[PATCH v2 0/2] AM335x-ICE: Add support for rotary switch

[PATCH v2 0/2] AM335x-ICE: Add support for rotary switch

[Vignesh R]

This series adds support for rotary-switch on AM335x-ICE that is
connected to TI PCA9536 I2C GPIO expander.
First patch adds new generic driver to read status of group of GPIO
lines and report the value as an input event. The second patch adds DT
entries for the same.

v1: https://lkml.org/lkml/2016/8/12/7

Vignesh R (2):
  input: misc: Add generic input driver to read encoded GPIO lines
  ARM: dts: am335x-icev2: Add nodes for gpio-decoder

 .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
 arch/arm/boot/dts/am335x-icev2.dts                 |   9 ++
 drivers/input/misc/Kconfig                         |  12 ++
 drivers/input/misc/Makefile                        |   1 +
 drivers/input/misc/gpio_decoder.c                  | 130 +++++++++++++++++++++
 5 files changed, 175 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/gpio-decoder.txt
 create mode 100644 drivers/input/misc/gpio_decoder.c

-- 
2.9.2

[PATCH v2 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Vignesh R]

Add a driver to read group of GPIO lines and provide its status as a
numerical value as input event to the system. This will help in
intefacing devices, that can be connected over GPIOs, that provide input
to the system by driving GPIO lines connected to them like a rotary dial
or a switch.

For example, a rotary switch can be connected to four GPIO lines. The
status of the GPIO lines reflect the actual position of the rotary
switch dial. For example, if dial points to 9, then the four GPIO lines
connected to the switch will read HLLH(0b'1001 = 9). This value
can be reported as an ABS_* event to the input subsystem.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
---

v2: Use decoder,max-value instead of gpio-decoder,max-value.

 .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
 drivers/input/misc/Kconfig                         |  12 ++
 drivers/input/misc/Makefile                        |   1 +
 drivers/input/misc/gpio_decoder.c                  | 130 +++++++++++++++++++++
 4 files changed, 166 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/gpio-decoder.txt
 create mode 100644 drivers/input/misc/gpio_decoder.c

diff --git a/Documentation/devicetree/bindings/input/gpio-decoder.txt b/Documentation/devicetree/bindings/input/gpio-decoder.txt
new file mode 100644
index 000000000000..f27f083a9075
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/gpio-decoder.txt
@@ -0,0 +1,23 @@
+* GPIO Decoder DT bindings
+
+Required Properties:
+- compatible: should be "gpio-decoder"
+- gpios: a spec of gpios (atleast two) to be decoded to a number with
+  first entry representing the MSB.
+
+Optional Properties:
+- decoder,max-value: Maximum possible value that can be reported by
+  the gpios.
+- linux,axis: the input subsystem axis to map to (ABS_X/ABS_Y).
+  Defaults to 0 (ABS_X).
+
+Example:
+	gpio-decoder0 {
+		compatible = "gpio-decoder";
+		gpios = <&pca9536 3 GPIO_ACTIVE_HIGH>,
+			<&pca9536 2 GPIO_ACTIVE_HIGH>,
+			<&pca9536 1 GPIO_ACTIVE_HIGH>,
+			<&pca9536 0 GPIO_ACTIVE_HIGH>;
+		linux,axis = <0>; /* ABS_X */
+		decoder,max-value = <9>;
+	};
diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index efb0ca871327..c44513cac3b7 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -292,6 +292,18 @@ config INPUT_GPIO_TILT_POLLED
 	  To compile this driver as a module, choose M here: the
 	  module will be called gpio_tilt_polled.
 
