[libcamera-devel] [RFC PATCH v3 01/16] controls: Add boolean constructor for ControlInfo

[paul.elder at ideasonboard.com]

Hi Jacopo,

On Mon, Jul 05, 2021 at 03:39:00PM +0200, Jacopo Mondi wrote:
> Hi Paul,
> 
> On Fri, Jul 02, 2021 at 07:37:45PM +0900, Paul Elder wrote:
> > It would be convenient to be able to iterate over available boolean
> > values, for example for controls that designate if some function can be
> > enabled/disabled. The current min/max/def constructor is insufficient,
> > as .values() is empty, so the values cannot be easily iterated over, and
> > creating a Span of booleans does not work for the values constructor.
> >
> > Add a new constructor to ControlInfo that takes a Span of booleans (to
> > allow specifiying one or two available values), and a default. The
> > default value is not optional, as it doesn't make sense to have a silent
> > default for boolean values.
> 
> So this is intended to be used as
>         ControlInfo({true}, true);
>         ControlInfo({false}, false);
>         ControlInfo({true, true}, true);

ControlInfo({false, true}, true)

>         ControlInfo({true, true}, false);

ControlInfo({false, true}, false)
> 
> ?

Yeah, that was the idea. tbh I don't feel so well about it but I'm not
sure how else to it it.

Although, since we have to declare a Span when we use it anyway, maybe
we can just use the exsiting Span constructor. Just have to make sure
false comes first, otherwise min_ = values.front() will choose the wrong
value.

So yeah, I guess I'll just drop this patch.


Thanks,

Paul

> 
> What is the purpose of having to specify a default if only one value
> is available ? Does it even make sense to have a ControlInfo that only

If we only have ControlInfo({true}) with no second parameter, then it'll
use the ControlInfo(Span<const ControlValue> values, const ControlValue
&def = {}) constructor.

> represents true or false ?
> 
> Can you make sure
>         ControlInfo({true}, false);
> doesn't happen ?

atm, not really.

> 
> >
> > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> >
> > ---
> > New in v3
> > ---
> >  include/libcamera/controls.h |  1 +
> >  src/libcamera/controls.cpp   | 20 ++++++++++++++++++++
> >  2 files changed, 21 insertions(+)
> >
> > diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> > index 1bc958a4..2dd147c8 100644
> > --- a/include/libcamera/controls.h
> > +++ b/include/libcamera/controls.h
> > @@ -272,6 +272,7 @@ public:
> >  			     const ControlValue &def = 0);
> >  	explicit ControlInfo(Span<const ControlValue> values,
> >  			     const ControlValue &def = {});
> > +	explicit ControlInfo(Span<const bool> values, bool def);
> 
> The explicit keyword is used to disallow implicit conversion and copy
> construction. It only applies to constructors with a single parameter
> afaict, so it is not required here.
> 
> >
> >  	const ControlValue &min() const { return min_; }
> >  	const ControlValue &max() const { return max_; }
> > diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
> > index 34317fa0..e32e22e2 100644
> > --- a/src/libcamera/controls.cpp
> > +++ b/src/libcamera/controls.cpp
> > @@ -514,6 +514,26 @@ ControlInfo::ControlInfo(Span<const ControlValue> values,
> >  		values_.push_back(value);
> >  }
> >
> > +/**
> > + * \brief Construct a ControlInfo from a list of valid boolean values
> > + * \param[in] values The control valid boolean vaalues
> 
> s/vaalues/values
> 
> The values can be just {true, false}, right ?
> 
> > + * \param[in] def The control default boolean value
> > + *
> > + * Construct a ControlInfo from a list of valid boolean values. The ControlInfo
> > + * minimum and maximum values are set to the first and last members of the
> > + * values list respectively. The default value is set to \a def.
> 
> So ControlInfo({true, false}) != ControlInfo({false, true}) ?
> 
> > + */
> > +ControlInfo::ControlInfo(Span<const bool> values, bool def)
> > +	: def_(def)
> > +{
> > +	min_ = values.front();
> > +	max_ = values.back();
> > +
> > +	values_.reserve(2);
> > +	for (const bool &value : values)
> > +		values_.push_back(value);
> > +}
> > +
> 
> Could you point me to where this constructor is used, as it seems
> suspicious to me :)

The pipeline handler uses this constructor to specify the valid values
for boolean controls, like AeEnable, AeLock, and AwbLock in this series.

> 
> 
> >  /**
> >   * \fn ControlInfo::min()
> >   * \brief Retrieve the minimum value of the control
> > --
> > 2.27.0
> >