[PATCH] libcamera: controls: Handle enum values without a cast

[Kieran Bingham]

Quoting Jacopo Mondi (2024-09-26 10:13:44)
> Hi Laurent
> 
> On Thu, Sep 26, 2024 at 03:24:27AM GMT, Laurent Pinchart wrote:
> > When constructing a ControlValue from an enum value, an explicit cast to
> > int32_t is needed as we use int32_t as the underlying type for all
> > enumerated controls. This makes users of ControlValue more complex. To
> > simplify them, specialize the control_type template for enum types, to
> > support construction of ControlValue directly without a cast.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> brilliant, less things to type in!
> 
> Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> 
> Thanks
>   j
> 
> > ---
> >  include/libcamera/controls.h         | 6 +++++-
> >  src/libcamera/pipeline/ipu3/ipu3.cpp | 2 +-
> >  2 files changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> > index 25f67ed948a3..c5131870d402 100644
> > --- a/include/libcamera/controls.h
> > +++ b/include/libcamera/controls.h
> > @@ -39,7 +39,7 @@ enum ControlType {
> >
> >  namespace details {
> >
> > -template<typename T>
> > +template<typename T, typename = std::void_t<>>
> >  struct control_type {
> >  };
> >
> > @@ -102,6 +102,10 @@ struct control_type<Span<T, N>> : public control_type<std::remove_cv_t<T>> {
> >       static constexpr std::size_t size = N;
> >  };
> >
> > +template<typename T>
> > +struct control_type<T, std::enable_if_t<std::is_enum_v<T>>> : public control_type<int32_t> {
> > +};
> > +

I have no idea how you get this black magic to work ... :-)

But if it works and is reducing boilerplate casts which impact readability
then \o/

So I think this makes a new templated control_type of the given enum
type, which is derived from an int32_t ...

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> >  } /* namespace details */
> >
> >  class ControlValue
> > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > index 430aa902eec8..29d3c6c194c1 100644
> > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > @@ -958,7 +958,7 @@ int PipelineHandlerIPU3::updateControls(IPU3CameraData *data)
> >               values.reserve(testPatternModes.size());
> >
> >               for (auto pattern : testPatternModes)
> > -                     values.emplace_back(static_cast<int32_t>(pattern));
> > +                     values.emplace_back(pattern);
> >
> >               controls[&controls::draft::TestPatternMode] = ControlInfo(values);
> >       }
> >
> > base-commit: f2088eb91fd6477b152233b9031cb115ca1ae824
> > --
> > Regards,
> >
> > Laurent Pinchart
> >