Re: [PATCH v4 2/2] input: add ADC resistor ladder driver

From: Dmitry Torokhov
Date: Thu Jul 28 2016 - 18:09:27 EST

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On Tue, Jul 12, 2016 at 05:41:50PM -0700, Dmitry Torokhov wrote:
> Hi Alexandre,
>
> On Tue, Jul 12, 2016 at 09:36:26PM +0200, 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.
>
> This looks quite reasonable, just a few small comments.

Ping.

Did the version below work for you? I am trying sweep in the brand new
drivers before we close merge window.

Thanks!

>
> >
> > Acked-by: Jonathan Cameron <jic23@xxxxxxxxxx>
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> > ---
> > 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;
>
> const
>
> > +};
> > +
> > +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;
> > + }
>
> I think this can be simplified a bit, see version below.
>
> > +
> > + 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;
> > + }
>
> There is no need to limit this driver to OF, generic device properties
> will allow us to use it on DT, ACPI and legacy boards.
>
> > +
> > + 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);
>
> You have to remember to drop node reference if you return early from
> for_each_child_of_node().
>
> > + 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;
>
> No need to do that for devm input devices - it is done for you.
>
> > +
> > + 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);
>
> Needs #ifdef CONFIG_OF.
>
> > +
> > +static struct platform_driver __refdata adc_keys_driver = {
> > + .driver = {
> > + .name = "adc_keys",
> > + .of_match_table = adc_keys_of_match,
>
> of_match_ptr().
>
> > + },
> > + .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");
> > --
> > 2.8.1
> >
>
> Thanks.
>
> --
> Dmitry
>
>
> Input: add ADC resistor ladder driver
>
> From: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
>
> 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.
>
> Acked-by: Jonathan Cameron <jic23@xxxxxxxxxx>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> ---
> .../devicetree/bindings/input/adc-keys.txt | 49 +++++
> drivers/input/keyboard/Kconfig | 15 +
> drivers/input/keyboard/Makefile | 1
> drivers/input/keyboard/adc-keys.c | 208 ++++++++++++++++++++
> 4 files changed, 273 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/input/adc-keys.txt
> create mode 100644 drivers/input/keyboard/adc-keys.c
>
> diff --git a/Documentation/devicetree/bindings/input/adc-keys.txt b/Documentation/devicetree/bindings/input/adc-keys.txt
> new file mode 100644
> index 0000000..feab05a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/adc-keys.txt
> @@ -0,0 +1,49 @@
> +ADC attached resistor ladder buttons
> +------------------------------------
> +
> +Required properties:
> + - compatible: "adc-keys"
> + - io-channels: Phandle to an ADC channel
> + - io-channel-names = "buttons";
> + - keyup-threshold-mvolt: Voltage at which all the keys are considered up.
> +
> +Optional properties:
> + - poll-interval: Poll interval time in milliseconds
> + - autorepeat: Boolean, Enable auto repeat feature of Linux input
> + subsystem.
> +
> +Each button (key) is represented as a sub-node of "adc-keys":
> +
> +Required subnode-properties:
> + - label: Descriptive name of the key.
> + - linux,code: Keycode to emit.
> + - press-threshold-mvolt: Voltage adc input when this key is pressed.
> +
> +Example:
> +
> +#include <dt-bindings/input/input.h>
> +
> + adc-keys {
> + compatible = "adc-keys";
> + io-channels = <&lradc 0>;
> + io-channel-names = "buttons";
> + keyup-threshold-mvolt = <2000>;
> +
> + button@1500 {
> + label = "Volume Up";
> + linux,code = <KEY_VOLUMEUP>;
> + press-threshold-mvolt = <1500>;
> + };
> +
> + button@1000 {
> + label = "Volume Down";
> + linux,code = <KEY_VOLUMEDOWN>;
> + press-threshold-mvolt = <1000>;
> + };
> +
> + button@500 {
> + label = "Enter";
> + linux,code = <KEY_ENTER>;
> + press-threshold-mvolt = <500>;
> + };
> + };
> diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
> index 509608c..cbd75cf 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
> + for 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 1d416dd..d9f4cfc 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 0000000..f91eec5
> --- /dev/null
> +++ b/drivers/input/keyboard/adc-keys.c
> @@ -0,0 +1,208 @@
> +/*
> + * 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/err.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/types.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>
> +#include <linux/property.h>
> +#include <linux/slab.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;
> + const 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 (unlikely(ret < 0)) {
> + /* Forcibly release key if any was pressed */
> + value = st->keyup_voltage;
> + } else {
> + 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)
> + keycode = 0;
> +
> + if (st->last_key && st->last_key != keycode)
> + input_report_key(dev->input, st->last_key, 0);
> +
> + if (keycode)
> + input_report_key(dev->input, keycode, 1);
> +
> + input_sync(dev->input);
> + st->last_key = keycode;
> +}
> +
> +static int adc_keys_load_keymap(struct device *dev, struct adc_keys_state *st)
> +{
> + struct adc_keys_button *map;
> + struct fwnode_handle *child;
> + int i;
> +
> + st->num_keys = device_get_child_node_count(dev);
> + if (st->num_keys == 0) {
> + dev_err(dev, "keymap is missing\n");
> + return -EINVAL;
> + }
> +
> + map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
> + if (!map)
> + return -ENOMEM;
> +
> + i = 0;
> + device_for_each_child_node(dev, child) {
> + if (fwnode_property_read_u32(child, "press-threshold-mvolt",
> + &map[i].voltage)) {
> + dev_err(dev, "Key with invalid or missing voltage\n");
> + fwnode_handle_put(child);
> + return -EINVAL;
> + }
> +
> + if (fwnode_property_read_u32(child, "linux,code",
> + &map[i].keycode)) {
> + dev_err(dev, "Key with invalid or missing linux,code\n");
> + fwnode_handle_put(child);
> + return -EINVAL;
> + }
> +
> + i++;
> + }
> +
> + st->map = map;
> + return 0;
> +}
> +
> +static int adc_keys_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct adc_keys_state *st;
> + struct input_polled_dev *poll_dev;
> + struct input_dev *input;
> + enum iio_chan_type type;
> + int i, value;
> + int error;
> +
> + 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 -ENXIO;
> +
> + error = iio_get_channel_type(st->channel, &type);
> + if (error < 0)
> + return error;
> +
> + if (type != IIO_VOLTAGE) {
> + dev_err(dev, "Incompatible channel type %d\n", type);
> + return -EINVAL;
> + }
> +
> + if (device_property_read_u32(dev, "keyup-threshold-mvolt",
> + &st->keyup_voltage)) {
> + dev_err(dev, "Invalid or missing keyup voltage\n");
> + return -EINVAL;
> + }
> +
> + error = adc_keys_load_keymap(dev, st);
> + if (error)
> + return error;
> +
> + 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 (!device_property_read_u32(dev, "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->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 (device_property_read_bool(dev, "autorepeat"))
> + __set_bit(EV_REP, input->evbit);
> +
> + error = input_register_polled_device(poll_dev);
> + if (error) {
> + dev_err(dev, "Unable to register input device: %d\n", error);
> + return error;
> + }
> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id adc_keys_of_match[] = {
> + { .compatible = "adc-keys", },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, adc_keys_of_match);
> +#endif
> +
> +static struct platform_driver __refdata adc_keys_driver = {
> + .driver = {
> + .name = "adc_keys",
> + .of_match_table = of_match_ptr(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");

--
Dmitry

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