[PATCH v3 02/11] drm/connector: Add FIXME for GETRESOURCES ioctl wrt. uninited connectors

[Imre Deak]

On Thu, Dec 12, 2024 at 12:06:12PM +0200, Jani Nikula wrote:
> On Thu, 12 Dec 2024, Imre Deak <imre.deak at intel.com> wrote:
> > The connectors enumerated by the GETRESOURCES ioctl may not be fully
> > initialized yet wrt. to the state set up during connector registration
> > (for instance the connector's debugfs/sysfs interfaces may not exist
> > yet). This can happen in two ways:
> >
> > 1. Connectors initialized and added to the
> >    drm_mode_config::connector_list during driver loading will be visible
> >    to the GETRESOURCES ioctl caller once the driver is registered via
> >    drm_dev_register()->drm_minor_register(DRM_MINOR_PRIMARY) and before
> >    the connectors are registered via drm_dev_register()->
> >    drm_modeset_register_all().
> >
> > 2. Dynamic connectors (MST) - after being initialized - may be added to
> >    the connector_list after the driver is loaded and registered and before
> >    the connector's userspace interfaces (debugfs, sysfs etc.) are added
> >    in drm_connector_dynamic_register().
> >
> > A solution for 1. would be to register the driver only after the
> > connectors are registered, for 2. to add the connector to connector_list
> > only after the userspace interfaces are registered.
> >
> > The fix would require a bigger change, not the topic of this patchset,
> > so adding only a FIXME comment here.
> 
> References to "this patchset" become meaningless after this has been
> committed.

I wondered if the Link: added when the patch is committed provides the
context, but I suppose the link can get stale. I can reword the above to:

"The fix requires a bigger change, for now adding a FIXME: comment for
it."

> Reviewed-by: Jani Nikula <jani.nikula at intel.com>
> 
> >
> > Suggested-by: Simona Vetter <simona.vetter at ffwll.ch>
> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > ---
> >  drivers/gpu/drm/drm_mode_config.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> > index 37d2e0a4ef4be..8642a2fb25a90 100644
> > --- a/drivers/gpu/drm/drm_mode_config.c
> > +++ b/drivers/gpu/drm/drm_mode_config.c
> > @@ -150,6 +150,15 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
> >  	drm_connector_list_iter_begin(dev, &conn_iter);
> >  	count = 0;
> >  	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
> > +	/*
> > +	 * FIXME: the connectors on the list may not be fully initialized yet,
> > +	 * if the ioctl is called before the connectors are registered. (See
> > +	 * drm_dev_register()->drm_modeset_register_all() for static and
> > +	 * drm_connector_dynamic_register() for dynamic connectors.)
> > +	 * The driver should only get registered after static connectors are
> > +	 * fully initialized and dynamic connectors should be added to the
> > +	 * connector list only after fully initializing them.
> > +	 */
> >  	drm_for_each_connector_iter(connector, &conn_iter) {
> >  		/* only expose writeback connectors if userspace understands them */
> >  		if (!file_priv->writeback_connectors &&
> 
> -- 
> Jani Nikula, Intel