From 7985e7c1003bc5cdfa20755f8cfdada946ed8e18 Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Fri, 14 Sep 2012 16:21:00 +0100 Subject: iio: Introduce a new fractional value type Currently IIO uses a decimal fixed point representations for real type numbers. This patch introduces a new representation for rational type numbers. The number will be expressed by specifying a numerator and denominator. For converting a raw value to a processed value multiply it by the numerator and divide it by the denominator. The reasoning for introducing this new type is that for a lot of devices the scale can be represented easily by a fractional number, but it is not possible to represent it as fixed point number without rounding. E.g. for a simple DAC the scale is often the reference voltage divided by the number of possible values (Usually 2**n_bits - 1). Each driver currently implements the conversion of this fraction to a fixed point number on its own. Also when it comes to the in-kernel interface this allows to directly use the fractional factors to convert a raw value to a processed value. This should on one hand require less instructions and on the other hand increase the precision. Signed-off-by: Lars-Peter Clausen Signed-off-by: Jonathan Cameron diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index 0499330..6eb24db 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -366,6 +366,7 @@ static ssize_t iio_read_channel_info(struct device *dev, { struct iio_dev *indio_dev = dev_to_iio_dev(dev); struct iio_dev_attr *this_attr = to_iio_dev_attr(attr); + unsigned long long tmp; int val, val2; bool scale_db = false; int ret = indio_dev->info->read_raw(indio_dev, this_attr->c, @@ -391,6 +392,11 @@ static ssize_t iio_read_channel_info(struct device *dev, return sprintf(buf, "-%d.%09u\n", val, -val2); else return sprintf(buf, "%d.%09u\n", val, val2); + case IIO_VAL_FRACTIONAL: + tmp = div_s64((s64)val * 1000000000LL, val2); + val2 = do_div(tmp, 1000000000LL); + val = tmp; + return sprintf(buf, "%d.%09u\n", val, val2); default: return 0; } diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h index 44e3977..5c647ec 100644 --- a/include/linux/iio/types.h +++ b/include/linux/iio/types.h @@ -57,5 +57,6 @@ enum iio_modifier { #define IIO_VAL_INT_PLUS_MICRO 2 #define IIO_VAL_INT_PLUS_NANO 3 #define IIO_VAL_INT_PLUS_MICRO_DB 4 +#define IIO_VAL_FRACTIONAL 10 #endif /* _IIO_TYPES_H_ */ -- cgit v0.10.2