[RFC 09/18] input: add input driver for polled GPIO buttons

[RFC 09/18] input: add input driver for polled GPIO buttons

[Gabor Juhos]

The existing gpio-keys driver can be usable only for GPIO lines with
interrupt support. Several devices have buttons connected to a GPIO
line which is not capable to generate interrupts. This patch adds a
new input driver using the generic GPIO layer and the input-polldev
to support such buttons.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: linux-input@vger.kernel.org
---
 drivers/input/misc/Kconfig        |   16 +++
 drivers/input/misc/Makefile       |    1 +
 drivers/input/misc/gpio_buttons.c |  232 +++++++++++++++++++++++++++++++++++++
 include/linux/gpio_buttons.h      |   33 +++++
 4 files changed, 282 insertions(+), 0 deletions(-)
 create mode 100644 drivers/input/misc/gpio_buttons.c
 create mode 100644 include/linux/gpio_buttons.h

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index b99b8cb..3439b79 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -448,4 +448,20 @@ config INPUT_ADXL34X_SPI
 	  To compile this driver as a module, choose M here: the
 	  module will be called adxl34x-spi.
 
+config INPUT_GPIO_BUTTONS
+	tristate "Polled GPIO buttons interface"
+	depends on GENERIC_GPIO
+	select INPUT_POLLDEV
+	help
+	  This driver implements support for buttons connected
+	  to GPIO pins of various CPUs (and some other chips).
+
+	  Say Y here if your device has buttons connected
+	  directly to such GPIO pins.  Your board-specific
+	  setup logic must also provide a platform device,
+	  with configuration data saying which GPIOs are used.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called gpio-buttons.
+
 endif
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 1fe1f6c..3791050 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -42,4 +42,5 @@ obj-$(CONFIG_INPUT_WINBOND_CIR)		+= winbond-cir.o
 obj-$(CONFIG_INPUT_WISTRON_BTNS)	+= wistron_btns.o
 obj-$(CONFIG_INPUT_WM831X_ON)		+= wm831x-on.o
 obj-$(CONFIG_INPUT_YEALINK)		+= yealink.o
+obj-$(CONFIG_INPUT_GPIO_BUTTONS)	+= gpio_buttons.o
 
