Hi Peter,
Le ven., juil. 22 2022 at 00:16:36 +0200, Peter Rosin <peda@xxxxxxxxxx>
a écrit :
Hi!
2022-07-21 at 21:15, Paul Cercueil wrote:
Implement write_raw by converting the value if writing the scale, or
just calling the managed channel driver's write_raw otherwise.
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
---
drivers/iio/afe/iio-rescale.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/drivers/iio/afe/iio-rescale.c
b/drivers/iio/afe/iio-rescale.c
index 5c9970b93384..0edb62ee4508 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -141,6 +141,27 @@ int rescale_process_offset(struct rescale
*rescale, int scale_type,
}
}
+static int rescale_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct rescale *rescale = iio_priv(indio_dev);
+ unsigned long long tmp;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ tmp = val * 1000000000LL;
+ do_div(tmp, rescale->numerator);
+ tmp *= rescale->denominator;
+ do_div(tmp, 1000000000LL);
do_div is for unsigned operands. Can val never ever be negative?
What about the numerator and denominator, can those be negative? I
think this code should live in a new rescale_process_inverse_scale
function, or something like that (and a few tests could be added to
drivers/iio/test/iio-test-rescale.c)
I can do that.
+ return iio_write_channel_attribute(rescale->source, tmp, 0,
+ IIO_CHAN_INFO_SCALE);
+ default:
What if the source driver has a .write_raw_get_fmt callback? That bit
of info is silently dropped (with no comment that a shortcut has been
taken). How does inverse rescaling mix with a .write_raw_get_fmt that
returns e.g. IIO_VAL_INT_PLUS_MICRO_DB anyway? I think all cases might
get a bit hairy to support, so I think you need to do some filtering
and somehow fail the .write_raw call if the .write_raw_get_fmt of the
source returns something that gets too difficult to support.
If the inverse rescale uses the same code as rescale_process_scale()
then it becomes problematic, yes, as it likes to change the type of the
value.
What I could try - compute the inverse of the value, then find the
closest scale value+type that the source driver supports, and use this
as the value+type. Then the only failure point would be if
.write_raw_get_fmt returns something different than the formats
returned by .read_avail, but that sounds unlikely to happen.
Cheers,
-Paul
+ return iio_write_channel_attribute(rescale->source,
+ val, val2, mask);
+ }
+}
+
static int rescale_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
@@ -250,6 +271,7 @@ static int rescale_read_avail(struct iio_dev
*indio_dev,
}
static const struct iio_info rescale_info = {
+ .write_raw = rescale_write_raw,
.read_raw = rescale_read_raw,
.read_avail = rescale_read_avail,
};
