linux-kernel - RE: [PATCH V1]iio: adc: spmi-vadc: Changes to support different scaling

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Date:   Wed, 26 Oct 2016 15:47:17 +0530
From:   "Sricharan" <sricharan@...eaurora.org>
To:     "'Phani A, Rama Krishna'" <rphani@...eaurora.org>,
        <linux-iio@...r.kernel.org>, <jic23@...nel.org>
Cc:     <linux-arm-msm@...r.kernel.org>, <smohanad@...eaurora.org>,
        <mgautam@...eaurora.org>, "'Hartmut Knaack'" <knaack.h@....de>,
        "'Lars-Peter Clausen'" <lars@...afoo.de>,
        "'Peter Meerwald-Stadler'" <pmeerw@...erw.net>,
        "'Julia Lawall'" <Julia.Lawall@...6.fr>,
        "'open list'" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V1]iio: adc: spmi-vadc: Changes to support different scaling

Hi Ramakrishna,

[snip..]

>>> +	u32 i = 0;
>>> +
>>> +	if (!pts)
>>> +		return -EINVAL;
>>> +
>>> +	/* Check if table is descending or ascending */
>>> +	if (tablesize > 1) {
>>> +		if (pts[0].x < pts[1].x)
>>> +			descending = 0;
>>> +	}
>>> +
>>> +	while (i < tablesize) {
>>> +		if ((descending == 1) && (pts[i].x < input)) {
>>
>>          Just if (descending) instead of (descending == 1) and so on for the below as well
>
>	Will change in next patch.
>
>>
>>> +			/* table entry is less than measured*/
>>> +			 /* value and table is descending, stop */
>>> +			break;
>>> +		} else if ((descending == 0) &&
>>> +				(pts[i].x > input)) {
>>> +			/* table entry is greater than measured*/
>>> +			/*value and table is ascending, stop */
>>> +			break;
>>> +		}
>>> +		i++;
>>> +	}
>>> +
>>> +	if (i == 0) {
>>> +		*output = pts[0].y;
>>> +	} else if (i == tablesize) {
>>> +		*output = pts[tablesize - 1].y;
>>> +	} else {
>>> +		/* result is between search_index and search_index-1 */
>>> +		/* interpolate linearly */
>>> +		*output = (((s32)((pts[i].y - pts[i - 1].y) *
>>> +			(input - pts[i - 1].x)) /
>>> +			(pts[i].x - pts[i - 1].x)) +
>>> +			pts[i - 1].y);
>>> +	}
>>
>>                hmm, so for descending, input - pts[i -1].x is negative and
>>                we are adding that to pts[i-1].y, is that correct ?
>
>		The formula used is to interpolate between two points 	using linear
>interpolation.

 Right, agree. my question can be ignored.

[snip..]

>>> #define VADC_CHAN_TEMP(_dname, _pre)					\
>>> -	VADC_CHAN(_dname, IIO_TEMP, BIT(IIO_CHAN_INFO_PROCESSED), _pre)	\
>>> +	VADC_CHAN(_dname, IIO_TEMP,	\
>>> +		BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_PROCESSED), \
>>> +		_pre)	\
>>>
>>> #define VADC_CHAN_VOLT(_dname, _pre)					\
>>> -	VADC_CHAN(_dname, IIO_VOLTAGE,					\
>>> -		  BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),	\
>>> +	VADC_CHAN(_dname, IIO_VOLTAGE,				\
>>> +		  BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_PROCESSED),\
>>> 		  _pre)							\
>>>
>>   For this and the below changes to VADC_CHAN_VOLT to TEMP, why is that done ?
>>    Now both macros are setting the same flags.
>
>	For Voltage channels IIO_VOLTAGE is needed where as for Temperature
>channels IIO_TEMP is needed.
>
>>
>>> /*
>>> @@ -637,12 +811,11 @@ struct vadc_channels {
>>> 	VADC_CHAN_TEMP(DIE_TEMP, 0)
>>> 	VADC_CHAN_VOLT(REF_625MV, 0)
>>> 	VADC_CHAN_VOLT(REF_1250MV, 0)
>>> -	VADC_CHAN_VOLT(CHG_TEMP, 0)
>>> +	VADC_CHAN_TEMP(CHG_TEMP, 0)
>>> 	VADC_CHAN_VOLT(SPARE1, 0)
>>> 	VADC_CHAN_VOLT(SPARE2, 0)
>>> 	VADC_CHAN_VOLT(GND_REF, 0)
>>> 	VADC_CHAN_VOLT(VDD_VADC, 0)
>>> -

And also looks like the deletion of these and below 
new lines are unnecessary ?

Regards,
 Sricharan