On Mon, Nov 18, 2024 at 02:09:29PM +0200, Jani Nikula wrote:
> On Fri, 15 Nov 2024, Imre Deak <imre.deak@xxxxxxxxx> wrote:
> > Atm when the connector is added to the drm_mode_config::connector_list,
> > the connector may not be fully initialized yet. This is not a problem
> > for user space, which will see the connector only after it's registered
> > later, it could be a problem for in-kernel users looking up connectors
> > via the above list.
> >
> > To resolve the above issue, add a way to separately initialize the DRM
> > core specific parts of the connector and add it to the above list. This
> > will move adding the connector to the list after the properties on the
> > connector have been added, this is ok since these steps don't have a
> > dependency.
> >
> > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_connector.c | 103 ++++++++++++++++++++++++++------
> > include/drm/drm_connector.h | 5 ++
> > 2 files changed, 91 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index fc35f47e2849e..6132a7917b20c 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -218,11 +218,11 @@ void drm_connector_free_work_fn(struct work_struct *work)
> > }
> > }
> >
> > -static int __drm_connector_init(struct drm_device *dev,
> > - struct drm_connector *connector,
> > - const struct drm_connector_funcs *funcs,
> > - int connector_type,
> > - struct i2c_adapter *ddc)
> > +static int __drm_connector_init_core(struct drm_device *dev,
> > + struct drm_connector *connector,
> > + const struct drm_connector_funcs *funcs,
> > + int connector_type,
> > + struct i2c_adapter *ddc)
> > {
> > struct drm_mode_config *config = &dev->mode_config;
> > int ret;
> > @@ -273,6 +273,7 @@ static int __drm_connector_init(struct drm_device *dev,
> > /* provide ddc symlink in sysfs */
> > connector->ddc = ddc;
> >
> > + INIT_LIST_HEAD(&connector->head);
> > INIT_LIST_HEAD(&connector->global_connector_list_entry);
> > INIT_LIST_HEAD(&connector->probed_modes);
> > INIT_LIST_HEAD(&connector->modes);
> > @@ -288,14 +289,6 @@ static int __drm_connector_init(struct drm_device *dev,
> >
> > drm_connector_get_cmdline_mode(connector);
> >
> > - /* We should add connectors at the end to avoid upsetting the connector
> > - * index too much.
> > - */
> > - spin_lock_irq(&config->connector_list_lock);
> > - list_add_tail(&connector->head, &config->connector_list);
> > - config->num_connector++;
> > - spin_unlock_irq(&config->connector_list_lock);
> > -
> > if (connector_type != DRM_MODE_CONNECTOR_VIRTUAL &&
> > connector_type != DRM_MODE_CONNECTOR_WRITEBACK)
> > drm_connector_attach_edid_property(connector);
> > @@ -332,6 +325,84 @@ static int __drm_connector_init(struct drm_device *dev,
> > return ret;
> > }
> >
> > +/**
> > + * drm_connector_init_core - Initialize the core state of a preallocated connector
> > + * @dev: DRM device
> > + * @connector: the connector to init
> > + * @funcs: callbacks for this connector
> > + * @connector_type: user visible type of the connector
> > + *
> > + * Initialises the core state of preallocated connector. This is
> > + * equivalent to drm_connector_init(), without adding the connector to
> > + * drm_mode_config::connector_list. This call must be followed by calling
> > + * drm_connector_add() during initialization to expose the connector to
> > + * in-kernel users via the above list.
> > + *
> > + * Returns:
> > + * Zero on success, error code on failure.
> > + */
> > +int drm_connector_init_core(struct drm_device *dev,
> > + struct drm_connector *connector,
> > + const struct drm_connector_funcs *funcs,
> > + int connector_type)
>
> Please include the ddc parameter here, and have callers pass NULL. We
> absolutely don't want to see drm_connector_init_core_with_ddc().
Ok.