diff --git a/drivers/input/misc/gpio_buttons.c b/drivers/input/misc/gpio_buttons.c
new file mode 100644
index 0000000..51288a3
--- /dev/null
+++ b/drivers/input/misc/gpio_buttons.c
@@ -0,0 +1,232 @@
+/*
+ *  Driver for buttons on GPIO lines not capable of generating interrupts
+ *
+ *  Copyright (C) 2007-2010 Gabor Juhos <juhosg@openwrt.org>
+ *  Copyright (C) 2010 Nuno Goncalves <nunojpg@gmail.com>
+ *
+ *  This file was based on: /drivers/input/misc/cobalt_btns.c
+ *	Copyright (C) 2007 Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
+ *
+ *  also was based on: /drivers/input/keyboard/gpio_keys.c
+ *	Copyright 2005 Phil Blundell
+ *
+ *  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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/input-polldev.h>
+#include <linux/ioport.h>
+#include <linux/platform_device.h>
+#include <linux/gpio.h>
+#include <linux/gpio_buttons.h>
+
+#define DRV_NAME	"gpio-buttons"
+
+struct gpio_button_data {
+	int last_state;
+	int count;
+	int can_sleep;
+};
+
+struct gpio_buttons_dev {
+	struct input_polled_dev *poll_dev;
+	struct gpio_buttons_platform_data *pdata;
+	struct gpio_button_data *data;
+};
+
+static void gpio_buttons_check_state(struct input_dev *input,
+				      struct gpio_button *button,
+				      struct gpio_button_data *bdata)
+{
+	int state;
+
+	if (bdata->can_sleep)
+		state = !!gpio_get_value_cansleep(button->gpio);
+	else
+		state = !!gpio_get_value(button->gpio);
+
+	if (state != bdata->last_state) {
+		unsigned int type = button->type ?: EV_KEY;
+
+		input_event(input, type, button->code,
+			    !!(state ^ button->active_low));
+		input_sync(input);
+		bdata->count = 0;
+		bdata->last_state = state;
+	}
+}
+
+static void gpio_buttons_poll(struct input_polled_dev *dev)
+{
+	struct gpio_buttons_dev *bdev = dev->private;
+	struct gpio_buttons_platform_data *pdata = bdev->pdata;
+	struct input_dev *input = dev->input;
+	int i;
+
+	for (i = 0; i < bdev->pdata->nbuttons; i++) {
+		struct gpio_button *button = &pdata->buttons[i];
+		struct gpio_button_data *bdata = &bdev->data[i];
+
+		if (bdata->count < button->threshold)
+			bdata->count++;
+		else
+			gpio_buttons_check_state(input, button, bdata);
+
+	}
+}
+
+static int __devinit gpio_buttons_probe(struct platform_device *pdev)
+{
+	struct gpio_buttons_platform_data *pdata = pdev->dev.platform_data;
+	struct device *dev = &pdev->dev;
+	struct gpio_buttons_dev *bdev;
+	struct input_polled_dev *poll_dev;
+	struct input_dev *input;
+	int error;
+	int i;
+
+	if (!pdata)
+		return -ENXIO;
+
+	bdev = kzalloc(sizeof(struct gpio_buttons_dev) +
+		       pdata->nbuttons * sizeof(struct gpio_button_data),
+		       GFP_KERNEL);
+	if (!bdev) {
+		dev_err(dev, "no memory for private data\n");
+		return -ENOMEM;
+	}
+
+	bdev->data = (struct gpio_button_data *) &bdev[1];
+
+	poll_dev = input_allocate_polled_device();
+	if (!poll_dev) {
+		dev_err(dev, "no memory for polled device\n");
+		error = -ENOMEM;
+		goto err_free_bdev;
+	}
+
+	poll_dev->private = bdev;
+	poll_dev->poll = gpio_buttons_poll;
+	poll_dev->poll_interval = pdata->poll_interval;
+
+	input = poll_dev->input;
+
+	input->evbit[0] = BIT(EV_KEY);
+	input->name = pdev->name;
+	input->phys = "gpio-buttons/input0";
+	input->dev.parent = &pdev->dev;
+
+	input->id.bustype = BUS_HOST;
+	input->id.vendor = 0x0001;
+	input->id.product = 0x0001;
+	input->id.version = 0x0100;
+
+	for (i = 0; i < pdata->nbuttons; i++) {
+		struct gpio_button *button = &pdata->buttons[i];
+		unsigned int gpio = button->gpio;
+		unsigned int type = button->type ?: EV_KEY;
+
+		error = gpio_request(gpio,
+				     button->desc ? button->desc : DRV_NAME);
+		if (error) {
+			dev_err(dev, "unable to claim gpio %u, err=%d\n",
+				gpio, error);
+			goto err_free_gpio;
+		}
+
+		error = gpio_direction_input(gpio);
+		if (error) {
+			dev_err(dev,
+				"unable to set direction on gpio %u, err=%d\n",
+				gpio, error);
+			goto err_free_gpio;
+		}
+
+		bdev->data[i].can_sleep = gpio_cansleep(gpio);
+		bdev->data[i].last_state = -1;
+
+		input_set_capability(input, type, button->code);
+	}
+
+	bdev->poll_dev = poll_dev;
+	bdev->pdata = pdata;
+	platform_set_drvdata(pdev, bdev);
+
+	error = input_register_polled_device(poll_dev);
+	if (error) {
+		dev_err(dev, "unable to register polled device, err=%d\n",
+			error);
+		goto err_free_gpio;
+	}
+
+	/* report initial state of the buttons */
+	for (i = 0; i < pdata->nbuttons; i++)
+		gpio_buttons_check_state(input, &pdata->buttons[i],
+					 &bdev->data[i]);
+
+	return 0;
+
+err_free_gpio:
+	for (i = i - 1; i >= 0; i--)
+		gpio_free(pdata->buttons[i].gpio);
+
+	input_free_polled_device(poll_dev);
+
+err_free_bdev:
+	kfree(bdev);
+
+	platform_set_drvdata(pdev, NULL);
+	return error;
+}
+
+static int __devexit gpio_buttons_remove(struct platform_device *pdev)
+{
+	struct gpio_buttons_dev *bdev = platform_get_drvdata(pdev);
+	struct gpio_buttons_platform_data *pdata = bdev->pdata;
+	int i;
+
+	input_unregister_polled_device(bdev->poll_dev);
+
+	for (i = 0; i < pdata->nbuttons; i++)
+		gpio_free(pdata->buttons[i].gpio);
+
+	input_free_polled_device(bdev->poll_dev);
+
+	kfree(bdev);
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static struct platform_driver gpio_buttons_driver = {
+	.probe	= gpio_buttons_probe,
+	.remove	= __devexit_p(gpio_buttons_remove),
+	.driver	= {
+		.name	= DRV_NAME,
+		.owner	= THIS_MODULE,
+	},
+};
+
+static int __init gpio_buttons_init(void)
+{
+	return platform_driver_register(&gpio_buttons_driver);
+}
+
+static void __exit gpio_buttons_exit(void)
+{
+	platform_driver_unregister(&gpio_buttons_driver);
+}
+
+module_init(gpio_buttons_init);
+module_exit(gpio_buttons_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_DESCRIPTION("Polled GPIO Buttons driver");
diff --git a/include/linux/gpio_buttons.h b/include/linux/gpio_buttons.h
new file mode 100644
index 0000000..f85b993
--- /dev/null
+++ b/include/linux/gpio_buttons.h
@@ -0,0 +1,33 @@
+/*
+ *  Definitions for the GPIO buttons interface driver
+ *
+ *  Copyright (C) 2007-2010 Gabor Juhos <juhosg@openwrt.org>
+ *
+ *  This file was based on: /include/linux/gpio_keys.h
+ *	The original gpio_keys.h seems not to have a license.
+ *
+ *  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 _GPIO_BUTTONS_H_
+#define _GPIO_BUTTONS_H_
+
+struct gpio_button {
+	int	gpio;		/* GPIO line number */
+	int	active_low;
+	char	*desc;		/* button description */
+	int	type;		/* input event type (EV_KEY, EV_SW) */
+	int	code;		/* input event code (KEY_*, SW_*) */
+	int	threshold;	/* count threshold */
+};
+
+struct gpio_buttons_platform_data {
+	struct gpio_button *buttons;
+	int	nbuttons;		/* number of buttons */
+	int	poll_interval;		/* polling interval */
+};
+
+#endif /* _GPIO_BUTTONS_H_ */
-- 
1.7.2.1

