On Wed, Jul 29, 2020 at 04:15:28PM +1000, Sam McNally wrote:
> As of commit d8bd15b37d32 ("drm/dp_mst: Fix the DDC I2C device
> registration of an MST port"), DP MST DDC I2C devices are consistently
> parented to the underlying DRM device, making it challenging to
> associate the ddc i2c device with its connector from userspace.
I can't see how was it less challenging before the commit. There is no
guarantee for a CSN message which was the only way for the i2c device to
get reparented to the connector.
> Given the need for further refactoring before the i2c devices can be
> parented to their connectors, in the meantime follow the pattern of
> commit e1a29c6c5955 ("drm: Add ddc link in sysfs created by
> drm_connector"), creating sysfs ddc links to the associated i2c device
> for MST DP connectors.
>
> If the connector is created and registered before the i2c device, create
> the link when registering the i2c device; otherwise, create the link
> during late connector registration.
>
> Signed-off-by: Sam McNally <sammc@xxxxxxxxxxxx>
> ---
>
> drivers/gpu/drm/drm_dp_mst_topology.c | 29 +++++++++++++++++++++++++--
> 1 file changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 1ac874e4e7a1..73a2299c2faa 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -2161,11 +2161,23 @@ static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
> int drm_dp_mst_connector_late_register(struct drm_connector *connector,
> struct drm_dp_mst_port *port)
> {
> + int ret;
> DRM_DEBUG_KMS("registering %s remote bus for %s\n",
> port->aux.name, connector->kdev->kobj.name);
>
> port->aux.dev = connector->kdev;
> - return drm_dp_aux_register_devnode(&port->aux);
> + ret = drm_dp_aux_register_devnode(&port->aux);
> + if (ret)
> + return ret;
> +
> + if (port->pdt != DP_PEER_DEVICE_NONE &&
> + drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
How can we get here when drm_dp_mst_is_end_device(port) is not true?
AFAICS that's only case where we should create a connector and an i2c
device. (IOW we don't create them for branch ports.)
> + ret = sysfs_create_link(&port->connector->kdev->kobj,
> + &port->aux.ddc.dev.kobj, "ddc");
> + if (ret)
> + drm_dp_aux_unregister_devnode(&port->aux);
> + }
> + return ret;
> }
> EXPORT_SYMBOL(drm_dp_mst_connector_late_register);
>
> @@ -5490,6 +5502,7 @@ static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port)
> {
> struct drm_dp_aux *aux = &port->aux;
> struct device *parent_dev = port->mgr->dev->dev;
> + int ret;
>
> aux->ddc.algo = &drm_dp_mst_i2c_algo;
> aux->ddc.algo_data = aux;
> @@ -5504,7 +5517,17 @@ static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port)
> strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(parent_dev),
> sizeof(aux->ddc.name));
>
> - return i2c_add_adapter(&aux->ddc);
> + ret = i2c_add_adapter(&aux->ddc);
> + if (ret)
> + return ret;
> +
> + if (port->connector && port->connector->kdev) {
> + ret = sysfs_create_link(&port->connector->kdev->kobj,
> + &port->aux.ddc.dev.kobj, "ddc");
> + if (ret)
> + i2c_del_adapter(&port->aux.ddc);
> + }
> + return ret;
> }
>
> /**
> @@ -5513,6 +5536,8 @@ static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port)
> */
> static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_mst_port *port)
> {
> + if (port->connector && port->connector->kdev)
> + sysfs_remove_link(&port->connector->kdev->kobj, "ddc");
> i2c_del_adapter(&port->aux.ddc);
> }
>
> --
> 2.28.0.rc0.142.g3c755180ce-goog
>
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