Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Input: add ADC resistor ladder driver
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@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
authored by
Alexandre Belloni
and committed by
Dmitry Torokhov
68077264
f959cd8c
+275
+49
Documentation/devicetree/bindings/input/adc-keys.txt
+49
Documentation/devicetree/bindings/input/adc-keys.txt
···
1
+
ADC attached resistor ladder buttons
2
+
------------------------------------
3
+
4
+
Required properties:
5
+
- compatible: "adc-keys"
6
+
- io-channels: Phandle to an ADC channel
7
+
- io-channel-names = "buttons";
8
+
- keyup-threshold-microvolt: Voltage at which all the keys are considered up.
9
+
10
+
Optional properties:
11
+
- poll-interval: Poll interval time in milliseconds
12
+
- autorepeat: Boolean, Enable auto repeat feature of Linux input
13
+
subsystem.
14
+
15
+
Each button (key) is represented as a sub-node of "adc-keys":
16
+
17
+
Required subnode-properties:
18
+
- label: Descriptive name of the key.
19
+
- linux,code: Keycode to emit.
20
+
- press-threshold-microvolt: Voltage ADC input when this key is pressed.
21
+
22
+
Example:
23
+
24
+
#include <dt-bindings/input/input.h>
25
+
26
+
adc-keys {
27
+
compatible = "adc-keys";
28
+
io-channels = <&lradc 0>;
29
+
io-channel-names = "buttons";
30
+
keyup-threshold-microvolt = <2000000>;
31
+
32
+
button-up {
33
+
label = "Volume Up";
34
+
linux,code = <KEY_VOLUMEUP>;
35
+
press-threshold-microvolt = <1500000>;
36
+
};
37
+
38
+
button-down {
39
+
label = "Volume Down";
40
+
linux,code = <KEY_VOLUMEDOWN>;
41
+
press-threshold-microvolt = <1000000>;
42
+
};
43
+
44
+
button-enter {
45
+
label = "Enter";
46
+
linux,code = <KEY_ENTER>;
47
+
press-threshold-microvolt = <500000>;
48
+
};
49
+
};
+15
drivers/input/keyboard/Kconfig
+15
drivers/input/keyboard/Kconfig
···
12
12
13
13
if INPUT_KEYBOARD
14
14
15
+
config KEYBOARD_ADC
16
+
tristate "ADC Ladder Buttons"
17
+
depends on IIO
18
+
select INPUT_POLLDEV
19
+
help
20
+
This driver implements support for buttons connected
21
+
to an ADC using a resistor ladder.
22
+
23
+
Say Y here if your device has such buttons connected to an ADC. Your
24
+
board-specific setup logic must also provide a configuration data
25
+
for mapping voltages to buttons.
26
+
27
+
To compile this driver as a module, choose M here: the
28
+
module will be called adc_keys.
29
+
15
30
config KEYBOARD_ADP5520
16
31
tristate "Keypad Support for ADP5520 PMIC"
17
32
depends on PMIC_ADP5520
+1
drivers/input/keyboard/Makefile
+1
drivers/input/keyboard/Makefile
+210
drivers/input/keyboard/adc-keys.c
+210
drivers/input/keyboard/adc-keys.c
···
1
+
/*
2
+
* Input driver for resistor ladder connected on ADC
3
+
*
4
+
* Copyright (c) 2016 Alexandre Belloni
5
+
*
6
+
* This program is free software; you can redistribute it and/or modify it
7
+
* under the terms of the GNU General Public License version 2 as published by
8
+
* the Free Software Foundation.
9
+
*/
10
+
11
+
#include <linux/err.h>
12
+
#include <linux/iio/consumer.h>
13
+
#include <linux/iio/types.h>
14
+
#include <linux/input.h>
15
+
#include <linux/input-polldev.h>
16
+
#include <linux/kernel.h>
17
+
#include <linux/module.h>
18
+
#include <linux/of.h>
19
+
#include <linux/platform_device.h>
20
+
#include <linux/property.h>
21
+
#include <linux/slab.h>
22
+
23
+
struct adc_keys_button {
24
+
u32 voltage;
25
+
u32 keycode;
26
+
};
27
+
28
+
struct adc_keys_state {
29
+
struct iio_channel *channel;
30
+
u32 num_keys;
31
+
u32 last_key;
32
+
u32 keyup_voltage;
33
+
const struct adc_keys_button *map;
34
+
};
35
+
36
+
static void adc_keys_poll(struct input_polled_dev *dev)
37
+
{
38
+
struct adc_keys_state *st = dev->private;
39
+
int i, value, ret;
40
+
u32 diff, closest = 0xffffffff;
41
+
int keycode = 0;
42
+
43
+
ret = iio_read_channel_processed(st->channel, &value);
44
+
if (unlikely(ret < 0)) {
45
+
/* Forcibly release key if any was pressed */
46
+
value = st->keyup_voltage;
47
+
} else {
48
+
for (i = 0; i < st->num_keys; i++) {
49
+
diff = abs(st->map[i].voltage - value);
50
+
if (diff < closest) {
51
+
closest = diff;
52
+
keycode = st->map[i].keycode;
53
+
}
54
+
}
55
+
}
56
+
57
+