+config INPUT_GPIO_DECODER
+	tristate "Polled GPIO Decoder Input driver"
+	depends on GPIOLIB && OF
+	select INPUT_POLLDEV
+	help
+	 Say Y here if you want driver to read status of multiple GPIO
+	 lines and report the encoded value as an absolute integer to
+	 input subsystem.
+
+	 To compile this driver as a module, choose M here: the module
+	 will will be called gpio_decoder.
+
 config INPUT_IXP4XX_BEEPER
 	tristate "IXP4XX Beeper support"
 	depends on ARCH_IXP4XX
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 6a1e5e20fc1c..0b6d025f0487 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_INPUT_DRV2667_HAPTICS)	+= drv2667.o
 obj-$(CONFIG_INPUT_GP2A)		+= gp2ap002a00f.o
 obj-$(CONFIG_INPUT_GPIO_BEEPER)		+= gpio-beeper.o
 obj-$(CONFIG_INPUT_GPIO_TILT_POLLED)	+= gpio_tilt_polled.o
+obj-$(CONFIG_INPUT_GPIO_DECODER)	+= gpio_decoder.o
 obj-$(CONFIG_INPUT_HISI_POWERKEY)	+= hisi_powerkey.o
 obj-$(CONFIG_HP_SDC_RTC)		+= hp_sdc_rtc.o
 obj-$(CONFIG_INPUT_IMS_PCU)		+= ims-pcu.o
diff --git a/drivers/input/misc/gpio_decoder.c b/drivers/input/misc/gpio_decoder.c
new file mode 100644
index 000000000000..eec0fda6f562
--- /dev/null
+++ b/drivers/input/misc/gpio_decoder.c
@@ -0,0 +1,130 @@
+/*
+ * gpio-decoder.c
+ *
+ * A generic driver to reads multiple gpio lines and translate the
+ * encoded numeric value into an input event.
+ *
+ * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/input.h>
+#include <linux/input-polldev.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct gpio_decoder {
+	struct input_polled_dev *poll_dev;
+	struct gpio_descs *input_gpios;
+	struct device *dev;
+	u32 axis;
+	u32 last_stable;
+};
+
+static unsigned int gpio_decoder_get_gpios_state(struct gpio_decoder
+						 *decoder)
+{
+	struct gpio_descs *gpios = decoder->input_gpios;
+	unsigned int ret = 0;
+	int i, val;
+
+	for (i = 0; i < gpios->ndescs; i++) {
+		val = gpiod_get_value_cansleep(gpios->desc[i]);
+		ret = ret << 1 | val;
+	}
+
+	return ret;
+}
+
+static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev)
+{
+	struct gpio_decoder *decoder = poll_dev->private;
+	unsigned int state = gpio_decoder_get_gpios_state(decoder);
+
+	if (state != decoder->last_stable) {
+		input_report_abs(poll_dev->input, decoder->axis, state);
+		input_sync(poll_dev->input);
+		decoder->last_stable = state;
+	}
+}
+
+static int gpio_decoder_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct gpio_decoder *decoder;
+	struct input_polled_dev *poll_dev;
+	u32  max;
+	int err;
+
+	decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);
+	if (!decoder)
+		return -ENOMEM;
+
+	device_property_read_u32(dev, "linux,axis", &decoder->axis);
+	decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
+	if (IS_ERR(decoder->input_gpios)) {
+		dev_err(dev, "unable to acquire input gpios\n");
+		return PTR_ERR(decoder->input_gpios);
+	}
+	if (decoder->input_gpios->ndescs < 2) {
+		dev_err(dev, "not enough gpios found\n");
+		return -EINVAL;
+	}
+
+	if (device_property_read_u32(dev, "decoder,max-value", &max))
+		max = BIT(decoder->input_gpios->ndescs);
+
+	decoder->dev = dev;
+	poll_dev = devm_input_allocate_polled_device(decoder->dev);
+	if (!poll_dev)
+		return -ENOMEM;
+
+	poll_dev->private = decoder;
+	poll_dev->poll = gpio_decoder_poll_gpios;
+	decoder->poll_dev = poll_dev;
+
+	poll_dev->input->name = pdev->name;
+	poll_dev->input->id.bustype = BUS_HOST;
+	poll_dev->input->dev.parent = dev;
+	input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 1);
+
+	err = input_register_polled_device(poll_dev);
+	if (err) {
+		dev_err(dev, "failed to register polled  device\n");
+		return err;
+	}
+	platform_set_drvdata(pdev, decoder);
+
+	return 0;
+}
+
+static const struct of_device_id gpio_decoder_of_match[] = {
+	{ .compatible = "gpio-decoder", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
+
+static struct platform_driver gpio_decoder_driver = {
+	.probe		= gpio_decoder_probe,
+	.driver		= {
+		.name	= "gpio-decoder",
+		.of_match_table = of_match_ptr(gpio_decoder_of_match),
+	}
+};
+module_platform_driver(gpio_decoder_driver);
+
+MODULE_DESCRIPTION("GPIO decoder input driver");
+MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
+MODULE_LICENSE("GPL v2");
-- 
2.9.2

[PATCH v2 2/2] ARM: dts: am335x-icev2: Add nodes for gpio-decoder

[Vignesh R]

AM335x ICE board has a rotary-switch connected to PCA9536 I2C GPIO
expander. The position of the rotary-switch is reflected by status of
GPIO lines. Add gpio-decoder node to read these GPIO line status via
gpio-decoder driver and report it as an input event to the system.

Signed-off-by: Vignesh R <vigneshr@ti.com>
---

v2: Update DT node name.

 arch/arm/boot/dts/am335x-icev2.dts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm/boot/dts/am335x-icev2.dts b/arch/arm/boot/dts/am335x-icev2.dts
index bc0190e4f10f..d3c53e5910c4 100644
--- a/arch/arm/boot/dts/am335x-icev2.dts
+++ b/arch/arm/boot/dts/am335x-icev2.dts
@@ -139,6 +139,15 @@
 			default-state = "off";
 		};
 	};
+	gpio-decoder {
+		compatible = "gpio-decoder";
+		gpios = <&pca9536 3 GPIO_ACTIVE_HIGH>,
+			<&pca9536 2 GPIO_ACTIVE_HIGH>,
+			<&pca9536 1 GPIO_ACTIVE_HIGH>,
+			<&pca9536 0 GPIO_ACTIVE_HIGH>;
+		linux,axis = <0>; /* ABS_X */
+		decoder,max-value = <9>;
+	};
 };
 
 &am33xx_pinmux {
-- 
2.9.2

Re: [PATCH v2 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Andrew F. Davis]

