libcamera: v4l2_videodevice: Add getSelection() function

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@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 93cb1697..14eba056 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -1215,6 +1215,38 @@ std::vector<SizeRange> V4L2VideoDevice::enumSizes(V4L2PixelFormat pixelFormat)
 }
 
 /**
+ * \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;
+	}
+
+	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
  * \param[inout] rect The selection rectangle to be applied