Date:   Wed, 30 Dec 2020 12:03:20 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Ye Xiang <xiang.ye@...el.com>
Cc:     jikos@...nel.org, srinivas.pandruvada@...ux.intel.com,
        linux-input@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/3] iio: hid-sensors: Add hinge sensor driver

On Tue, 15 Dec 2020 13:44:43 +0800
Ye Xiang <xiang.ye@...el.com> wrote:

> The Hinge sensor is a common custom sensor on laptops. It calculates
> the angle between the lid (screen) and the base (keyboard). In addition,
> it also exposes screen and the keyboard angles with respect to the
> ground. Applications can easily get laptop's status in space through
> this sensor, in order to display appropriate user interface.
> 
> Signed-off-by: Ye Xiang <xiang.ye@...el.com>
Hi.

A few things spotted on a fresh read through.  If this is all that comes
up in this round of review, I can tidy them up whilst applying.
If you are doing a v5 for any reason, please fix them up whilst doing that.

Thanks,

Jonathan

> ---
>  .../hid-sensors/hid-sensor-attributes.c       |   2 +
>  drivers/iio/position/Kconfig                  |  16 +
>  drivers/iio/position/Makefile                 |   1 +
>  .../position/hid-sensor-custom-intel-hinge.c  | 391 ++++++++++++++++++
>  4 files changed, 410 insertions(+)
>  create mode 100644 drivers/iio/position/hid-sensor-custom-intel-hinge.c
> 
> diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> index 442ff787f7af..5b822a4298a0 100644
> --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> @@ -71,6 +71,8 @@ static struct {
>  	{HID_USAGE_SENSOR_TEMPERATURE, HID_USAGE_SENSOR_UNITS_DEGREES, 1000, 0},
>  
>  	{HID_USAGE_SENSOR_HUMIDITY, 0, 1000, 0},
> +	{HID_USAGE_SENSOR_HINGE, 0, 0, 17453293},
> +	{HID_USAGE_SENSOR_HINGE, HID_USAGE_SENSOR_UNITS_DEGREES, 0, 17453293},
>  };
>  
>  static void simple_div(int dividend, int divisor, int *whole,
> diff --git a/drivers/iio/position/Kconfig b/drivers/iio/position/Kconfig
> index eda67f008c5b..1576a6380b53 100644
> --- a/drivers/iio/position/Kconfig
> +++ b/drivers/iio/position/Kconfig
> @@ -16,4 +16,20 @@ config IQS624_POS
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called iqs624-pos.
>  
> +config HID_SENSOR_CUSTOM_INTEL_HINGE
> +	depends on HID_SENSOR_HUB
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	select HID_SENSOR_IIO_COMMON
> +	select HID_SENSOR_IIO_TRIGGER
> +	tristate "HID Hinge"
> +	help
> +	  This sensor present three angles, hinge angel, screen angles
> +	  and keyboard angle respect to horizon (ground).
> +	  Say yes here to build support for the HID custom
> +	  intel hinge sensor.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called hid-sensor-custom-hinge.
> +
>  endmenu
> diff --git a/drivers/iio/position/Makefile b/drivers/iio/position/Makefile
> index 3cbe7a734352..d70902f2979d 100644
> --- a/drivers/iio/position/Makefile
> +++ b/drivers/iio/position/Makefile
> @@ -4,4 +4,5 @@
>  
>  # When adding new entries keep the list in alphabetical order
>  
> +obj-$(CONFIG_HID_SENSOR_CUSTOM_INTEL_HINGE) += hid-sensor-custom-intel-hinge.o
>  obj-$(CONFIG_IQS624_POS)	+= iqs624-pos.o
> diff --git a/drivers/iio/position/hid-sensor-custom-intel-hinge.c b/drivers/iio/position/hid-sensor-custom-intel-hinge.c
> new file mode 100644
> index 000000000000..24cf31c039a3
> --- /dev/null
> +++ b/drivers/iio/position/hid-sensor-custom-intel-hinge.c
> @@ -0,0 +1,391 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * HID Sensors Driver
> + * Copyright (c) 2020, Intel Corporation.
> + */
> +#include <linux/hid-sensor-hub.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/platform_device.h>
> +
> +#include "../common/hid-sensors/hid-sensor-trigger.h"
> +
> +enum hinge_channel {
> +	CHANNEL_SCAN_INDEX_HINGE_ANGLE,
> +	CHANNEL_SCAN_INDEX_SCREEN_ANGLE,
> +	CHANNEL_SCAN_INDEX_KEYBOARD_ANGLE,
> +	CHANNEL_SCAN_INDEX_MAX,
> +};
> +
> +#define CHANNEL_SCAN_INDEX_TIMESTAMP CHANNEL_SCAN_INDEX_MAX
> +
> +static const u32 hinge_addresses[CHANNEL_SCAN_INDEX_MAX] = {
