[PATCH] input: generic driver for slide switches

[PATCH] input: generic driver for slide switches

[Alexander Stein]

This patch adds a generic driver for slide switches connected to GPIO
pins of a system. It requires gpiolib and generic hardware irqs.

Signed-off-by: Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>
---
 drivers/input/misc/Kconfig         |    9 ++
 drivers/input/misc/Makefile        |    1 +
 drivers/input/misc/slide_switch.c  |  268 ++++++++++++++++++++++++++++++++++++
 include/linux/input/slide_switch.h |   16 ++
 4 files changed, 294 insertions(+), 0 deletions(-)
 create mode 100644 drivers/input/misc/slide_switch.c
 create mode 100644 include/linux/input/slide_switch.h

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index b0c6772..ba9395c 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -341,6 +341,15 @@ config INPUT_GPIO_ROTARY_ENCODER
 	  To compile this driver as a module, choose M here: the
 	  module will be called rotary_encoder.
 
+config INPUT_GPIO_SLIDE_SWITCH
+	tristate "Slide switches connected to GPIO pins"
+	depends on GPIOLIB && GENERIC_GPIO
+	help
+	  Say Y here to add support for slide switches connected to GPIO lines.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called slide_switch.
+
 config INPUT_RB532_BUTTON
 	tristate "Mikrotik Routerboard 532 button interface"
 	depends on MIKROTIK_RB532
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 9b47971..d81fdc9 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_INPUT_POWERMATE)		+= powermate.o
 obj-$(CONFIG_INPUT_PWM_BEEPER)		+= pwm-beeper.o
 obj-$(CONFIG_INPUT_RB532_BUTTON)	+= rb532_button.o
 obj-$(CONFIG_INPUT_GPIO_ROTARY_ENCODER)	+= rotary_encoder.o
+obj-$(CONFIG_INPUT_GPIO_SLIDE_SWITCH)	+= slide_switch.o
 obj-$(CONFIG_INPUT_SGI_BTNS)		+= sgi_btns.o
 obj-$(CONFIG_INPUT_SPARCSPKR)		+= sparcspkr.o
 obj-$(CONFIG_INPUT_TWL4030_PWRBUTTON)	+= twl4030-pwrbutton.o
diff --git a/drivers/input/misc/slide_switch.c b/drivers/input/misc/slide_switch.c
new file mode 100644
index 0000000..0f69b3a
--- /dev/null
+++ b/drivers/input/misc/slide_switch.c
@@ -0,0 +1,268 @@
+/*
+ * slide_switch.c
+ *
+ * (c) 2011 Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>
+ *
+ * A generic driver for slide switches connected to GPIO lines.
+ *
+ * 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.
+ */
+#define DEBUG
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/gpio.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <linux/input/slide_switch.h>
+
+#define DRV_NAME "slide-switch"
+
+struct slide_switch {
+	struct input_dev *input;
+	struct slide_switch_platform_data *pdata;
+
+	struct timer_list timer;
+	struct work_struct work;
+	int timer_debounce;	/* in msecs */
+};
+
+static void slide_switch_report_event(struct slide_switch *slide_switch)
+{
+	struct input_dev *input = slide_switch->input;
+	struct slide_switch_platform_data *pdata = slide_switch->pdata;
+	unsigned long posbit;
+	int i, on, pos, invalidpos;
+
+	posbit = 0;
+	for (i = 0; i < pdata->gpios; i++) {
+		on = gpio_get_value(pdata->gpiolist[i].gpio) ? 1 : 0;
