| Message ID | 20220626122938.582107-12-jic23@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v3,01/17] iio: core: Increase precision of IIO_VAL_FRACTIONAL_LOG2 when possible | expand |
On Sun, Jun 26, 2022 at 2:20 PM Jonathan Cameron <jic23@kernel.org> wrote: > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > Address an ABI gap for device where the offset of both lines in a > differential pair may be controlled so as to allow a wider range of > inputs, but without having any direct effect of the differential > measurement. > > _offset cannot be used as to remain in line with existing usage, > userspace would be expected to apply it as (_raw + _offset) * _scale > whereas _zeropoint is not. i.e. If we were computing the differential > in software it would be. > ((postive_raw + _zeropoint) - (negative_raw + zeropoint) + _offset) * _scale > = ((postive_raw - negative_raw) + _offset) * _scale > = (differential_raw + _offset) * _scale > > Similarly calibbias is expected to tweak the measurement seen, not > the adjust the two lines of the differential pair. > > Needed for in_capacitanceX-capacitanceY_zeropoint for the > AD7746 CDC driver. ... > +What: /sys/.../iio:deviceX/in_capacitanceY-capacitanceZ_zeropoint > +KernelVersion: 5.19 5.20? > +Contact: linux-iio@vger.kernel.org > +Description: > + For differential channels, this an offset that is applied > + equally to both inputs. As the reading is of the difference > + between the two inputs, this should not be applied to the _raw > + reading by userspace (unlike _offset) and unlike calibbias > + it does not affect the differential value measured because > + the effect of _zeropoint cancels out across the two inputs > + that make up the differential pair. It's purpose is to bring makes > + the individual signals, before the differential is measured, > + within the measurement range of the device. The naming is > + chosen because if the separate inputs that make the > + differential pair are drawn on a graph in their > + _raw units, this is the value that the zero point on the > + measurement axis represents. It is expressed with the > + same scaling as _raw.
On Tue, 28 Jun 2022 14:17:33 +0200 Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Sun, Jun 26, 2022 at 2:20 PM Jonathan Cameron <jic23@kernel.org> wrote: > > > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > > > Address an ABI gap for device where the offset of both lines in a > > differential pair may be controlled so as to allow a wider range of > > inputs, but without having any direct effect of the differential > > measurement. > > > > _offset cannot be used as to remain in line with existing usage, > > userspace would be expected to apply it as (_raw + _offset) * _scale > > whereas _zeropoint is not. i.e. If we were computing the differential > > in software it would be. > > ((postive_raw + _zeropoint) - (negative_raw + zeropoint) + _offset) * _scale > > = ((postive_raw - negative_raw) + _offset) * _scale > > = (differential_raw + _offset) * _scale > > > > Similarly calibbias is expected to tweak the measurement seen, not > > the adjust the two lines of the differential pair. > > > > Needed for in_capacitanceX-capacitanceY_zeropoint for the > > AD7746 CDC driver. > > ... > > > +What: /sys/.../iio:deviceX/in_capacitanceY-capacitanceZ_zeropoint > > +KernelVersion: 5.19 > > 5.20? :) Probably 5.21 as I'm not going to rush this in now, but good point none the less. > > > +Contact: linux-iio@vger.kernel.org > > +Description: > > + For differential channels, this an offset that is applied > > + equally to both inputs. As the reading is of the difference > > + between the two inputs, this should not be applied to the _raw > > + reading by userspace (unlike _offset) and unlike calibbias > > + it does not affect the differential value measured because > > + the effect of _zeropoint cancels out across the two inputs > > + that make up the differential pair. It's purpose is to bring > > makes No. make is correct. That's indeed an odd corner of English and honestly I'm not sure I could successfully argue why it should be make :) > > > + the individual signals, before the differential is measured, > > + within the measurement range of the device. The naming is > > + chosen because if the separate inputs that make the > > + differential pair are drawn on a graph in their > > + _raw units, this is the value that the zero point on the > > + measurement axis represents. It is expressed with the > > + same scaling as _raw. >
