[PATCH] libcamera: v4l2_videodevice: Add getSelection() function

[Jacopo Mondi]

On Thu, Sep 26, 2024 at 12:33:27PM GMT, Laurent Pinchart wrote:
> On Thu, Sep 26, 2024 at 10:06:14AM +0200, Jacopo Mondi wrote:
> > Hi Laurent
> >
> > On Wed, Sep 25, 2024 at 09:07:13PM GMT, Laurent Pinchart wrote:
> > > The V4L2VideoDevice class implements setSelection() but not
> > > getSelection(). The latter is useful for instance to query crop bounds.
> > > Implement the function.
> > >
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > > ---
> > >  include/libcamera/internal/v4l2_videodevice.h |  1 +
> > >  src/libcamera/v4l2_videodevice.cpp            | 32 +++++++++++++++++++
> > >  2 files changed, 33 insertions(+)
> > >
> > > diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
> > > index 9057be08f18a..f021c2a0177b 100644
> > > --- a/include/libcamera/internal/v4l2_videodevice.h
> > > +++ b/include/libcamera/internal/v4l2_videodevice.h
> > > @@ -208,6 +208,7 @@ public:
> > >  	int setFormat(V4L2DeviceFormat *format);
> > >  	Formats formats(uint32_t code = 0);
> > >
> > > +	int getSelection(unsigned int target, Rectangle *rect);
> > >  	int setSelection(unsigned int target, Rectangle *rect);
> > >
> > >  	int allocateBuffers(unsigned int count,
> > > diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> > > index 93cb1697935e..14eba0561d6a 100644
> > > --- a/src/libcamera/v4l2_videodevice.cpp
> > > +++ b/src/libcamera/v4l2_videodevice.cpp
> > > @@ -1214,6 +1214,38 @@ std::vector<SizeRange> V4L2VideoDevice::enumSizes(V4L2PixelFormat pixelFormat)
> > >  	return sizes;
> > >  }
> > >
> > > +/**
> > > + * \brief Get the selection rectangle for \a target
> > > + * \param[in] target The selection target defined by the V4L2_SEL_TGT_* flags
> > > + * \param[out] rect The selection rectangle to retrieve
> > > + *
> > > + * \todo Define a V4L2SelectionTarget enum for the selection target
> > > + *
> > > + * \return 0 on success or a negative error code otherwise
> > > + */
> > > +int V4L2VideoDevice::getSelection(unsigned int target, Rectangle *rect)
> > > +{
> > > +	struct v4l2_selection sel = {};
> > > +
> > > +	sel.type = bufferType_;
> > > +	sel.target = target;
> > > +	sel.flags = 0;
> > > +
> > > +	int ret = ioctl(VIDIOC_G_SELECTION, &sel);
> > > +	if (ret < 0) {
> > > +		LOG(V4L2, Error) << "Unable to get rectangle " << target
> > > +				 << ": " << strerror(-ret);
> > > +		return ret;
> >
> > Just noticed in this class we don't
> >
> > 		ret = -errno;
> > 		LOG(V4L2, Error) <<
> > 				 << strerror(-ret);
> > 		return ret;
>
> That's because we're calling V4L2Device::ioctl(), which returns -errno.

I thought the whole point of the above churn was because writing to an
iostream like LOG() << does overwrites errno, but indeed in this case
errno is already returned by the ioctl() function. Sorry for the noise!

>
> > Not related to this patch though
> > Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> >
> > > +	}
> > > +
> > > +	rect->x = sel.r.left;
> > > +	rect->y = sel.r.top;
> > > +	rect->width = sel.r.width;
> > > +	rect->height = sel.r.height;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  /**
> > >   * \brief Set a selection rectangle \a rect for \a target
> > >   * \param[in] target The selection target defined by the V4L2_SEL_TGT_* flags
> > >
> > > base-commit: 8bcec687344e5cc2ccef1361c03b87f0fd2cc59b
>
> --
> Regards,
>
> Laurent Pinchart