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Date:   Sun, 22 Nov 2020 16:50:47 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     "Pandruvada, Srinivas" <srinivas.pandruvada@intel.com>
Cc:     "jikos@kernel.org" <jikos@kernel.org>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        "Ye, Xiang" <xiang.ye@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>
Subject: Re: [PATCH v2 4/4] iio: hid-sensors: Add hinge sensor driver
Message-ID: <20201122165047.3ceae561@archlinux>
In-Reply-To: <48fc6cd8b0ac0cc4c10aa1e677bdc293ad75476b.camel@intel.com>
References: <20201119100331.2594-1-xiang.ye@intel.com>
        <20201119100331.2594-5-xiang.ye@intel.com>
        <20201121175629.057031af@archlinux>
        <218c8869f799d701ddd5c22ce9524a765f43a0de.camel@intel.com>
        <1de3727a37fe1d793b6146d9c19b101e32bb1c71.camel@intel.com>
        <20201122141416.7f446793@archlinux>
        <48fc6cd8b0ac0cc4c10aa1e677bdc293ad75476b.camel@intel.com>
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On Sun, 22 Nov 2020 15:51:18 +0000
"Pandruvada, Srinivas" <srinivas.pandruvada@intel.com> wrote:

> On Sun, 2020-11-22 at 14:14 +0000, Jonathan Cameron wrote:
> > On Sun, 22 Nov 2020 02:14:16 +0000
> > "Pandruvada, Srinivas" <srinivas.pandruvada@intel.com> wrote:
> >   
> > > On Sat, 2020-11-21 at 17:46 -0800, Srinivas Pandruvada wrote:  
> > > > On Sat, 2020-11-21 at 17:56 +0000, Jonathan Cameron wrote:    
> > > > > On Thu, 19 Nov 2020 18:03:31 +0800
> > > > > Ye Xiang <xiang.ye@intel.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 angels with respect
> > > > > > to
> > > > > > the
> > > > > > ground. Applications can easily get laptop's status in space
> > > > > > through
> > > > > > this sensor, in order to display appropriate user
> > > > > > interface.    
> > > > > 
> > > > > I'm a little unclear on why the 3 axes aren't treated as a
> > > > > single
> > > > > sensor.
> > > > > You seem to always grab the 3 together or am I missing
> > > > > something?
> > > > > 
> > > > > That will greatly simplify things and get rid of the need to
> > > > > have
> > > > > a shared trigger with the problems that causes in the previous
> > > > > patch.    
> > > > 
> > > > They are not three axes, they are independent. Xiang did try
> > > > adding
> > > > x,
> > > > y and z component to represent x as hinge, y as keyboard and z as
> > > > lid.
> > > > But I was not convinced.
> > > > The problem is that then what will be sysfs interface? They are
> > > > really
> > > > a three sensors. Or we create new interface to call
> > > > in_angl_raw_keyboard
> > > > in_angl_raw_screen
> > > > in_angl_raw_lid.
> > > >     
> > > You seem to indicate this is possible now some new "label" patch.
> > > Is this the patch?
> > > commit 2c3d0c9ffd24d9b4c62c5dfb2104695a614be28c
> > > Author: Phil Reid <preid@electromag.com.au>
> > > Date:   Thu Sep 19 22:36:08 2019 +0800  
> > 
> > Nope, this one 
> > https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=1d4ef9b39ebecca827642b8897d2d79ea2026682
> > 
> > The one above adds a per device label which wouldn't be much use for
> > your
> > case, but this one adds a per channel label.
> > 
> > Done via a read_label callback.
> > 
> > Here you'd want to use indexed channels so something like.
> > 
> > in_angl0_raw
> > in_angl1_raw
> > in_angl2_raw
> > 
> > and
> > 
> > in_angl0_label = keyboard
> > in_angl1_label = screen
> > in_angl2_label = lid  
> 
> Thanks Jonathan. This will make the job easier.
> Xiang,
> You can use this method. Then you will not need other changes except
> patch 1/4.
> Also add a documentation patch to explain the mapping.

Ah.  So we have a slightly problem with sysfs ABI docs at the moment.
