[PATCH v2 3/8] ipa: libipa: Add ExposureModeHelper

[Jacopo Mondi]

Hi

On Tue, Apr 23, 2024 at 03:01:34PM +0000, Barnabás Pőcze wrote:
> Hi
>
>
> 2024. április 23., kedd 16:41 keltezéssel, Dan Scally <dan.scally at ideasonboard.com> írta:
>
> > [...]
> > >> [...]
> > >> +/**
> > >> + * \brief Initialize an ExposureModeHelper instance
> > >> + * \param[in] stages The vector of paired shutter time and gain limits
> > >> + *
> > >> + * This function is expected to be called a single time once the algorithm that
> > >> + * is using these helpers has built the necessary list of shutter and gain pairs
> > >> + * to use (archetypically by parsing them from a tuning file during the
> > >> + * algorithm's .init() call).
> > >> + *
> > >> + * The input steps are shutter and _total_ gain pairs; the gain encompasses both
> > >> + * analogue and digital gain.
> > >> + *
> > >> + * The vector of stages may be empty. In that case, the helper will simply use
> > >> + * the runtime limits set through setShutterGainLimits() instead.
> > >> + */
> > >> +void ExposureModeHelper::init(const std::vector<std::pair<utils::Duration, double>> stages)
> > > Any reason for not using span here?
> >
> >
> > The shutter time and gain vectors are initially separate, and need combining like so:
> >
> >
> >  std::vector<std::pair<utils::Duration, double>> stages;
> >  for (unsigned int i = 0; i < shutters.size(); i++) {
> >    stages.push_back({
> >      std::chrono::microseconds(shutters[i]),
> >      gains[i]
> >    });
> >  }
> >
> >  std::shared_ptr<ExposureModeHelper> helper =
> >    std::make_shared<ExposureModeHelper>();
> >  helper->init(stages);
> >
> > So given I have to build a new vector with the paired stages anyway I couldn't
> > see value in then using a Span for the init() instead of just passing the vector...but quite
> > possibly I am just not understanding why it's the better choice here.
>
> Note that in the code above, there is a copy when calling init(), using a span avoids that.
>

Or just by passing the vector by reference and not value.
The pairs' items will be copied inside the helper anyway.

>
> > [...]
>
>
> Regards,
> Barnabás Pőcze