Re: [PATCH v3 1/2] input: misc: Add generic input driver to read encoded GPIO lines

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Mon, Aug 29, 2016 at 09:50:28AM +0530, Vignesh R wrote:
> 
> 
> On Thursday 25 August 2016 10:26 PM, Dmitry Torokhov wrote:
> > On Wed, Aug 24, 2016 at 01:28:58PM +0530, 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
> >> interfacing 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>
> >> ---
> >>
> >> v3: Fix comments by Andrew and Dmitry
> >> Link to v2: https://lkml.org/lkml/2016/8/23/79
> >>
> >>  .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
> >>  drivers/input/misc/Kconfig                         |  12 ++
> >>  drivers/input/misc/Makefile                        |   1 +
> >>  drivers/input/misc/gpio_decoder.c                  | 134 +++++++++++++++++++++
> >>  4 files changed, 170 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..14a77fb96cf0
> >> --- /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 (at least 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..7cdb89397d18 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 || COMPILE_TEST
> >> +	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 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..1c2191d4b143
> >> --- /dev/null
> >> +++ b/drivers/input/misc/gpio_decoder.c
> >> @@ -0,0 +1,134 @@
> >> +/*
> >> + * 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.
> >> + *
> >> + * A generic driver to read multiple gpio lines and translate the
> >> + * encoded numeric value into an input event.
> >> + */
> >> +
> >> +#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]);
> >> +		if (val >= 0) {
> >> +			ret = (ret << 1) | !!val;
> >> +		} else {
> >> +			dev_err(decoder->dev, "Error reading gpio\n");
> >> +			break;
> > 
> > I think if we fail reading any one of gpio lines we should skip
> > reporting the event.
> > 
> 
> Ok.
> 
> >> +		}
> >> +	}
> >> +
> >> +	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);
> > 
> > Shouldn't this be
> > 
> > 		max = (1U << decoder->input_gpios->ndescs) - 1;
> > 
> > ?
> 
> Oops, you are right.
> 
> > 
> >> +
> >> +	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;
> >> +	input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 1);
> > 
> > Why do you need flat == 1? Do you actually use joydev for this device?
> > 
> 
> Sorry, I overlooked flat param when I copied this line from
> rotary-encoder.c.
> 
> >> +
> >> +	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;
> >> +}
> >> +
> >> +#ifdef CONFIG_OF
> >> +static const struct of_device_id gpio_decoder_of_match[] = {
> >> +	{ .compatible = "gpio-decoder", },
> >> +	{ },
> >> +};
> >> +MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
> >> +#endif
> >> +
> >> +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
> >>
> > 
> > No need to resubmit, I can adjust on my side.
> 
> Thanks a lot!

Applied, thank you.

DTS change should go through some other tree though.

-- 
Dmitry