ps2-gpio.h>
>> +#include <linux/of.h>
>> +#include <linux/of_gpio.h>
>> +#include <linux/jiffies.h>
>> +#include <linux/delay.h>
>> +
>> +#define DRIVER_NAME		"ps2-gpio"
>> +
>> +#define PS2_MODE_RX		0
>> +#define PS2_MODE_TX		1
>> +
>> +#define PS2_START_BIT		0
>> +#define PS2_DATA_BIT0		1
>> +#define PS2_DATA_BIT1		2
>> +#define PS2_DATA_BIT2		3
>> +#define PS2_DATA_BIT3		4
>> +#define PS2_DATA_BIT4		5
>> +#define PS2_DATA_BIT5		6
>> +#define PS2_DATA_BIT6		7
>> +#define PS2_DATA_BIT7		8
>> +#define PS2_PARITY_BIT		9
>> +#define PS2_STOP_BIT		10
>> +#define PS2_ACK_BIT		11
>> +
>> +#define PS2_DEV_RET_ACK		0xfa
>> +#define PS2_DEV_RET_NACK	0xfe
>> +
>> +#define PS2_CMD_RESEND		0xfe
>> +
>> +struct ps2_gpio_data {
>> +	struct device *dev;
>> +	struct serio *serio;
>> +	unsigned char mode;
>> +	unsigned int gpio_clk;
>> +	unsigned int gpio_data;
>> +	unsigned int write_enable;
>> +	unsigned int irq;
>> +	unsigned char rx_cnt;
>> +	unsigned char rx_byte;
>> +	unsigned char tx_cnt;
>> +	unsigned char tx_byte;
>> +	struct delayed_work tx_work;
>> +};
>> +
>> +static int ps2_gpio_open(struct serio *serio)
>> +{
>> +	struct ps2_gpio_data *drvdata = serio->port_data;
>> +
>> +	enable_irq(drvdata->irq);
>> +	return 0;
>> +}
>> +
>> +static void ps2_gpio_close(struct serio *serio)
>> +{
>> +	struct ps2_gpio_data *drvdata = serio->port_data;
>> +
>> +	disable_irq(drvdata->irq);
>> +}
>> +
>> +static int ps2_gpio_write(struct serio *serio, unsigned char val)
>> +{
>> +	struct ps2_gpio_data *drvdata = serio->port_data;
>> +
>> +	drvdata->mode = PS2_MODE_TX;
>> +	drvdata->tx_byte = val;
>> +	/* Make sure ISR running on other CPU notice changes. */
>> +	barrier();
>> +	disable_irq_nosync(drvdata->irq);
> 
> Why do you need to disable IRQ here? Shouldn't you let the device
> complete transmitting the current byte (if any)?
> 
The PS/2 protocol allows the host to interrupt the device at any point
point of time. If device's current message was not transferred
completely it will resend the last message.
>> +	gpio_direction_output(drvdata->gpio_clk, 0);
>> +	schedule_delayed_work(&drvdata->tx_work, usecs_to_jiffies(200));
> 
> What do we do if there are concurrent requests? The function returns
> before it completes write.
> 
Oops, I missed this case completely. I will fix that.