The scripts that auto generate the html and similar docs from them
don't cope with the same name of attribute in multiple documentation
files.

https://lore.kernel.org/linux-iio/20201110082658.2edc1ab5@coco.lan/

The upshot being we can't have more specific docs for a particular
part that match up with the generic docs.  That will apply in this
case.

So for now, our solution is to put it in the main docs, but provide
a subsection in there talking about more specific constraints for
a particular device.

Note I haven't actually proposed any fixes for this problem yet so
you get to do the first one ;)

Thanks,

Jonathan


> 
> Thanks,
> Srinivas
> 
> > 
> > 
> >   
> > > Ideally, one iio device here is much easy to manage as other HID
> > > sensors. If we can add something other that "x", "y" and "z"
> > > component.  
> > 
> > Agreed, using axes makes no real sense here and extended_name is
> > just a mess from ABI point of view.  Trying to solve this was the
> > reason we added the _label interface.
> > 
> > Jonathan
> > 
> >   
> > > Thanks,
> > > Srinivas
> > >   
> > > > Thanks,
> > > > Srinivas
> > > > 
> > > >     
> > > > > Thanks,
> > > > > 
> > > > > Jonathan
> > > > >     
> > > > > > Signed-off-by: Ye Xiang <xiang.ye@intel.com>
> > > > > > ---
> > > > > >  .../hid-sensors/hid-sensor-attributes.c       |   2 +
> > > > > >  drivers/iio/position/Kconfig                  |  16 +
> > > > > >  drivers/iio/position/Makefile                 |   3 +
> > > > > >  .../iio/position/hid-sensor-custom-hinge.c    | 412
> > > > > > ++++++++++++++++++    
> > > > > 
> > > > > Given it's custom probably needs a more specific name.  I guess
> > > > > hid-sensor-custom-intel-hinge.c might be safe?
> > > > > 
> > > > > Same for other places we need names in here.
> > > > >     
> > > > > >  4 files changed, 433 insertions(+)
> > > > > >  create mode 100644 drivers/iio/position/hid-sensor-custom-
> > > > > > 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..0346f6f2b422 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_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 SENSOR
> > > > > > CUSTOM
> > > > > > +	  HINGE.    
> > > > > 
> > > > > Capitalization is a bit odd looking. I'd drop it.
> > > > >     
> > > > > > +
> > > > > > +	  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..7a6225977a01 100644
> > > > > > --- a/drivers/iio/position/Makefile
> > > > > > +++ b/drivers/iio/position/Makefile
> > > > > > @@ -5,3 +5,6 @@
> > > > > >  # When adding new entries keep the list in alphabetical
> > > > > > order
> > > > > >  
> > > > > >  obj-$(CONFIG_IQS624_POS)	+= iqs624-pos.o
> > > > > > +
> > > > > > +obj-$(CONFIG_HID_SENSOR_CUSTOM_HINGE) += hid-sensor-custom-
> > > > > > hinge.o    
> > > > > 
> > > > > Alphabetical order preferred.
> > > > >     
> > > > > > +ccflags-y	+= -I$(srctree)/drivers/iio/common/hid-
> > > > > > sensors    
> > > > > 
> > > > > Why?
> > > > >     
> > > > > > diff --git a/drivers/iio/position/hid-sensor-custom-hinge.c
> > > > > > b/drivers/iio/position/hid-sensor-custom-hinge.c
> > > > > > new file mode 100644
> > > > > > index 000000000000..a91b333f36fa
> > > > > > --- /dev/null
> > > > > > +++ b/drivers/iio/position/hid-sensor-custom-hinge.c
> > > > > > @@ -0,0 +1,412 @@
> > > > > > +// 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 "hid-sensor-trigger.h"
> > > > > > +
> > > > > > +/* Channel definitions */
> > > > > > +static const struct iio_chan_spec hinge_channels[] = {
> > > > > > +	{ .type = IIO_ANGL,
> > > > > > +	  .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_type.realbits = 16,
> > > > > > +	  .scan_type.storagebits = 32,    
> > > > > 
> > > > > It a bit odd to see a single channel that is 16 bits inside a
> > > > > 32
> > > > > bit
> > > > > with
> > > > > no shift or similar.  Why not just pack it into 16 bits?