+		on ^= pdata->gpiolist[i].inverted;
+		if (on)
+			set_bit(i, &posbit);
+	}
+
+	pos = find_first_bit(&posbit, pdata->gpios);
+	invalidpos = find_next_bit(&posbit, pdata->gpios, pos + 1);
+
+	/* Check if there is only one bit set */
+	if (pos < pdata->gpios && invalidpos == pdata->gpios) {
+		input_report_abs(slide_switch->input, pdata->axis, pos);
+		input_sync(input);
+	}
+}
+
+static void slide_switch_work_func(struct work_struct *work)
+{
+	struct slide_switch *slide_switch =
+		container_of(work, struct slide_switch, work);
+
+	slide_switch_report_event(slide_switch);
+}
+
+static void slide_switch_timer(unsigned long _data)
+{
+	struct slide_switch *slide_switch = (struct slide_switch *)_data;
+
+	schedule_work(&slide_switch->work);
+}
+
+static irqreturn_t slide_switch_irq(int irq, void *dev_id)
+{
+	struct slide_switch *slide_switch = dev_id;
+
+	if (slide_switch->timer_debounce)
+		mod_timer(&slide_switch->timer,
+			jiffies + msecs_to_jiffies(slide_switch->timer_debounce));
+	else
+		schedule_work(&slide_switch->work);
+
+	return IRQ_HANDLED;
+}
+
+static int slide_switch_register_gpios(struct device *dev,
+		const struct slide_switch_gpio *gpio,
+		struct slide_switch *slide_switch)
+{
+	int err, gpio_num, irq;
+	struct slide_switch_platform_data *pdata = slide_switch->pdata;
+
+	gpio_num = gpio->gpio;
+	irq = gpio_to_irq(gpio_num);
+
+	err = gpio_request(gpio_num, DRV_NAME);
+	if (err) {
+		dev_err(dev, "unable to request GPIO %d\n",
+			gpio_num);
+		goto exit_fail;
+	}
+
+	err = gpio_direction_input(gpio_num);
+	if (err) {
+		dev_err(dev, "unable to set GPIO %d for input\n",
+			gpio_num);
+		goto exit_unregister_gpio;
+	}
+
+	if (pdata->debounce_ms) {
+		err = gpio_set_debounce(gpio_num,
+					pdata->debounce_ms * 1000);
+		/* use timer if gpiolib doesn't provide debounce */
+		if (err < 0)
+			slide_switch->timer_debounce = pdata->debounce_ms;
+	}
+
+	/* request the IRQs */
+	err = request_irq(irq, &slide_switch_irq,
+			IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+			DRV_NAME, slide_switch);
+	if (err) {
+		dev_err(dev, "unable to request IRQ %d\n",
+			irq);
+		goto exit_unregister_gpio;
+	}
+
+	return 0;
+
+exit_unregister_gpio:
+	gpio_free(gpio_num);
+exit_fail:
+
+	return 1;
+}
+
+static void slide_switch_unregister_gpios(struct device *dev,
+		const struct slide_switch_gpio *gpio,
+		struct slide_switch *slide_switch)
+{
+	int gpio_num, irq;
+
+	gpio_num = gpio->gpio;
+	irq = gpio_to_irq(gpio_num);
+
+	free_irq(irq, slide_switch);
+	gpio_free(gpio_num);
+}
+
+static int __devinit slide_switch_probe(struct platform_device *pdev)
+{
+	struct slide_switch_platform_data *pdata = pdev->dev.platform_data;
+	struct slide_switch *slide_switch;
+	struct input_dev *input;
+	int err, i;
+
+	if (!pdata) {
+		dev_err(&pdev->dev, "missing platform data\n");
+		return -ENOENT;
+	}
+
+	if (!pdata->gpios || !pdata->gpiolist) {
+		dev_err(&pdev->dev, "no GPIOs provided\n");
+		return -ENOENT;
+	}
+
+	slide_switch = kzalloc(sizeof(struct slide_switch), GFP_KERNEL);
+	input = input_allocate_device();
