[PATCH 2/3] ipa: libipa: agc_mean_luminance: Error out when effectiveExposureValue is zero

[Stefan Klug]

Hi Isaac,

Thank you for the review. 

On Fri, Feb 28, 2025 at 02:28:19PM +0000, Isaac Scott wrote:
> Hi Stefan,
> 
> On Fri, 2025-02-28 at 13:55 +0100, Stefan Klug wrote:
> > In a proper system it never happens that the effectiveExposureValue
> > drops to zero. If that still happens due to a bug outside of
> > agc_mean_luminance, the calculated gain goes towards infinity but the
> > newExposureValue is still 0 because it is the it never happens that
> > the effectiveExposureValue drops to zero. If that still happens due
> > to a bug outside of
> 
> What conditions lead to this being zero when it shouldn't?

One condition of this kind gets fixed in the next patch. In that case
the sensor was set to an exposure time of 0 (the root cause). Now a bit
later statistics for that frame come in and as the frame context
contains an exposure time of 0 the effectiveExposureValue is also 0,
breaking all calculations.

> 
> If they can be zero, this looks good to me!

Great :-). Would you mind giving it a reviewed-by?

Best regards,
Stefan

> 
> > +
> >  	double gain = estimateInitialGain();
> >  	gain = constraintClampGain(constraintModeIndex, yHist,
> > gain);
> >  
>