On 08/23/2016 01:16 AM, Vignesh R wrote:
> Add a driver to read group of GPIO lines and provide its status as a
> numerical value as input event to the system. This will help in
> intefacing devices, that can be connected over GPIOs, that provide input
> to the system by driving GPIO lines connected to them like a rotary dial
> or a switch.
> 
> For example, a rotary switch can be connected to four GPIO lines. The
> status of the GPIO lines reflect the actual position of the rotary
> switch dial. For example, if dial points to 9, then the four GPIO lines
> connected to the switch will read HLLH(0b'1001 = 9). This value
> can be reported as an ABS_* event to the input subsystem.
> 
> Signed-off-by: Vignesh R <vigneshr@ti.com>
> Acked-by: Rob Herring <robh@kernel.org>
> ---
> 
> v2: Use decoder,max-value instead of gpio-decoder,max-value.
> 
>  .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
>  drivers/input/misc/Kconfig                         |  12 ++
>  drivers/input/misc/Makefile                        |   1 +
>  drivers/input/misc/gpio_decoder.c                  | 130 +++++++++++++++++++++
>  4 files changed, 166 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/input/gpio-decoder.txt
>  create mode 100644 drivers/input/misc/gpio_decoder.c
> 
> diff --git a/Documentation/devicetree/bindings/input/gpio-decoder.txt b/Documentation/devicetree/bindings/input/gpio-decoder.txt
> new file mode 100644
> index 000000000000..f27f083a9075
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/gpio-decoder.txt
> @@ -0,0 +1,23 @@
> +* GPIO Decoder DT bindings
> +
> +Required Properties:
> +- compatible: should be "gpio-decoder"
> +- gpios: a spec of gpios (atleast two) to be decoded to a number with

                              ^^ two words

> +  first entry representing the MSB.
> +
> +Optional Properties:
> +- decoder,max-value: Maximum possible value that can be reported by
> +  the gpios.
> +- linux,axis: the input subsystem axis to map to (ABS_X/ABS_Y).
> +  Defaults to 0 (ABS_X).
> +
> +Example:
> +	gpio-decoder0 {
> +		compatible = "gpio-decoder";
> +		gpios = <&pca9536 3 GPIO_ACTIVE_HIGH>,
> +			<&pca9536 2 GPIO_ACTIVE_HIGH>,
> +			<&pca9536 1 GPIO_ACTIVE_HIGH>,
> +			<&pca9536 0 GPIO_ACTIVE_HIGH>;
> +		linux,axis = <0>; /* ABS_X */
> +		decoder,max-value = <9>;
> +	};
> diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
> index efb0ca871327..c44513cac3b7 100644
> --- a/drivers/input/misc/Kconfig
> +++ b/drivers/input/misc/Kconfig
> @@ -292,6 +292,18 @@ config INPUT_GPIO_TILT_POLLED
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called gpio_tilt_polled.
>  
> +config INPUT_GPIO_DECODER
> +	tristate "Polled GPIO Decoder Input driver"
> +	depends on GPIOLIB && OF
> +	select INPUT_POLLDEV
> +	help
> +	 Say Y here if you want driver to read status of multiple GPIO
> +	 lines and report the encoded value as an absolute integer to
> +	 input subsystem.
> +
> +	 To compile this driver as a module, choose M here: the module
> +	 will will be called gpio_decoder.
> +
>  config INPUT_IXP4XX_BEEPER
>  	tristate "IXP4XX Beeper support"
>  	depends on ARCH_IXP4XX
> diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
> index 6a1e5e20fc1c..0b6d025f0487 100644
> --- a/drivers/input/misc/Makefile
> +++ b/drivers/input/misc/Makefile
> @@ -35,6 +35,7 @@ obj-$(CONFIG_INPUT_DRV2667_HAPTICS)	+= drv2667.o
>  obj-$(CONFIG_INPUT_GP2A)		+= gp2ap002a00f.o
>  obj-$(CONFIG_INPUT_GPIO_BEEPER)		+= gpio-beeper.o
>  obj-$(CONFIG_INPUT_GPIO_TILT_POLLED)	+= gpio_tilt_polled.o
> +obj-$(CONFIG_INPUT_GPIO_DECODER)	+= gpio_decoder.o
>  obj-$(CONFIG_INPUT_HISI_POWERKEY)	+= hisi_powerkey.o
>  obj-$(CONFIG_HP_SDC_RTC)		+= hp_sdc_rtc.o
>  obj-$(CONFIG_INPUT_IMS_PCU)		+= ims-pcu.o
> diff --git a/drivers/input/misc/gpio_decoder.c b/drivers/input/misc/gpio_decoder.c
> new file mode 100644
> index 000000000000..eec0fda6f562
> --- /dev/null
> +++ b/drivers/input/misc/gpio_decoder.c
> @@ -0,0 +1,130 @@
> +/*
> + * gpio-decoder.c
> + *

^ the name of the file often changes without this being updated, it
really doesn't add anything anyway, would recommend dropping it.

> + * A generic driver to reads multiple gpio lines and translate the
> + * encoded numeric value into an input event.
> + *
> + * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation version 2.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/input.h>
> +#include <linux/input-polldev.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +struct gpio_decoder {
> +	struct input_polled_dev *poll_dev;
> +	struct gpio_descs *input_gpios;
> +	struct device *dev;
> +	u32 axis;
> +	u32 last_stable;
> +};
> +
> +static unsigned int gpio_decoder_get_gpios_state(struct gpio_decoder
> +						 *decoder)
> +{
> +	struct gpio_descs *gpios = decoder->input_gpios;
> +	unsigned int ret = 0;
> +	int i, val;
> +
> +	for (i = 0; i < gpios->ndescs; i++) {
> +		val = gpiod_get_value_cansleep(gpios->desc[i]);
> +		ret = ret << 1 | val;

Just to be safe, could you mask val with 0x1 here.