On Mon, 18 Jul 2022 19:02:35 +0100 Jonathan Cameron <jic23@kernel.org> wrote: > On Tue, 28 Jun 2022 14:17:33 +0200 > Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > > > On Sun, Jun 26, 2022 at 2:20 PM Jonathan Cameron <jic23@kernel.org> wrote: > > > > > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > > > > > Address an ABI gap for device where the offset of both lines in a > > > differential pair may be controlled so as to allow a wider range of > > > inputs, but without having any direct effect of the differential > > > measurement. > > > > > > _offset cannot be used as to remain in line with existing usage, > > > userspace would be expected to apply it as (_raw + _offset) * _scale > > > whereas _zeropoint is not. i.e. If we were computing the differential > > > in software it would be. > > > ((postive_raw + _zeropoint) - (negative_raw + zeropoint) + _offset) * _scale > > > = ((postive_raw - negative_raw) + _offset) * _scale > > > = (differential_raw + _offset) * _scale > > > > > > Similarly calibbias is expected to tweak the measurement seen, not > > > the adjust the two lines of the differential pair. > > > > > > Needed for in_capacitanceX-capacitanceY_zeropoint for the > > > AD7746 CDC driver. > > > > ... > > > > > +What: /sys/.../iio:deviceX/in_capacitanceY-capacitanceZ_zeropoint > > > +KernelVersion: 5.19 > > > > 5.20? > > :) Probably 5.21 as I'm not going to rush this in now, but good point none the less. 6.0 I guess :) Anyhow I've applied this with Andy's tag on the assumption that the below English quirk is fine by Andy. Jonathan > > > > > > +Contact: linux-iio@vger.kernel.org > > > +Description: > > > + For differential channels, this an offset that is applied > > > + equally to both inputs. As the reading is of the difference > > > + between the two inputs, this should not be applied to the _raw > > > + reading by userspace (unlike _offset) and unlike calibbias > > > + it does not affect the differential value measured because > > > + the effect of _zeropoint cancels out across the two inputs > > > + that make up the differential pair. It's purpose is to bring > > > > makes > > No. make is correct. > That's indeed an odd corner of English and honestly I'm not sure I could successfully > argue why it should be make :) > > > > > > + the individual signals, before the differential is measured, > > > + within the measurement range of the device. The naming is > > > + chosen because if the separate inputs that make the > > > + differential pair are drawn on a graph in their > > > + _raw units, this is the value that the zero point on the > > > + measurement axis represents. It is expressed with the > > > + same scaling as _raw. > > >
On Sun, 7 Aug 2022 14:46:51 +0100 Jonathan Cameron <jic23@kernel.org> wrote: > On Mon, 18 Jul 2022 19:02:35 +0100 > Jonathan Cameron <jic23@kernel.org> wrote: > > > On Tue, 28 Jun 2022 14:17:33 +0200 > > Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > > > > > On Sun, Jun 26, 2022 at 2:20 PM Jonathan Cameron <jic23@kernel.org> wrote: > > > > > > > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > > > > > > > Address an ABI gap for device where the offset of both lines in a > > > > differential pair may be controlled so as to allow a wider range of > > > > inputs, but without having any direct effect of the differential > > > > measurement. > > > > > > > > _offset cannot be used as to remain in line with existing usage, > > > > userspace would be expected to apply it as (_raw + _offset) * _scale > > > > whereas _zeropoint is not. i.e. If we were computing the differential > > > > in software it would be. > > > > ((postive_raw + _zeropoint) - (negative_raw + zeropoint) + _offset) * _scale > > > > = ((postive_raw - negative_raw) + _offset) * _scale > > > > = (differential_raw + _offset) * _scale > > > > > > > > Similarly calibbias is expected to tweak the measurement seen, not > > > > the adjust the two lines of the differential pair. > > > > > > > > Needed for in_capacitanceX-capacitanceY_zeropoint for the > > > > AD7746 CDC driver. > > > > > > ... > > > > > > > +What: /sys/.../iio:deviceX/in_capacitanceY-capacitanceZ_zeropoint > > > > +KernelVersion: 5.19 > > > > > > 5.20? > > > > :) Probably 5.21 as I'm not going to rush this in now, but good point none the less. > 6.0 I guess :) Anyhow I've applied this with Andy's tag on the assumption that the below > English quirk is fine by Andy. 6.1. As sounds like Linus will tag this merge window as 6.0 and this is being queued for the next one. oops. > > Jonathan > > > > > > > > > > +Contact: linux-iio@vger.kernel.org > > > > +Description: > > > > + For differential channels, this an offset that is applied > > > > + equally to both inputs. As the reading is of the difference > > > > + between the two inputs, this should not be applied to the _raw > > > > + reading by userspace (unlike _offset) and unlike calibbias > > > > + it does not affect the differential value measured because > > > > + the effect of _zeropoint cancels out across the two inputs > > > > + that make up the differential pair. It's purpose is to bring > > > > > > makes > > > > No. make is correct. > > That's indeed an odd corner of English and honestly I'm not sure I could successfully > > argue why it should be make :) > > > > > > > > > + the individual signals, before the differential is measured, > > > > + within the measurement range of the device. The naming is > > > > + chosen because if the separate inputs that make the > > > > + differential pair are drawn on a graph in their > > > > + _raw units, this is the value that the zero point on the > > > > + measurement axis represents. It is expressed with the > > > > + same scaling as _raw. > > > > > >
diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio index d3a0c0ef8948..1dfd6c3f2bd0 100644 --- a/Documentation/ABI/testing/sysfs-bus-iio +++ b/Documentation/ABI/testing/sysfs-bus-iio @@ -204,6 +204,25 @@ Description: is required is a consistent labeling. Units after application of scale and offset are nanofarads. +What: /sys/.../iio:deviceX/in_capacitanceY-capacitanceZ_zeropoint +KernelVersion: 5.19 +Contact: linux-iio@vger.kernel.org +Description: + For differential channels, this an offset that is applied + equally to both inputs. As the reading is of the difference + between the two inputs, this should not be applied to the _raw + reading by userspace (unlike _offset) and unlike calibbias + it does not affect the differential value measured because + the effect of _zeropoint cancels out across the two inputs + that make up the differential pair. It's purpose is to bring + the individual signals, before the differential is measured, + within the measurement range of the device. The naming is + chosen because if the separate inputs that make the + differential pair are drawn on a graph in their + _raw units, this is the value that the zero point on the + measurement axis represents. It is expressed with the + same scaling as _raw. + What: /sys/bus/iio/devices/iio:deviceX/in_temp_raw What: /sys/bus/iio/devices/iio:deviceX/in_tempX_raw What: /sys/bus/iio/devices/iio:deviceX/in_temp_x_raw diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index 8225d0c43010..fbd7d6bd6f98 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -169,6 +169,7 @@ static const char * const iio_chan_info_postfix[] = { [IIO_CHAN_INFO_OVERSAMPLING_RATIO] = "oversampling_ratio", [IIO_CHAN_INFO_THERMOCOUPLE_TYPE] = "thermocouple_type", [IIO_CHAN_INFO_CALIBAMBIENT] = "calibambient", + [IIO_CHAN_INFO_ZEROPOINT] = "zeropoint", }; /** * iio_device_id() - query the unique ID for the device diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h index a7aa91f3a8dc..27143b03909d 100644 --- a/include/linux/iio/types.h +++ b/include/linux/iio/types.h @@ -63,6 +63,7 @@ enum iio_chan_info_enum { IIO_CHAN_INFO_OVERSAMPLING_RATIO, IIO_CHAN_INFO_THERMOCOUPLE_TYPE, IIO_CHAN_INFO_CALIBAMBIENT, + IIO_CHAN_INFO_ZEROPOINT, }; #endif /* _IIO_TYPES_H_ */