From 103d9fb907058e4eb052f4f7302d1b07eb6a7792 Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Tue, 16 Oct 2012 17:29:00 +0100 Subject: 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 Signed-off-by: Jonathan Cameron --- drivers/iio/industrialio-core.c | 5 +++++ drivers/iio/inkern.c | 3 +++ 2 files changed, 8 insertions(+) (limited to 'drivers/iio') diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index 6eb24db..37650a7 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 5230a33..b394621d 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; } -- cgit v1.1