[PATCH 10/10] drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

[Luca Ceresoli]

Up to now drm_of_find_panel_or_bridge() can be called with a bridge pointer
only, a panel pointer only, or both a bridge and a panel pointers. The
logic to handle all the three cases is somewhat complex to read however.

Now all bridge-only callers have been converted to
of_drm_get_bridge_by_endpoint(), which is simpler and handles bridge
refcounting. So forbid new bridge-only users by mandating a non-NULL panel
pointer in the docs and in the sanity checks along with a warning.

Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>
---
 drivers/gpu/drm/drm_of.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index 4f65ce729a47..25568e0c3ffb 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -225,15 +225,15 @@ EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
  * @np: device tree node containing encoder output ports
  * @port: port in the device tree node
  * @endpoint: endpoint in the device tree node
- * @panel: pointer to hold returned drm_panel
+ * @panel: pointer to hold returned drm_panel, must not be NULL
  * @bridge: pointer to hold returned drm_bridge
  *
  * Given a DT node's port and endpoint number, find the connected node and
- * return either the associated struct drm_panel or drm_bridge device. Either
- * @panel or @bridge must not be NULL.
+ * return either the associated struct drm_panel or drm_bridge device.
  *
  * This function is deprecated and should not be used in new drivers. Use
- * devm_drm_of_get_bridge() instead.
+ * of_drm_get_bridge_by_endpoint() instead when not looking for a panel, or
+ * devm_drm_of_get_bridge() otherwise.
  *
  * Returns zero if successful, or one of the standard error codes if it fails.
  */
@@ -245,10 +245,10 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 	int ret = -EPROBE_DEFER;
 	struct device_node *remote;
 
-	if (!panel && !bridge)
+	if (WARN_ON(!panel))
 		return -EINVAL;
-	if (panel)
-		*panel = NULL;
+
+	*panel = NULL;
 
 	/*
 	 * of_graph_get_remote_node() produces a noisy error message if port
@@ -263,13 +263,11 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 	if (!remote)
 		return -ENODEV;
 
-	if (panel) {
-		*panel = of_drm_find_panel(remote);
-		if (!IS_ERR(*panel))
-			ret = 0;
-		else
-			*panel = NULL;
-	}
+	*panel = of_drm_find_panel(remote);
+	if (!IS_ERR(*panel))
+		ret = 0;
+	else
+		*panel = NULL;
 
 	if (bridge) {
 		if (ret) {

-- 
2.53.0