On Sat, 19 Oct 2024 15:33:59 +0100 Jonathan Cameron jic23@kernel.org wrote:
On Wed, 16 Oct 2024 19:04:31 +0200 Javier Carrasco javier.carrasco.cruz@gmail.com wrote:
The raw value conversion to obtain a measurement in lux as INT_PLUS_MICRO does not calculate the decimal part properly to display it as micro (in this case microlux). It only calculates the module to obtain the decimal part from a resolution that is 10000 times the provided in the datasheet (0.5376 lux/cnt for the veml6030). The resulting value must still be multiplied by 100 to make it micro.
This bug was introduced with the original implementation of the driver.
Cc: stable@vger.kernel.org Fixes: 7b779f573c48 ("iio: light: add driver for veml6030 ambient light sensor") Signed-off-by: Javier Carrasco javier.carrasco.cruz@gmail.com
Applied to the fixes-togreg branch of iio.git.
As per the linux-next merge conflict email that I've just +CC linux-iio on, I messed this up and it landed on the wrong code block.
Tried again...
Jonathan
Thanks,
Jonathan
I found this almost by chance while testing new supported devices. The decimal part was always suspiciously small, and when I compared samples to the expected value according to the datasheet, it became clear what was going on.
Example with a veml7700 (same resolution as the veml6030):
Resolution for gain = 1/8, IT = 100 ms: 0.5736 lux/cnt.
cat in_illuminance_raw in_illuminance_input 40 21.005040 -> wrong! 40 * 0.5736 is 21.504.
Tested with a veml6035 and a veml7700, the same will happen with the original veml6030, as the operation is identical for all devices.
drivers/iio/light/veml6030.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iio/light/veml6030.c b/drivers/iio/light/veml6030.c index d6f3b104b0e6..a0bf03e37df7 100644 --- a/drivers/iio/light/veml6030.c +++ b/drivers/iio/light/veml6030.c @@ -691,7 +691,7 @@ static int veml6030_read_raw(struct iio_dev *indio_dev, } if (mask == IIO_CHAN_INFO_PROCESSED) { *val = (reg * data->cur_resolution) / 10000;
*val2 = (reg * data->cur_resolution) % 10000;
*val2 = (reg * data->cur_resolution) % 10000 * 100; return IIO_VAL_INT_PLUS_MICRO; } *val = reg;
base-commit: 15e7d45e786a62a211dd0098fee7c57f84f8c681 change-id: 20241016-veml6030-fix-processed-micro-616d00d555dc
Best regards,