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Date:   Tue, 24 Nov 2020 11:30:50 +0800
From:   "Ye, Xiang" <xiang.ye@intel.com>
To:     Jonathan Cameron <jic23@kernel.org>,
        srinivas.pandruvada@linux.intel.com
Cc:     jikos@kernel.org, jic23@kernel.org, linux-input@vger.kernel.org,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        even.xu@intel.com
Subject: Re: [PATCH v2 4/4] iio: hid-sensors: Add hinge sensor driver
Message-ID: <20201124033050.GA14328@host>
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>
 <20201122165047.3ceae561@archlinux>
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On Sun, Nov 22, 2020 at 04:50:47PM +0000, Jonathan Cameron wrote:
> 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
@Srinivas
Yes, I will try this indexed channel and label based method.

@Jonathan
So, I need to add in_angl0_raw, in_angl1_raw, in_angl2_raw and in_angl0_label,
in_angl1_label,in_angl2_label description in sysfs-bus-iio. such as

What:		/sys/bus/iio/devices/iio:deviceX/in_angl0_raw
What:		/sys/bus/iio/devices/iio:deviceX/in_angl1_raw
What:		/sys/bus/iio/devices/iio:deviceX/in_angl2_raw
KernelVersion:	5.12
Contact:	linux-iio@vger.kernel.org
Description:
		Angle of rotation. Units after application of scale and offset
		are radians.

What:		/sys/bus/iio/devices/iio:deviceX/in_angl0_label
What:		/sys/bus/iio/devices/iio:deviceX/in_angl1_label
What:		/sys/bus/iio/devices/iio:deviceX/in_angl2_label
KernelVersion:	5.12
Contact:	linux-iio@vger.kernel.org
Description:
		Optional symbolic label to a device channel.


Am i right?

> 
> 
> 
> > 
> > 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");    
>