[RFC 09/18] input: add input driver for polled GPIO buttons

[Gabor Juhos]

The existing gpio-keys driver can be usable only for GPIO lines with
interrupt support. Several devices have buttons connected to a GPIO
line which is not capable to generate interrupts. This patch adds a
new input driver using the generic GPIO layer and the input-polldev
to support such buttons.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: linux-input@vger.kernel.org
---
Sorry for sending this twice, i forgot to add some CCs in the first round.

 drivers/input/misc/Kconfig        |   16 +++
 drivers/input/misc/Makefile       |    1 +
 drivers/input/misc/gpio_buttons.c |  232 +++++++++++++++++++++++++++++++++++++
 include/linux/gpio_buttons.h      |   33 +++++
 4 files changed, 282 insertions(+), 0 deletions(-)
 create mode 100644 drivers/input/misc/gpio_buttons.c
 create mode 100644 include/linux/gpio_buttons.h

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index b99b8cb..3439b79 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -448,4 +448,20 @@ config INPUT_ADXL34X_SPI
 	  To compile this driver as a module, choose M here: the
 	  module will be called adxl34x-spi.
 
+config INPUT_GPIO_BUTTONS
+	tristate "Polled GPIO buttons interface"
+	depends on GENERIC_GPIO
+	select INPUT_POLLDEV
+	help
+	  This driver implements support for buttons connected
+	  to GPIO pins of various CPUs (and some other chips).
+
+	  Say Y here if your device has buttons connected
+	  directly to such GPIO pins.  Your board-specific
+	  setup logic must also provide a platform device,
+	  with configuration data saying which GPIOs are used.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called gpio-buttons.
+
 endif
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 1fe1f6c..3791050 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -42,4 +42,5 @@ obj-$(CONFIG_INPUT_WINBOND_CIR)		+= winbond-cir.o
 obj-$(CONFIG_INPUT_WISTRON_BTNS)	+= wistron_btns.o
 obj-$(CONFIG_INPUT_WM831X_ON)		+= wm831x-on.o
 obj-$(CONFIG_INPUT_YEALINK)		+= yealink.o
+obj-$(CONFIG_INPUT_GPIO_BUTTONS)	+= gpio_buttons.o
 