>> +
>> +	return 0;
>> +}
>> +
>> +static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata)
>> +{
>> +	unsigned char byte, cnt;
>> +	int data;
>> +	int rxflags = 0;
>> +	static unsigned long old_jiffies;
>> +
>> +	byte = drvdata->rx_byte;
>> +	cnt = drvdata->rx_cnt;
>> +
>> +	if (old_jiffies == 0)
>> +		old_jiffies = jiffies;
>> +
>> +	if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) {
>> +		dev_err(drvdata->dev,
>> +			"RX: timeout, probably we missed an interrupt\n");
>> +		goto err;
>> +	}
>> +	old_jiffies = jiffies;
>> +
>> +	data = gpio_get_value(drvdata->gpio_data);
>> +	if (unlikely(data < 0)) {
>> +		dev_err(drvdata->dev, "RX: failed to get gpio %u value: %d\n",
>> +			drvdata->gpio_data, data);
>> +		goto err;
>> +	}
>> +
>> +	switch (cnt) {
>> +	case PS2_START_BIT:
>> +		/* start bit should be low */
>> +		if (unlikely(data)) {
>> +			dev_err(drvdata->dev, "RX: start bit should be low\n");
>> +			goto err;
>> +		}
>> +		break;
>> +	case PS2_DATA_BIT0:
>> +	case PS2_DATA_BIT1:
>> +	case PS2_DATA_BIT2:
>> +	case PS2_DATA_BIT3:
>> +	case PS2_DATA_BIT4:
>> +	case PS2_DATA_BIT5:
>> +	case PS2_DATA_BIT6:
>> +	case PS2_DATA_BIT7:
>> +		/* processing data bits */
>> +		if (data)
>> +			byte |= (data << (cnt - 1));
>> +		break;
>> +	case PS2_PARITY_BIT:
>> +		/* check odd parity */
>> +		if (!((hweight8(byte) & 1) ^ data)) {
>> +			rxflags |= SERIO_PARITY;
>> +			dev_warn(drvdata->dev, "RX: parity error\n");
>> +			if (!drvdata->write_enable)
>> +				goto err;
>> +		}
>> +		/* Let's send the data without waiting for the stop bit to be
>> +		 * sent. It may happen that we miss the stop bit. When this
>> +		 * happens we have no way to recover from this, certainly
>> +		 * missing the parity bit would be recognized when processing
>> +		 * the stop bit. When missing both, data is lost.
>> +		 * Additionally, we do not send spurious ACK's and NACK's.
>> +		 */
>> +		if (byte == PS2_DEV_RET_NACK)
>> +			goto err;
>> +		if (byte == PS2_DEV_RET_ACK)
>> +			break;
>> +		serio_interrupt(drvdata->serio, byte, rxflags);
>> +		dev_dbg(drvdata->dev, "RX: sending byte 0x%x\n", byte);
>> +		break;
>> +	case PS2_STOP_BIT:
>> +		/* stop bit should be high */
>> +		if (unlikely(!data)) {
>> +			dev_err(drvdata->dev, "RX: stop bit should be high\n");
>> +			goto err;
>> +		}
>> +		cnt = byte = 0;
>> +		old_jiffies = 0;
>> +		goto end; /* success */
>> +	default:
>> +		dev_err(drvdata->dev, "RX: got out of sync with the device\n");
>> +		goto err;
>> +	}
>> +
>> +	cnt++;
>> +	goto end; /* success */
>> +
>> +err:
>> +	cnt = byte = 0;
>> +	old_jiffies = 0;
>> +	ps2_gpio_write(drvdata->serio, PS2_CMD_RESEND);
>> +end:
>> +	drvdata->rx_cnt = cnt;
>> +	drvdata->rx_byte = byte;
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata)
>> +{
>> +	unsigned char byte, cnt;
>> +	int data;
>> +	static unsigned long old_jiffies;
>> +
>> +	cnt = drvdata->tx_cnt;
>> +	byte = drvdata->tx_byte;
>> +
>> +	if (old_jiffies == 0)
>> +		old_jiffies = jiffies;
>> +
>> +	if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) {
>> +		dev_err(drvdata->dev,
>> +			"TX: timeout, probably we missed an interrupt\n");
>> +		goto err;
>> +	}
>> +	old_jiffies = jiffies;
>> +
>> +	switch (cnt) {
>> +	case PS2_START_BIT:
>> +		/* should never happen */
>> +		dev_err(drvdata->dev,
>> +			"TX: start bit should have been sent already\n");
>> +		goto err;
>> +	case PS2_DATA_BIT0:
>> +	case PS2_DATA_BIT1:
>> +	case PS2_DATA_BIT2:
>> +	case PS2_DATA_BIT3:
>> +	case PS2_DATA_BIT4:
>> +	case PS2_DATA_BIT5:
>> +	case PS2_DATA_BIT6:
>> +	case PS2_DATA_BIT7:
>> +		data = byte & (1 << (cnt - 1));
> 
> 		data = byte & BIT(cnt - 1);
> 
Will be done.