+	if (!slide_switch || !input) {
+		dev_err(&pdev->dev, "failed to allocate memory for device\n");
+		err = -ENOMEM;
+		goto exit_free_mem;
+	}
+
+	slide_switch->input = input;
+	slide_switch->pdata = pdata;
+
+	/* create and register the input driver */
+	input->name = pdev->name;
+	input->id.bustype = BUS_HOST;
+	input->dev.parent = &pdev->dev;
+
+	input->evbit[0] = BIT_MASK(EV_ABS);
+	input_set_abs_params(slide_switch->input,
+				pdata->axis, 0, pdata->gpios, 0, 0);
+
+	err = input_register_device(input);
+	if (err) {
+		dev_err(&pdev->dev, "failed to register input device\n");
+		goto exit_free_mem;
+	}
+
+	setup_timer(&slide_switch->timer, slide_switch_timer,
+				(unsigned long)slide_switch);
+	INIT_WORK(&slide_switch->work, slide_switch_work_func);
+
+	/* Register GPIOs */
+	for (i = 0; i < pdata->gpios; i++) {
+		err = slide_switch_register_gpios(&pdev->dev,
+			&pdata->gpiolist[i], slide_switch);
+		if (err) {
+			for (i--; i >= 0; i--) {
+				slide_switch_unregister_gpios(&pdev->dev,
+					&pdata->gpiolist[i], slide_switch);
+			}
+			goto exit_unregister_input;
+		}
+	}
+
+	platform_set_drvdata(pdev, slide_switch);
+
+	return 0;
+
+exit_unregister_input:
+	input_unregister_device(input);
+	input = NULL; /* so we don't try to free it */
+exit_free_mem:
+	input_free_device(input);
+	kfree(slide_switch);
+	return err;
+}
+
+static int __devexit slide_switch_remove(struct platform_device *pdev)
+{
+	struct slide_switch *slide_switch = platform_get_drvdata(pdev);
+	struct slide_switch_platform_data *pdata = pdev->dev.platform_data;
+	int i;
+
+	/* Unregister GPIOs */
+	for (i = 0; i < pdata->gpios; i++)
+		slide_switch_unregister_gpios(&pdev->dev,
+				&pdata->gpiolist[i], slide_switch);
+
+	input_unregister_device(slide_switch->input);
+	platform_set_drvdata(pdev, NULL);
+	kfree(slide_switch);
+
+	return 0;
+}
+
+static struct platform_driver slide_switch_driver = {
+	.probe		= slide_switch_probe,
+	.remove		= __devexit_p(slide_switch_remove),
+	.driver		= {
+		.name	= DRV_NAME,
+		.owner	= THIS_MODULE,
+	}
+};
+
+static int __init slide_switch_init(void)
+{
+	return platform_driver_register(&slide_switch_driver);
+}
+
+static void __exit slide_switch_exit(void)
+{
+	platform_driver_unregister(&slide_switch_driver);
+}
+
+module_init(slide_switch_init);
+module_exit(slide_switch_exit);
+
+MODULE_ALIAS("platform:" DRV_NAME);
+MODULE_DESCRIPTION("GPIO slide switch driver");
+MODULE_AUTHOR("Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>");
+MODULE_LICENSE("GPL v2");
+
diff --git a/include/linux/input/slide_switch.h b/include/linux/input/slide_switch.h
new file mode 100644
index 0000000..b7544cb
--- /dev/null
+++ b/include/linux/input/slide_switch.h
@@ -0,0 +1,16 @@
+#ifndef __SLIDE_SWITCH_H__
+#define __SLIDE_SWITCH_H__
+
+struct slide_switch_gpio {
+	unsigned int gpio;
+	unsigned int inverted;
+};
+
+struct slide_switch_platform_data {
+	unsigned int axis;
+	const struct slide_switch_gpio *gpiolist;
+	unsigned int gpios;
+	unsigned int debounce_ms;
+};
+
+#endif /* __SLIDE_SWITCH_H__ */
-- 
1.7.4.1