> +	}
> +
> +	return ret;
> +}
> +
> +static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev)
> +{
> +	struct gpio_decoder *decoder = poll_dev->private;
> +	unsigned int state = gpio_decoder_get_gpios_state(decoder);
> +
> +	if (state != decoder->last_stable) {
> +		input_report_abs(poll_dev->input, decoder->axis, state);
> +		input_sync(poll_dev->input);
> +		decoder->last_stable = state;
> +	}
> +}
> +
> +static int gpio_decoder_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct gpio_decoder *decoder;
> +	struct input_polled_dev *poll_dev;
> +	u32  max;
> +	int err;
> +
> +	decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);
> +	if (!decoder)
> +		return -ENOMEM;
> +
> +	device_property_read_u32(dev, "linux,axis", &decoder->axis);
> +	decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
> +	if (IS_ERR(decoder->input_gpios)) {
> +		dev_err(dev, "unable to acquire input gpios\n");
> +		return PTR_ERR(decoder->input_gpios);
> +	}
> +	if (decoder->input_gpios->ndescs < 2) {
> +		dev_err(dev, "not enough gpios found\n");
> +		return -EINVAL;
> +	}
> +
> +	if (device_property_read_u32(dev, "decoder,max-value", &max))
> +		max = BIT(decoder->input_gpios->ndescs);
> +
> +	decoder->dev = dev;
> +	poll_dev = devm_input_allocate_polled_device(decoder->dev);
> +	if (!poll_dev)
> +		return -ENOMEM;
> +
> +	poll_dev->private = decoder;
> +	poll_dev->poll = gpio_decoder_poll_gpios;
> +	decoder->poll_dev = poll_dev;
> +
> +	poll_dev->input->name = pdev->name;
> +	poll_dev->input->id.bustype = BUS_HOST;
> +	poll_dev->input->dev.parent = dev;
> +	input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 1);
> +
> +	err = input_register_polled_device(poll_dev);
> +	if (err) {
> +		dev_err(dev, "failed to register polled  device\n");
> +		return err;
> +	}
> +	platform_set_drvdata(pdev, decoder);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id gpio_decoder_of_match[] = {
> +	{ .compatible = "gpio-decoder", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
> +
> +static struct platform_driver gpio_decoder_driver = {
> +	.probe		= gpio_decoder_probe,
> +	.driver		= {
> +		.name	= "gpio-decoder",
> +		.of_match_table = of_match_ptr(gpio_decoder_of_match),

When the struct 'gpio_decoder_of_match' is always defined (not
conditional on OF support), then 'of_match_ptr' does nothing and can be
dropped here.

> +	}
> +};
> +module_platform_driver(gpio_decoder_driver);
> +
> +MODULE_DESCRIPTION("GPIO decoder input driver");
> +MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
> +MODULE_LICENSE("GPL v2");

Re: [PATCH v2 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Dmitry Torokhov]

