Re: [PATCH v2 2/2] input: add ADC resistor ladder driver

[Jonathan Cameron]

On 09/07/16 02:24, Alexandre Belloni wrote:
> A common way of multiplexing buttons on a single input in cheap devices is
> to use a resistor ladder on an ADC. This driver supports that configuration
> by polling an ADC channel provided by IIO.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
Acked-by: Jonathan Cameron <jic23@xxxxxxxxxx>
> ---
> Changes in v2:
>  - removed dependency on COMPILE_TEST which is not useful anyway
>  - use new bindings
> 
>  drivers/input/keyboard/Kconfig    |  15 +++
>  drivers/input/keyboard/Makefile   |   1 +
>  drivers/input/keyboard/adc-keys.c | 210 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 226 insertions(+)
>  create mode 100644 drivers/input/keyboard/adc-keys.c
> 
> diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
> index 509608c95994..4cf042cc5e63 100644
> --- a/drivers/input/keyboard/Kconfig
> +++ b/drivers/input/keyboard/Kconfig
> @@ -12,6 +12,21 @@ menuconfig INPUT_KEYBOARD
>  
>  if INPUT_KEYBOARD
>  
> +config KEYBOARD_ADC
> +	tristate "ADC ladder Buttons"
> +	depends on IIO
> +	select INPUT_POLLDEV
> +	help
> +	  This driver implements support for buttons connected
> +	  to an ADC using a resistor ladder.
> +
> +	  Say Y here if your device has such buttons connected to an ADC.  Your
> +	  board-specific setup logic must also provide a configuration data
> +	  saying mapping voltages to buttons.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called adc_keys.
> +
>  config KEYBOARD_ADP5520
>  	tristate "Keypad Support for ADP5520 PMIC"
>  	depends on PMIC_ADP5520
> diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
> index 1d416ddf84e4..d9f4cfcf3410 100644
> --- a/drivers/input/keyboard/Makefile
> +++ b/drivers/input/keyboard/Makefile
> @@ -4,6 +4,7 @@
>  
>  # Each configuration option enables a list of files.
>  
> +obj-$(CONFIG_KEYBOARD_ADC)		+= adc-keys.o
>  obj-$(CONFIG_KEYBOARD_ADP5520)		+= adp5520-keys.o
>  obj-$(CONFIG_KEYBOARD_ADP5588)		+= adp5588-keys.o
>  obj-$(CONFIG_KEYBOARD_ADP5589)		+= adp5589-keys.o
> diff --git a/drivers/input/keyboard/adc-keys.c b/drivers/input/keyboard/adc-keys.c
> new file mode 100644
> index 000000000000..cf299ff517a0
> --- /dev/null
> +++ b/drivers/input/keyboard/adc-keys.c
> @@ -0,0 +1,210 @@
> +/* Input driver for resistor ladder connected on ADC
> + *
> + * Copyright (c) 2016 Alexandre Belloni
> + *
> + * 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/slab.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/input.h>
> +#include <linux/input-polldev.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/types.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +
> +struct adc_keys_button {
> +	u32 voltage;
> +	u32 keycode;
> +};
> +
> +struct adc_keys_state {
> +	struct iio_channel *channel;
> +	u32 num_keys;
> +	u32 last_key;
> +	u32 keyup_voltage;
> +	struct adc_keys_button *map;
> +};
> +
> +static void adc_keys_poll(struct input_polled_dev *dev)
> +{
> +	struct adc_keys_state *st = dev->private;
> +	int i, value, ret;
> +	u32 diff, closest = 0xffffffff;
> +	int keycode = 0;
> +
> +	ret = iio_read_channel_processed(st->channel, &value);
> +	if (ret < 0) {
> +		if (st->last_key) {
> +			input_report_key(dev->input, st->last_key, 0);
> +			input_sync(dev->input);
> +			st->last_key = 0;
> +		}
> +		return;
> +	}
> +
> +	for (i = 0; i < st->num_keys; i++) {
> +		diff = abs(st->map[i].voltage - value);
> +		if (diff < closest) {
> +			closest = diff;
> +			keycode = st->map[i].keycode;
> +		}
> +	}
> +
> +	if (abs(st->keyup_voltage - value) < closest) {
> +		input_report_key(dev->input, st->last_key, 0);
> +		st->last_key = 0;
> +	} else {
