Re: [PATCH] iio: afe: rescale: Fix logic bug

[Mighty <bavishimithil@gmail.com>]

On Wed, Aug 23, 2023 at 1:51 PM Linus Walleij <linus.walleij@linaro.org> wrote:

> OK so twl6030 is providing some channels with IIO_CHAN_INFO_RAW
> without IIO_CHAN_INFO_SCALE.

Exactly, checking the driver there doesnt seem to be any scaler used. The two functions to read raw[1] and processed[2] are quite simple, with processed using the raw function as well. Since there is no mention of SCALE, could I just patch that in with the RAW, it wouldnt change anything in the driver (the driver has cases for RAW and PROCESSED only) and would fix the issue at hand as well.

> Say the raw value is 100, then 100 what? Microvolts?

I'd assume Volts, I couldnt find a datasheet for TWL6032 hence the assumption based on code https://github.com/torvalds/linux/blob/master/drivers/iio/adc/twl6030-gpadc.c#L504.

> patch the twl6030 driver to convert all IIO_CHAN_INFO_RAW to IIO_CHAN_INFO_PROCESSED.

That would break the case here https://github.com/torvalds/linux/blob/master/drivers/iio/adc/twl6030-gpadc.c#L541 hence I think we just comply to adding scale as well, even though it would be 1:1?
There is this https://github.com/torvalds/linux/blob/master/drivers/iio/adc/twl6030-gpadc.c#L447 but I'm not very sure about how it changes the scale.

[1] https://github.com/torvalds/linux/blob/master/drivers/iio/adc/twl6030-gpadc.c#L462
[2] https://github.com/torvalds/linux/blob/master/drivers/iio/adc/twl6030-gpadc.c#L487

Mithil