Re: [PATCH 5/5] input: joystick: Add ADC attached joystick driver.

[Jonathan Cameron]

On Sun,  5 Jan 2020 01:16:39 +0100
Artur Rojek <contact@xxxxxxxxxxxxxx> wrote:

> Add a driver for joystick devices connected to ADC controllers
> supporting the Industrial I/O subsystem.
> 
> Signed-off-by: Artur Rojek <contact@xxxxxxxxxxxxxx>
> Tested-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>

Looks pretty good, but I'd like to see a little more sanity checking
on probe that the channels are in a format this driver can actually
handle.  Given we can check channel size and consistency etc early
it would be better to fail to probe than just report error data later.

Thanks,

Jonathan

> ---
>  drivers/input/joystick/Kconfig        |  10 ++
>  drivers/input/joystick/Makefile       |   1 +
>  drivers/input/joystick/adc-joystick.c | 230 ++++++++++++++++++++++++++
>  3 files changed, 241 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..0dfc4218dafa
> --- /dev/null
> +++ b/drivers/input/joystick/adc-joystick.c
> @@ -0,0 +1,230 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Input driver for joysticks connected over ADC.
> + * Copyright (c) 2019-2020 Artur Rojek <contact@xxxxxxxxxxxxxx>
> + */
> +#include <linux/ctype.h>
> +#include <linux/input.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/of.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;
> +
> +	/* Assume all channels have the same storage size. */

Would be better to check that and report an error if not!

> +	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:
> +			val = ((const u16 *)data)[i];
> +			if (endianness == IIO_BE)
> +				val = be16_to_cpu(val);
> +			else if (endianness == IIO_LE)
> +				val = le16_to_cpu(val);
> +			break;
> +		default:

Good to have sanity checked this earlier and refused to probe.

> +			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_disable(void *data)
> +{
> +	iio_channel_release_all_cb(data);

Given what it does, and the fact it basically matches the iio_channel_get_all_cb call,
seems like an odd name for this function.

> +}
> +
> +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, i = 0;
> +
> +	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) {
> +		if (fwnode_property_read_u32(child, "linux,abs-code",
> +					     &axes[i].code)) {
> +			dev_err(dev, "linux,abs-code invalid or missing");
> +			goto err;
> +		}
> +
> +		if (fwnode_property_read_u32_array(child, "linux,abs-range",
> +						   axes[i].range, 2)) {
> +			dev_err(dev, "linux,abs-range invalid or missing");
> +			goto err;
> +		}
> +
> +		fwnode_property_read_u32(child, "linux,abs-fuzz",
> +					 &axes[i].fuzz);
> +		fwnode_property_read_u32(child, "linux,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);
> +
> +		++i;
> +	}
> +
> +	joy->axes = axes;
> +
> +	return 0;
> +
> +err:
> +	fwnode_handle_put(child);
> +	return -EINVAL;
> +}
> +
> +static int adc_joystick_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct adc_joystick *joy;
> +	struct input_dev *input;
> +	int ret;
> +
> +	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++;
> +
> +	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_disable, 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 = of_match_ptr(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@xxxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");