RE: [PATCH v2] drm/bridge: panel: Fix device link for DRM_BRIDGE_ATTACH_NO_CONNECTOR

[Ying Liu]

On Wednesday, September 20, 2023 4:27 PM AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:
> 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: 199cf07ebd2b ("drm/bridge: panel: Add a device link between drm
> device and panel device")
> Signed-off-by: AngeloGioacchino Del Regno
> <angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
> 
> Changes in v2:
>  - Added device_link_del() for (!bridge->encoder) error condition
> 
>  drivers/gpu/drm/bridge/panel.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)

Reviewed-by: Liu Ying <victor.liu@xxxxxxx>