> > > > >     
> > > > > > +	  .scan_type.sign = 's',
> > > > > > +	  .scan_index = 0 },
> > > > > > +
> > > > > > +	IIO_CHAN_SOFT_TIMESTAMP(1)
> > > > > > +};
> > > > > > +
> > > > > > +struct hinge_state {
> > > > > > +	struct iio_dev *indio_dev;
> > > > > > +	struct hid_sensor_hub_attribute_info hinge;
> > > > > > +	/* Reserve for 1 channel + pading + timestamp */
> > > > > > +	u32 hinge_val[1 + 3];    
> > > > > 
> > > > > __aligned(8)
> > > > > 
> > > > > see below for requirements on this.
> > > > > Perhaps better to use
> > > > > 
> > > > > 	struct hinge_scan {
> > > > > 		u32 val;
> > > > > 		s64 timestamp __aligned(8); // Note this is
> > > > > needed for
> > > > > x86_32
> > > > > 	} scan;
> > > > >     
> > > > > > +	int scale_pre_decml;
> > > > > > +	int scale_post_decml;
> > > > > > +	int scale_precision;
> > > > > > +	int value_offset;
> > > > > > +	int64_t timestamp;
> > > > > > +	u32 hinge_address;
> > > > > > +};
> > > > > > +
> > > > > > +#define IIO_DEV_NUM 3    
> > > > > 
> > > > > That needs a prefix to make it clear it's not a generic
> > > > > constant
> > > > > but is specific to this driver.
> > > > >     
> > > > > > +
> > > > > > +struct hinge_group {
> > > > > > +	struct hinge_state *hg_states[IIO_DEV_NUM];
> > > > > > +	struct hid_sensor_hub_callbacks callbacks;
> > > > > > +	struct hid_sensor_common common_attributes;
> > > > > > +};
> > > > > > +
> > > > > > +static struct hinge_group *hg_group;    
> > > > > 
> > > > > We shouldn't see globals like this. Please figure out how to
> > > > > avoid
> > > > > it.
> > > > >     
> > > > > > +
> > > > > > +/* 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 *hg_state = iio_priv(indio_dev);
> > > > > > +	struct hid_sensor_hub_device *hsdev;
> > > > > > +	int report_id = -1;
> > > > > > +	int ret_type;
> > > > > > +	s32 min;
> > > > > > +
> > > > > > +	hsdev = hg_group->common_attributes.hsdev;
> > > > > > +
> > > > > > +	*val = 0;
> > > > > > +	*val2 = 0;
> > > > > > +	switch (mask) {
> > > > > > +	case IIO_CHAN_INFO_RAW:
> > > > > > +		hid_sensor_power_state(&hg_group-  
> > > > > > >common_attributes,  
> > > > > > true);
> > > > > > +		report_id = hg_state->hinge.report_id;
> > > > > > +		min = hg_state->hinge.logical_minimum;
> > > > > > +		if (report_id < 0) {
> > > > > > +			*val = 0;
> > > > > > +			hid_sensor_power_state(&hg_group-    
> > > > > > > common_attributes,    
> > > > > > +					       false);
> > > > > > +			return -EINVAL;
> > > > > > +		}
> > > > > > +
> > > > > > +		*val = sensor_hub_input_attr_get_raw_value(
> > > > > > +			hg_group->common_attributes.hsdev,
> > > > > > hsdev-    
> > > > > > > usage,    
> > > > > > +			hg_state->hinge_address, report_id,
> > > > > > SENSOR_HUB_SYNC,
> > > > > > +			min < 0);
> > > > > > +
> > > > > > +		hid_sensor_power_state(&hg_group-  
> > > > > > >common_attributes,  
> > > > > > false);
> > > > > > +		ret_type = IIO_VAL_INT;
> > > > > > +		break;
> > > > > > +	case IIO_CHAN_INFO_SCALE:
