[PATCH AUTOSEL 5.4 4/9] drm/bridge: panel: forbid initializing a panel with unknown connector type

Sasha Levin
2025-04-03T19:21:01Z

From: Luca Ceresoli <luca.ceresoli@bootlin.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@linaro.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250214-drm-assorted-cleanups-v7-5-88ca5827d7af@bootlin.com
Signed-off-by: Sasha Levin <sashal@kernel.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 ed7985c0535a2..b81c57267a408 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -47,7 +47,7 @@ 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().
@@ -55,6 +55,9 @@ 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);
panel->dev = dev;
panel->funcs = funcs;
--
2.39.5