Re: [PATCH] input: generic driver for slide switches

[Alexander Stein]

On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> This patch adds a generic driver for slide switches connected to GPIO
> pins of a system. It requires gpiolib and generic hardware irqs.
> 
> Signed-off-by: Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>
> ---
>  drivers/input/misc/Kconfig         |    9 ++
>  drivers/input/misc/Makefile        |    1 +
>  drivers/input/misc/slide_switch.c  |  268
> ++++++++++++++++++++++++++++++++++++ include/linux/input/slide_switch.h | 
>  16 ++
>  4 files changed, 294 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/input/misc/slide_switch.c
>  create mode 100644 include/linux/input/slide_switch.h

Did this get overlooked accidentaly?

Alexander

Re: [PATCH] input: generic driver for slide switches

[Dmitry Torokhov]

On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > This patch adds a generic driver for slide switches connected to GPIO
> > pins of a system. It requires gpiolib and generic hardware irqs.
> > 
> > Signed-off-by: Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>
> > ---
> >  drivers/input/misc/Kconfig         |    9 ++
> >  drivers/input/misc/Makefile        |    1 +
> >  drivers/input/misc/slide_switch.c  |  268
> > ++++++++++++++++++++++++++++++++++++ include/linux/input/slide_switch.h | 
> >  16 ++
> >  4 files changed, 294 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/input/misc/slide_switch.c
> >  create mode 100644 include/linux/input/slide_switch.h
> 
> Did this get overlooked accidentaly?
> 

Hi Alexander,

Hm, can't it be merged with gpio_keys? Just add the 'value' to the
gpio_keys_button structure that would be valid for EV_ABS (or even
EV_REL) types. Debouncing should filter out jittery events...

Thanks.

-- 
Dmitry

Re: [PATCH] input: generic driver for slide switches

[Alexander Stein]

Hello Dimitry,

On Wednesday 16 March 2011 07:36:18 Dmitry Torokhov wrote:
> On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> > On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > > This patch adds a generic driver for slide switches connected to GPIO
> > > pins of a system. It requires gpiolib and generic hardware irqs.

> Hm, can't it be merged with gpio_keys? Just add the 'value' to the
> gpio_keys_button structure that would be valid for EV_ABS (or even
> EV_REL) types. Debouncing should filter out jittery events...

Sorry, for no answer long time.
I just tried merging both. The problem i noticed is that the PGIO interrupts 
are independable and each GPIO will generate an event, which is wrong.
Assume the switch state change from position 2 to 1 it will actually generate 
lots of interrupts: e.g. 2, 1, 2, 1.
Depending from the order of such interrupts the last event shows a possible 
wrong position.
This can only be avoided if each GPIO interrupt starts the same state checking 
routine. Thus reading the GPIO pin state and report just one event.
Some ideas to still merge those drivers?

Regards,
Alexander

Re: [PATCH] input: generic driver for slide switches

[Dmitry Torokhov]

On Sat, Apr 02, 2011 at 10:31:53AM +0200, Alexander Stein wrote:
> Hello Dimitry,
> 
> On Wednesday 16 March 2011 07:36:18 Dmitry Torokhov wrote:
> > On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> > > On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > > > This patch adds a generic driver for slide switches connected to GPIO
> > > > pins of a system. It requires gpiolib and generic hardware irqs.
> 
> > Hm, can't it be merged with gpio_keys? Just add the 'value' to the
> > gpio_keys_button structure that would be valid for EV_ABS (or even
> > EV_REL) types. Debouncing should filter out jittery events...
> 
> Sorry, for no answer long time.
> I just tried merging both. The problem i noticed is that the PGIO interrupts 
> are independable and each GPIO will generate an event, which is wrong.
> Assume the switch state change from position 2 to 1 it will actually generate 
> lots of interrupts: e.g. 2, 1, 2, 1.
> Depending from the order of such interrupts the last event shows a possible 
> wrong position.

However at some point the output should stabilize. Does not setting
appropriate debouncing interval help here?

Thanks.

