Re: [PATCH v2 2/6] iio: light: Add gain-time-scale helpers

[Matti Vaittinen]

Hi Jonathan, all

On 3/4/23 20:35, Jonathan Cameron wrote:
> On Thu, 2 Mar 2023 12:57:54 +0200
> Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
>
> > Some light sensors can adjust both the HW-gain and integration time.
> > There are cases where adjusting the integration time has similar impact
> > to the scale of the reported values as gain setting has.
> >
> > IIO users do typically expect to handle scale by a single writable 'scale'
> > entry. Driver should then adjust the gain/time accordingly.
> >
> > It however is difficult for a driver to know whether it should change
> > gain or integration time to meet the requested scale. Usually it is
> > preferred to have longer integration time which usually improves
> > accuracy, but there may be use-cases where long measurement times can be
> > an issue. Thus it can be preferable to allow also changing the
> > integration time - but mitigate the scale impact by also changing the gain
> > underneath. Eg, if integration time change doubles the measured values,
> > the driver can reduce the HW-gain to half.
> >
> > The theory of the computations of gain-time-scale is simple. However,
> > some people (undersigned) got that implemented wrong for more than once.
> >
> > Add some gain-time-scale helpers in order to not dublicate errors in all
> > drivers needing these computations.
> >
> > Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
>
> Probably makes sense to put the exports in their own namespace.

Andy asked for that as well. And, while I do not really see the 
usefulness of the namespaces when all symbols are properly prefixed (I 
only see added complexity there) - I agreed to use one.

> I've been meaning to finish namespacing the rest of IIO but not
> gotten around to it yet.
> As this is a separate library probably makes sense to have a unique
> namespace for it that the users opt in on.
> Perhaps IIO_GTS makes sense?

Thanks. I think I'll use that. Although, as all of the symbols are 
prefixed with iio_gts - if I really saw a risk of symbol clash it would 
probably make more sense to use just about anything else ;) This because 
if someone else were prefixing symbols with iio_gts - he would likely be 
using the exactly same namespace.

> Otherwise, as Andy's done a detailed review of this version I'll let
> you update it for those comments and take another look at v3.

This suits me fine. I have v3 almost prepared - but I'll be very much 
away from the computer next week so it may be the v3 will not be out 
until later. It may be I won't continue work with this until about after 
a week.

Yours,
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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