if (abs(st->keyup_voltage - value) < closest)
58
+
keycode = 0;
59
+
60
+
if (st->last_key && st->last_key != keycode)
61
+
input_report_key(dev->input, st->last_key, 0);
62
+
63
+
if (keycode)
64
+
input_report_key(dev->input, keycode, 1);
65
+
66
+
input_sync(dev->input);
67
+
st->last_key = keycode;
68
+
}
69
+
70
+
static int adc_keys_load_keymap(struct device *dev, struct adc_keys_state *st)
71
+
{
72
+
struct adc_keys_button *map;
73
+
struct fwnode_handle *child;
74
+
int i;
75
+
76
+
st->num_keys = device_get_child_node_count(dev);
77
+
if (st->num_keys == 0) {
78
+
dev_err(dev, "keymap is missing\n");
79
+
return -EINVAL;
80
+
}
81
+
82
+
map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
83
+
if (!map)
84
+
return -ENOMEM;
85
+
86
+
i = 0;
87
+
device_for_each_child_node(dev, child) {
88
+
if (fwnode_property_read_u32(child, "press-threshold-microvolt",
89
+
&map[i].voltage)) {
90
+
dev_err(dev, "Key with invalid or missing voltage\n");
91
+
fwnode_handle_put(child);
92
+
return -EINVAL;
93
+
}
94
+
map[i].voltage /= 1000;
95
+
96
+
if (fwnode_property_read_u32(child, "linux,code",
97
+
&map[i].keycode)) {
98
+
dev_err(dev, "Key with invalid or missing linux,code\n");
99
+
fwnode_handle_put(child);
100
+
return -EINVAL;
101
+
}
102
+
103
+
i++;
104
+
}
105
+
106
+
st->map = map;
107
+
return 0;
108
+
}
109
+
110
+
static int adc_keys_probe(struct platform_device *pdev)
111
+
{
112
+
struct device *dev = &pdev->dev;
113
+
struct adc_keys_state *st;
114
+
struct input_polled_dev *poll_dev;
115
+
struct input_dev *input;
116
+
enum iio_chan_type type;
117
+
int i, value;
118
+
int error;
119
+
120
+
st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
121
+
if (!st)
122
+
return -ENOMEM;
123
+
124
+
st->channel = devm_iio_channel_get(dev, "buttons");
125
+
if (IS_ERR(st->channel))
126
+
return PTR_ERR(st->channel);
127
+
128
+
if (!st->channel->indio_dev)
129
+
return -ENXIO;
130
+
131
+
error = iio_get_channel_type(st->channel, &type);
132
+
if (error < 0)
133
+
return error;
134
+
135
+
if (type != IIO_VOLTAGE) {
136
+
dev_err(dev, "Incompatible channel type %d\n", type);
137
+
return -EINVAL;
138
+
}
139
+
140
+
if (device_property_read_u32(dev, "keyup-threshold-microvolt",
141
+
&st->keyup_voltage)) {
142
+
dev_err(dev, "Invalid or missing keyup voltage\n");
143
+
return -EINVAL;
144
+
}
145
+
st->keyup_voltage /= 1000;
146
+
147
+
error = adc_keys_load_keymap(dev, st);
148
+
if (error)
149
+
return error;
150
+
151
+
platform_set_drvdata(pdev, st);
152
+
153
+
poll_dev = devm_input_allocate_polled_device(dev);
154
+
if (!poll_dev) {
155
+
dev_err(dev, "failed to allocate input device\n");
156
+
return -ENOMEM;
157
+
}
158
+
159
+
if (!device_property_read_u32(dev, "poll-interval", &value))
160
+
poll_dev->poll_interval = value;
161
+
162
+
poll_dev->poll = adc_keys_poll;
163
+
poll_dev->private = st;
164
+
165
+
input = poll_dev->input;
166
+
167
+
input->name = pdev->name;
168
+
input->phys = "adc-keys/input0";
169
+
170
+
input->id.bustype = BUS_HOST;
171
+
input->id.vendor = 0x0001;
172
+
input->id.product = 0x0001;
173
+
input->id.version = 0x0100;
174
+
175
+
__set_bit(EV_KEY, input->evbit);
176
+
for (i = 0; i < st->num_keys; i++)
177
+
__set_bit(st->map[i].keycode, input->keybit);
178
+
179
+
if (device_property_read_bool(dev, "autorepeat"))
180
+
__set_bit(EV_REP, input->evbit);
181
+
182
+
error = input_register_polled_device(poll_dev);
183
+
if (error) {
184
+
dev_err(dev, "Unable to register input device: %d\n", error);
185
+
return error;
186
+
}
187
+
188
+
return 0;
189
+
}
190
+
191
+
#ifdef CONFIG_OF
192
+
static const struct of_device_id adc_keys_of_match[] = {
193
+
{ .compatible = "adc-keys", },
194
+
{ }
195
+
};
196
+
MODULE_DEVICE_TABLE(of, adc_keys_of_match);
197
+
#endif
198
+
199
+
static struct platform_driver __refdata adc_keys_driver = {
200
+
.driver = {
201
+
.name = "adc_keys",
202
+
.of_match_table = of_match_ptr(adc_keys_of_match),
203
+
},
204
+
.probe = adc_keys_probe,
205
+
};
206
+
module_platform_driver(adc_keys_driver);
207
+
208
+
MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
209
+
MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
210
+
MODULE_LICENSE("GPL v2");