[PATCH] drm/bridge/panel: Fix runtime warning on panel bridge release

[PATCH] drm/bridge/panel: Fix runtime warning on panel bridge release

[Adam Miotk]

Device managed panel bridge wrappers are created by calling to
drm_panel_bridge_add_typed() and registering a release handler for
clean-up when the device gets unbound.

Since the memory for this bridge is also managed and linked to the panel
device, the release function should not try to free that memory.
Moreover, the call to devm_kfree() inside drm_panel_bridge_remove() will
fail in this case and emit a warning because the panel bridge resource
is no longer on the device resources list (it has been removed from
there before the call to release handlers).

Signed-off-by: Adam Miotk <adam.miotk@arm.com>
---
 drivers/gpu/drm/bridge/panel.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 32506524d9a2..fe5fb08c9fc4 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -360,9 +360,12 @@ EXPORT_SYMBOL(drm_panel_bridge_set_orientation);
 
 static void devm_drm_panel_bridge_release(struct device *dev, void *res)
 {
-	struct drm_bridge **bridge = res;
+	struct drm_bridge *bridge = *(struct drm_bridge **)res;
 
-	drm_panel_bridge_remove(*bridge);
+	if (!bridge)
+		return;
+
+	drm_bridge_remove(bridge);
 }
 
 /**
-- 
2.25.1

Re: [PATCH] drm/bridge/panel: Fix runtime warning on panel bridge release

[Maxime Ripard]

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On Mon, Jun 10, 2024 at 11:27:39AM GMT, Adam Miotk wrote:
> Device managed panel bridge wrappers are created by calling to
> drm_panel_bridge_add_typed() and registering a release handler for
> clean-up when the device gets unbound.
> 
> Since the memory for this bridge is also managed and linked to the panel
> device, the release function should not try to free that memory.
> Moreover, the call to devm_kfree() inside drm_panel_bridge_remove() will
> fail in this case and emit a warning because the panel bridge resource
> is no longer on the device resources list (it has been removed from
> there before the call to release handlers).
> 
> Signed-off-by: Adam Miotk <adam.miotk@arm.com>

I've added a Fixes tag and applied to drm-misc-fixes, thanks!
Maxime

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