> +	HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(1),
> +	HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(2),
> +	HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(3)
> +};
> +
> +static const char *const hinge_labels[CHANNEL_SCAN_INDEX_MAX] = { "hinge",
> +								  "screen",
> +								  "keyboard" };
> +
> +struct hinge_state {
> +	struct iio_dev *indio_dev;
> +	struct hid_sensor_hub_attribute_info hinge[CHANNEL_SCAN_INDEX_MAX];
> +	struct hid_sensor_hub_callbacks callbacks;
> +	struct hid_sensor_common common_attributes;
> +	const char *labels[CHANNEL_SCAN_INDEX_MAX];
> +	struct {
> +		u32 hinge_val[3];
> +		u64 timestamp __aligned(8);
> +	} scan;
> +
> +	int scale_pre_decml;
> +	int scale_post_decml;
> +	int scale_precision;
> +	int value_offset;
> +	u64 timestamp;
> +};
> +
> +/* Channel definitions */
> +static const struct iio_chan_spec hinge_channels[] = {
> +	{
> +		.type = IIO_ANGL,
> +		.indexed = 1,
> +		.channel = 0,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type =
> +			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE) |
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ) | BIT(IIO_CHAN_INFO_HYSTERESIS),
> +		.scan_index = CHANNEL_SCAN_INDEX_HINGE_ANGLE,
> +		.scan_type = {
> +			.sign = 's',
> +			.storagebits = 32,
> +		},
> +	}, {
> +		.type = IIO_ANGL,
> +		.indexed = 1,
> +		.channel = 1,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type =
> +			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE) |
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ) | BIT(IIO_CHAN_INFO_HYSTERESIS),
> +		.scan_index = CHANNEL_SCAN_INDEX_SCREEN_ANGLE,
> +		.scan_type = {
> +			.sign = 's',
> +			.storagebits = 32,
> +		},
> +	}, {
> +		.type = IIO_ANGL,
> +		.indexed = 1,
> +		.channel = 2,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type =
> +			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE) |
> +			BIT(IIO_CHAN_INFO_SAMP_FREQ) | BIT(IIO_CHAN_INFO_HYSTERESIS),
> +		.scan_index = CHANNEL_SCAN_INDEX_KEYBOARD_ANGLE,
> +		.scan_type = {
> +			.sign = 's',
> +			.storagebits = 32,
> +		},
> +	},
> +	IIO_CHAN_SOFT_TIMESTAMP(CHANNEL_SCAN_INDEX_TIMESTAMP)
> +};
> +
> +/* Adjust channel real bits based on report descriptor */
> +static void hinge_adjust_channel_realbits(struct iio_chan_spec *channels,
> +					  int channel, int size)
> +{
> +	channels[channel].scan_type.realbits = size * 8;
> +}
> +
> +/* Channel read_raw handler */
> +static int hinge_read_raw(struct iio_dev *indio_dev,
> +			  struct iio_chan_spec const *chan, int *val, int *val2,
> +			  long mask)
> +{
> +	struct hinge_state *st = iio_priv(indio_dev);
> +	struct hid_sensor_hub_device *hsdev;
> +	int report_id;
> +	int ret_type;
> +	s32 min;
> +
> +	hsdev = st->common_attributes.hsdev;
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		hid_sensor_power_state(&st->common_attributes, true);
> +		report_id = st->hinge[chan->scan_index].report_id;
> +		min = st->hinge[chan->scan_index].logical_minimum;
> +		if (report_id < 0) {
> +			hid_sensor_power_state(&st->common_attributes, false);
> +			return -EINVAL;
> +		}
> +
> +		*val = sensor_hub_input_attr_get_raw_value(st->common_attributes.hsdev,
> +							   hsdev->usage,
> +							   hinge_addresses[chan->scan_index],
> +							   report_id,
> +							   SENSOR_HUB_SYNC, min < 0);
> +
> +		hid_sensor_power_state(&st->common_attributes, false);
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->scale_pre_decml;
> +		*val2 = st->scale_post_decml;
> +		return st->scale_precision;
> +	case IIO_CHAN_INFO_OFFSET:
> +		*val = st->value_offset;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		ret_type = hid_sensor_read_samp_freq_value(&st->common_attributes,
> +							   val, val2);
> +		return ret_type;
> +	case IIO_CHAN_INFO_HYSTERESIS:
> +		ret_type = hid_sensor_read_raw_hyst_value(&st->common_attributes,
> +							  val, val2);
> +		return ret_type;

As below, I would return directly rather than use the local variable.

> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +/* Channel write_raw handler */
> +static int hinge_write_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan, int val, int val2,
> +			   long mask)
> +{
> +	struct hinge_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		ret = hid_sensor_write_samp_freq_value(&st->common_attributes,
> +						       val, val2);
> +		return ret;

If you happen to be respinning I'd go with the slightly shorter option of...

		return hid_sensor_write_samp_freq_value(&st->common_attributes,

> +	case IIO_CHAN_INFO_HYSTERESIS:
> +		ret = hid_sensor_write_raw_hyst_value(&st->common_attributes,
> +						      val, val2);
> +
> +		return ret;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int hinge_read_label(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan, char *label)
> +{
> +	struct hinge_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(label, "%s\n", st->labels[chan->channel]);
> +}
> +
> +static const struct iio_info hinge_info = {
> +	.read_raw = hinge_read_raw,
> +	.write_raw = hinge_write_raw,
> +	.read_label = hinge_read_label,
> +};
> +
> +/*
> + * Callback handler to send event after all samples are received
> + * and captured.
> + */
> +static int hinge_proc_event(struct hid_sensor_hub_device *hsdev,
> +			    unsigned int usage_id, void *priv)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(priv);
> +	struct hinge_state *st = iio_priv(indio_dev);
> +
> +	if (atomic_read(&st->common_attributes.data_ready)) {
> +		if (!st->timestamp)
> +			st->timestamp = iio_get_time_ns(indio_dev);
> +
> +		iio_push_to_buffers_with_timestamp(indio_dev, &st->scan,
> +						   st->timestamp);
> +
> +		st->timestamp = 0;
> +	}
> +	return 0;
> +}
> +
> +/* Capture samples in local storage */
> +static int hinge_capture_sample(struct hid_sensor_hub_device *hsdev,
> +				unsigned int usage_id, size_t raw_len,
> +				char *raw_data, void *priv)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(priv);
> +	struct hinge_state *st = iio_priv(indio_dev);
> +	int offset;
> +
> +	switch (usage_id) {
> +	case HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(1):
> +	case HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(2):
> +	case HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(3):
> +		offset = usage_id - HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(1);
> +		st->scan.hinge_val[offset] = *(u32 *)raw_data;
> +		return 0;
> +	case HID_USAGE_SENSOR_TIME_TIMESTAMP:
> +		st->timestamp = hid_sensor_convert_timestamp(&st->common_attributes,
> +							     *(int64_t *)raw_data);
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +/* Parse report which is specific to an usage id */
> +static int hinge_parse_report(struct platform_device *pdev,
> +			      struct hid_sensor_hub_device *hsdev,
> +			      struct iio_chan_spec *channels,
> +			      unsigned int usage_id, struct hinge_state *st)
> +{
> +	int ret;
> +	int i;
> +
> +	for (i = 0; i < CHANNEL_SCAN_INDEX_MAX; ++i) {
> +		ret = sensor_hub_input_get_attribute_info(hsdev,
> +							  HID_INPUT_REPORT,
> +							  usage_id,
> +							  hinge_addresses[i],
> +							  &st->hinge[i]);
> +		if (ret < 0)
> +			return ret;
> +
> +		hinge_adjust_channel_realbits(channels, i, st->hinge[i].size);
> +	}
> +
> +	st->scale_precision = hid_sensor_format_scale(HID_USAGE_SENSOR_HINGE,
> +			&st->hinge[CHANNEL_SCAN_INDEX_HINGE_ANGLE],
> +			&st->scale_pre_decml, &st->scale_post_decml);
> +
> +	/* Set Sensitivity field ids, when there is no individual modifier */
> +	if (st->common_attributes.sensitivity.index < 0) {
> +		sensor_hub_input_get_attribute_info(hsdev,
> +				HID_FEATURE_REPORT, usage_id,
> +				HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_ABS |
> +					HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE(1),
> +				&st->common_attributes.sensitivity);
> +		dev_dbg(&pdev->dev, "Sensitivity index:report %d:%d\n",
> +			st->common_attributes.sensitivity.index,
> +			st->common_attributes.sensitivity.report_id);
> +	}
> +
> +	return ret;
> +}
> +
> +/* Function to initialize the processing for usage id */
> +static int hid_hinge_probe(struct platform_device *pdev)
> +{
> +	struct hinge_state *st;
> +	struct iio_dev *indio_dev;
> +	struct hid_sensor_hub_device *hsdev = pdev->dev.platform_data;
> +	int ret;
> +	int i;
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	st = iio_priv(indio_dev);
> +	st->common_attributes.hsdev = hsdev;
> +	st->common_attributes.pdev = pdev;
> +	st->indio_dev = indio_dev;
> +	for (i = 0; i < CHANNEL_SCAN_INDEX_MAX; i++)
> +		st->labels[i] = hinge_labels[i];
> +
> +	ret = hid_sensor_parse_common_attributes(hsdev, hsdev->usage,
> +						 &st->common_attributes);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to setup common attributes\n");
> +		return ret;
> +	}
> +
> +	indio_dev->num_channels = ARRAY_SIZE(hinge_channels);
> +	indio_dev->channels = devm_kmemdup(&indio_dev->dev, hinge_channels,
> +					   sizeof(hinge_channels), GFP_KERNEL);
> +	if (!indio_dev->channels)
> +		return -ENOMEM;
> +
> +	ret = hinge_parse_report(pdev, hsdev,
> +				 (struct iio_chan_spec *)indio_dev->channels,
> +				 hsdev->usage, st);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to setup attributes\n");
> +		return ret;
> +	}
> +
> +	indio_dev->dev.parent = &pdev->dev;
> +	indio_dev->info = &hinge_info;
> +	indio_dev->name = "hinge";
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	atomic_set(&st->common_attributes.data_ready, 0);
> +	ret = hid_sensor_setup_trigger(indio_dev, indio_dev->name,
> +				       &st->common_attributes);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "trigger setup failed\n");
> +		return ret;
> +	}
> +
> +	st->callbacks.send_event = hinge_proc_event;
> +	st->callbacks.capture_sample = hinge_capture_sample;
> +	st->callbacks.pdev = pdev;
> +	ret = sensor_hub_register_callback(hsdev, hsdev->usage, &st->callbacks);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "callback reg failed\n");
> +		goto error_remove_trigger;
> +	}
> +
> +	ret = devm_iio_device_register(&pdev->dev, indio_dev);

