Re: [PATCH 2/3] hid-sensor-common: Add relative sensitivity check

[Srinivas Pandruvada]

On Sun, 2021-01-31 at 11:26 +0000, Jonathan Cameron wrote:
> On Fri, 29 Jan 2021 00:35:49 +0800
> "Ye, Xiang" <xiang.ye@xxxxxxxxx> wrote:
> 
> > Hi Srinivas andd Jonathan
> > 
> > Thanks for the review.
> > 
> > On Sun, Jan 24, 2021 at 08:20:12AM -0800, Srinivas Pandruvada
> > wrote:
> > > On Sun, 2021-01-24 at 13:14 +0000, Jonathan Cameron wrote:  
> > > > On Wed, 20 Jan 2021 15:47:05 +0800
> > > > Ye Xiang <xiang.ye@xxxxxxxxx> wrote:
> > > >   
> > > > > Some hid sensors may use relative sensitivity such as als
> > > > > sensor.
> > > > > This patch add relative sensitivity check for all hid-
> > > > > sensors.
> > > > > 
> > > > > Signed-off-by: Ye Xiang <xiang.ye@xxxxxxxxx>
> > > > > ---
> > > > >  .../iio/common/hid-sensors/hid-sensor-attributes.c    | 11
> > > > > ++++++++++-
> > > > >  include/linux/hid-sensor-ids.h                        |  1 +
> > > > >  2 files changed, 11 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/iio/common/hid-sensors/hid-sensor-
> > > > > attributes.c 
> > > > > b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > > > index d349ace2e33f..b685c292a179 100644
> > > > > --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > > > +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > > > @@ -480,7 +480,7 @@ int
> > > > > hid_sensor_parse_common_attributes(struct
> > > > > hid_sensor_hub_device *hsdev,
> > > > >  
> > > > >  	/*
> > > > >  	 * Set Sensitivity field ids, when there is no
> > > > > individualsha512sum
> > > > > modifier, will
> > > > > -	 * check absolute sensitivity of data field
> > > > > +	 * check absolute sensitivity and relative sensitivity
> > > > > of data
> > > > > field
> > > > >  	 */
> > > > >  	for (i = 0; i < sensitivity_addresses_len && st-  
> > > > > > sensitivity.index < 0; i++) {  
> > > > >  		sensor_hub_input_get_attribute_info(hsdev,
> > > > > @@ -488,6 +488,15 @@ int
> > > > > hid_sensor_parse_common_attributes(struct
> > > > > hid_sensor_hub_device *hsdev,
> > > > >  				HID_USAGE_SENSOR_DATA_MOD_CHANG
> > > > > E_SENSIT
> > > > > IVITY_ABS |
> > > > >  					sensitivity_addresses[i
> > > > > ],
> > > > >  				&st->sensitivity);
> > > > > +
> > > > > +		if (st->sensitivity.index >= 0)
> > > > > +			break;
> > > > > +
> > > > > +		sensor_hub_input_get_attribute_info(hsdev,
> > > > > +				HID_FEATURE_REPORT, usage_id,
> > > > > +				HID_USAGE_SENSOR_DATA_MOD_CHANG
> > > > > E_SENSIT
> > > > > IVITY_REL_PCT |
> > > > > +					sensitivity_addresses[i
> > > > > ],
> > > > > +				&st->sensitivity);  
> > > > 
> > > > We can't provide the value to userspace without reflecting the
> > > > difference between
> > > > the two ways of expressing it.
> > > > 
> > > > It seems there are 3 ways sensitivity is expressed.
> > > > 1. Raw value in same units as the measurement (easy one and
> > > > what is
> > > > currently reported)
> > > > 2. Percentage of range - also relatively easy to transform into
> > > > the
> > > > same as 1.
> > > > 3. Percentage of prior reading..  This one doesn't fit in any
> > > > existing ABI, so
> > > >    unfortunately we'll have to invent something new along the
> > > > lines
> > > > of
> > > >    *_hysteresis_relative   
> > 
> > yes, the 3th version sensitivity (Percentage of prior reading) is
> > what we 
> > are using for als sensor now. the 1th version sensitivity is common
> > used 
> > by other hid sensors. Do you have suggestion or reference about 
> > how to add *_hysteresis_relative field to iio model?
> 
> Follow through how elements of iio_chan_info_enum in
> include/linux/iio/types.h are used and you should see how to add a
> new
> one (basically add an entry to that and also the string to the
> right array in industrialio-core.c + document it in
> Documentation/ABI/testing/sysfs-bus-iio.
> 
> The issue with putting this in is we are going to be 'fixing' the ABI
> for
> that ALS sensor which is going to cause problems for any userspace
> users
> of that interface... I have no idea how commonly this is used, but it
> is
> possible we'll have to leave that one as incorrect :(
Currently we don't have relative usage id treatment, So user space gets
error in read/write for ALS. So I think it shouldn't be a problem.

Thanks,
Srinivas

> 
> > > This is why it was not added before when I developed.  But later
> > > few
> > > years back there was a patch to add this by one of our developer.
> > > There
> > > was some discussion, I thought it was decided it is OK to add.
> > > 
> > > But I agree, we should add new ABI as you suggested. Now almost
> > > every
> > > laptop has HID sensors, better to address this. 
> > >   
> > 
> > I think the add relative hystersis patch should be separated into a
> > independent
> > patch series, for it's a independent function and need more effort
> > for coding and 
> > testing. And I can submit the other two patch in this patch series
> > first.
> 
> Sure, if they are independent that should be fine.
> 
> Thanks,
> 
> Jonathan
> 
> > > > 
> > > >   
> > > > >  	}
> > > > >  
> > > > >  	st->raw_hystersis = -1;
> > > > > diff --git a/include/linux/hid-sensor-ids.h
> > > > > b/include/linux/hid-
> > > > > sensor-ids.h
> > > > > index 3bbdbccc5805..ac631159403a 100644
> > > > > --- a/include/linux/hid-sensor-ids.h
> > > > > +++ b/include/linux/hid-sensor-ids.h
> > > > > @@ -149,6 +149,7 @@
> > > > >  /* Per data field properties */
> > > > >  #define HID_USAGE_SENSOR_DATA_MOD_NONE			
> > > > > 	
> > > > > 	0x00
> > > > >  #define HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_ABS	
> > > > > 	
> > > > > 0x1000
> > > > > +#define
> > > > > HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_REL_PCT         
> > > > >    0xE
> > > > > 000
> > > > >  
> > > > >  /* Power state enumerations */
> > > > >  #define HID_USAGE_SENSOR_PROP_POWER_STATE_UNDEFINED_ENUM	
> > > > > 0x20085
> > > > > 0  
> > >