linux-kernel - [PATCH AUTOSEL 6.14 18/44] drm/bridge: panel: forbid initializing a panel with unknown connector type

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Message-Id: <20250403191313.2679091-18-sashal@kernel.org>
Date: Thu,  3 Apr 2025 15:12:47 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	neil.armstrong@...aro.org,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.14 18/44] drm/bridge: panel: forbid initializing a panel with unknown connector type

From: Luca Ceresoli <luca.ceresoli@...tlin.com>

[ Upstream commit b296955b3a740ecc8b3b08e34fd64f1ceabb8fb4 ]

Having an DRM_MODE_CONNECTOR_Unknown connector type is considered bad, and
drm_panel_bridge_add_typed() and derivatives are deprecated for this.

drm_panel_init() won't prevent initializing a panel with a
DRM_MODE_CONNECTOR_Unknown connector type. Luckily there are no in-tree
users doing it, so take this as an opportinuty to document a valid
connector type must be passed.

Returning an error if this rule is violated is not possible because
drm_panel_init() is a void function. Add at least a warning to make any
violations noticeable, especially to non-upstream drivers.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
Signed-off-by: Robert Foss <rfoss@...nel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250214-drm-assorted-cleanups-v7-5-88ca5827d7af@bootlin.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/drm_panel.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 9940e96d35e30..c627e42a7ce70 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -50,7 +50,7 @@ static LIST_HEAD(panel_list);
  * @dev: parent device of the panel
  * @funcs: panel operations
  * @connector_type: the connector type (DRM_MODE_CONNECTOR_*) corresponding to
- *	the panel interface
+ *	the panel interface (must NOT be DRM_MODE_CONNECTOR_Unknown)
  *
  * Initialize the panel structure for subsequent registration with
  * drm_panel_add().
@@ -58,6 +58,9 @@ static LIST_HEAD(panel_list);
 void drm_panel_init(struct drm_panel *panel, struct device *dev,
 		    const struct drm_panel_funcs *funcs, int connector_type)
 {
+	if (connector_type == DRM_MODE_CONNECTOR_Unknown)
+		DRM_WARN("%s: %s: a valid connector type is required!\n", __func__, dev_name(dev));
+
 	INIT_LIST_HEAD(&panel->list);
 	INIT_LIST_HEAD(&panel->followers);
 	mutex_init(&panel->follower_lock);
-- 
2.39.5