On Tue, Aug 23, 2016 at 10:27:59AM -0500, Andrew F. Davis wrote:
> On 08/23/2016 01:16 AM, Vignesh R wrote:
> > Add a driver to read group of GPIO lines and provide its status as a
> > numerical value as input event to the system. This will help in
> > intefacing devices, that can be connected over GPIOs, that provide input
> > to the system by driving GPIO lines connected to them like a rotary dial
> > or a switch.
> > 
> > For example, a rotary switch can be connected to four GPIO lines. The
> > status of the GPIO lines reflect the actual position of the rotary
> > switch dial. For example, if dial points to 9, then the four GPIO lines
> > connected to the switch will read HLLH(0b'1001 = 9). This value
> > can be reported as an ABS_* event to the input subsystem.
> > 
> > Signed-off-by: Vignesh R <vigneshr@ti.com>
> > Acked-by: Rob Herring <robh@kernel.org>
> > ---
> > 
> > v2: Use decoder,max-value instead of gpio-decoder,max-value.
> > 
> >  .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
> >  drivers/input/misc/Kconfig                         |  12 ++
> >  drivers/input/misc/Makefile                        |   1 +
> >  drivers/input/misc/gpio_decoder.c                  | 130 +++++++++++++++++++++
> >  4 files changed, 166 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/input/gpio-decoder.txt
> >  create mode 100644 drivers/input/misc/gpio_decoder.c
> > 
> > diff --git a/Documentation/devicetree/bindings/input/gpio-decoder.txt b/Documentation/devicetree/bindings/input/gpio-decoder.txt
> > new file mode 100644
> > index 000000000000..f27f083a9075
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/input/gpio-decoder.txt
> > @@ -0,0 +1,23 @@
> > +* GPIO Decoder DT bindings
> > +
> > +Required Properties:
> > +- compatible: should be "gpio-decoder"
> > +- gpios: a spec of gpios (atleast two) to be decoded to a number with
> 
>                               ^^ two words
> 
> > +  first entry representing the MSB.
> > +
> > +Optional Properties:
> > +- decoder,max-value: Maximum possible value that can be reported by
> > +  the gpios.
> > +- linux,axis: the input subsystem axis to map to (ABS_X/ABS_Y).
> > +  Defaults to 0 (ABS_X).
> > +
> > +Example:
> > +	gpio-decoder0 {
> > +		compatible = "gpio-decoder";
> > +		gpios = <&pca9536 3 GPIO_ACTIVE_HIGH>,
> > +			<&pca9536 2 GPIO_ACTIVE_HIGH>,
> > +			<&pca9536 1 GPIO_ACTIVE_HIGH>,
> > +			<&pca9536 0 GPIO_ACTIVE_HIGH>;
> > +		linux,axis = <0>; /* ABS_X */
> > +		decoder,max-value = <9>;
> > +	};
> > diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
> > index efb0ca871327..c44513cac3b7 100644
> > --- a/drivers/input/misc/Kconfig
> > +++ b/drivers/input/misc/Kconfig
> > @@ -292,6 +292,18 @@ config INPUT_GPIO_TILT_POLLED
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called gpio_tilt_polled.
> >  
> > +config INPUT_GPIO_DECODER
> > +	tristate "Polled GPIO Decoder Input driver"
> > +	depends on GPIOLIB && OF
> > +	select INPUT_POLLDEV
> > +	help
> > +	 Say Y here if you want driver to read status of multiple GPIO
> > +	 lines and report the encoded value as an absolute integer to
> > +	 input subsystem.
> > +
> > +	 To compile this driver as a module, choose M here: the module
> > +	 will will be called gpio_decoder.
> > +
> >  config INPUT_IXP4XX_BEEPER
> >  	tristate "IXP4XX Beeper support"
> >  	depends on ARCH_IXP4XX
> > diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
> > index 6a1e5e20fc1c..0b6d025f0487 100644
> > --- a/drivers/input/misc/Makefile
> > +++ b/drivers/input/misc/Makefile
> > @@ -35,6 +35,7 @@ obj-$(CONFIG_INPUT_DRV2667_HAPTICS)	+= drv2667.o
> >  obj-$(CONFIG_INPUT_GP2A)		+= gp2ap002a00f.o
> >  obj-$(CONFIG_INPUT_GPIO_BEEPER)		+= gpio-beeper.o
> >  obj-$(CONFIG_INPUT_GPIO_TILT_POLLED)	+= gpio_tilt_polled.o
> > +obj-$(CONFIG_INPUT_GPIO_DECODER)	+= gpio_decoder.o
> >  obj-$(CONFIG_INPUT_HISI_POWERKEY)	+= hisi_powerkey.o
> >  obj-$(CONFIG_HP_SDC_RTC)		+= hp_sdc_rtc.o
> >  obj-$(CONFIG_INPUT_IMS_PCU)		+= ims-pcu.o
> > diff --git a/drivers/input/misc/gpio_decoder.c b/drivers/input/misc/gpio_decoder.c
> > new file mode 100644
> > index 000000000000..eec0fda6f562
> > --- /dev/null
> > +++ b/drivers/input/misc/gpio_decoder.c
> > @@ -0,0 +1,130 @@
> > +/*
> > + * gpio-decoder.c
> > + *
> 
> ^ the name of the file often changes without this being updated, it
> really doesn't add anything anyway, would recommend dropping it.
> 
> > + * A generic driver to reads multiple gpio lines and translate the
> > + * encoded numeric value into an input event.
> > + *
> > + * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation version 2.
> > + *
> > + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> > + * kind, whether express or implied; without even the implied warranty
> > + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/device.h>
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/input.h>
> > +#include <linux/input-polldev.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +
> > +struct gpio_decoder {
> > +	struct input_polled_dev *poll_dev;
> > +	struct gpio_descs *input_gpios;
> > +	struct device *dev;
> > +	u32 axis;
> > +	u32 last_stable;
> > +};
> > +
> > +static unsigned int gpio_decoder_get_gpios_state(struct gpio_decoder
> > +						 *decoder)
> > +{
> > +	struct gpio_descs *gpios = decoder->input_gpios;
> > +	unsigned int ret = 0;
> > +	int i, val;
> > +
> > +	for (i = 0; i < gpios->ndescs; i++) {
> > +		val = gpiod_get_value_cansleep(gpios->desc[i]);
> > +		ret = ret << 1 | val;
> 
> Just to be safe, could you mask val with 0x1 here.

We also want to check for negative. So I guess:

		val = gpiod_get_value_cansleep(gpios->desc[i]);
		if (val >= 0)
			ret = (ret << 1) | !!val;

?

> 
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev)
> > +{
> > +	struct gpio_decoder *decoder = poll_dev->private;
> > +	unsigned int state = gpio_decoder_get_gpios_state(decoder);
> > +
> > +	if (state != decoder->last_stable) {
> > +		input_report_abs(poll_dev->input, decoder->axis, state);
> > +		input_sync(poll_dev->input);
> > +		decoder->last_stable = state;
> > +	}
> > +}
> > +
> > +static int gpio_decoder_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct gpio_decoder *decoder;
> > +	struct input_polled_dev *poll_dev;
> > +	u32  max;
> > +	int err;
> > +
> > +	decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);
> > +	if (!decoder)
> > +		return -ENOMEM;
> > +
> > +	device_property_read_u32(dev, "linux,axis", &decoder->axis);
> > +	decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
> > +	if (IS_ERR(decoder->input_gpios)) {
> > +		dev_err(dev, "unable to acquire input gpios\n");
> > +		return PTR_ERR(decoder->input_gpios);
> > +	}
> > +	if (decoder->input_gpios->ndescs < 2) {
> > +		dev_err(dev, "not enough gpios found\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (device_property_read_u32(dev, "decoder,max-value", &max))
> > +		max = BIT(decoder->input_gpios->ndescs);
> > +
> > +	decoder->dev = dev;
> > +	poll_dev = devm_input_allocate_polled_device(decoder->dev);
> > +	if (!poll_dev)
> > +		return -ENOMEM;
> > +
> > +	poll_dev->private = decoder;
> > +	poll_dev->poll = gpio_decoder_poll_gpios;
> > +	decoder->poll_dev = poll_dev;
> > +
> > +	poll_dev->input->name = pdev->name;
> > +	poll_dev->input->id.bustype = BUS_HOST;
> > +	poll_dev->input->dev.parent = dev;

