[PATCH] drm/bridge: panel: Fix device link for DRM_BRIDGE_ATTACH_NO_CONNECTOR
AngeloGioacchino Del Regno
angelogioacchino.delregno at collabora.com
Wed Sep 20 08:24:39 UTC 2023
Il 19/09/23 03:45, Ying Liu ha scritto:
> Hi Angelo,
>
> Thank you for the patch.
>
> On Monday, September 18, 2023 11:01 PM, AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com> 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 at collabora.com>
>> ---
>> drivers/gpu/drm/bridge/panel.c | 16 ++++++++--------
>> 1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/panel.c
>> b/drivers/gpu/drm/bridge/panel.c
>> index e00d2e94c751..8c507dfd589e 100644
>> --- a/drivers/gpu/drm/bridge/panel.c
>> +++ b/drivers/gpu/drm/bridge/panel.c
>> @@ -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 +75,14 @@ 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");
>
> Shouldn't the device link be deleted in case of error?
>
Whoops! Yes, that's right. I'm sending a v2 right now.
Thanks!
Angelo
> Regards,
> Liu Ying
>
>> + return -ENODEV;
>> + }
>> +
>> drm_connector_helper_add(connector,
>> &panel_bridge_connector_helper_funcs);
>>
>> --
>> 2.42.0
>
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