> > > > > > +		*val = hg_state->scale_pre_decml;
> > > > > > +		*val2 = hg_state->scale_post_decml;
> > > > > > +		ret_type = hg_state->scale_precision;
> > > > > > +		break;
> > > > > > +	case IIO_CHAN_INFO_OFFSET:
> > > > > > +		*val = hg_state->value_offset;
> > > > > > +		ret_type = IIO_VAL_INT;
> > > > > > +		break;
> > > > > > +	case IIO_CHAN_INFO_SAMP_FREQ:
> > > > > > +		ret_type = hid_sensor_read_samp_freq_value(
> > > > > > +			&hg_group->common_attributes, val,
> > > > > > val2);
> > > > > > +		break;
> > > > > > +	case IIO_CHAN_INFO_HYSTERESIS:
> > > > > > +		ret_type = hid_sensor_read_raw_hyst_value(
> > > > > > +			&hg_group->common_attributes, val,
> > > > > > val2);
> > > > > > +		break;
> > > > > > +	default:
> > > > > > +		ret_type = -EINVAL;
> > > > > > +		break;
> > > > > > +	}
> > > > > > +
> > > > > > +	return ret_type;
> > > > > > +}
> > > > > > +
> > > > > > +/* 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)
> > > > > > +{
> > > > > > +	int ret;
> > > > > > +
> > > > > > +	switch (mask) {
> > > > > > +	case IIO_CHAN_INFO_SAMP_FREQ:
> > > > > > +		ret = hid_sensor_write_samp_freq_value(
> > > > > > +			&hg_group->common_attributes, val,
> > > > > > val2);
> > > > > > +		break;
> > > > > > +	case IIO_CHAN_INFO_HYSTERESIS:
> > > > > > +		ret = hid_sensor_write_raw_hyst_value(
> > > > > > +			&hg_group->common_attributes, val,
> > > > > > val2);
> > > > > > +
> > > > > > +		break;
> > > > > > +	default:
> > > > > > +		ret = -EINVAL;
> > > > > > +	}
> > > > > > +
> > > > > > +	return ret;
> > > > > > +}
> > > > > > +
> > > > > > +static const struct iio_info hinge_info = {
> > > > > > +	.read_raw = &hinge_read_raw,
> > > > > > +	.write_raw = &hinge_write_raw,
> > > > > > +};
> > > > > > +
> > > > > > +/*
> > > > > > + * Function to push data to buffer;
> > > > > > + * wrapper added for symmetry with other hid-sensor drivers
> > > > > > + */
> > > > > > +static void hid_sensor_push_data(struct iio_dev *indio_dev,
> > > > > > void
> > > > > > *data, int len,    
> > > > > 
> > > > > This doesn't seem to be generic, so don't name it as such.
> > > > >     
> > > > > > +				 int64_t timestamp)
> > > > > > +{
> > > > > > +	iio_push_to_buffers_with_timestamp(indio_dev, data,
> > > > > > timestamp);    
> > > > > I hope that data buffer obeys the various rules needed by (and
> > > > > admittedly
> > > > > not that well documented) iio_push_to_buffers_with_timestamp()
> > > > > 
> > > > > 1. Needs to be 8 byte aligned.
> > > > > 2. Needs to have space for an aligned 8 byte timestamp at the
> > > > > end.
> > > > >     
> > > > > > +}
> > > > > > +
> > > > > > +/*
> > > > > > + * 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)
> > > > > > +{
> > > > > > +	int i;
> > > > > > +
> > > > > > +	for (i = 0; i < IIO_DEV_NUM; ++i) {    
> > > > > If we push for all sensors together, better to have
> > > > > this as a single iio_device with 3 channels.
> > > > > 
> > > > > Use the channel labels (just added to IIO) to identify which is
> > > > > which.