diff --git a/drivers/input/misc/gpio_buttons.c b/drivers/input/misc/gpio_buttons.c
new file mode 100644
index 0000000..51288a3
--- /dev/null
+++ b/drivers/input/misc/gpio_buttons.c
@@ -0,0 +1,232 @@
+/*
+ *  Driver for buttons on GPIO lines not capable of generating interrupts
+ *
+ *  Copyright (C) 2007-2010 Gabor Juhos <juhosg@openwrt.org>
+ *  Copyright (C) 2010 Nuno Goncalves <nunojpg@gmail.com>
+ *
+ *  This file was based on: /drivers/input/misc/cobalt_btns.c
+ *	Copyright (C) 2007 Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
+ *
+ *  also was based on: /drivers/input/keyboard/gpio_keys.c
+ *	Copyright 2005 Phil Blundell
+ *
+ *  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/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/input-polldev.h>
+#include <linux/ioport.h>
+#include <linux/platform_device.h>
+#include <linux/gpio.h>
+#include <linux/gpio_buttons.h>
+
+#define DRV_NAME	"gpio-buttons"
+
+struct gpio_button_data {
+	int last_state;
+	int count;
+	int can_sleep;
+};
+
+struct gpio_buttons_dev {
+	struct input_polled_dev *poll_dev;
+	struct gpio_buttons_platform_data *pdata;
+	struct gpio_button_data *data;
+};
+
+static void gpio_buttons_check_state(struct input_dev *input,
+				      struct gpio_button *button,
+				      struct gpio_button_data *bdata)
+{
+	int state;
+
+	if (bdata->can_sleep)
+		state = !!gpio_get_value_cansleep(button->gpio);
+	else
+		state = !!gpio_get_value(button->gpio);
+
+	if (state != bdata->last_state) {
+		unsigned int type = button->type ?: EV_KEY;
+
+		input_event(input, type, button->code,
+			    !!(state ^ button->active_low));
+		input_sync(input);
+		bdata->count = 0;
+		bdata->last_state = state;
+	}
+}
+
+static void gpio_buttons_poll(struct input_polled_dev *dev)
+{
+	struct gpio_buttons_dev *bdev = dev->private;
+	struct gpio_buttons_platform_data *pdata = bdev->pdata;
+	struct input_dev *input = dev->input;
+	int i;
+
+	for (i = 0; i < bdev->pdata->nbuttons; i++) {
+		struct gpio_button *button = &pdata->buttons[i];
+		struct gpio_button_data *bdata = &bdev->data[i];
+
+		if (bdata->count < button->threshold)
+			bdata->count++;
+		else
+			gpio_buttons_check_state(input, button, bdata);
+
+	}
+}
+
+static int __devinit gpio_buttons_probe(struct platform_device *pdev)
+{
+	struct gpio_buttons_platform_data *pdata = pdev->dev.platform_data;
+	struct device *dev = &pdev->dev;
+	struct gpio_buttons_dev *bdev;
+	struct input_polled_dev *poll_dev;
+	struct input_dev *input;
+	int error;
+	int i;
+
+	if (!pdata)
+		return -ENXIO;
+
+	bdev = kzalloc(sizeof(struct gpio_buttons_dev) +
+		       pdata->nbuttons * sizeof(struct gpio_button_data),
+		       GFP_KERNEL);
+	if (!bdev) {
+		dev_err(dev, "no memory for private data\n");
+		return -ENOMEM;
+	}
+
+	bdev->data = (struct gpio_button_data *) &bdev[1];
+
+	poll_dev = input_allocate_polled_device();
+	if (!poll_dev) {
+		dev_err(dev, "no memory for polled device\n");
+		error = -ENOMEM;
+		goto err_free_bdev;
+	}
+
+	poll_dev->private = bdev;
+	poll_dev->poll = gpio_buttons_poll;
+	poll_dev->poll_interval = pdata->poll_interval;
+
+	input = poll_dev->input;
+
+	input->evbit[0] = BIT(EV_KEY);
+	input->name = pdev->name;
+	input->phys = "gpio-buttons/input0";
+	input->dev.parent = &pdev->dev;
+
+	input->id.bustype = BUS_HOST;
+	input->id.vendor = 0x0001;
+	input->id.product = 0x0001;
+	input->id.version = 0x0100;