No need to set for devices allocated with
devm_input_allocate_polled_device.

> > +	input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 1);
> > +
> > +	err = input_register_polled_device(poll_dev);
> > +	if (err) {
> > +		dev_err(dev, "failed to register polled  device\n");
> > +		return err;
> > +	}
> > +	platform_set_drvdata(pdev, decoder);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id gpio_decoder_of_match[] = {
> > +	{ .compatible = "gpio-decoder", },
> > +	{ },
> > +};
> > +MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
> > +
> > +static struct platform_driver gpio_decoder_driver = {
> > +	.probe		= gpio_decoder_probe,
> > +	.driver		= {
> > +		.name	= "gpio-decoder",
> > +		.of_match_table = of_match_ptr(gpio_decoder_of_match),
> 
> When the struct 'gpio_decoder_of_match' is always defined (not
> conditional on OF support), then 'of_match_ptr' does nothing and can be
> dropped here.

There is nothing in this driver that makes it OF-specific. I'd leave
of_match_ptr() as is, added #ifdef CONFIG_OF guard around
gpio_decoder_of_match, and changed "depends on GPIOLIB && OF" to
"depends on GPIOLIB || COMPILE_TEST".

Thanks.

> 
> > +	}
> > +};
> > +module_platform_driver(gpio_decoder_driver);
> > +
> > +MODULE_DESCRIPTION("GPIO decoder input driver");
> > +MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
> > +MODULE_LICENSE("GPL v2");

-- 
Dmitry

Re: [PATCH v2 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Dmitry Torokhov]

On Tue, Aug 23, 2016 at 10:27:59AM -0500, Andrew F. Davis wrote:
> On 08/23/2016 01:16 AM, Vignesh R wrote:
> > Add a driver to read group of GPIO lines and provide its status as a
> > numerical value as input event to the system. This will help in
> > intefacing devices, that can be connected over GPIOs, that provide input
> > to the system by driving GPIO lines connected to them like a rotary dial
> > or a switch.
> > 
> > For example, a rotary switch can be connected to four GPIO lines. The
> > status of the GPIO lines reflect the actual position of the rotary
> > switch dial. For example, if dial points to 9, then the four GPIO lines
> > connected to the switch will read HLLH(0b'1001 = 9). This value
> > can be reported as an ABS_* event to the input subsystem.
> > 
> > Signed-off-by: Vignesh R <vigneshr@ti.com>
> > Acked-by: Rob Herring <robh@kernel.org>
> > ---
> > 
> > v2: Use decoder,max-value instead of gpio-decoder,max-value.

That's not what Rob asked for. "decoder-max-value", not "decoder" vendor
prefix.

Thanks.

-- 
Dmitry

Re: [PATCH v2 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Vignesh R]

Hi Andrew, Dmitry,

On Wednesday 24 August 2016 01:31 AM, Dmitry Torokhov wrote:
> On Tue, Aug 23, 2016 at 10:27:59AM -0500, Andrew F. Davis wrote:
>> On 08/23/2016 01:16 AM, Vignesh R wrote:
>>> Add a driver to read group of GPIO lines and provide its status as a
>>> numerical value as input event to the system. This will help in
>>> intefacing devices, that can be connected over GPIOs, that provide input
>>> to the system by driving GPIO lines connected to them like a rotary dial
>>> or a switch.
>>>
>>> For example, a rotary switch can be connected to four GPIO lines. The
>>> status of the GPIO lines reflect the actual position of the rotary
>>> switch dial. For example, if dial points to 9, then the four GPIO lines
>>> connected to the switch will read HLLH(0b'1001 = 9). This value
>>> can be reported as an ABS_* event to the input subsystem.
>>>
>>> Signed-off-by: Vignesh R <vigneshr@ti.com>
>>> Acked-by: Rob Herring <robh@kernel.org>
>>> ---
>>>
>>> v2: Use decoder,max-value instead of gpio-decoder,max-value.
>>>
>>>  .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
>>>  drivers/input/misc/Kconfig                         |  12 ++
>>>  drivers/input/misc/Makefile                        |   1 +
>>>  drivers/input/misc/gpio_decoder.c                  | 130 +++++++++++++++++++++
>>>  4 files changed, 166 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/input/gpio-decoder.txt
>>>  create mode 100644 drivers/input/misc/gpio_decoder.c
>>>
>>> diff --git a/Documentation/devicetree/bindings/input/gpio-decoder.txt b/Documentation/devicetree/bindings/input/gpio-decoder.txt
>>> new file mode 100644
>>> index 000000000000..f27f083a9075
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/input/gpio-decoder.txt
>>> @@ -0,0 +1,23 @@
>>> +* GPIO Decoder DT bindings
>>> +
>>> +Required Properties:
>>> +- compatible: should be "gpio-decoder"
>>> +- gpios: a spec of gpios (atleast two) to be decoded to a number with
>>
>>                               ^^ two words

Ok.