> > > > >     
> > > > > > +		struct hinge_state *hg_state;
> > > > > > +		struct iio_dev *indio_dev;
> > > > > > +
> > > > > > +		hg_state = hg_group->hg_states[i];
> > > > > > +		indio_dev = hg_state->indio_dev;
> > > > > > +
> > > > > > +		dev_dbg(&indio_dev->dev, "%s timestamp:%llu
> > > > > > scan_bytes:%d\n",
> > > > > > +			__func__, hg_state->timestamp,
> > > > > > indio_dev-    
> > > > > > > scan_bytes);    
> > > > > > +
> > > > > > +		if (!hg_state->timestamp)
> > > > > > +			hg_state->timestamp =
> > > > > > iio_get_time_ns(indio_dev);
> > > > > > +
> > > > > > +		hid_sensor_push_data(indio_dev, hg_state-  
> > > > > > >hinge_val,  
> > > > > > +				     sizeof(hg_state-  
> > > > > > >hinge_val),  
> > > > > > +				     hg_state->timestamp);
> > > > > > +
> > > > > > +		hg_state->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 hinge_state *hg_state;
> > > > > > +	int offset;
> > > > > > +	int ret = -EINVAL;
> > > > > > +	int i;
> > > > > > +
> > > > > > +	if (usage_id == HID_USAGE_SENSOR_TIME_TIMESTAMP) {
> > > > > > +		for (i = 0; i < IIO_DEV_NUM; i++)
> > > > > > +			hg_group->hg_states[i]->timestamp =    
> > > > > 
> > > > > This rather implies all the data is captured together... If so
> > > > > single
> > > > > iio_device may make more sense.
> > > > >     
> > > > > > +				hid_sensor_convert_timestamp(
> > > > > > +					&hg_group-  
> > > > > > >common_attributes,  
> > > > > > +					*(int64_t *)raw_data);
> > > > > > +		return 0;
> > > > > > +	}
> > > > > > +
> > > > > > +	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;
> > > > > > +		hg_state = hg_group->hg_states[offset];
> > > > > > +		hg_state->hinge_val[0] = *(u32 *)raw_data;
> > > > > > +		ret = 0;    
> > > > > 
> > > > > 		return 0;
> > > > >     
> > > > > > +		break;
> > > > > > +	default:    
> > > > > 		return -EINVAL;    
> > > > > > +		break;
> > > > > > +	}
> > > > > > +
> > > > > > +	return ret;
> > > > > > +}
> > > > > > +
> > > > > > +/* Parse report which is specific to an usage id */
> > > > > > +static int hinge_parse_report(struct platform_device *pdev,
> > > > > > +			      struct hid_sensor_hub_device
> > > > > > *hsdev,
> > > > > > +			      unsigned int usage_id, unsigned
> > > > > > int
> > > > > > attr_usage_id,
> > > > > > +			      struct hinge_state *st)
> > > > > > +{
> > > > > > +	int ret;
> > > > > > +
> > > > > > +	ret = sensor_hub_input_get_attribute_info(
> > > > > > +		hsdev, HID_INPUT_REPORT, usage_id,
> > > > > > attr_usage_id, &st-    
> > > > > > > hinge);    
> > > > > > +	if (ret < 0)
> > > > > > +		return ret;
> > > > > > +
> > > > > > +	st->hinge_address = attr_usage_id;
> > > > > > +	st->scale_precision =
> > > > > > +		hid_sensor_format_scale(HID_USAGE_SENSOR_HINGE,
> > > > > > &st-    
> > > > > > > hinge,    
> > > > > > +					&st->scale_pre_decml,
> > > > > > +					&st->scale_post_decml);
> > > > > > +
> > > > > > +	/* Set Sensitivity field ids, when there is no
> > > > > > individual
> > > > > > modifier */
> > > > > > +	if (hg_group->common_attributes.sensitivity.index < 0)
> > > > > > {
> > > > > > +		sensor_hub_input_get_attribute_info(
> > > > > > +			hsdev, HID_FEATURE_REPORT, usage_id,
> > > > > > +			HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSIT
> > > > > > IVITY_AB
> > > > > > S |
> > > > > > +				HID_USAGE_SENSOR_DATA_FIELD_CUS
> > > > > > TOM_VALU
> > > > > > E_1,
> > > > > > +			&hg_group-  
> > > > > > >common_attributes.sensitivity);  
> > > > > > +		dev_dbg(&pdev->dev, "Sensitivity index:report
> > > > > > %d:%d\n",
> > > > > > +			hg_group-  
> > > > > > >common_attributes.sensitivity.index,  
> > > > > > +			hg_group-    
> > > > > > > common_attributes.sensitivity.report_id);    
> > > > > > +	}
> > > > > > +
> > > > > > +	return ret;
> > > > > > +}
> > > > > > +
> > > > > > +/* Function to initialize the processing for usage id */
> > > > > > +static int hinge_add_iio_device(struct platform_device
> > > > > > *pdev,
> > > > > > int
> > > > > > index,
> > > > > > +				const char *name, struct
> > > > > > hinge_state
> > > > > > **st)
> > > > > > +{
> > > > > > +	struct hid_sensor_hub_device *hsdev = pdev-  
> > > > > > >dev.platform_data;  
> > > > > > +	struct hinge_state *hg_state;
> > > > > > +	struct iio_dev *indio_dev;
> > > > > > +	int ret;
> > > > > > +
> > > > > > +	indio_dev =
> > > > > > +		devm_iio_device_alloc(&pdev->dev, sizeof(struct
> > > > > > hinge_state));    
> > > > > 
> > > > > sizeof (*hg_state) preferred.
