[PATCH v7 7/7] input: joystick: Add ADC attached joystick driver.

[Artur Rojek <contact@artur-rojek.eu>]

Add a driver for joystick devices connected to ADC controllers
supporting the Industrial I/O subsystem.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
Tested-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---

 Changes:

 v2: - sanity check supported channel format on probe,
     - rename adc_joystick_disable to a more sensible adc_joystick_cleanup, 
     - enforce correct axis order by checking the `reg` property of
       child nodes

 v3-v5: no change

 v6: - remove redundant `<linux/of.h>`
     - set `val` for each endianness case in their respective branches
     - pass received error codes to return value of `adc_joystick_set_axes`
     - change `(bits >> 3) > 2` to `bits > 16` for readability
     - drop `of_match_ptr`

 v7: no change

 drivers/input/joystick/Kconfig        |  10 +
 drivers/input/joystick/Makefile       |   1 +
 drivers/input/joystick/adc-joystick.c | 253 ++++++++++++++++++++++++++
 3 files changed, 264 insertions(+)
 create mode 100644 drivers/input/joystick/adc-joystick.c

diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
index 940b744639c7..efbc20ec5099 100644
--- a/drivers/input/joystick/Kconfig
+++ b/drivers/input/joystick/Kconfig
@@ -42,6 +42,16 @@ config JOYSTICK_A3D
 	  To compile this driver as a module, choose M here: the
 	  module will be called a3d.
 
+config JOYSTICK_ADC
+	tristate "Simple joystick connected over ADC"
+	depends on IIO
+	select IIO_BUFFER_CB
+	help
+	  Say Y here if you have a simple joystick connected over ADC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called adc-joystick.
+
 config JOYSTICK_ADI
 	tristate "Logitech ADI digital joysticks and gamepads"
 	select GAMEPORT
diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
index 8656023f6ef5..58232b3057d3 100644
--- a/drivers/input/joystick/Makefile
+++ b/drivers/input/joystick/Makefile
@@ -6,6 +6,7 @@
 # Each configuration option enables a list of files.
 
 obj-$(CONFIG_JOYSTICK_A3D)		+= a3d.o
+obj-$(CONFIG_JOYSTICK_ADC)		+= adc-joystick.o
 obj-$(CONFIG_JOYSTICK_ADI)		+= adi.o
 obj-$(CONFIG_JOYSTICK_AMIGA)		+= amijoy.o
 obj-$(CONFIG_JOYSTICK_AS5011)		+= as5011.o
diff --git a/drivers/input/joystick/adc-joystick.c b/drivers/input/joystick/adc-joystick.c
new file mode 100644
index 000000000000..a4ba8eac5a12
--- /dev/null
+++ b/drivers/input/joystick/adc-joystick.c
@@ -0,0 +1,253 @@
+// 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>
+
+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, i;
+	bool sign;
+
+	bytes = joy->chans[0].channel->scan_type.storagebits >> 3;
+
+	for (i = 0; i < joy->num_chans; ++i) {
+		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)[i];
+			break;
+		case 2:
+			if (endianness == IIO_BE)
+				val = be16_to_cpu(((const u16 *)data)[i]);
+			else if (endianness == IIO_LE)
+				val = le16_to_cpu(((const u16 *)data)[i]);
+			else /* IIO_CPU */
+				val = ((const u16 *)data)[i];
+			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);
+	int ret;
+
+	ret = iio_channel_start_all_cb(joy->buffer);
+	if (ret)
+		dev_err(dev->dev.parent, "Unable to start callback buffer");
+
+	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, ret, i;
+
+	num_axes = device_get_child_node_count(dev);
+	if (!num_axes) {
+		dev_err(dev, "Unable to find child nodes");
+		return -EINVAL;
+	}
+
+	if (num_axes != joy->num_chans) {
+		dev_err(dev, "Got %d child nodes for %d channels",
+			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) {
+		ret = fwnode_property_read_u32(child, "reg", &i);
+		if (ret) {
+			dev_err(dev, "reg invalid or missing");
+			goto err;
+		}
+
+		if (i >= num_axes) {
+			ret = -EINVAL;
+			dev_err(dev, "No matching axis for reg %d", i);
+			goto err;
+		}
+
+		ret = fwnode_property_read_u32(child, "linux,code",
+					     &axes[i].code);
+		if (ret) {
+			dev_err(dev, "linux,code invalid or missing");
+			goto err;
+		}
+
+		ret = fwnode_property_read_u32_array(child, "abs-range",
+						   axes[i].range, 2);
+		if (ret) {
+			dev_err(dev, "abs-range invalid or missing");
+			goto err;
+		}
+
+		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_handle_put(child);
+	return ret;
+}
+
+static int adc_joystick_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct adc_joystick *joy;
+	struct input_dev *input;
+	int bits, ret, 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)) {
+		ret = PTR_ERR(joy->chans);
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "Unable to get IIO channels");
+		return ret;
+	}
+
+	/* Count how many channels we got. NULL terminated. */
+	while (joy->chans[joy->num_chans].indio_dev)
+		joy->num_chans++;
+
+	bits = joy->chans[0].channel->scan_type.storagebits;
+	if (!bits || (bits > 16)) {
+		dev_err(dev, "Unsupported channel storage size");
+		return -EINVAL;
+	}
+	for (i = 1; i < joy->num_chans; ++i)
+		if (joy->chans[i].channel->scan_type.storagebits != bits) {
+			dev_err(dev, "Channels must have equal storage size");
+			return -EINVAL;
+		}
+
+	input = devm_input_allocate_device(dev);
+	if (!input) {
+		dev_err(dev, "Unable to allocate input device");
+		return -ENOMEM;
+	}
+
+	joy->input = input;
+	input->name = pdev->name;
+	input->id.bustype = BUS_HOST;
+	input->open = adc_joystick_open;
+	input->close = adc_joystick_close;
+
+	ret = adc_joystick_set_axes(dev, joy);
+	if (ret)
+		return ret;
+
+	input_set_drvdata(input, joy);
+	ret = input_register_device(input);
+	if (ret) {
+		dev_err(dev, "Unable to register input device: %d", ret);
+		return ret;
+	}
+
+	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");
+		return PTR_ERR(joy->buffer);
+	}
+
+	ret = devm_add_action_or_reset(dev, adc_joystick_cleanup, joy->buffer);
+	if (ret)
+		dev_err(dev, "Unable to add action");
+
+	return ret;
+}
+
+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");
-- 
2.26.2