--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * GPIO driven charlieplex keypad driver
+ *
+ * Copyright (c) 2026 Hugo Villeneuve <hvilleneuve@dimonoff.com>
+ *
+ * Based on matrix_keyboard.c
+ */
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/dev_printk.h>
+#include <linux/device/devres.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/input.h>
+#include <linux/input/matrix_keypad.h>
+#include <linux/math.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/string_helpers.h>
+#include <linux/types.h>
+
+struct charlieplex_keypad {
+ struct input_dev *input_dev;
+ struct gpio_descs *line_gpios;
+ unsigned int nlines;
+ unsigned int settling_time_us;
+ unsigned int debounce_threshold;
+ unsigned int debounce_count;
+ int debounce_code;
+ int current_code;
+};
+
+static void charlieplex_keypad_report_key(struct input_dev *input)
+{
+ struct charlieplex_keypad *keypad = input_get_drvdata(input);
+ const unsigned short *keycodes = input->keycode;
+
+ if (keypad->current_code > 0) {
+ input_event(input, EV_MSC, MSC_SCAN, keypad->current_code);
+ input_report_key(input, keycodes[keypad->current_code], 0);
+ input_sync(input);
+ }
+
+ if (keypad->debounce_code) {
+ input_event(input, EV_MSC, MSC_SCAN, keypad->debounce_code);
+ input_report_key(input, keycodes[keypad->debounce_code], 1);
+ input_sync(input);
+ }
+
+ keypad->current_code = keypad->debounce_code;
+}
+
+static void charlieplex_keypad_check_switch_change(struct input_dev *input,
+ unsigned int code)
+{
+ struct charlieplex_keypad *keypad = input_get_drvdata(input);
+
+ if (code != keypad->debounce_code) {
+ keypad->debounce_count = 0;
+ keypad->debounce_code = code;
+ }
+
+ if (keypad->debounce_code != keypad->current_code) {
+ if (keypad->debounce_count++ >= keypad->debounce_threshold)
+ charlieplex_keypad_report_key(input);
+ }
+}
+
+static int charlieplex_keypad_scan_line(struct charlieplex_keypad *keypad,
+ unsigned int oline)
+{
+ struct gpio_descs *line_gpios = keypad->line_gpios;
+ DECLARE_BITMAP(values, MATRIX_MAX_ROWS);
+ int err;
+
+ /* Activate only one line as output at a time. */
+ gpiod_direction_output(line_gpios->desc[oline], 1);
+
+ if (keypad->settling_time_us)
+ fsleep(keypad->settling_time_us);
+
+ /* Read input on all other lines. */
+ err = gpiod_get_array_value_cansleep(line_gpios->ndescs, line_gpios->desc,
+ line_gpios->info, values);
+
+ gpiod_direction_input(line_gpios->desc[oline]);
+
+ if (err)
+ return err;
+
+ for (unsigned int iline = 0; iline < keypad->nlines; iline++) {
+ if (iline == oline)
+ continue; /* Do not read active output line. */
+
+ /* Check if GPIO is asserted. */
+ if (test_bit(iline, values))
+ return MATRIX_SCAN_CODE(oline, iline,
+ get_count_order(keypad->nlines));
+ }
+
+ return 0;
+}
+
+static void charlieplex_keypad_poll(struct input_dev *input)
+{
+ struct charlieplex_keypad *keypad = input_get_drvdata(input);
+ int code = 0;
+
+ for (unsigned int oline = 0; oline < keypad->nlines; oline++) {
+ code = charlieplex_keypad_scan_line(keypad, oline);
+ if (code != 0)
+ break;
+ }
+
+ if (code >= 0)
+ charlieplex_keypad_check_switch_change(input, code);
+}
+
+static int charlieplex_keypad_init_gpio(struct platform_device *pdev,
