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>
---
Changes in v6:
- switched to microvolts
Changes in v5:
- Dmitry's changes
- s/mvolt/millivolt/
.../devicetree/bindings/input/adc-keys.txt | 49 +++++
drivers/input/keyboard/Kconfig | 15 ++
drivers/input/keyboard/Makefile | 1 +
drivers/input/keyboard/adc-keys.c | 210 +++++++++++++++++++++
4 files changed, 275 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 000000000000..e551814629b4
--- /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-microvolt: 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-microvolt: 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-microvolt = <2000000>;
+
+ button-up {
+ label = "Volume Up";
+ linux,code = <KEY_VOLUMEUP>;
+ press-threshold-microvolt = <1500000>;
+ };
+
+ button-down {
+ label = "Volume Down";
+ linux,code = <KEY_VOLUMEDOWN>;
+ press-threshold-microvolt = <1000000>;
+ };
+
+ button-enter {
+ label = "Enter";
+ linux,code = <KEY_ENTER>;
+ press-threshold-microvolt = <500000>;
+ };
+ };
diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index 509608c95994..cbd75cf44739 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 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..f8cf2ccacefd
--- /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/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-microvolt",
+ &map[i].voltage)) {
+ dev_err(dev, "Key with invalid or missing voltage\n");
+ fwnode_handle_put(child);
+ return -EINVAL;
+ }
+ map[i].voltage /= 1000;
+
+ 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-microvolt",
+ &st->keyup_voltage)) {
+ dev_err(dev, "Invalid or missing keyup voltage\n");
+ return -EINVAL;
+ }
+ st->keyup_voltage /= 1000;
+
+ 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");
--
2.8.1
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