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authorLars-Peter Clausen <lars@metafoo.de>2012-10-16 20:29:00 +0400
committerJonathan Cameron <jic23@kernel.org>2012-10-19 21:46:51 +0400
commit103d9fb907058e4eb052f4f7302d1b07eb6a7792 (patch)
tree8ab834da14137f068195eb30660ffdd19f41acdd /drivers/iio
parent948ad20504894436c008c8a50f74e277edeff9a1 (diff)
downloadlinux-103d9fb907058e4eb052f4f7302d1b07eb6a7792.tar.xz
iio: Add a logarithmic fractional value type
For ADCs or DACs the denominator for fractional types often is a power of two. In this case we can use a shift operation instead of the rather expensive 64 bit division. This patch adds a new fractional type which expects the denominator to be specified as the log2 of the actual denominator. E.g. for ADCs and DACs this will usually be the number of significant bits. 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.c5
-rw-r--r--drivers/iio/inkern.c3
2 files changed, 8 insertions, 0 deletions
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 6eb24dbc081e..37650a72b31f 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -397,6 +397,11 @@ static ssize_t iio_read_channel_info(struct device *dev,
val2 = do_div(tmp, 1000000000LL);
val = tmp;
return sprintf(buf, "%d.%09u\n", val, val2);
+ case IIO_VAL_FRACTIONAL_LOG2:
+ tmp = (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/drivers/iio/inkern.c b/drivers/iio/inkern.c
index 5230a33886c0..b394621d362c 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -314,6 +314,9 @@ static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
*processed = div_s64(raw64 * (s64)scale_val * scale,
scale_val2);
break;
+ case IIO_VAL_FRACTIONAL_LOG2:
+ *processed = (raw64 * (s64)scale_val * scale) >> scale_val2;
+ break;
default:
return -EINVAL;
}