>> +		gpio_set_value(drvdata->gpio_data, data);
>> +		break;
>> +	case PS2_PARITY_BIT:
>> +		/* do odd parity */
>> +		data = !(hweight8(byte) & 1);
>> +		gpio_set_value(drvdata->gpio_data, data);
>> +		break;
>> +	case PS2_STOP_BIT:
>> +		/* release data line to generate stop bit */
>> +		gpio_direction_input(drvdata->gpio_data);
>> +		break;
>> +	case PS2_ACK_BIT:
>> +		gpio_direction_input(drvdata->gpio_data);
>> +		data = gpio_get_value(drvdata->gpio_data);
>> +		if (data)
>> +			dev_warn(drvdata->dev, "TX: received NACK, retry\n");
>> +		if (data)
>> +			goto err;
>> +		drvdata->mode = PS2_MODE_RX;
>> +		/* Make sure ISR running on other CPU notice mode change. */
>> +		barrier();
>> +		cnt = 1;
>> +		old_jiffies = 0;
>> +		goto end; /* success */
>> +	default:
>> +		/* Probably we missed the stop bit. Therefore we release data
>> +		 * line and try again.
>> +		 */
>> +		gpio_direction_input(drvdata->gpio_data);
>> +		dev_err(drvdata->dev, "TX: got out of sync with the device\n");
>> +		goto err;
>> +	}
>> +
>> +	cnt++;
>> +	goto end; /* success */
>> +
>> +err:
>> +	cnt = 1;
>> +	old_jiffies = 0;
>> +	gpio_direction_input(drvdata->gpio_data);
>> +	ps2_gpio_write(drvdata->serio, PS2_CMD_RESEND);
>> +end:
>> +	drvdata->tx_cnt = cnt;
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static irqreturn_t ps2_gpio_irq(int irq, void *dev_id)
>> +{
>> +	struct ps2_gpio_data *drvdata = dev_id;
>> +
>> +	return drvdata->mode ? ps2_gpio_irq_tx(drvdata) :
>> +		ps2_gpio_irq_rx(drvdata);
>> +}
>> +
>> +static void ps2_gpio_tx_work_fn(struct work_struct *work)
>> +{
>> +	struct delayed_work *dwork = to_delayed_work(work);
>> +	struct ps2_gpio_data *drvdata = container_of(dwork,
>> +						    struct ps2_gpio_data,
>> +						    tx_work);
>> +	enable_irq(drvdata->irq);
>> +	gpio_direction_output(drvdata->gpio_data, 0);
>> +	gpio_direction_input(drvdata->gpio_clk);
>> +}
>> +
>> +static int of_ps2_gpio_get_props(struct device *dev,
>> +				 struct ps2_gpio_data *drvdata)
>> +{
>> +	if (of_gpio_count(dev->of_node) < 2)
>> +		return -ENODEV;
>> +
>> +	drvdata->gpio_data = of_get_gpio(dev->of_node, 0);
>> +	drvdata->gpio_clk = of_get_gpio(dev->of_node, 1);
> 
> No, please use gpiod API and simply do:
> 
> 	drvdata->gpio_data = devm_gpiod_get(dev, "data", GPIOD_IN);
> 	if (IS_ERR(drvdata->gpio_data)
> 		...
> 
> 	drvdata->gpio_clk = devm_gpiod_get(dev, "clk", GPIOD_IN);
> 	if (IS_ERR(drvdata->gpio_clk)
> 		...
> 
Will fix this...
