Re: [PATCH v4 2/2] input: add ADC resistor ladder driver
From: Dmitry Torokhov
Date: Tue Jul 12 2016 - 20:42:47 EST
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.
>
> 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");