Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> writes:
> On Tue, Feb 15, 2022 at 9:17 AM Gabriel Krisman Bertazi
> <krisman@xxxxxxxxxxxxx> wrote:
>>
>> Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> writes:
>>
>> > drm_dev_register() sets connector->registration_state to
>> > DRM_CONNECTOR_REGISTERED and dev->registered to true. If
>> > drm_connector_set_panel_orientation() is first called after
>> > drm_dev_register(), it will fail several checks and results in following
>> > warning.
>>
>> Hi,
>>
>> I stumbled upon this when investigating the same WARN_ON on amdgpu.
>> Thanks for the patch :)
>>
>> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
>> > index a50c82bc2b2fec..572ead7ac10690 100644
>> > --- a/drivers/gpu/drm/drm_connector.c
>> > +++ b/drivers/gpu/drm/drm_connector.c
>> > @@ -1252,7 +1252,7 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
>> > * INPUT_PROP_DIRECT) will still map 1:1 to the actual LCD panel
>> > * coordinates, so if userspace rotates the picture to adjust for
>> > * the orientation it must also apply the same transformation to the
>> > - * touchscreen input coordinates. This property is initialized by calling
>> > + * touchscreen input coordinates. This property value is set by calling
>> > * drm_connector_set_panel_orientation() or
>> > * drm_connector_set_panel_orientation_with_quirk()
>> > *
>> > @@ -2341,8 +2341,8 @@ EXPORT_SYMBOL(drm_connector_set_vrr_capable_property);
>> > * @connector: connector for which to set the panel-orientation property.
>> > * @panel_orientation: drm_panel_orientation value to set
>> > *
>> > - * This function sets the connector's panel_orientation and attaches
>> > - * a "panel orientation" property to the connector.
>> > + * This function sets the connector's panel_orientation value. If the property
>> > + * doesn't exist, it will try to create one.
>> > *
>> > * Calling this function on a connector where the panel_orientation has
>> > * already been set is a no-op (e.g. the orientation has been overridden with
>> > @@ -2373,19 +2373,12 @@ int drm_connector_set_panel_orientation(
>> > info->panel_orientation = panel_orientation;
>> >
>> > prop = dev->mode_config.panel_orientation_property;
>> > - if (!prop) {
>> > - prop = drm_property_create_enum(dev, DRM_MODE_PROP_IMMUTABLE,
>> > - "panel orientation",
>> > - drm_panel_orientation_enum_list,
>> > - ARRAY_SIZE(drm_panel_orientation_enum_list));
>> > - if (!prop)
>> > - return -ENOMEM;
>> > -
>> > - dev->mode_config.panel_orientation_property = prop;
>> > - }
>> > + if (!prop &&
>> > + drm_connector_init_panel_orientation_property(connector) < 0)
>> > + return -ENOMEM;
>> >
>>
>> In the case where the property has not been created beforehand, you
>> forgot to reinitialize prop here, after calling
>> drm_connector_init_panel_orientation_property(). This means
> hi Gabriel,
>
> drm_connector_init_panel_orientation_property() will create prop if
> it's null. If prop fails to be created there, it will return -ENOMEM.
Yes. But *after the property is successfully created*, the prop variable is still
NULL. And then you call the following, using prop, which is still NULL:
>> > + drm_object_property_set_value(&connector->base, prop,
>> > + info->panel_orientation);
This will do property->dev right on the first line of code, and dereference the
null prop pointer.
You must do
prop = dev->mode_config.panel_orientation_property;
again after drm_connector_init_panel_orientation_property successfully
returns, or call drm_object_property_set_value using
dev->mode_config.panel_orientation_property directly:
drm_object_property_set_value(&connector->base,
dev->mode_config.panel_orientation_property
info->panel_orientation);
--
Gabriel Krisman Bertazi
