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authorLars-Peter Clausen <lars@metafoo.de>2012-09-14 19:21:00 +0400
committerJonathan Cameron <jic23@kernel.org>2012-09-15 13:12:22 +0400
commit7985e7c1003bc5cdfa20755f8cfdada946ed8e18 (patch)
tree94adb3cf91ec3406361c2bc9d0c66485e1bf2436 /drivers/iio
parentca7d1b32d2a0d4c62533b9401cf9ce4d14d183f7 (diff)
downloadlinux-7985e7c1003bc5cdfa20755f8cfdada946ed8e18.tar.xz
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 <lars@metafoo.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'drivers/iio')
-rw-r--r--drivers/iio/industrialio-core.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 0499330d6e98..6eb24dbc081e 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;
}