-- 
Dmitry

Re: [PATCH] input: generic driver for slide switches

[Alexander Stein]

Hello Dimitry,

On Sunday 03 April 2011 06:23:05 Dmitry Torokhov wrote:
> On Sat, Apr 02, 2011 at 10:31:53AM +0200, Alexander Stein wrote:
> > Hello Dimitry,
> > 
> > On Wednesday 16 March 2011 07:36:18 Dmitry Torokhov wrote:
> > > On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> > > > On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > > > > This patch adds a generic driver for slide switches connected to
> > > > > GPIO pins of a system. It requires gpiolib and generic hardware
> > > > > irqs.
> > > 
> > > Hm, can't it be merged with gpio_keys? Just add the 'value' to the
> > > gpio_keys_button structure that would be valid for EV_ABS (or even
> > > EV_REL) types. Debouncing should filter out jittery events...
> > 
> > Sorry, for no answer long time.
> > I just tried merging both. The problem i noticed is that the PGIO
> > interrupts are independable and each GPIO will generate an event, which
> > is wrong. Assume the switch state change from position 2 to 1 it will
> > actually generate lots of interrupts: e.g. 2, 1, 2, 1.
> > Depending from the order of such interrupts the last event shows a
> > possible wrong position.
> 
> However at some point the output should stabilize. Does not setting
> appropriate debouncing interval help here?

Well, a debounce interval will prevent to get events for position 2, 1, 2, 1 
(from the example above). You will get only 2 and 1.
The debounce will only decrease the amount of events for _each_ GPIO 
interrupt. It will not prevent GPIO interrupts from different pins while moving 
the switch one position.

Alexander

Re: [PATCH] input: generic driver for slide switches

[Dmitry Torokhov]

Hi Alexander,

On Sun, Apr 03, 2011 at 10:21:26AM +0200, Alexander Stein wrote:
> Hello Dimitry,
> 
> On Sunday 03 April 2011 06:23:05 Dmitry Torokhov wrote:
> > On Sat, Apr 02, 2011 at 10:31:53AM +0200, Alexander Stein wrote:
> > > Hello Dimitry,
> > > 
> > > On Wednesday 16 March 2011 07:36:18 Dmitry Torokhov wrote:
> > > > On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> > > > > On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > > > > > This patch adds a generic driver for slide switches connected to
> > > > > > GPIO pins of a system. It requires gpiolib and generic hardware
> > > > > > irqs.
> > > > 
> > > > Hm, can't it be merged with gpio_keys? Just add the 'value' to the
> > > > gpio_keys_button structure that would be valid for EV_ABS (or even
> > > > EV_REL) types. Debouncing should filter out jittery events...
> > > 
> > > Sorry, for no answer long time.
> > > I just tried merging both. The problem i noticed is that the PGIO
> > > interrupts are independable and each GPIO will generate an event, which
> > > is wrong. Assume the switch state change from position 2 to 1 it will
> > > actually generate lots of interrupts: e.g. 2, 1, 2, 1.
> > > Depending from the order of such interrupts the last event shows a
> > > possible wrong position.
> > 
> > However at some point the output should stabilize. Does not setting
> > appropriate debouncing interval help here?
> 
> Well, a debounce interval will prevent to get events for position 2, 1, 2, 1 
> (from the example above). You will get only 2 and 1.

No, if the switch settles in position 2 then we will report only 2. I.e.
if you set debounce interval for 200 msecs for all gpios at the end of
this period gpio representing "1" position will not be active so you
will not send any event for it. The gpio representing "2" will still be
active and thus you will send ABS_whatever/2.

> The debounce will only decrease the amount of events for _each_ GPIO 
> interrupt. It will not prevent GPIO interrupts from different pins while moving 
> the switch one position.

It will not prevent interrupts but should prevent unstable events. It
might be beneficial if you posted the code you tried and we'd see why
debouncing does not work for you.

Thanks.

