Re: [PATCH v5 3/4] drm/display: bridge_connector: init scdc debugfs for HDMI

[Nicolas Frattaroli <nicolas.frattaroli@collabora.com>]

On Saturday, 6 June 2026 10:54:23 Central European Summer Time Maxime Ripard wrote:
> Hi,
> 
> On Thu, Jun 04, 2026 at 05:52:08PM +0200, Nicolas Frattaroli wrote:
> > On drm_bridge_connectors that contain an HDMI bridge, initialise the
> > SCDC debugfs entry under the connector's debugfs root.
> > 
> > Reviewed-by: Daniel Stone <daniels@collabora.com>
> > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> > ---
> >  drivers/gpu/drm/display/drm_bridge_connector.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
> > index cafa498c3848..629d9b8aff22 100644
> > --- a/drivers/gpu/drm/display/drm_bridge_connector.c
> > +++ b/drivers/gpu/drm/display/drm_bridge_connector.c
> > @@ -25,6 +25,7 @@
> >  #include <drm/display/drm_hdmi_cec_helper.h>
> >  #include <drm/display/drm_hdmi_helper.h>
> >  #include <drm/display/drm_hdmi_state_helper.h>
> > +#include <drm/display/drm_scdc_helper.h>
> >  
> >  /**
> >   * DOC: overview
> > @@ -263,6 +264,9 @@ static void drm_bridge_connector_debugfs_init(struct drm_connector *connector,
> >  		if (bridge->funcs->debugfs_init)
> >  			bridge->funcs->debugfs_init(bridge, root);
> >  	}
> > +
> > +	if (bridge_connector->bridge_hdmi)
> > +		drm_scdc_debugfs_init(connector, root);
> >  }
> 
> We register the other debugfs entries in drm_debugfs_connector_add /
> hdmi_debugfs_add. I don't think there's anything specific to bridge
> connector here and it would benefit to drivers that don't use it as
> well, so I think putting it in the generic part of the framework would
> be better.

Yeah, I tried that, but unfortunately this creates a dependency cycle
during linking:

depmod: ERROR: Cycle detected: drm_display_helper -> drm_kms_helper -> drm -> drm_display_helper
depmod: ERROR: Cycle detected: drm_display_helper -> drm -> drm_display_helper
depmod: ERROR: Found 3 modules in dependency cycles!

My way of working around this was to move it into the target of the
indirect function call for the connector, in this case the bridge
connector.

If you have alternate suggestions I'm open to them; I don't know
enough about the kernel's linking process and how people usually
resolve these issues.

Kind regards,
Nicolas Frattaroli

> 
> Maxime
>