Re: [PATCH v2] hwmon: (ntc_thermistor): try reading processed

[Linus Walleij <linus.walleij@linaro.org>]

On Sun, Dec 27, 2020 at 7:54 PM Chris Lesiak <chris.lesiak@licor.com> wrote:
> Linus Walleij <linus.walleij@linaro.org> wrote:
> > But do you agree with the general stance that we should
> > give precedence to using iio_read_channel_processed()
> > and multiply the result with 1000? It should work with
> > any driver I think.
>
> In order to preserve resolution of the microVolt value for existing code,

Aha you mean that iio_read_channel_processed() loses
precision when converting raw to scaled?

> I'd prefer a solution similar to the existing implementation of
> iio_read_channel_processed.

That seems like the wrong way to work around a problem in
the core.

If iio_read_channel_processed() loses precision we should
fix iio_read_channel_processed() and not try to work around
the problem in the consumers.

It's fine to fix all the consumers in the kernel.

What about changing the signature of:

int iio_read_channel_processed(struct iio_channel *chan, int *val)

to:

int iio_read_channel_processed(struct iio_channel *chan, int *val,
unsigned int scale)

And just augment all calls to pass 1 except the ntc driver
which then passes 1000 in the last argument?

If Jonathan agrees I can fix a patch to alter all the ~50
call sites like this and include the change to this NTC
driver.

Yours,
Linus Walleij