> > > > >     
> > > > > > +	if (indio_dev == NULL)
> > > > > > +		return -ENOMEM;
> > > > > > +
> > > > > > +	hg_state = iio_priv(indio_dev);
> > > > > > +	hg_state->indio_dev = indio_dev;
> > > > > > +
> > > > > > +	indio_dev->num_channels = ARRAY_SIZE(hinge_channels);
> > > > > > +	indio_dev->channels =
> > > > > > +		kmemdup(hinge_channels, sizeof(hinge_channels),
> > > > > > GFP_KERNEL);    
> > > > > 
> > > > > I don't immediately see anything that is modifying channels. As
> > > > > such
> > > > > you
> > > > > should be able have it shared by all the instances.
> > > > >     
> > > > > > +	if (!indio_dev->channels)
> > > > > > +		return -ENOMEM;
> > > > > > +
> > > > > > +	ret = hinge_parse_report(
> > > > > > +		pdev, hsdev, hsdev->usage,
> > > > > > +		HID_USAGE_SENSOR_DATA_FIELD_CUSTOM_VALUE_1 +
> > > > > > index,
> > > > > > hg_state);
> > > > > > +	if (ret) {
> > > > > > +		dev_err(&pdev->dev, "failed to setup
> > > > > > attributes\n");
> > > > > > +		goto error_free_dev_mem;
> > > > > > +	}
> > > > > > +
> > > > > > +	indio_dev->dev.parent = &pdev->dev;
> > > > > > +	indio_dev->info = &hinge_info;
> > > > > > +	indio_dev->name = name;
> > > > > > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > > > > > +
> > > > > > +	ret = hid_sensor_setup_trigger(indio_dev, name,
> > > > > > +				       &hg_group-  
> > > > > > >common_attributes);  
> > > > > > +	if (ret < 0) {
> > > > > > +		dev_err(&pdev->dev, "trigger setup failed\n");
> > > > > > +		goto error_free_dev_mem;
> > > > > > +	}
> > > > > > +
> > > > > > +	ret = iio_device_register(indio_dev);
> > > > > > +	if (ret) {
> > > > > > +		dev_err(&pdev->dev, "device register
> > > > > > failed\n");
> > > > > > +		goto error_remove_trigger;
> > > > > > +	}
> > > > > > +
> > > > > > +	*st = hg_state;
> > > > > > +
> > > > > > +	return ret;
> > > > > > +
> > > > > > +error_remove_trigger:
> > > > > > +	hid_sensor_remove_trigger(indio_dev, &hg_group-    
> > > > > > > common_attributes);    
> > > > > > +error_free_dev_mem:
> > > > > > +	kfree(indio_dev->channels);
> > > > > > +	return ret;
> > > > > > +}
> > > > > > +
> > > > > > +/* Function to deinitialize the processing for usage id */
> > > > > > +static int hinge_remove_iio_device(struct platform_device
> > > > > > *pdev,
> > > > > > int index)
> > > > > > +{
> > > > > > +	struct hinge_state *hg_state = hg_group-  
> > > > > > >hg_states[index];  
> > > > > > +	struct iio_dev *indio_dev = hg_state->indio_dev;
> > > > > > +
> > > > > > +	iio_device_unregister(indio_dev);
> > > > > > +	hid_sensor_remove_trigger(indio_dev, &hg_group-    
> > > > > > > common_attributes);    
> > > > > > +	kfree(indio_dev->channels);
> > > > > > +
> > > > > > +	return 0;
> > > > > > +}
> > > > > > +
> > > > > > +static int hid_hinge_probe(struct platform_device *pdev)
> > > > > > +{
> > > > > > +	struct hinge_state *hg_state;
> > > > > > +	struct hid_sensor_hub_device *hsdev = pdev-  
> > > > > > >dev.platform_data;  
> > > > > > +	static const char *const names[] = { "hinge", "screen",
> > > > > > "keyboard" };
> > > > > > +	int ret;
> > > > > > +	int i;
> > > > > > +
> > > > > > +	hg_group = devm_kzalloc(&pdev->dev, sizeof(struct
> > > > > > hinge_group),
> > > > > > +				GFP_KERNEL);    
> > > > > 
> > > > > As mentioned above, I'd really not expect to see a global like
> > > > > this.