Please don't mix devm and non devm functions.  The first time we
hit a non devm function that needs manual unwinding, then all later functions
in probe should also go the manual unwind route.

What you have here leads to a remove order which is not the precise reverse of
probe and makes it a lot harder to review for subtle race conditions. In this
case you leave the userspace interface exposed whilst removing some of the
underlying infrastructure.  I really don't want to have to figure out if
that is safe (probably isn't!)

Much better to just use iio_device_register here and
have an explicit iio_device_unregister in the remove function.

If nothing else comes up I can tidy that up whilst applying rather than
you needing to do a v5.

> +	if (ret) {
> +		dev_err(&pdev->dev, "device register failed\n");
> +		goto error_remove_callback;
> +	}
> +
> +	return ret;
> +
> +error_remove_callback:
> +	sensor_hub_remove_callback(hsdev, hsdev->usage);
> +error_remove_trigger:
> +	hid_sensor_remove_trigger(indio_dev, &st->common_attributes);
> +	return ret;
> +}
> +
> +/* Function to deinitialize the processing for usage id */
> +static int hid_hinge_remove(struct platform_device *pdev)
> +{
> +	struct hid_sensor_hub_device *hsdev = pdev->dev.platform_data;
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +	struct hinge_state *st = iio_priv(indio_dev);
> +
> +	sensor_hub_remove_callback(hsdev, hsdev->usage);
> +	hid_sensor_remove_trigger(indio_dev, &st->common_attributes);
> +
> +	return 0;
> +}
> +
> +static const struct platform_device_id hid_hinge_ids[] = {
> +	{
> +		/* Format: HID-SENSOR-INT-usage_id_in_hex_lowercase */
> +		.name = "HID-SENSOR-INT-020b",
> +	},
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(platform, hid_hinge_ids);
> +
> +static struct platform_driver hid_hinge_platform_driver = {
> +	.id_table = hid_hinge_ids,
> +	.driver = {
> +		.name	= KBUILD_MODNAME,
> +		.pm	= &hid_sensor_pm_ops,
> +	},
> +	.probe		= hid_hinge_probe,
> +	.remove		= hid_hinge_remove,
> +};
> +module_platform_driver(hid_hinge_platform_driver);
> +
> +MODULE_DESCRIPTION("HID Sensor INTEL Hinge");
> +MODULE_AUTHOR("Ye Xiang <xiang.ye@...el.com>");
> +MODULE_LICENSE("GPL");

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