On Tue, Feb 15, 2022 at 12:03 PM Gabriel Krisman Bertazi
<krisman@xxxxxxxxxxxxx> wrote:
>
> 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.
Ah, right. Sorry that I totally missed this.
I'll fix it in the next version if the idea of this patch is accepted.
There might be another preferred solution for this.
>
> 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