> +		if (st->last_key && st->last_key != keycode)
> +			input_report_key(dev->input, st->last_key, 0);
> +		input_report_key(dev->input, keycode, 1);
> +		st->last_key = keycode;
> +	}
> +
> +	input_sync(dev->input);
> +}
> +
> +static int adc_keys_load_dt_keymap(struct device *dev,
> +				   struct adc_keys_state *st)
> +{
> +	struct device_node *pp, *np = dev->of_node;
> +	int i;
> +
> +	st->num_keys = of_get_child_count(np);
> +	if (st->num_keys == 0) {
> +		dev_err(dev, "keymap is missing\n");
> +		return -EINVAL;
> +	}
> +
> +	st->map = devm_kmalloc_array(dev, st->num_keys, sizeof(*st->map),
> +				     GFP_KERNEL);
> +	if (!st->map)
> +		return -ENOMEM;
> +
> +	i = 0;
> +	for_each_child_of_node(np, pp) {
> +		struct adc_keys_button *map = &st->map[i];
> +
> +		if (of_property_read_u32(pp, "press-threshold-mvolt",
> +					 &map->voltage)) {
> +			dev_err(dev, "%s: Invalid or missing voltage\n",
> +				pp->name);
> +			return -EINVAL;
> +		}
> +
> +		if (of_property_read_u32(pp, "linux,code", &map->keycode)) {
> +			dev_err(dev, "%s: Invalid or missing linux,code\n",
> +				pp->name);
> +			return -EINVAL;
> +		}
> +
> +		i++;
> +	}
> +
> +	return 0;
> +}
> +
> +static int adc_keys_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *node = dev->of_node;
> +	struct adc_keys_state *st;
> +	struct input_polled_dev *poll_dev = NULL;
> +	struct input_dev *input;
> +	enum iio_chan_type type;
> +	int i, value, ret;
> +
> +	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
> +	if (!st)
> +		return -ENOMEM;
> +
> +	st->channel = devm_iio_channel_get(dev, "buttons");
> +	if (IS_ERR(st->channel))
> +		return PTR_ERR(st->channel);
> +
> +	if (!st->channel->indio_dev)
> +		return -ENODEV;
> +
> +	ret = iio_get_channel_type(st->channel, &type);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (type != IIO_VOLTAGE) {
> +		dev_err(dev, "Incompatible channel type %d\n", type);
> +		return -EINVAL;
> +	}
> +
> +	if (of_property_read_u32(node, "keyup-threshold-mvolt",
> +				 &st->keyup_voltage)) {
> +		dev_err(dev, "Invalid or missing keyup voltage\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = adc_keys_load_dt_keymap(dev, st);
> +	if (ret)
> +		return ret;
> +
> +	platform_set_drvdata(pdev, st);
> +
> +	poll_dev = devm_input_allocate_polled_device(dev);
> +	if (!poll_dev) {
> +		dev_err(dev, "failed to allocate input device\n");
> +		return -ENOMEM;
> +	}
> +
> +	if (!of_property_read_u32(node, "poll-interval", &value))
> +		poll_dev->poll_interval = value;
> +	poll_dev->poll = adc_keys_poll;
> +	poll_dev->private = st;
> +
> +	input = poll_dev->input;
> +
> +	input->name = pdev->name;
> +	input->phys = "adc-keys/input0";
> +	input->dev.parent = &pdev->dev;
> +
> +	input->id.bustype = BUS_HOST;
> +	input->id.vendor = 0x0001;
> +	input->id.product = 0x0001;
> +	input->id.version = 0x0100;
> +
> +	__set_bit(EV_KEY, input->evbit);
> +	for (i = 0; i < st->num_keys; i++)
> +		__set_bit(st->map[i].keycode, input->keybit);
> +
> +	if (!!of_get_property(node, "autorepeat", NULL))
> +		__set_bit(EV_REP, input->evbit);
> +
> +	ret = input_register_polled_device(poll_dev);
> +	if (ret) {
> +		dev_err(dev, "Unable to register input device\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id adc_keys_of_match[] = {
> +	{ .compatible = "adc-keys", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, adc_keys_of_match);
> +
> +static struct platform_driver __refdata adc_keys_driver = {
> +	.driver = {
> +		.name = "adc_keys",
> +		.of_match_table = adc_keys_of_match,
> +	},
> +	.probe = adc_keys_probe,
> +};
> +
> +module_platform_driver(adc_keys_driver);
> +
> +MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
> +MODULE_LICENSE("GPL v2");
>