[RFC v2 5/5] media: v4l2-ctrls: Add __v4l2_s_ctrl_single_to_multi helper function

[Mirela Rabulea <mirela.rabulea@nxp.com>]

Helper function to be used in new sensor drivers to implement s_ctrl
for single controls for backward compatibility.

This function finds the corresponding multi-capture control for a given
single-capture control, and updates only the value corresponding to the
first capture with the same value as the single-capture control value.

Signed-off-by: Mirela Rabulea <mirela.rabulea@nxp.com>
---

Changes in v2:
	New patch
	We need to choose either this patch or patch #4

 drivers/media/v4l2-core/v4l2-ctrls-core.c | 12 ++++++++++++
 include/media/v4l2-ctrls.h                | 17 +++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
index 8d706070c041..f16809a04c29 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
@@ -2823,3 +2823,15 @@ int __v4l2_s_ctrl_multi_to_single(struct v4l2_ctrl *ctrl_multi)
 }
 EXPORT_SYMBOL(__v4l2_s_ctrl_multi_to_single);
 
+int __v4l2_s_ctrl_single_to_multi(struct v4l2_ctrl *ctrl_single)
+{
+	struct v4l2_ctrl *ctrl_multi = __v4l2_get_multi_ctrl(ctrl_single);
+
+	if (!ctrl_multi || !ctrl_single)
+		return -EINVAL;
+
+	ctrl_multi->p_cur.p_u32[0] = ctrl_single->val;
+	return __v4l2_ctrl_s_ctrl_compound(ctrl_multi, V4L2_CTRL_TYPE_U32,
+					  ctrl_multi->p_cur.p_u32);
+}
+EXPORT_SYMBOL(__v4l2_s_ctrl_single_to_multi);
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index d3a9dde47349..ea9973178556 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -1663,6 +1663,23 @@ struct v4l2_ctrl *__v4l2_get_single_ctrl(struct v4l2_ctrl *ctrl_multi);
  */
 int __v4l2_s_ctrl_multi_to_single(struct v4l2_ctrl *ctrl_multi);
 
+/**
+ * __v4l2_s_ctrl_single_to_multi() - Set the multi-capture control for a
+ *				     given single-capture control
+ *
+ * @ctrl_single: pointer to &struct v4l2_ctrl for the single-capture control
+ *
+ * This function finds the corresponding multi-capture control for a given
+ * single-capture control, and updates only the value corresponding to the
+ * first capture with the same value as the single-capture control value.
+ *
+ * This function assumes the control's handler is already locked,
+ * allowing it to be used from within the &v4l2_ctrl_ops functions.
+ *
+ * Return: 0 on success, a negative error code on failure.
+ */
+int __v4l2_s_ctrl_single_to_multi(struct v4l2_ctrl *ctrl_single);
+
 /**
  * v4l2_ctrl_type_op_equal - Default v4l2_ctrl_type_ops equal callback.
  *
-- 
2.43.0