-- 
Dmitry

Re: [PATCH] input: generic driver for slide switches

[Alexander Stein]

On Tuesday 05 April 2011 20:36:52 Dmitry Torokhov wrote:
> Hi Alexander,
> 
> On Sun, Apr 03, 2011 at 10:21:26AM +0200, Alexander Stein wrote:
> > Hello Dimitry,
> > 
> > On Sunday 03 April 2011 06:23:05 Dmitry Torokhov wrote:
> > > On Sat, Apr 02, 2011 at 10:31:53AM +0200, Alexander Stein wrote:
> > > > Hello Dimitry,
> > > > 
> > > > On Wednesday 16 March 2011 07:36:18 Dmitry Torokhov wrote:
> > > > > On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> > > > > > On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > > > > > > This patch adds a generic driver for slide switches connected
> > > > > > > to GPIO pins of a system. It requires gpiolib and generic
> > > > > > > hardware irqs.
> > > > > 
> > > > > Hm, can't it be merged with gpio_keys? Just add the 'value' to the
> > > > > gpio_keys_button structure that would be valid for EV_ABS (or even
> > > > > EV_REL) types. Debouncing should filter out jittery events...
> > > > 
> > > > Sorry, for no answer long time.
> > > > I just tried merging both. The problem i noticed is that the PGIO
> > > > interrupts are independable and each GPIO will generate an event,
> > > > which is wrong. Assume the switch state change from position 2 to 1
> > > > it will actually generate lots of interrupts: e.g. 2, 1, 2, 1.
> > > > Depending from the order of such interrupts the last event shows a
> > > > possible wrong position.
> > > 
> > > However at some point the output should stabilize. Does not setting
> > > appropriate debouncing interval help here?
> > 
> > Well, a debounce interval will prevent to get events for position 2, 1,
> > 2, 1 (from the example above). You will get only 2 and 1.
> 
> No, if the switch settles in position 2 then we will report only 2. I.e.
> if you set debounce interval for 200 msecs for all gpios at the end of
> this period gpio representing "1" position will not be active so you
> will not send any event for it. The gpio representing "2" will still be
> active and thus you will send ABS_whatever/2.

Mh, i think you had a slightly different implementation in mind than me.

> > The debounce will only decrease the amount of events for _each_ GPIO
> > interrupt. It will not prevent GPIO interrupts from different pins while
> > moving the switch one position.
> 
> It will not prevent interrupts but should prevent unstable events. It
> might be beneficial if you posted the code you tried and we'd see why
> debouncing does not work for you.

Here we go:

diff --git a/drivers/input/keyboard/gpio_keys.c 
b/drivers/input/keyboard/gpio_keys.c
index eb30063..544db8f 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c
@@ -324,7 +324,10 @@ static void gpio_keys_report_event(struct 
gpio_button_data *bdata)
 	unsigned int type = button->type ?: EV_KEY;
 	int state = (gpio_get_value_cansleep(button->gpio) ? 1 : 0) ^ button-
>active_low;
 
-	input_event(input, type, button->code, !!state);
+	if ((type == EV_ABS) || (type == EV_REL))
+		input_event(input, type, button->code, button->value);
+	else
+		input_event(input, type, button->code, !!state);
 	input_sync(input);
 }
 
diff --git a/include/linux/gpio_keys.h b/include/linux/gpio_keys.h
index dd1a56f..3cfb26f 100644
--- a/include/linux/gpio_keys.h
+++ b/include/linux/gpio_keys.h
@@ -8,6 +8,7 @@ struct gpio_keys_button {
 	int active_low;
 	char *desc;
 	int type;		/* input event type (EV_KEY, EV_SW) */
+	int value;		/* axis value for EV_ABS and EV_REL */
 	int wakeup;		/* configure the button as a wake-up source */
 	int debounce_interval;	/* debounce ticks interval in msecs */
 	bool can_disable;

Regards,
Alexander

Re: [PATCH] input: generic driver for slide switches

[Dmitry Torokhov]

