Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756607AbcKCNhE (ORCPT ); Thu, 3 Nov 2016 09:37:04 -0400 Received: from mga11.intel.com ([192.55.52.93]:19330 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbcKCNhD (ORCPT ); Thu, 3 Nov 2016 09:37:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,438,1473145200"; d="scan'208";a="27333853" Message-ID: <1478180219.27477.4.camel@linux.intel.com> Subject: Re: [PATCH] iio: common: hid-sensors: change the precision of scale values From: Srinivas Pandruvada To: "Ooi, Joyce" , Jonathan Cameron Cc: Song Hongyan , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Kweh Hock Leong , Ong Boon Leong , Lay Kuan Loon Date: Thu, 03 Nov 2016 06:36:59 -0700 In-Reply-To: <1478166093-23109-1-git-send-email-joyce.ooi@intel.com> References: <1478166093-23109-1-git-send-email-joyce.ooi@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5972 Lines: 177 On Thu, 2016-11-03 at 17:41 +0800, Ooi, Joyce wrote: > Extension of the scale precision is needed as there are some scale > values > that exceed 6 decimal points precision. For example, the scale for > gyroscope from degrees/second to radians/second is 0.017453. If the > unit > exponent for gyroscope is -5, it will be > 0.017453 -> exp: -5 -> 0.00000017453 > > However, because the decimal precision is up to 6, the mentioned > scale > value will be truncated to 0.000000. To avoid this, changes are made > to > extend the precision to 9 decimal points precision. This change is already submitted by Song Hongyan Thanks, Srinivas > > Signed-off-by: Ooi, Joyce > --- >  .../iio/common/hid-sensors/hid-sensor-attributes.c | 65 +++++++++++- > ---------- >  1 file changed, 33 insertions(+), 32 deletions(-) > > diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > index dc33c1d..c1f8c22 100644 > --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > @@ -30,34 +30,34 @@ >   u32 usage_id; >   int unit; /* 0 for default others from HID sensor spec */ >   int scale_val0; /* scale, whole number */ > - int scale_val1; /* scale, fraction in micros */ > + int scale_val1; /* scale, fraction in nanos */ >  } unit_conversion[] = { > - {HID_USAGE_SENSOR_ACCEL_3D, 0, 9, 806650}, > + {HID_USAGE_SENSOR_ACCEL_3D, 0, 9, 806650000}, >   {HID_USAGE_SENSOR_ACCEL_3D, >   HID_USAGE_SENSOR_UNITS_METERS_PER_SEC_SQRD, 1, 0}, >   {HID_USAGE_SENSOR_ACCEL_3D, > - HID_USAGE_SENSOR_UNITS_G, 9, 806650}, > + HID_USAGE_SENSOR_UNITS_G, 9, 806650000}, >   > - {HID_USAGE_SENSOR_GYRO_3D, 0, 0, 17453}, > + {HID_USAGE_SENSOR_GYRO_3D, 0, 0, 17453293}, >   {HID_USAGE_SENSOR_GYRO_3D, >   HID_USAGE_SENSOR_UNITS_RADIANS_PER_SECOND, 1, 0}, >   {HID_USAGE_SENSOR_GYRO_3D, > - HID_USAGE_SENSOR_UNITS_DEGREES_PER_SECOND, 0, > 17453}, > + HID_USAGE_SENSOR_UNITS_DEGREES_PER_SECOND, 0, > 17453293}, >   > - {HID_USAGE_SENSOR_COMPASS_3D, 0, 0, 1000}, > + {HID_USAGE_SENSOR_COMPASS_3D, 0, 0, 1000000}, >   {HID_USAGE_SENSOR_COMPASS_3D, HID_USAGE_SENSOR_UNITS_GAUSS, > 1, 0}, >   > - {HID_USAGE_SENSOR_INCLINOMETER_3D, 0, 0, 17453}, > + {HID_USAGE_SENSOR_INCLINOMETER_3D, 0, 0, 17453293}, >   {HID_USAGE_SENSOR_INCLINOMETER_3D, > - HID_USAGE_SENSOR_UNITS_DEGREES, 0, 17453}, > + HID_USAGE_SENSOR_UNITS_DEGREES, 0, 17453293}, >   {HID_USAGE_SENSOR_INCLINOMETER_3D, >   