>> +
>> +	if (drvdata->gpio_data == -EPROBE_DEFER ||
>> +	    drvdata->gpio_clk == -EPROBE_DEFER)
>> +		return -EPROBE_DEFER;
>> +
>> +	if (!gpio_is_valid(drvdata->gpio_data) ||
>> +	    !gpio_is_valid(drvdata->gpio_clk)) {
>> +		dev_err(dev, "invalid GPIOs, data=%d, clk=%d\n",
>> +			drvdata->gpio_data, drvdata->gpio_clk);
>> +		return -ENODEV;
>> +	}
>> +
>> +	of_property_read_u32(dev->of_node, "ps2-gpio,write-enable",
>> +			     &drvdata->write_enable);
> 
> 	device_property_read_bool(dev, ...);
> 
and this.
>> +
>> +	return 0;
>> +}
>> +
>> +static int ps2_gpio_probe(struct platform_device *pdev)
>> +{
>> +	struct ps2_gpio_data *drvdata;
>> +	struct ps2_gpio_platform_data *pdata;
>> +	struct serio *serio;
>> +	struct device *dev = &pdev->dev;
>> +	unsigned int irq;
>> +	int error;
>> +
>> +	drvdata = devm_kzalloc(dev, sizeof(struct ps2_gpio_data), 
>> GFP_KERNEL);
>> +	serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
>> +	if (!drvdata || !serio) {
>> +		error = -ENOMEM;
>> +		goto err_free_serio;
>> +	}
>> +
>> +	if (dev->of_node) {
>> +		error = of_ps2_gpio_get_props(dev, drvdata);
>> +		if (error)
>> +			goto err_free_serio;
>> +	} else {
>> +		if (!dev_get_platdata(dev)) {
>> +			error = -ENXIO;
>> +			goto err_free_serio;
>> +		}
>> +		pdata = dev_get_platdata(dev);
> 
> I'd rather we did not add any more platform data but relied on generic
> device properties (which are available on static boards, in addition to
> OF and ACPI systems).
> 
I will change that to use generic device properties instead of platform 
data.
>> +		drvdata->gpio_data = pdata->gpio_data;
>> +		drvdata->gpio_clk = pdata->gpio_clk;
>> +		drvdata->write_enable = pdata->write_enable;
>> +	}
>> +
>> +	error = devm_gpio_request(dev, drvdata->gpio_clk, "ps2 clk");
>> +	if (error) {
>> +		dev_err(dev, "failed to request gpio %u: %d",
>> +				drvdata->gpio_clk, error);
>> +		goto err_free_serio;
>> +	}
>> +
>> +	error = devm_gpio_request(dev, drvdata->gpio_data, "ps2 data");
>> +	if (error) {
>> +		dev_err(dev, "failed to request gpio %u: %d",
>> +				drvdata->gpio_data, error);
>> +		goto err_free_serio;
>> +	}
>> +
>> +	gpio_direction_input(drvdata->gpio_clk);
>> +	gpio_direction_input(drvdata->gpio_data);
>> +
>> +	irq = gpio_to_irq(drvdata->gpio_clk);
>> +	if (!irq) {
>> +		dev_err(dev, "cannot get irq from gpio %u\n",
>> +			drvdata->gpio_clk);
>> +		error = -ENXIO;
>> +		goto err_free_serio;
>> +	}
> 
> 
> IRQ line does not have to be the same as GPIO pin. Describe it
> separately in device properties and just do:
> 
> 	irq = platform_get_irq(pdev, 0);
> 
> and use it in the request below.
> 
In which constellation can they be different?
>> +
>> +	error = devm_request_irq(dev, irq, ps2_gpio_irq, IRQF_NO_THREAD |
>> +			IRQF_TRIGGER_FALLING, DRIVER_NAME, drvdata);
> 
> This will not work if GPIO is behind I2C or other slow bus. Is it
> essential that there is no scheduling delay here?
> 
Yes it is. You are right, this wouldn't work. Was this the scenario you 
had in mind while
writing the comment above?