+ struct charlieplex_keypad *keypad)
+{
+ char **pin_names;
+ char label[32];
+
+ snprintf(label, sizeof(label), "%s-pin", pdev->name);
+
+ keypad->line_gpios = devm_gpiod_get_array(&pdev->dev, "line", GPIOD_IN);
+ if (IS_ERR(keypad->line_gpios))
+ return PTR_ERR(keypad->line_gpios);
+
+ keypad->nlines = keypad->line_gpios->ndescs;
+
+ if (keypad->nlines > MATRIX_MAX_ROWS)
+ return -EINVAL;
+
+ pin_names = devm_kasprintf_strarray(&pdev->dev, label, keypad->nlines);
+ if (IS_ERR(pin_names))
+ return PTR_ERR(pin_names);
+
+ for (unsigned int i = 0; i < keypad->line_gpios->ndescs; i++)
+ gpiod_set_consumer_name(keypad->line_gpios->desc[i], pin_names[i]);
+
+ return 0;
+}
+
+static int charlieplex_keypad_probe(struct platform_device *pdev)
+{
+ struct charlieplex_keypad *keypad;
+ struct input_dev *input_dev;
+ unsigned int debounce_interval_ms = 5;
+ unsigned int poll_interval_ms;
+ int err;
+
+ keypad = devm_kzalloc(&pdev->dev, sizeof(*keypad), GFP_KERNEL);
+ if (!keypad)
+ return -ENOMEM;
+
+ input_dev = devm_input_allocate_device(&pdev->dev);
+ if (!input_dev)
+ return -ENOMEM;
+
+ keypad->input_dev = input_dev;
+
+ err = device_property_read_u32(&pdev->dev, "poll-interval", &poll_interval_ms);
+ if (err)
+ return dev_err_probe(&pdev->dev, err,
+ "failed to parse 'poll-interval' property\n");
+
+ if (poll_interval_ms == 0)
+ return dev_err_probe(&pdev->dev, -EINVAL, "invalid 'poll-interval' value\n");
+
+ device_property_read_u32(&pdev->dev, "debounce-delay-ms", &debounce_interval_ms);
+ device_property_read_u32(&pdev->dev, "settling-time-us", &keypad->settling_time_us);
+
+ keypad->current_code = -1;
+ keypad->debounce_code = -1;
+ keypad->debounce_threshold = DIV_ROUND_UP(debounce_interval_ms, poll_interval_ms);
+
+ err = charlieplex_keypad_init_gpio(pdev, keypad);
+ if (err)
+ return err;
+
+ input_dev->name = pdev->name;
+ input_dev->id.bustype = BUS_HOST;
+
+ err = matrix_keypad_build_keymap(NULL, NULL, keypad->nlines,
+ keypad->nlines, NULL, input_dev);
+ if (err)
+ return dev_err_probe(&pdev->dev, err, "failed to build keymap\n");
+
+ if (device_property_read_bool(&pdev->dev, "autorepeat"))
+ __set_bit(EV_REP, input_dev->evbit);
+
+ input_set_capability(input_dev, EV_MSC, MSC_SCAN);
+
+ err = input_setup_polling(input_dev, charlieplex_keypad_poll);
+ if (err)
+ return dev_err_probe(&pdev->dev, err, "unable to set up polling\n");
+
+ input_set_poll_interval(input_dev, poll_interval_ms);
+
+ input_set_drvdata(input_dev, keypad);
+
+ err = input_register_device(keypad->input_dev);
+ if (err)
+ return err;
+
+ return 0;
+}
+
+static const struct of_device_id charlieplex_keypad_dt_match[] = {
+ { .compatible = "gpio-charlieplex-keypad" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, charlieplex_keypad_dt_match);
+
+static struct platform_driver charlieplex_keypad_driver = {
+ .probe = charlieplex_keypad_probe,
+ .driver = {
+ .name = "charlieplex-keypad",
+ .of_match_table = charlieplex_keypad_dt_match,
+ },
+};
+module_platform_driver(charlieplex_keypad_driver);
+
+MODULE_AUTHOR("Hugo Villeneuve <hvilleneuve@dimonoff.com>");
+MODULE_DESCRIPTION("GPIO driven charlieplex keypad driver");
+MODULE_LICENSE("GPL");
projects / thirdparty / kernel / stable.git / commitdiff