> > +{
> > + if (drm_WARN_ON(dev, !(funcs && funcs->destroy)))
> > + return -EINVAL;
> > +
> > + return __drm_connector_init_core(dev, connector, funcs, connector_type, NULL);
> > +}
> > +EXPORT_SYMBOL(drm_connector_init_core);
> > +
> > +/**
> > + * drm_connector_add - Add the connector
> > + * @connector: the connector to add
> > + *
> > + * Add the connector to the drm_mode_config::connector_list, exposing the
> > + * connector to in-kernel users. This call must be preceded by a call to
> > + * drm_connector_init_core().
> > + */
> > +void drm_connector_add(struct drm_connector *connector)
> > +{
> > + struct drm_device *dev = connector->dev;
> > + struct drm_mode_config *config = &dev->mode_config;
> > +
> > + spin_lock_irq(&config->connector_list_lock);
> > + list_add_tail(&connector->head, &config->connector_list);
> > + config->num_connector++;
> > + spin_unlock_irq(&config->connector_list_lock);
> > +}
> > +EXPORT_SYMBOL(drm_connector_add);
> > +
> > +static void drm_connector_remove(struct drm_connector *connector)
> > +{
> > + struct drm_device *dev = connector->dev;
> > +
> > + if (list_empty(&connector->head))
> > + return;
> > +
> > + spin_lock_irq(&dev->mode_config.connector_list_lock);
> > + list_del_init(&connector->head);
> > + dev->mode_config.num_connector--;
> > + spin_unlock_irq(&dev->mode_config.connector_list_lock);
> > +}
> > +
> > +static int __drm_connector_init(struct drm_device *dev,
> > + struct drm_connector *connector,
> > + const struct drm_connector_funcs *funcs,
> > + int connector_type,
> > + struct i2c_adapter *ddc)
>
> I'd nuke this wrapper altogether, and put the stuff inline.
Not sure, since it's used in a few places. Could rename it to
drm_connector_init_core_and_add() for clarity.
> Which kind of highlights that drmm_connector_init() still has the same
> problem, everyone's encouraged to move towards that, but then what?
Not sure how the drmm API would work on MST where connectors should be
freed dynamically, at least it doesn't work as-is; and MST is where
initialising and adding a connector separately matters - at least for
i915 - vs. other static connector types where it doesn't.
If needed, adding a drmm version of initialising a connector without
adding it would be simple, but based on the above I don't think it's
needed atm.
> > +{
> > + int ret;
> > +
> > + ret = __drm_connector_init_core(dev, connector, funcs, connector_type, ddc);
> > + if (ret)
> > + return ret;
> > +
> > + drm_connector_add(connector);
> > +
> > + return 0;
> > +}
> > +
> > /**
> > * drm_connector_init - Init a preallocated connector
> > * @dev: DRM device
> > @@ -659,10 +730,8 @@ void drm_connector_cleanup(struct drm_connector *connector)
> > connector->name = NULL;
> > fwnode_handle_put(connector->fwnode);
> > connector->fwnode = NULL;
> > - spin_lock_irq(&dev->mode_config.connector_list_lock);
> > - list_del(&connector->head);
> > - dev->mode_config.num_connector--;
> > - spin_unlock_irq(&dev->mode_config.connector_list_lock);
> > +
> > + drm_connector_remove(connector);
> >
> > WARN_ON(connector->state && !connector->funcs->atomic_destroy_state);
> > if (connector->state && connector->funcs->atomic_destroy_state)
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index e3fa43291f449..8e8d130b40f98 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -2122,6 +2122,11 @@ struct drm_connector {
> >
> > #define obj_to_connector(x) container_of(x, struct drm_connector, base)
> >
> > +int drm_connector_init_core(struct drm_device *dev,
> > + struct drm_connector *connector,
> > + const struct drm_connector_funcs *funcs,
> > + int connector_type);
> > +void drm_connector_add(struct drm_connector *connector);
> > int drm_connector_init(struct drm_device *dev,
> > struct drm_connector *connector,
> > const struct drm_connector_funcs *funcs,
>
> --
> Jani Nikula, Intel