>>
>>> +  first entry representing the MSB.
>>> +
>>> +Optional Properties:
>>> +- decoder,max-value: Maximum possible value that can be reported by
>>> +  the gpios.

I will change this to decoder-max-value as suggested previously.

>>> +- linux,axis: the input subsystem axis to map to (ABS_X/ABS_Y).
>>> +  Defaults to 0 (ABS_X).
>>> +
>>> +Example:
>>> +	gpio-decoder0 {
>>> +		compatible = "gpio-decoder";
>>> +		gpios = <&pca9536 3 GPIO_ACTIVE_HIGH>,
>>> +			<&pca9536 2 GPIO_ACTIVE_HIGH>,
>>> +			<&pca9536 1 GPIO_ACTIVE_HIGH>,
>>> +			<&pca9536 0 GPIO_ACTIVE_HIGH>;
>>> +		linux,axis = <0>; /* ABS_X */
>>> +		decoder,max-value = <9>;
>>> +	};
>>> diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
>>> index efb0ca871327..c44513cac3b7 100644
>>> --- a/drivers/input/misc/Kconfig
>>> +++ b/drivers/input/misc/Kconfig
>>> @@ -292,6 +292,18 @@ config INPUT_GPIO_TILT_POLLED
>>>  	  To compile this driver as a module, choose M here: the
>>>  	  module will be called gpio_tilt_polled.
>>>  
>>> +config INPUT_GPIO_DECODER
>>> +	tristate "Polled GPIO Decoder Input driver"
>>> +	depends on GPIOLIB && OF
>>> +	select INPUT_POLLDEV
>>> +	help
>>> +	 Say Y here if you want driver to read status of multiple GPIO
>>> +	 lines and report the encoded value as an absolute integer to
>>> +	 input subsystem.
>>> +
>>> +	 To compile this driver as a module, choose M here: the module
>>> +	 will will be called gpio_decoder.
>>> +
>>>  config INPUT_IXP4XX_BEEPER
>>>  	tristate "IXP4XX Beeper support"
>>>  	depends on ARCH_IXP4XX
>>> diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
>>> index 6a1e5e20fc1c..0b6d025f0487 100644
>>> --- a/drivers/input/misc/Makefile
>>> +++ b/drivers/input/misc/Makefile
>>> @@ -35,6 +35,7 @@ obj-$(CONFIG_INPUT_DRV2667_HAPTICS)	+= drv2667.o
>>>  obj-$(CONFIG_INPUT_GP2A)		+= gp2ap002a00f.o
>>>  obj-$(CONFIG_INPUT_GPIO_BEEPER)		+= gpio-beeper.o
>>>  obj-$(CONFIG_INPUT_GPIO_TILT_POLLED)	+= gpio_tilt_polled.o
>>> +obj-$(CONFIG_INPUT_GPIO_DECODER)	+= gpio_decoder.o
>>>  obj-$(CONFIG_INPUT_HISI_POWERKEY)	+= hisi_powerkey.o
>>>  obj-$(CONFIG_HP_SDC_RTC)		+= hp_sdc_rtc.o
>>>  obj-$(CONFIG_INPUT_IMS_PCU)		+= ims-pcu.o
>>> diff --git a/drivers/input/misc/gpio_decoder.c b/drivers/input/misc/gpio_decoder.c
>>> new file mode 100644
>>> index 000000000000..eec0fda6f562
>>> --- /dev/null
>>> +++ b/drivers/input/misc/gpio_decoder.c
>>> @@ -0,0 +1,130 @@
>>> +/*
>>> + * gpio-decoder.c
>>> + *
>>
>> ^ the name of the file often changes without this being updated, it
>> really doesn't add anything anyway, would recommend dropping it.

Ok.

>>
>>> + * A generic driver to reads multiple gpio lines and translate the
>>> + * encoded numeric value into an input event.
>>> + *
>>> + * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
>>> + *
>>> + * This program is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU General Public License as
>>> + * published by the Free Software Foundation version 2.
>>> + *
>>> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
>>> + * kind, whether express or implied; without even the implied warranty
>>> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + * GNU General Public License for more details.
>>> + */
>>> +
>>> +#include <linux/device.h>
>>> +#include <linux/gpio/consumer.h>
>>> +#include <linux/input.h>
>>> +#include <linux/input-polldev.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/platform_device.h>
>>> +
>>> +struct gpio_decoder {
>>> +	struct input_polled_dev *poll_dev;
>>> +	struct gpio_descs *input_gpios;
>>> +	struct device *dev;
>>> +	u32 axis;
>>> +	u32 last_stable;
>>> +};
>>> +
>>> +static unsigned int gpio_decoder_get_gpios_state(struct gpio_decoder
>>> +						 *decoder)
>>> +{
>>> +	struct gpio_descs *gpios = decoder->input_gpios;
>>> +	unsigned int ret = 0;
>>> +	int i, val;
>>> +
>>> +	for (i = 0; i < gpios->ndescs; i++) {
>>> +		val = gpiod_get_value_cansleep(gpios->desc[i]);
>>> +		ret = ret << 1 | val;
>>
>> Just to be safe, could you mask val with 0x1 here.
> 
> We also want to check for negative. So I guess:
> 
> 		val = gpiod_get_value_cansleep(gpios->desc[i]);
> 		if (val >= 0)
> 			ret = (ret << 1) | !!val;
> 
> ?