+
+	for (i = 0; i < pdata->nbuttons; i++) {
+		struct gpio_button *button = &pdata->buttons[i];
+		unsigned int gpio = button->gpio;
+		unsigned int type = button->type ?: EV_KEY;
+
+		error = gpio_request(gpio,
+				     button->desc ? button->desc : DRV_NAME);
+		if (error) {
+			dev_err(dev, "unable to claim gpio %u, err=%d\n",
+				gpio, error);
+			goto err_free_gpio;
+		}
+
+		error = gpio_direction_input(gpio);
+		if (error) {
+			dev_err(dev,
+				"unable to set direction on gpio %u, err=%d\n",
+				gpio, error);
+			goto err_free_gpio;
+		}
+
+		bdev->data[i].can_sleep = gpio_cansleep(gpio);
+		bdev->data[i].last_state = -1;
+
+		input_set_capability(input, type, button->code);
+	}
+
+	bdev->poll_dev = poll_dev;
+	bdev->pdata = pdata;
+	platform_set_drvdata(pdev, bdev);
+
+	error = input_register_polled_device(poll_dev);
+	if (error) {
+		dev_err(dev, "unable to register polled device, err=%d\n",
+			error);
+		goto err_free_gpio;
+	}
+
+	/* report initial state of the buttons */
+	for (i = 0; i < pdata->nbuttons; i++)
+		gpio_buttons_check_state(input, &pdata->buttons[i],
+					 &bdev->data[i]);
+
+	return 0;
+
+err_free_gpio:
+	for (i = i - 1; i >= 0; i--)
+		gpio_free(pdata->buttons[i].gpio);
+
+	input_free_polled_device(poll_dev);
+
+err_free_bdev:
+	kfree(bdev);
+
+	platform_set_drvdata(pdev, NULL);
+	return error;
+}
+
+static int __devexit gpio_buttons_remove(struct platform_device *pdev)
+{
+	struct gpio_buttons_dev *bdev = platform_get_drvdata(pdev);
+	struct gpio_buttons_platform_data *pdata = bdev->pdata;
+	int i;
+
+	input_unregister_polled_device(bdev->poll_dev);
+
+	for (i = 0; i < pdata->nbuttons; i++)
+		gpio_free(pdata->buttons[i].gpio);
+
+	input_free_polled_device(bdev->poll_dev);
+
+	kfree(bdev);
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static struct platform_driver gpio_buttons_driver = {
+	.probe	= gpio_buttons_probe,
+	.remove	= __devexit_p(gpio_buttons_remove),
+	.driver	= {
+		.name	= DRV_NAME,
+		.owner	= THIS_MODULE,
+	},
+};
+
+static int __init gpio_buttons_init(void)
+{
+	return platform_driver_register(&gpio_buttons_driver);
+}
+
+static void __exit gpio_buttons_exit(void)
+{
+	platform_driver_unregister(&gpio_buttons_driver);
+}
+
+module_init(gpio_buttons_init);
+module_exit(gpio_buttons_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_DESCRIPTION("Polled GPIO Buttons driver");
diff --git a/include/linux/gpio_buttons.h b/include/linux/gpio_buttons.h
new file mode 100644
index 0000000..f85b993
--- /dev/null
+++ b/include/linux/gpio_buttons.h
@@ -0,0 +1,33 @@
+/*
+ *  Definitions for the GPIO buttons interface driver
+ *
+ *  Copyright (C) 2007-2010 Gabor Juhos <juhosg@openwrt.org>
+ *
+ *  This file was based on: /include/linux/gpio_keys.h
+ *	The original gpio_keys.h seems not to have a license.
+ *
+ *  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 _GPIO_BUTTONS_H_
+#define _GPIO_BUTTONS_H_
+
+struct gpio_button {
+	int	gpio;		/* GPIO line number */
+	int	active_low;
+	char	*desc;		/* button description */
+	int	type;		/* input event type (EV_KEY, EV_SW) */
+	int	code;		/* input event code (KEY_*, SW_*) */
+	int	threshold;	/* count threshold */
+};
+
+struct gpio_buttons_platform_data {
+	struct gpio_button *buttons;
+	int	nbuttons;		/* number of buttons */
+	int	poll_interval;		/* polling interval */
+};
+
+#endif /* _GPIO_BUTTONS_H_ */
-- 
1.7.2.1

