--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Input driver for joysticks connected over ADC.
+ * Copyright (c) 2019-2020 Artur Rojek <contact@artur-rojek.eu>
+ */
+#include <linux/ctype.h>
+#include <linux/input.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/consumer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#include <asm/unaligned.h>
+
+struct adc_joystick_axis {
+ u32 code;
+ s32 range[2];
+ s32 fuzz;
+ s32 flat;
+};
+
+struct adc_joystick {
+ struct input_dev *input;
+ struct iio_cb_buffer *buffer;
+ struct adc_joystick_axis *axes;
+ struct iio_channel *chans;
+ int num_chans;
+};
+
+static int adc_joystick_handle(const void *data, void *private)
+{
+ struct adc_joystick *joy = private;
+ enum iio_endian endianness;
+ int bytes, msb, val, idx, i;
+ const u16 *data_u16;
+ bool sign;
+
+ bytes = joy->chans[0].channel->scan_type.storagebits >> 3;
+
+ for (i = 0; i < joy->num_chans; ++i) {
+ idx = joy->chans[i].channel->scan_index;
+ endianness = joy->chans[i].channel->scan_type.endianness;
+ msb = joy->chans[i].channel->scan_type.realbits - 1;
+ sign = tolower(joy->chans[i].channel->scan_type.sign) == 's';
+
+ switch (bytes) {
+ case 1:
+ val = ((const u8 *)data)[idx];
+ break;
+ case 2:
+ data_u16 = (const u16 *)data + idx;
+
+ /*
+ * Data is aligned to the sample size by IIO core.
+ * Call `get_unaligned_xe16` to hide type casting.
+ */
+ if (endianness == IIO_BE)
+ val = get_unaligned_be16(data_u16);
+ else if (endianness == IIO_LE)
+ val = get_unaligned_le16(data_u16);
+ else /* IIO_CPU */
+ val = *data_u16;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ val >>= joy->chans[i].channel->scan_type.shift;
+ if (sign)
+ val = sign_extend32(val, msb);
+ else
+ val &= GENMASK(msb, 0);
+ input_report_abs(joy->input, joy->axes[i].code, val);
+ }
+
+ input_sync(joy->input);
+
+ return 0;
+}
+
+static int adc_joystick_open(struct input_dev *dev)
+{
+ struct adc_joystick *joy = input_get_drvdata(dev);
+ struct device *devp = &dev->dev;
+ int ret;
+
+ ret = iio_channel_start_all_cb(joy->buffer);
+ if (ret)
+ dev_err(devp, "Unable to start callback buffer: %d\n", ret);
+
+ return ret;
+}
+
+static void adc_joystick_close(struct input_dev *dev)
+{
+ struct adc_joystick *joy = input_get_drvdata(dev);
+
+ iio_channel_stop_all_cb(joy->buffer);
+}
+
+static void adc_joystick_cleanup(void *data)
+{
+ iio_channel_release_all_cb(data);
+}
+
+static int adc_joystick_set_axes(struct device *dev, struct adc_joystick *joy)
+{
+ struct adc_joystick_axis *axes;
+ struct fwnode_handle *child;
+ int num_axes, error, i;
+
+ num_axes = device_get_child_node_count(dev);
+ if (!num_axes) {
+ dev_err(dev, "Unable to find child nodes\n");
+ return -EINVAL;
+ }
+
+ if (num_axes != joy->num_chans) {
+ dev_err(dev, "Got %d child nodes for %d channels\n",
+ num_axes, joy->num_chans);
+ return -EINVAL;
+ }
+
+ axes = devm_kmalloc_array(dev, num_axes, sizeof(*axes), GFP_KERNEL);
+ if (!axes)
+ return -ENOMEM;
+
+ device_for_each_child_node(dev, child) {
+ error = fwnode_property_read_u32(child, "reg", &i);
+ if (error) {
+ dev_err(dev, "reg invalid or missing\n");
+ goto err_fwnode_put;
+ }
+
+ if (i >= num_axes) {
+ error = -EINVAL;
