[PATCH v5 5/6] media: subdev: add v4l2_subdev_call_state_active()

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

Add v4l2_subdev_call_state_active() macro to help calling subdev ops
that take a subdev state as a parameter. Normally the v4l2 framework
will lock and pass the correct subdev state to the subdev ops, but there
are legacy situations where this is not the case (e.g. non-MC video
device driver calling set_fmt in a source subdev).

As this macro is only needed for legacy use cases, the macro is added in
a new header file, v4l2-subdev-legacy.h.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 include/media/v4l2-subdev-legacy.h | 42 ++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 include/media/v4l2-subdev-legacy.h

diff --git a/include/media/v4l2-subdev-legacy.h b/include/media/v4l2-subdev-legacy.h
new file mode 100644
index 000000000000..6a61e579b629
--- /dev/null
+++ b/include/media/v4l2-subdev-legacy.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *  V4L2 sub-device legacy support header.
+ *
+ *  Copyright (C) 2022  Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
+ */
+
+#ifndef _V4L2_SUBDEV_LEGACY_H
+#define _V4L2_SUBDEV_LEGACY_H
+
+/**
+ * v4l2_subdev_call_state_active - call an operation of a v4l2_subdev which
+ *				   takes state as a parameter, passing the
+ *				   subdev its active state.
+ *
+ * @sd: pointer to the &struct v4l2_subdev
+ * @o: name of the element at &struct v4l2_subdev_ops that contains @f.
+ *     Each element there groups a set of callbacks functions.
+ * @f: callback function to be called.
+ *     The callback functions are defined in groups, according to
+ *     each element at &struct v4l2_subdev_ops.
+ * @args: arguments for @f.
+ *
+ * This is similar to v4l2_subdev_call(), except that this version can only be
+ * used for ops that take a subdev state as a parameter. The macro will get the
+ * active state and lock it before calling the op, and unlock it after the
+ * call.
+ */
+#define v4l2_subdev_call_state_active(sd, o, f, args...)		\
+	({								\
+		int __result;						\
+		struct v4l2_subdev_state *state;			\
+		state = v4l2_subdev_get_active_state(sd);		\
+		if (state)						\
+			v4l2_subdev_lock_state(state);			\
+		__result = v4l2_subdev_call(sd, o, f, state, ##args);	\
+		if (state)						\
+			v4l2_subdev_unlock_state(state);		\
+		__result;						\
+	})
+
+#endif
-- 
2.25.1