> > > > > Technically nothing stops there being more than one instance of
> > > > > this
> > > > > device on a platform (even if that would be a bit odd) + it's
> > > > > almost
> > > > > always cleaner to not use a global in the first place.
> > > > >     
> > > > > > +	if (!hg_group)
> > > > > > +		return -ENOMEM;
> > > > > > +
> > > > > > +	hg_group->common_attributes.hsdev = hsdev;
> > > > > > +	hg_group->common_attributes.pdev = pdev;
> > > > > > +
> > > > > > +	ret = hid_sensor_parse_common_attributes(hsdev, hsdev-  
> > > > > > >usage,  
> > > > > > +						 &hg_group-    
> > > > > > > common_attributes);    
> > > > > > +	if (ret) {
> > > > > > +		dev_err(&pdev->dev, "failed to setup common
> > > > > > attributes\n");
> > > > > > +		return ret;
> > > > > > +	}
> > > > > > +
> > > > > > +	atomic_set(&hg_group->common_attributes.data_ready, 0);
> > > > > > +	for (i = 0; i < IIO_DEV_NUM; i++) {
> > > > > > +		ret = hinge_add_iio_device(pdev, i, names[i],
> > > > > > &hg_state);
> > > > > > +		if (ret)
> > > > > > +			goto err_probe;
> > > > > > +
> > > > > > +		hg_group->hg_states[i] = hg_state;
> > > > > > +	}
> > > > > > +
> > > > > > +	/* use the first iio device to do the PM */
> > > > > > +	platform_set_drvdata(pdev, hg_group->hg_states[0]-  
> > > > > > >indio_dev);  
> > > > > > +
> > > > > > +	hg_group->callbacks.send_event = hinge_proc_event;
> > > > > > +	hg_group->callbacks.capture_sample =
> > > > > > hinge_capture_sample;
> > > > > > +	hg_group->callbacks.pdev = pdev;
> > > > > > +	ret = sensor_hub_register_callback(hsdev, hsdev->usage,
> > > > > > +					   &hg_group-  
> > > > > > >callbacks);  
> > > > > > +	if (ret < 0)
> > > > > > +		dev_err(&pdev->dev, "callback reg failed\n");
> > > > > > +
> > > > > > +	return ret;
> > > > > > +
> > > > > > +err_probe:
> > > > > > +	for (i--; i >= 0; i--)
> > > > > > +		hinge_remove_iio_device(pdev, i);
> > > > > > +
> > > > > > +	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;  
> > > > > > +	int i;
> > > > > > +
> > > > > > +	sensor_hub_remove_callback(hsdev, hsdev->usage);
> > > > > > +
> > > > > > +	for (i = 0; i < IIO_DEV_NUM; i++)
> > > > > > +		hinge_remove_iio_device(pdev, i);
> > > > > > +
> > > > > > +	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 Custom Hinge");
> > > > > > +MODULE_AUTHOR("Ye Xiang <xiang.ye@intel.com>");
> > > > > > +MODULE_LICENSE("GPL");