>> +	if (error) {
>> +		dev_err(dev, "failed to request irq %u: %d\n",
>> +			drvdata->irq, error);
>> +		goto err_free_serio;
>> +	}
>> +
>> +	serio->id.type = SERIO_8042;
>> +	serio->open = ps2_gpio_open;
>> +	serio->close = ps2_gpio_close;
>> +	/* Write can be enabled in platform/dt data, but most probably it 
>> will
>> +	 * not work because of the tough timings.
>> +	 */
>> +	serio->write = drvdata->write_enable ? ps2_gpio_write : NULL;
>> +	serio->port_data = drvdata;
>> +	serio->dev.parent = dev;
>> +	strlcpy(serio->name, dev_name(dev), sizeof(serio->name));
>> +	strlcpy(serio->phys, dev_name(dev), sizeof(serio->phys));
>> +
>> +	drvdata->irq = irq;
>> +	drvdata->serio = serio;
>> +	drvdata->dev = dev;
>> +	drvdata->mode = PS2_MODE_RX;
>> +
>> +	/* Tx count always starts at 1, as the start bit is sent implicitly 
>> by
>> +	 * host-to-device communication initialization.
>> +	 */
>> +	drvdata->tx_cnt = 1;
>> +
>> +	INIT_DELAYED_WORK(&drvdata->tx_work, ps2_gpio_tx_work_fn);
>> +
>> +	serio_register_port(serio);
>> +	platform_set_drvdata(pdev, drvdata);
>> +
>> +	return 0;	/* success */
>> +
>> +err_free_serio:
>> +	kfree(serio);
>> +	return error;
>> +}
>> +
>> +static int ps2_gpio_remove(struct platform_device *pdev)
>> +{
>> +	struct ps2_gpio_data *drvdata = platform_get_drvdata(pdev);
>> +
>> +	serio_unregister_port(drvdata->serio);
>> +	return 0;
>> +}
>> +
>> +#if defined(CONFIG_OF)
>> +static const struct of_device_id ps2_gpio_match[] = {
>> +	{ .compatible = "ps2-gpio", },
>> +	{ },
>> +};
>> +MODULE_DEVICE_TABLE(of, ps2_gpio_match);
>> +#endif
>> +
>> +static struct platform_driver ps2_gpio_driver = {
>> +	.probe		= ps2_gpio_probe,
>> +	.remove		= ps2_gpio_remove,
>> +	.driver = {
>> +		.name = DRIVER_NAME,
>> +		.of_match_table = ps2_gpio_match,
>> +	},
>> +};
>> +module_platform_driver(ps2_gpio_driver);
>> +
>> +MODULE_AUTHOR("Danilo Krummrich <danilokrummrich@...develop.de>");
>> +MODULE_DESCRIPTION("GPIO PS2 driver");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/linux/ps2-gpio.h b/include/linux/ps2-gpio.h
>> new file mode 100644
>> index 0000000..b65480d
>> --- /dev/null
>> +++ b/include/linux/ps2-gpio.h
>> @@ -0,0 +1,27 @@
>> +/*
>> + * ps2-gpio interface to platform code
>> + *
>> + * Author: Danilo Krummrich <danilokrummrich@...develop.de>
>> + *
>> + * This program is free software; you can redistribute it and/or 
>> modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +#ifndef _LINUX_PS2_GPIO_H
>> +#define _LINUX_PS2_GPIO_H
>> +
>> +/**
>> + * struct ps2_gpio_platform_data - Platform-dependent data for 
>> ps2-gpio
>> + * @gpio_data: GPIO pin ID to use for DATA
>> + * @gpio_clk: GPIO pin ID to use for CLOCK
>> + * @write_enable: Indicates whether write function is provided to 
>> serio
>> + *	device. Most probably providing the write fn will not work,
>> + *	because of the tough timing libps2 requires.
>> + */
>> +struct ps2_gpio_platform_data {
>> +	unsigned int	gpio_data;
>> +	unsigned int	gpio_clk;
>> +	unsigned int	write_enable;
>> +};
>> +
>> +#endif /* _LINUX_PS2_GPIO_H */
>> --
>> 2.9.3
>> 
> 
> Thanks.

Regards,
Danilo

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