Re: [RFC 09/18] input: add input driver for polled GPIO buttons

[Mike Frysinger]

[-- Attachment #1: Type: Text/Plain, Size: 832 bytes --]

On Friday, November 12, 2010 14:50:36 Gabor Juhos wrote:
> The existing gpio-keys driver can be usable only for GPIO lines with
> interrupt support. Several devices have buttons connected to a GPIO
> line which is not capable to generate interrupts. This patch adds a
> new input driver using the generic GPIO layer and the input-polldev
> to support such buttons.

i havent looked at the two drivers to compare, but my gut reaction is "do we 
really need two drivers" ?  cant the existing one be extended to support both 
types ?  conceivably, you could have a device with both sources and a sep 
driver would mean user space needs to watch two different devices.  and it 
implicitly means userspace needs to be aware of interrupt vs polled 
limitations of the hardware instead of it simply caring about GPIOs.
-mike

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [RFC 09/18] input: add input driver for polled GPIO buttons

[Dmitry Torokhov]

On Fri, Nov 12, 2010 at 08:14:59PM -0500, Mike Frysinger wrote:
> On Friday, November 12, 2010 14:50:36 Gabor Juhos wrote:
> > The existing gpio-keys driver can be usable only for GPIO lines with
> > interrupt support. Several devices have buttons connected to a GPIO
> > line which is not capable to generate interrupts. This patch adds a
> > new input driver using the generic GPIO layer and the input-polldev
> > to support such buttons.
> 
> i havent looked at the two drivers to compare, but my gut reaction is "do we 
> really need two drivers" ?  cant the existing one be extended to support both 
> types ? 

I actually like it being separate. All previous attempts to combine
interrupt-driven and polled devices complicated the drivers and had
driver picking in the guts of the polled device implementation.

> conceivably, you could have a device with both sources and a sep 
> driver would mean user space needs to watch two different devices.

This is unlikely, however userspace usually watches a few devices
anyway, nothing new here.

>  and it 
> implicitly means userspace needs to be aware of interrupt vs polled 
> limitations of the hardware instead of it simply caring about GPIOs.

No, as long as userspace simply listens to all devices whose
capabilities they are interested in they will be fine.

-- 
Dmitry