[libcamera-devel] [PATCH v2 4/7] libcamera: v4l2_controls: Construct from a list of ids

[Jacopo Mondi]

Hi Niklas,

On Wed, Aug 28, 2019 at 01:18:40PM +0200, Niklas Söderlund wrote:
> Hi Jacopo,
>
> Thanks for your work.
>
> On 2019-08-27 11:50:04 +0200, Jacopo Mondi wrote:
> > Add a constructor for the V4L2ControlList class that accepts a list of
> > V4L2 control IDs (V4L2_CID_*). The constructor returns a V4L2ControlList
> > instance to be used for reading controls only.
> >
> > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > ---
> >  src/libcamera/include/v4l2_controls.h |  3 +++
> >  src/libcamera/v4l2_controls.cpp       | 17 +++++++++++++++++
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/src/libcamera/include/v4l2_controls.h b/src/libcamera/include/v4l2_controls.h
> > index 10b726504951..86c84e06d741 100644
> > --- a/src/libcamera/include/v4l2_controls.h
> > +++ b/src/libcamera/include/v4l2_controls.h
> > @@ -65,6 +65,9 @@ public:
> >  	using iterator = std::vector<V4L2Control>::iterator;
> >  	using const_iterator = std::vector<V4L2Control>::const_iterator;
> >
> > +	V4L2ControlList() {}
> > +	V4L2ControlList(std::vector<unsigned int> ids);
> > +
> >  	iterator begin() { return controls_.begin(); }
> >  	const_iterator begin() const { return controls_.begin(); }
> >  	iterator end() { return controls_.end(); }
> > diff --git a/src/libcamera/v4l2_controls.cpp b/src/libcamera/v4l2_controls.cpp
> > index 84258d9954d0..eeb325cbfff9 100644
> > --- a/src/libcamera/v4l2_controls.cpp
> > +++ b/src/libcamera/v4l2_controls.cpp
> > @@ -202,6 +202,23 @@ V4L2ControlInfo::V4L2ControlInfo(const struct v4l2_query_ext_ctrl &ctrl)
> >   * and prepare to be re-used for a new control write/read sequence.
> >   */
> >
> > +/**
> > + * \brief Construct a V4L2ControlList from a list of V4L2 controls identifiers
> > + * \param ids A list of V4L2 control identifiers (V4L2_CID_*)
> > + *
> > + * Construct a V4L2ControlList from a list of control identifiers without any
> > + * value associated. This constructor is particularly useful to create a
> > + * V4L2ControlList that is used to read the values of all controls in the
> > + * \a ids list. The created V4L2ControlList should not be used to write control
> > + * values unless it is cleared first and then controls with an associated value
> > + * are manually added to it.
> > + */
>
> Do you think it would be worth it to add some code to enforce that no
> controls can be written if it's initialized with this constructor?
>

How would you do so? The most naive implementation that comes to mind
it's to add a 'writable' flag to initialize to true only if the
control has a value assigned and check for the flag
V4L2Device::setControls()

> > +V4L2ControlList::V4L2ControlList(std::vector<unsigned int> ids)
> > +{
> > +	for (auto id : ids)
> > +		add(id);
> > +}
> > +
> >  /**
> >   * \typedef V4L2ControlList::iterator
> >   * \brief Iterator on the V4L2 controls contained in the instance
> > --
> > 2.23.0
> >
> > _______________________________________________
> > libcamera-devel mailing list
> > libcamera-devel at lists.libcamera.org
> > https://lists.libcamera.org/listinfo/libcamera-devel
>
> --
> Regards,
> Niklas Söderlund
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