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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 static connectors initialized/added during driver loading, for which the driver ensures that look-ups via the above list are not possible until all the connector and other required state is fully initialized already. It's also not a problem for user space looking up either a static or dynamic (see what this is below) connector, since this will be only possible once the connector is registered. A dynamic - atm only a DP MST - connector can be initialized and added after the load time initialization is done. Such a connector may be looked up by in-kernel users once it's added to the connector list. In particular a hotplug handler could perform a detection on all the connectors on the list and hence find a connector there which isn't yet initialized. For instance the connector's helper hooks may be unset, leading to a NULL dereference while the detect helper calls the connector's drm_connector_helper_funcs::detect() or detect_ctx() handler. To resolve the above issue, add a way for dynamic connectors to separately initialize the DRM core specific parts of the connector without adding it to the connector list - by calling the new drm_connector_dynamic_init() - and to add the connector to the list later once all the initialization is complete and the connector is registered - by calling the new drm_connector_dynamic_register(). Adding the above 2 functions was also motivated to make the distinction of the interface between static and dynamic connectors clearer: Drivers should manually initialize and register only dynamic connectors (with the above 2 functions). A driver should only initialize a static connector (with one of the drm_connector_init*, drmm_connector_init* functions) while the registration of the connector will be done automatically by DRM core. v2: (Jani) - Let initing DDC as well via drm_connector_init_core(). - Rename __drm_connector_init to drm_connector_init_core_and_add(). v3: - Rename drm_connector_init_core() to drm_connector_dynamic_init(). (Sima) - Instead of exporting drm_connector_add(), move adding the connector to the registration step via a new drm_connector_dynamic_register(). (Sima) - Update drm_connector_dynamic_init()'s function documentation and the commit log according to the above changes. - Update the commit log describing the problematic scenario during connector detection. (Maxime) Cc: Jani Nikula <jani.nikula@intel.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Maxime Ripard <mripard@kernel.org> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> (v1) Reviewed-by: Lyude Paul <lyude@redhat.com> Reviewed-by: Jani Nikula <jani.nikula@intel.com> Reviewed-by: Maxime Ripard <mripard@kernel.org> Acked-by: Alex Deucher <alexander.deucher@amd.com> Acked-by: Wayne Lin <Wayne.Lin@amd.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241211230328.4012496-2-imre.deak@intel.com |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.