Commit 88787801 authored Sep 20, 2023 by AngeloGioacchino Del Regno Committed by Neil Armstrong Sep 20, 2023

drm/bridge: panel: Fix device link for DRM_BRIDGE_ATTACH_NO_CONNECTOR

When external bridges are attached with DRM_BRIDGE_ATTACH_NO_CONNECTOR,
the panel bridge may also get the same flag, but in the .attach()
callback for the panel bridge a device link is added only when this
flag is not present; To make things worse, the .detach() callback
tries to delete the device link unconditionally and without checking
if it was created in the first place, crashing the kernel with a NULL
pointer kernel panic upon calling panel_bridge_detach().

Fix that by moving the device_link_add() call before checking if the
DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is present.

Fixes: 199cf07e ("drm/bridge: panel: Add a device link between drm device and panel device")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230920082727.57729-1-angelogioacchino.delregno@collabora.com

parent 1c7a387f

drivers/gpu/drm/bridge/panel.c

+9 −8

Original line number	Diff line number	Diff line
		@@ -67,14 +67,6 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
		struct drm_device *drm_dev = bridge->dev;
		int ret;

		if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
		return 0;

		if (!bridge->encoder) {
		DRM_ERROR("Missing encoder\n");
		return -ENODEV;
		}

		panel_bridge->link = device_link_add(drm_dev->dev, panel->dev,
		DL_FLAG_STATELESS);
		if (!panel_bridge->link) {
		@@ -83,6 +75,15 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
		return -EINVAL;
		}

		if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
		return 0;

		if (!bridge->encoder) {
		DRM_ERROR("Missing encoder\n");
		device_link_del(panel_bridge->link);
		return -ENODEV;
		}

		drm_connector_helper_add(connector,
		&panel_bridge_connector_helper_funcs);