+ dev_err(dev, "No matching axis for reg %d\n", i);
+ goto err_fwnode_put;
+ }
+
+ error = fwnode_property_read_u32(child, "linux,code",
+ &axes[i].code);
+ if (error) {
+ dev_err(dev, "linux,code invalid or missing\n");
+ goto err_fwnode_put;
+ }
+
+ error = fwnode_property_read_u32_array(child, "abs-range",
+ axes[i].range, 2);
+ if (error) {
+ dev_err(dev, "abs-range invalid or missing\n");
+ goto err_fwnode_put;
+ }
+
+ fwnode_property_read_u32(child, "abs-fuzz", &axes[i].fuzz);
+ fwnode_property_read_u32(child, "abs-flat", &axes[i].flat);
+
+ input_set_abs_params(joy->input, axes[i].code,
+ axes[i].range[0], axes[i].range[1],
+ axes[i].fuzz, axes[i].flat);
+ input_set_capability(joy->input, EV_ABS, axes[i].code);
+ }
+
+ joy->axes = axes;
+
+ return 0;
+
+err_fwnode_put:
+ fwnode_handle_put(child);
+ return error;
+}
+
+static int adc_joystick_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct adc_joystick *joy;
+ struct input_dev *input;
+ int error;
+ int bits;
+ int i;
+
+ joy = devm_kzalloc(dev, sizeof(*joy), GFP_KERNEL);
+ if (!joy)
+ return -ENOMEM;
+
+ joy->chans = devm_iio_channel_get_all(dev);
+ if (IS_ERR(joy->chans)) {
+ error = PTR_ERR(joy->chans);
+ if (error != -EPROBE_DEFER)
+ dev_err(dev, "Unable to get IIO channels");
+ return error;
+ }
+
+ /* Count how many channels we got. NULL terminated. */
+ for (i = 0; joy->chans[i].indio_dev; i++) {
+ bits = joy->chans[i].channel->scan_type.storagebits;
+ if (!bits || bits > 16) {
+ dev_err(dev, "Unsupported channel storage size\n");
+ return -EINVAL;
+ }
+ if (bits != joy->chans[0].channel->scan_type.storagebits) {
+ dev_err(dev, "Channels must have equal storage size\n");
+ return -EINVAL;
+ }
+ }
+ joy->num_chans = i;
+
+ input = devm_input_allocate_device(dev);
+ if (!input) {
+ dev_err(dev, "Unable to allocate input device\n");
+ return -ENOMEM;
+ }
+
+ joy->input = input;
+ input->name = pdev->name;
+ input->id.bustype = BUS_HOST;
+ input->open = adc_joystick_open;
+ input->close = adc_joystick_close;
+
+ error = adc_joystick_set_axes(dev, joy);
+ if (error)
+ return error;
+
+ input_set_drvdata(input, joy);
+ error = input_register_device(input);
+ if (error) {
+ dev_err(dev, "Unable to register input device\n");
+ return error;
+ }
+
+ joy->buffer = iio_channel_get_all_cb(dev, adc_joystick_handle, joy);
+ if (IS_ERR(joy->buffer)) {
+ dev_err(dev, "Unable to allocate callback buffer\n");
+ return PTR_ERR(joy->buffer);
+ }
+
+ error = devm_add_action_or_reset(dev, adc_joystick_cleanup, joy->buffer);
+ if (error) {
+ dev_err(dev, "Unable to add action\n");
+ return error;
+ }
+
+ return 0;
+}
+
+static const struct of_device_id adc_joystick_of_match[] = {
+ { .compatible = "adc-joystick", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, adc_joystick_of_match);
+
+static struct platform_driver adc_joystick_driver = {
+ .driver = {
+ .name = "adc-joystick",
+ .of_match_table = adc_joystick_of_match,
+ },
+ .probe = adc_joystick_probe,
+};
+module_platform_driver(adc_joystick_driver);
+
+MODULE_DESCRIPTION("Input driver for joysticks connected over ADC");
+MODULE_AUTHOR("Artur Rojek <contact@artur-rojek.eu>");
+MODULE_LICENSE("GPL");
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