HID_USAGE_SENSOR_UNITS_RADIANS, 1, 0}, >   >   {HID_USAGE_SENSOR_ALS, 0, 1, 0}, >   {HID_USAGE_SENSOR_ALS, HID_USAGE_SENSOR_UNITS_LUX, 1, 0}, >   > - {HID_USAGE_SENSOR_PRESSURE, 0, 100, 0}, > - {HID_USAGE_SENSOR_PRESSURE, HID_USAGE_SENSOR_UNITS_PASCAL, > 0, 1000}, > + {HID_USAGE_SENSOR_PRESSURE, 0, 100000, 0}, > + {HID_USAGE_SENSOR_PRESSURE, HID_USAGE_SENSOR_UNITS_PASCAL, > 0, 1000000}, >  }; >   >  static int pow_10(unsigned power) > @@ -266,16 +266,16 @@ int hid_sensor_write_raw_hyst_value(struct > hid_sensor_common *st, >  /* >   * This fuction applies the unit exponent to the scale. >   * For example: > - * 9.806650 ->exp:2-> val0[980]val1[665000] > - * 9.000806 ->exp:2-> val0[900]val1[80600] > - * 0.174535 ->exp:2-> val0[17]val1[453500] > - * 1.001745 ->exp:0-> val0[1]val1[1745] > - * 1.001745 ->exp:2-> val0[100]val1[174500] > - * 1.001745 ->exp:4-> val0[10017]val1[450000] > - * 9.806650 ->exp:-2-> val0[0]val1[98066] > + * 9.806650000 ->exp:2-> val0[980]val1[665000000] > + * 9.000806000 ->exp:2-> val0[900]val1[80600000] > + * 0.17453293 ->exp:2-> val0[17]val1[453293000] > + * 1.00174532 ->exp:0-> val0[1]val1[1745320] > + * 1.00174532 ->exp:2-> val0[100]val1[174532000] > + * 1.00174532 ->exp:4-> val0[10017]val1[453200000] > + * 9.80665000 ->exp:-2-> val0[0]val1[98066500] >   */ > -static void adjust_exponent_micro(int *val0, int *val1, int scale0, > -   int scale1, int exp) > +static void adjust_exponent_nano(int *val0, int *val1, int scale0, > +  int scale1, int exp) >  { >   int i; >   int x; > @@ -285,32 +285,32 @@ static void adjust_exponent_micro(int *val0, > int *val1, int scale0, >   if (exp > 0) { >   *val0 = scale0 * pow_10(exp); >   res = 0; > - if (exp > 6) { > + if (exp > 9) { >   *val1 = 0; >   return; >   } >   for (i = 0; i < exp; ++i) { > - x = scale1 / pow_10(5 - i); > + x = scale1 / pow_10(8 - i); >   res += (pow_10(exp - 1 - i) * x); > - scale1 = scale1 % pow_10(5 - i); > + scale1 = scale1 % pow_10(8 - i); >   } >   *val0 += res; >   *val1 = scale1 * pow_10(exp); >   } else if (exp < 0) { >   exp = abs(exp); > - if (exp > 6) { > + if (exp > 9) { >   *val0 = *val1 = 0; >   return; >   } >   *val0 = scale0 / pow_10(exp); >   rem = scale0 % pow_10(exp); >   res = 0; > - for (i = 0; i < (6 - exp); ++i) { > - x = scale1 / pow_10(5 - i); > - res += (pow_10(5 - exp - i) * x); > - scale1 = scale1 % pow_10(5 - i); > + for (i = 0; i < (9 - exp); ++i) { > + x = scale1 / pow_10(8 - i); > + res += (pow_10(8 - exp - i) * x); > + scale1 = scale1 % pow_10(8 - i); >   } > - *val1 = rem * pow_10(6 - exp) + res; > + *val1 = rem * pow_10(9 - exp) + res; >   } else { >   *val0 = scale0; >   *val1 = scale1; > @@ -332,14 +332,15 @@ int hid_sensor_format_scale(u32 usage_id, >   unit_conversion[i].unit == attr_info->units) > { >   exp  = hid_sensor_convert_exponent( >   attr_info- > >unit_expo); > - adjust_exponent_micro(val0, val1, > - unit_conversion[i].scale_val > 0, > - unit_conversion[i].scale_val > 1, exp); > + adjust_exponent_nano(val0, val1, > +      unit_conversion[i].scal > e_val0, > +      unit_conversion[i].scal > e_val1, > +      exp); >   break; >   } >   } >   > - return IIO_VAL_INT_PLUS_MICRO; > + return IIO_VAL_INT_PLUS_NANO; >  } >  EXPORT_SYMBOL(hid_sensor_format_scale); >