Agreed.

> 
>>
>>> +	}
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev)
>>> +{
>>> +	struct gpio_decoder *decoder = poll_dev->private;
>>> +	unsigned int state = gpio_decoder_get_gpios_state(decoder);
>>> +
>>> +	if (state != decoder->last_stable) {
>>> +		input_report_abs(poll_dev->input, decoder->axis, state);
>>> +		input_sync(poll_dev->input);
>>> +		decoder->last_stable = state;
>>> +	}
>>> +}
>>> +
>>> +static int gpio_decoder_probe(struct platform_device *pdev)
>>> +{
>>> +	struct device *dev = &pdev->dev;
>>> +	struct gpio_decoder *decoder;
>>> +	struct input_polled_dev *poll_dev;
>>> +	u32  max;
>>> +	int err;
>>> +
>>> +	decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);
>>> +	if (!decoder)
>>> +		return -ENOMEM;
>>> +
>>> +	device_property_read_u32(dev, "linux,axis", &decoder->axis);
>>> +	decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
>>> +	if (IS_ERR(decoder->input_gpios)) {
>>> +		dev_err(dev, "unable to acquire input gpios\n");
>>> +		return PTR_ERR(decoder->input_gpios);
>>> +	}
>>> +	if (decoder->input_gpios->ndescs < 2) {
>>> +		dev_err(dev, "not enough gpios found\n");
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	if (device_property_read_u32(dev, "decoder,max-value", &max))
>>> +		max = BIT(decoder->input_gpios->ndescs);
>>> +
>>> +	decoder->dev = dev;
>>> +	poll_dev = devm_input_allocate_polled_device(decoder->dev);
>>> +	if (!poll_dev)
>>> +		return -ENOMEM;
>>> +
>>> +	poll_dev->private = decoder;
>>> +	poll_dev->poll = gpio_decoder_poll_gpios;
>>> +	decoder->poll_dev = poll_dev;
>>> +
>>> +	poll_dev->input->name = pdev->name;
>>> +	poll_dev->input->id.bustype = BUS_HOST;
>>> +	poll_dev->input->dev.parent = dev;
> 
> No need to set for devices allocated with
> devm_input_allocate_polled_device.

Will drop this.

> 
>>> +	input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 1);
>>> +
>>> +	err = input_register_polled_device(poll_dev);
>>> +	if (err) {
>>> +		dev_err(dev, "failed to register polled  device\n");
>>> +		return err;
>>> +	}
>>> +	platform_set_drvdata(pdev, decoder);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static const struct of_device_id gpio_decoder_of_match[] = {
>>> +	{ .compatible = "gpio-decoder", },
>>> +	{ },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
>>> +
>>> +static struct platform_driver gpio_decoder_driver = {
>>> +	.probe		= gpio_decoder_probe,
>>> +	.driver		= {
>>> +		.name	= "gpio-decoder",
>>> +		.of_match_table = of_match_ptr(gpio_decoder_of_match),
>>
>> When the struct 'gpio_decoder_of_match' is always defined (not
>> conditional on OF support), then 'of_match_ptr' does nothing and can be
>> dropped here.
> 
> There is nothing in this driver that makes it OF-specific. I'd leave
> of_match_ptr() as is, added #ifdef CONFIG_OF guard around
> gpio_decoder_of_match, 
>and changed "depends on GPIOLIB && OF" to "depends on GPIOLIB || COMPILE_TEST".
> 

Agreed. Thanks for the review!


-- 
Regards
Vignesh

Re: [PATCH v2 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Vignesh R]

On Wednesday 24 August 2016 01:33 AM, Dmitry Torokhov wrote:
> On Tue, Aug 23, 2016 at 10:27:59AM -0500, Andrew F. Davis wrote:
>> On 08/23/2016 01:16 AM, Vignesh R wrote:
>>> Add a driver to read group of GPIO lines and provide its status as a
>>> numerical value as input event to the system. This will help in
>>> intefacing devices, that can be connected over GPIOs, that provide input
>>> to the system by driving GPIO lines connected to them like a rotary dial
>>> or a switch.
>>>
>>> For example, a rotary switch can be connected to four GPIO lines. The
>>> status of the GPIO lines reflect the actual position of the rotary
>>> switch dial. For example, if dial points to 9, then the four GPIO lines
>>> connected to the switch will read HLLH(0b'1001 = 9). This value
>>> can be reported as an ABS_* event to the input subsystem.
>>>
>>> Signed-off-by: Vignesh R <vigneshr@ti.com>
>>> Acked-by: Rob Herring <robh@kernel.org>
>>> ---
>>>
>>> v2: Use decoder,max-value instead of gpio-decoder,max-value.
> 
> That's not what Rob asked for. "decoder-max-value", not "decoder" vendor
> prefix.
> 

Sorry.. Will fix this in v3.


-- 
Regards
Vignesh