On Thu, Apr 07, 2011 at 07:45:51PM +0200, Alexander Stein wrote:
> On Tuesday 05 April 2011 20:36:52 Dmitry Torokhov wrote:
> > Hi Alexander,
> > 
> > On Sun, Apr 03, 2011 at 10:21:26AM +0200, Alexander Stein wrote:
> > > Hello Dimitry,
> > > 
> > > On Sunday 03 April 2011 06:23:05 Dmitry Torokhov wrote:
> > > > On Sat, Apr 02, 2011 at 10:31:53AM +0200, Alexander Stein wrote:
> > > > > Hello Dimitry,
> > > > > 
> > > > > On Wednesday 16 March 2011 07:36:18 Dmitry Torokhov wrote:
> > > > > > On Tue, Mar 15, 2011 at 02:13:49PM +0100, Alexander Stein wrote:
> > > > > > > On Friday 25 February 2011, 14:29:18 Alexander Stein wrote:
> > > > > > > > This patch adds a generic driver for slide switches connected
> > > > > > > > to GPIO pins of a system. It requires gpiolib and generic
> > > > > > > > hardware irqs.
> > > > > > 
> > > > > > Hm, can't it be merged with gpio_keys? Just add the 'value' to the
> > > > > > gpio_keys_button structure that would be valid for EV_ABS (or even
> > > > > > EV_REL) types. Debouncing should filter out jittery events...
> > > > > 
> > > > > Sorry, for no answer long time.
> > > > > I just tried merging both. The problem i noticed is that the PGIO
> > > > > interrupts are independable and each GPIO will generate an event,
> > > > > which is wrong. Assume the switch state change from position 2 to 1
> > > > > it will actually generate lots of interrupts: e.g. 2, 1, 2, 1.
> > > > > Depending from the order of such interrupts the last event shows a
> > > > > possible wrong position.
> > > > 
> > > > However at some point the output should stabilize. Does not setting
> > > > appropriate debouncing interval help here?
> > > 
> > > Well, a debounce interval will prevent to get events for position 2, 1,
> > > 2, 1 (from the example above). You will get only 2 and 1.
> > 
> > No, if the switch settles in position 2 then we will report only 2. I.e.
> > if you set debounce interval for 200 msecs for all gpios at the end of
> > this period gpio representing "1" position will not be active so you
> > will not send any event for it. The gpio representing "2" will still be
> > active and thus you will send ABS_whatever/2.
> 
> Mh, i think you had a slightly different implementation in mind than me.
> 
> > > The debounce will only decrease the amount of events for _each_ GPIO
> > > interrupt. It will not prevent GPIO interrupts from different pins while
> > > moving the switch one position.
> > 
> > It will not prevent interrupts but should prevent unstable events. It
> > might be beneficial if you posted the code you tried and we'd see why
> > debouncing does not work for you.
> 
> Here we go:
> 
> diff --git a/drivers/input/keyboard/gpio_keys.c 
> b/drivers/input/keyboard/gpio_keys.c
> index eb30063..544db8f 100644
> --- a/drivers/input/keyboard/gpio_keys.c
> +++ b/drivers/input/keyboard/gpio_keys.c
> @@ -324,7 +324,10 @@ static void gpio_keys_report_event(struct 
> gpio_button_data *bdata)
>  	unsigned int type = button->type ?: EV_KEY;
>  	int state = (gpio_get_value_cansleep(button->gpio) ? 1 : 0) ^ button-
> >active_low;
>  
> -	input_event(input, type, button->code, !!state);
> +	if ((type == EV_ABS) || (type == EV_REL))
> +		input_event(input, type, button->code, button->value);

Ok, so here you unconditionally send the event, regardless of the state
of the gpio. I think that you should only send the ABS event if the GPIO
is in active state. I.e.

	if (type == EV_ABS) {
		if (state)
			input_report_abs(input, button->code, button->value);
	} else {
		input_event(input, type, button->code, !!state);
	}

Thanks.

-- 
Dmitry